Grape production - lrrpublic.cli.det.nsw.edu.aulrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/hsc_agriculture/... · Part 3: Pests and diseases of grapes ... that interfere with

Grape production Part 3: Pests and diseases of grapes

Introduction ............................................................................... 2

Vineyard pests .......................................................................... 3

A grape epidemic - phylloxera..........................................................3

Fungal infections ....................................................................... 8

Black spot .........................................................................................9

Downy mildew ................................................................................10

Powdery mildew .............................................................................12

Fungicides ......................................................................................13

The natural balance................................................................. 15

The farm community.......................................................................15

Mites, friend or foe?........................................................................17

Insect pests ....................................................................................20

Competitors............................................................................. 22

Chemical control - herbicides.........................................................23

Organic weed control .....................................................................27

Plant associations ..........................................................................30

Additional resources................................................................ 32

Suggested answers................................................................. 40

Exercises – Part 3 ................................................................... 45

Part 3: Pests and diseases of grapes 1

Introduction Introduction In this part, you will be focussing on a number of different organisms that interfere with grape production - weeds, insect pests and fungi. These pests can damage the leaves, roots and fruit of a plant. Pest damage results in reduced yields, quality and financial returns.

The management of pests in a vineyard is important to ensure the best quality vintage (harvest) possible. There are many ways this can be done including integrated pest management (IPM). An understanding of the life cycle of an organism, including the relationship to its host, helps to devise ways to manage populations. Every pest control program has its advantages and disadvantages in the short and the long term. An important problem you will be examining is resistance to chemicals.

Netting is placed over vines in this vineyard in the Berry area to reduce damage to grapes by birds. (Photograph: Julie Robinson)

This part contributes towards an understanding of Outcomes H1.1 and H2.1 from the Agriculture Stage 6 HSC Course. The syllabus can be found on the Board of Studies, NSW website at http://www.boardofstudies.nsw.edu.au

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http://www.boardofstudies.nsw.edu.au/

Vineyard pests Vineyard pests Market demand for high quality grape products means that pests must be controlled effectively. Damaged grapes mean lower returns, particularly in the table grape market. The term ‘pests’ in this module refers to: • disease-causing organisms, for example bacteria, viruses, nematodes,

fungi • insect pests, for example light brown apple moth, Rutherglen bug • arachnids, for example blister mites, bud mites • larger pests, for example rabbits, snails, birds.

The grapevines first introduced into Australia were free from most diseases. Around the turn of the last century there was a lot of movement of vine material (mainly cuttings) around the globe. With these came the spread of vine pests. Fungi, viruses and insects spread from North America to Europe and then to Australia. The most devastating of the insect pests that entered the country in this way is phylloxera.

A grape epidemic – phylloxera Phylloxera is a tiny insect (like an aphid) that is extremely destructive, destroying vineyards all over the world. They feed on the roots, weakening vines and making them more susceptible to disease.

By 1920 phylloxera had spread from North America to most of the major grape growing countries of the world. Source: Robinson J. (1986). Vines Grapes and Wines. Mitchell Beazley Publications. London. England.


Portugal, South Africa, New Zealand, France, Spain, the United States and Australia are major grapegrowing countries affected by outbreaks of phylloxera.

Brisbane 1902

Sydney 1902

Geelong 1877

Bendigo 1893Heathcote 1899Rutherglen 1899

• Phylloxera was first detected in Australia in the Geelong area in 1877.• The pest quickly spread throughout much of eastern Australia.• Vines were uprooted in an effort to stop the spread of this insect pest.• Rutherglen’s vineyard area was reduced to a quarter of its size as a result!

The spread of phylloxera throughout Australia.

The life and times of phylloxera A study of the life cycle of phylloxera has lead to more effective control measures. The life of phylloxera is complicated by the type of vine.

There are several species of vines used in commercial grape production. Vitus vinifera is native to Europe and Central Asia. It is known as the European vine. There are a number of vine species native to America, for example, Vitus labrusca. This species, native to North America, was suspected of harbouring phylloxera which then ‘hitchhiked’ into Europe and Australia. Some American species are resistant to phylloxera; the European species is not.

There are three main stages in the life cycle of phylloxera on Vitus vinifera: the wingless adult; eggs; and nymphs. These occur on the host’s roots. Other stages exist on different vine species. Nymphs are brown in colour and much smaller than the adults which are green, brown or orange and around 1 mm long.

Phylloxera survive the winter (overwinter) as nymphs sheltering under the bark of the older roots. During the growing season, nymphs develop into wingless adults which can lay up to 200 eggs. This cycle can occur

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several times, producing numerous pests. During spring, nymphs feed on the younger roots, weakening the vine. Root galls develop which stop the roots from growing. Older vines with more extensive root systems last longer when infected.

nymphsfeed(spring)nymphs infest

other vine rootsadult

eggsnymph

several generationsduring a season

Vitus vinifera(the host)

nymphsoverwinter(winter)

A simplified life cycle of phylloxera in the soil around European vines.

Phylloxera can spread to nearby vines in various ways. Nymphs can travel through cracks in the soil. They cannot move through coarse sandy soil, preferring heavy clay soils. Nymphs can also travel on the surface of the ground. They can be blown onto other plants by the wind. Phylloxera can also reach nearby vineyards by the movement of machinery or equipment.


1 Describe the features of a vineyard that can be badly affected by phylloxera.

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2 Describe the features of a vineyard least threatened by phylloxera.

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Check your answers.

Control of phylloxera

Quarantine regulations to prevent the introduction of grape phylloxera into areas free of phylloxera. Scanned from Are you alert to quarantine? (1990). Department of Primary Industries and Energy. Australian Quarantine and Inspection Service. Canberra. Australia. Commonwealth of Australia copyright reproduced by permission.

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Most grapevines in Australia are varieties of the European grapevine Vitus vinifera which is susceptible to attack by phylloxera. In areas where phylloxera is present, vines are often grafted onto resistant rootstocks (from American grapevine species). Establishing a vineyard with resistant rootstocks greatly increases the cost but reduces the risk.

Quarantine regulations, in force since 1899, have contained the pest to the original outbreak areas. The movement of vine material is restricted in areas where phylloxera is still active, for example, in the Sydney region. An understanding of how the pest spreads is essential to its control.

1 Quarantine areas are often signposted with rules. What regulations might be on a sign when you were:

a) entering the Hunter region

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b) entering the Corowa district.

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2 How do quarantine restrictions help to control the spread of disease?

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Check your answers.

Are grapes grown in your area? If so, what pests are likely to cause damage?

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Are there any quarantine regulations for your area? If so, what are they?

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Summary • Vine pests can spread through the soil, on cuttings or other vine

material.

• Phylloxera is an extremely destructive insect pest of grapevines.

• The spread of phylloxera can be controlled by quarantine restrictions and planting vines with resistant rootstocks.


Fungal infections Fungal infections

Grapevines are regularly monitored. The manager looks for signs of nutrient imbalance, weather damage or the presence of pests. Indications of pests might include: eaten leaves; the presence of spots or patches; small grapes or a poor berry set; yellowing leaves; or a powdery covering on grapes. Pests are identified and their damage levels determined. If necessary, control measures can be adopted.

Anthracnose (black spot) is a disease caused by a fungus. Other common fungal diseases include downy mildew, oidium (powdery mildew), botrytis (bunch rot) and phomopsis (dead arm).

Fungi reproduce by spores. Each fungus has different spores which can be used in identification. However, the damage is well underway when the disease is evident. That is why many of the pest control programs for these pests are preventative.

Downy mildew Powdery mildew Botrytis

on the underside of leaf on the leaf surface on the leaf surface

clustered spores single strands clustered spores

Features of the spores of three different diseases of grapevines.

Many of the fungal diseases respond well to chemical sprays called fungicides. Information about the disease organism’s life cycle and the favourable climatic conditions help to determine the best time to control the disease.

Does the pest damage cost more than the control measures? The manager must know the value of the crop, the cost of the damage and the cost of control. When the damage costs more than control the economic threshold level has been reached.

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Black spot Pests can be identified in a number of ways. Very small pests can be identified by the damage they do. For example, black spot disease is identified by black spots on bark, leaves and berries.

Some varieties, for example, Semillon, are highly resistant to black spot; others such as Grenache, are not.

This diagram shows some of the symptoms of this fungal disease.

Tell tale signs of anthracnose (black spot) on grapevines.

Look at the grapevine in the following photograph. Evaluate whether you think it is infected with black spot.

Check your answer.

Grapevine. (Photograph by Julie Robinson)


Downy mildew Downy mildew was first detected in Australia, in Rutherglen, in 1917. Since then, it has spread to most of the vineyards in eastern Australia. Grape varieties vary in their susceptibility to downy mildew. For example, Pinot Noir vines are more susceptible than Cabernet Sauvignon.

All green parts of the vine are affected. Circular oil spots on young leaves are an indication of the presence of downy mildew. Downy white spores are produced on the underside of the leaves (under the oil spots), on young berries and bunch stalks. Infections may cause the leaves on vines to fall, the flowers and bunch stalks to wither and the young berries to shrivel and harden, resulting in crop losses of up to 20%.

During winter, spores rest on fallen and decaying leaves. In spring when temperatures are more than 10°C, the spores reinfect leaves. They are spread by rain splashing on the leaves. The spread of downy mildew is encouraged by conditions of high humidity.

Many viticulturists carry out preventative programs, for example, regular spraying, in addition to canopy management to control mildew. The timing of fungicide application is critical. Vines are most susceptible to infection in warm, humid weather, so spraying is often done between budburst and berry development (in spring).

Spraying equipment. Seldom seen vineyard, Mudgee. July, 1996. (Photograph: Julie Robinson)

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sporeproducing

body

mobile spores

resting spores

leaf fall

fallen leaves

restingspores(winter)

(late summer/autumn)

(spring/summer)

wet leaves

overhead sprinkler or rainfall

infection

germination

Life cycle of downy mildew fungus.

1 Use information in the diagram to describe the life cycle of downy mildew in the vineyard.

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2 Warm, wet and humid conditions favour the development of downy mildew. From your other work in this module describe two management practices which would help to control downy mildew.

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Check your answers.


Powdery mildew Powdery mildew is another fungal disease common in Australian vineyards. Like downy mildew, powdery mildew spread from North America to Europe and Australia. It appeared in Australia around 1866. All grapevines are susceptible to powdery mildew, though Riesling, Semillon and Chardonnay are particularly affected.

poor berry set

small berries

mature grapes split

pale green spots

red brown areas

dried out berries

grey white powderypatches (spores)

The effects of powdery mildew on a grapevine.

1 Outline how a severe infection of powdery mildew might affect the production of grapes.

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Infection by powdery mildew is encouraged by warm temperatures (optimum temperature is 25°C) and low light levels. At higher temperatures the spread of infection slows down. Ideal conditions are likely to occur between budburst and flowering.

2 Describe a disease management strategy for the control of powdery mildew in vineyards. Refer to your previous work for relevant information.

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3 Explain why timing is important in the control of powdery mildew.

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Check your answers.

Fungicides There are a number of different fungicides registered for use in vineyards. These include:

• Bordeaux mixture

• ziram, mancozeb, benomyl

• sulfur, lime sulfur (very toxic to predators)

• copper oxychloride, copper hydroxide.

The choice of a fungicide depends on environmental and economic considerations. It is also important that the control program is varied to avoid the pests building up resistance to chemicals.

Rotating chemicals is one strategy used to prevent resistance, which is a major problem in some European vineyards. The use of other management strategies such as canopy management and the removal of dead leaves where some pests overwinter, will reduce the use of chemicals.

Fungicides are usually applied more than once in a prevention program. Before spraying, the economic threshold of the pest problem must be considered. The vineyard manager needs to know:

• what type of disease is present or likely to occur (and when)

• how much the damage is likely to cost

• the cost of a spraying program

• the destination of the produce (wine, juice, table grapes, dried vine fruit) since different products have different quality requirements and chemical residue levels allowed.


Environmental consequences need to be considered when choosing to use particular chemicals on farms. For example, agricultural chemicals can:

• leave residues in farm produce or the soil, reducing quality

• leach through the soil profile to pollute ground water

• affect nearby crops or pastures when sprayed on a windy day

• vary in how toxic they are to humans

• affect soil organisms, bees, fish or birdlife.

Information provided on container labels gives users guidelines. These must be read by the user. If the user cannot read English then the information must be read out to them.

Organically grown grapes do not use artificial or synthetic chemicals. Sulfur and Bordeaux mixture can be used to control fungus diseases in organic vineyards.

Complete Exercise 3.1: Bunch rot.

Summary • Fungi such as black spot, downy mildew, powdery mildew and

botrytis interfere with grapevine production.

• Fungal diseases can be identified by their spores and the damage caused to the green parts of vines.

• Fungicides can be used to prevent and control fungal diseases of grapevines.

• Control programs are devised from information about the disease’s life cycle and favourable climatic conditions.

Pest control programs in vineyards include a range of strategies including spraying pesticides. In the next part you will be examining a holistic approach which takes account of the natural ecological balance of the vineyard – working with nature instead of against it.

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The natural balance The natural balance

Plants in nature seldom grow alone. They usually grow in a community whose characteristics depend on the environment they live in. For example, the plants and animals that live together in the tropics are quite different to those of the desert.

The farm community On a farm, the natural community has been modified. Exotic plants and animals have been introduced. Some of these provide food and fibre; others are as escapees or ‘hitchhikers’. A vineyard community is shown below.

sheep grazing

native andimportedgrasses

wattle tree

parrots

bees eucalyptus trees

caterpillar

Plants and animals living in a vineyard community. Some organisms are more obvious than others.


Agricultural activities Agricultural activities, for example spraying chemicals, alters the environment by changing the composition of soil and water, as well as plant and animal populations.

machineryeg tractor and airseeder

soil structuresoil organisms

clearing for grazing and cropping

biodiversitysalinityerosion

removal of productseg harvest, hay

nutrientssoil pH

Farming activities alter the environment.

1 Use the diagram to describe some of the changes that agricultural production makes to the environment. Give examples.

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2 Chemical control of pests, diseases and weeds also affects the environment. From your knowledge of chemicals, briefly describe the effects spraying might have on the environment.

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Check your answers.

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Mites – friend or foe? As well as bees, birds and fish, chemicals may affect the natural balance of mites in a vineyard.

What are mites?

These animals form part of a larger group known as arthropods. Other members include crabs, scorpions, ticks, centipedes and insects. Mites and ticks are part of a subgroup. Some are parasitic, for example, cattle tick.

What balance are we talking about?

In a vineyard, there are a number of different mites with various feeding patterns. Some mites, for example, bunch mite, blister mite and rust mite are considered pests because they feed on grapevines. Others are predatory; they feed on other mites. An understanding of the balance between pest and predatory mites is essential to the development of integrated pest management (IPM) in vineyards with mite problems.

Mite research Understanding the population dynamics within each vineyard, and therefore the balance between organisms, is a major ‘tool’ in the implementation of biological mite management.

Research carried out by Dr David James and Jennifer Whitney at Yanco Agricultural Institute shows that some chemicals affect this balance more than others. Read about what Jennifer Whitney has to say about mite research in the transcript of an interview with her in the Additional resources section.

1 Jennifer mentions ‘population dynamics’ several times during the interview. Outline what you think this term means.

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2 From this research, explain how you think pest mites might be controlled by biological means.

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3 Comment on the design of the research. Explain why you think this research was carried out in different vineyards over many years.

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Check your answers.

Chemical control of mites Chemicals used in vineyards affect mite populations. Sulfur sprays don’t alter the mite populations too much but other ‘harder’ chemicals are indiscriminate and may destroy all mite populations. Sulfur based sprays (except lime sulfur) usually do not affect mites too much.

Vineyards where extensive chemical control is carried out have few, if any, of the native predator mites. Read about what Jennifer has to say about chemical control of mites in the interview in the Additional resources section. Jennifer relates the methods used to find out how fungicides and miticides used in vineyards affect mite numbers

1 Identify the information found by the first research method. Outline the conclusions that could be made.

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2 Identify the information determined by the bioassay in the laboratory. Outline the conclusions that could be made.

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3 Explain why research was carried out both in the field and in the laboratory.

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4 Population dynamics and chemical sprays affect mite numbers in vineyards. Identify other factors that might influence mite populations.

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Check your answers.

The influence of climate on mite populations

The research involved looking at how different factors influenced mite populations. Read further in the transcript in the Additional resources section to find out how Jennifer finds environmental factors affect mite populations.

Identify aspects of the research design that would have allowed the researchers to come up with these types of conclusions.

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Check your answer.

Integrated pest management

Pest populations need to be managed in vineyards to keep damage below the economic threshold. There are various strategies that may be used depending on things such as the vineyard manager’s goals. Read the rest of the interview transcript in the Additional resources section to find out about the use of integrated pest management (IPM) in vineyards.

In the interview Integrated pest management was described as being a responsible approach to pest control. Outline what is meant by the term integrated pest management.

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Check your answers.


Insect pests There are many insects that may be pests of grapevines. Some are sap suckers; others eat the leaves. Their activities reduce grape productivity. The table below shows the effects of some insect pests and common methods of control.

Insect pest Damage Control

lightbrown apple moth

larvae hatch from eggs laid on weeds then eat leaves, young shoots, berries and flowers

• predators, for example spiders

• parasites, for example Trichogramma

• insecticides, for example chlorpryifos

• biocide, for example Bacillus thuringiensis

• remove weeds

grapevine moth overwinters on vine wood or posts then eats leaves, flowers and young berries

• predators, for example shield bug

• parasites of larvae and pupae

• insecticide, for example carbaryl

• biocide, for example Bacillus thuringiensis

longtailed mealybug

overwinters on vines, cover crops and weeds; secretes honeydew that develops into sooty mould; grape productivity is reduced

• good canopy management

• insecticide, for example methidathion

grapevine scale overwinters on canes or wood; secretes honeydew which develops sooty mould; growth is restricted; young eat leaves

• parasites, for example parasitic wasp

• predators, for example ladybird

• insecticide, for example winter oil

Rutherglen bug normally lives among weeds; can kill young vines; reduces grape quality; eats all green parts

• control weeds where bugs breed

• insecticide, for example maldison applied to vine and soil where they lay eggs

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As you can see, there are various methods used to manage insect pests. Pests may be controlled by culture, natural, chemical or biological means. Write an example of each type of control. The first one is done for you.

Control method Example

Cultural control remove weeds, canopy management

Natural control

Chemical control

Biological control

Check your answers.

If you were a vineyard manager how would you manage pests?

Would you grow grapes organically? Why? Why not?

Complete Exercise 3.2: Mites.

Summary • Many different plants and animals live in a vineyard community.

• Farming activities may upset plant and animal population dynamics.

• Biological control exploits the natural management of pest populations.

• Integrated pest management combines several control measures to manage pest populations.

• There are many insect pests of grapevines which are managed in a variety of ways.

There are several types of fungi, mites and insects that interfere with grape production in a vineyard. In the next section you will examine the effects weeds have on production and how their populations can be managed.


Competitors Competitors It is common practice in agriculture to crop large areas. Most people are familiar with broadacre cropping, for example wheat, oats, barley, rice. Vineyards also have many plants in rows. Even in these highly controlled situations there are plant invaders called weeds. In this section, you will be examining various methods used to control weeds in vineyards. By comparing these you will be able to make recommendations for sustainable weed management strategies.

Access an interactive version of Competitors using this link. This material will complete this part of the module.

water

nutrients

thistle

young grapevine

Weeds compete for resources.

Very simply, weeds are unwanted plants. Weeds, like cover crops, compete for valuable resources and may harbour pests. However, weeds can also harbour beneficial mites and insects. Weeds need to be managed since their total removal may not benefit the vineyard.

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Chemical control – herbicides

Herbicides contain an active chemical constituent. Usually they are mixed with water before spraying. It is extremely important that this is done safely and correctly. This includes getting the quantities right and wearing protective clothing. Your health and grapevine vigour are both at stake. So, read the instructions!

General

Protection of Livestock

First Aid

Safety Directions

Protection of Wildlife

For control of...

Agricultural chemicals are required to include information on safety procedures, directions for use and environmental information.

Identify at least four reasons why it is critical that farm chemicals are used safely and efficiently.

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Check your answers.


Types of herbicides In Australia, herbicides are grouped according to their mode of action the way they control weeds. There are fourteen herbicide groups (A – N). These groups are rated as being a high, moderate or low risk.

Ris

k

AllyGroup B

®®Fusilade

Group A

[Group A-B]

TreflanGroup D

®®Simazine

Group C

[Group C – H]

DiquatGroup L

®®Roundup

Group M

[Group I – N]overal ls

respirator

gloves

Herbicides are labelled to show their group. This gives users an indication of their risk.

Some herbicides are selective, they control only particular sorts of weeds. Examples include Treflan® and Hoegrass®.

Broadspectrum herbicides, also known as knockdown herbicides, are not selective. Examples include Roundup® and Gramoxone®.

There are a number of government authorities that regulate the production of chemicals used on farms. The efficient and safe use of farm chemicals is extremely important. In 1993, the Farm Chemical User Training Program was launched to assist people working on the land to more safely handle and better understand herbicide use on farms.

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Herbicides in the vineyard Chemicals used in vineyards must be registered for that purpose. The different sorts of herbicides are as follows.

• Pre-emergent herbicides - extremely effective for control of weeds before they emerge. They are residual chemicals usually sprayed onto bare ground. Some pre-emergents can accumulate in the soil.

• Contact (knockdown) herbicides kill weeds when they are touched. These herbicides are very effective at killing all the weeds they touch. Regrowth of weeds is unaffected.

• Systemic herbicides are translocated within the plant. They are very effective especially if they are applied when weeds are actively growing.

The diagrams below illustrate the action of three different types of herbicides. Label each as either pre-emergent, contact or systemic.

all dead

dead

dead

healthy

weed seeds

healthy

Check your labels.


Herbicide resistance One major drawback of chemical use is the build up of resistant weed populations. Many agricultural weeds have developed resistance to chemicals. These weeds can survive a herbicide applied at the recommended rate. Herbicide resistant weeds include annual rye grass, wild oats, capeweed, barley grass, dirty dora and starfruit.

A number of non chemical strategies can be used to reduce the build up of herbicide resistant weeds.

• Agricultural plants should be grown under optimum conditions so they can successfully compete with weeds.

• Weeds can be cultivated, for example slashed, ploughed in.

• Crops can be grown to compete with weeds, for example a cover crop, pasture, green manure crop.

• Weeds can be smothered by mulching or composting.

• Weeds can be grazed by sheep in winter.

Part of a weed management program may however, include chemical use. When using chemicals as part of a weed management strategy farmers should:

• rotate chemicals from different groups

• try to use low and moderate risk chemicals

• use knockdown herbicides before cropping

• spray weeds before they set seed (spray topping, crop topping)

• analyse herbicides when the weeds are out of control.

It is important to keep accurate paddock records that show which herbicides were used in which paddock and when.

Is resistance to herbicides something that farmers really need to be concerned about? Why? Why not?

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Complete Exercise 3.3: Resistance.

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Organic weed control There are production standards that must be met by organic grape growers. Synthetic chemicals are not allowed for use in organic vineyards. Methods of control that are acceptable include:

• mechanical or cultural control, for example hand weeding, cultivation with machinery, mulching

• planting cover crops

• biological control.

Mechanical/cultural control Weeds in vineyards can be slashed, mowed, or cultivated. However, this may damage the vine or its root system. Cultivation was the most common form of weed control before modern herbicides were developed. Now, mechanical cultivation is less popular because of the soil damage that may occur.

Think about the advantages and disadvantages of mechanical cultivation. Complete the table to list at least two advantages and two disadvantages of cultivating weeds.

Advantages Disadvantages

Check your answers.


Cover crops Planting cover crops in vineyards can reduce weeds. However, there are advantages and disadvantages as show in the table below.

Advantages Disadvantages

• provides nutrients , for example, legumes

• competition for water

• improves soil structure • competition for nutrients

• additional produce , for example, hay

• can host pests

• reduces weeds • competition for space

• reduces erosion • may shade other plants

1 Briefly explain, using examples, three advantages and three disadvantages of using cover crops in vineyards. One advantage is shown below.

• A legume cover crop, for example lucerne, may increase the nitrogen levels in the soil.

• __________________________________________________

• __________________________________________________

• __________________________________________________

• __________________________________________________

• __________________________________________________

2 Discuss whether you would grow a cover crop if you were a vineyard manager.

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Check your answers.

28 Grape production

Biological control In the last part you learned how effective predator mites were in the control of blister, rust and bunch mites on grapevines. The natural enemies of weeds work in essentially the same way. Biological control of weeds uses natural enemies such as insects, mites and pathogens.

There are rigorous procedures that must be followed before biological control agents (natural enemies) can be released.

• The Australian Quarantine Inspection Service (AQIS) and Environment Australia must approve their importation into Australia.

• A series of tests must ensure that the agent attacks only the target. This ensures the safety of native species.

• An application for release of the biological control agent must be approved by several government departments, research organisations and state departments.

• The effect of the control agent must be observed in quarantine.

• Performance in the field is monitored at research sites.

Biological control does not eradicate pests. It does, however, offer a natural, environmentally safe long term method of control.

Many different organisms have been released as biological control agents. For example, the CSIRO has released a rust fungus for skeleton weed management.

Read the article Weevil causes destruction on Paterson’s curse in the Additional resources section. It outlines the release of a biological agent used in the control of Paterson’s curse, otherwise known as Salvation Jane. This research is being done by Dr Andy Sheppard. As you read, think about the potential of this form of control and any possible drawbacks.

1 Identify at least two advantages in using biological weed control.

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2 Identify at least one disadvantage in using biological weed control.

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3 Evaluate biological control of weeds considering the advantages and disadvantages you have identified.

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Check your answers.

Plant associations You may have heard of companion planting where plants are grown next to a crop to benefit the crop’s growth and development. For example, growing basil with tomato plants benefits the crop in ways that are not entirely understood. The basil may deter insect pests that would otherwise damage the tomatoes.

The weed, silverleaf nightshade reduces the growth of crop and pasture plants. Studies suggest that the roots of silverleaf nightshade release a chemical which stops the growth of other plants.

The affects of one plant on another may be beneficial or adverse. This is called allelopathy. Allelopathy is another example of crop interference.

The effects of some plants on others have been observed for a very long time. Democritus in the third century BC first recorded that some plants don’t grow near others. Molisch coined the term ‘allelopathy’ to describe this effect in 1937. The term was coined from the Greek words below.

allelon – of each other; pathos – to suffer

Plants that lower crop yields include parthenium, Johnson grass, cotton, purslane and lantana. These plants don’t affect all plants. They are selective. For example; tall fescue inhibits the growth of canola and red clover; thistles affect oats; and rye inhibits wheat. There is little known about allelopathic plants and grapes.

Allelopathic plants affect other plants in a variety of ways. The chemicals released can:

• make seeds and buds dormant

• promote disease infections

• make plants more susceptible to disease

• disrupt water balance

• interfere with photosynthesis

30 Grape production

• interfere with nitrogen fixation

• slows down the uptake of nutrients.

What are the implications? Allelopathic plants can cause problems in many agricultural enterprises. For example, as weeds in crops and pastures, as stubble mulch for the next crop, in crop rotations, when orchards are replanted and when forests are regenerated.

Research into allelopathic plants may result in isolating chemicals that can be used in weed control.

Complete Exercise 3.4: Interference.

Summary • Weeds compete for resources, reducing plant productivity.

• Weeds can be managed in a variety of ways. They can be:

– slashed by machinery

– grazed by sheep

– sprayed with herbicides

– attacked by biological control agents

– covered with mulch or compost

– smothered by a cover crop.

• A combination of non chemical strategies is recommended to reduce the build up of herbicide resistant plants.

• Some plants have an allelopathic affect on another.

Methods used to control weeds, pests and diseases of grapevines are changing. In fact, many things are different. In the next part you will be finding out what’s new in viticulture.


Additional resources Additional resources

Interview with Jennifer Whitney Jennifer Whitney at Yanco Agricultural Institute has researched the biological control of grapevine mites for seven years and shares her experience with us in the following interview.

Mite research

How did you gain knowledge of the balance that exists between organisms in vineyards? ‘To obtain this knowledge, we have to understand the population dynamics of pest and predatory mites in each vineyard. Population dynamics display regional differences, although regional ‘trends’ are usually obvious. Within regions, the population dynamics can vary considerably from vineyard to vineyard depending on management practices used,, for example, use or non use of chemicals. We studied the population dynamics of individual sites the following ways.

• Sites were selected in viticultural regions across Australia. Most sites selected were ‘low input’ (minimal chemical usage) sites to give a more accurate reflection of the natural grapevine fauna. Some sites that received conventional spray programs were also used as a comparison.

• Grapevine material (leaf, shoot, cane) was sampled from each site throughout the season (August to May). Material was returned to the laboratory and examined using a stereomicroscope.

• Pest and predatory mite numbers were recorded and the occurrence of other fauna was noted. Predatory mites were collected and retained in alcohol for later species identification.

• Pest and predatory mites numbers were collated and graphed at the end of each season. Comparison of these data over several seasons gave us a detailed picture of the population dynamics of these mites.

• Predator species identifications were done. This provided a species profile for each site and region and gave us an indication of how effective they were as pest control agents.

Studying mite numbers for extended periods therefore provides information on pest and predator populations and their affect on each other.’

32 Grape production

Chemical control of mites

What are the effects of chemical sprays on mite populations? ‘In most vineyards, chemicals are applied mainly for disease control, although some miticides and insecticides are still used. Although these products are aimed at diseases, they can still have a detrimental effect on the natural grapevine fauna. We therefore need to understand their effects on predators.

We determined the effects of chemical sprays on mites in two ways.

• At the end of each season, we obtained seasonal spray information from each grower or vineyard manager. This information contained product details, rate of application and date of application. This information was incorporated with details of pest and predatory mite populations for the same site.

Using a graphical representation of the mite fauna in each vineyard, we were able to see the effects of chemicals on mite populations throughout the season, by determining the chemical application date from the graph. Any effect on mites can be easily seen.

In some cases where chemicals were applied for pest mite control, an initial decline in numbers was apparent as well as a drop in predators. This was usually preceded by a pest mite outbreak! Clearly, when predators are reduced, pests are not controlled.

• Another method of determining the effects of chemicals on predatory mites is by laboratory bioassay technique. That is, exposing predators to selected volumes of chemicals and monitoring the survival rate.’


How do different environmental factors affect mite populations? ‘Environmental factors affect pest and predatory mite populations seasonally and geographically.

Our studies show that pest mite outbreaks are usually reflective of each season’s climatic characteristics. That is, bunch mite being more prevalent in the warmer grape growing regions and rust mite usually prevalent in the cooler grape growing regions.

The study of population dynamics, as detailed above, has enabled us to observe these ‘trends’ in pest mite outbreaks, but in most seasons, we still see varying combinations of the three main grapevine mite pests – bunch mite, rust mite and blister mite.

The occurrence of predatory mites is more of a geographical/ environmental factor. Some species of predators prefer the warmer inland regions of Australia, while others occur in the cooler, more southerly climes. We are also aware of several species of predator that are only found in coastal regions and likewise others, that prefer inland habitats.

Continued monitoring of regular sites over many seasons has allowed us to gain comprehensive knowledge of the predatory fauna on Australian grapevines. This understanding allows us to recommend regional strategies for biological mite management.’



How can integrated pest management (IPM) in vineyards be achieved?

‘Our knowledge of IPM in vineyards is derived from the above information. Understanding population dynamics at a regional level, enables the appropriate regional recommendations to be made, for example, suitable spray programs, techniques for enhancing the natural vineyard fauna via cultural and management practices etc. Therefore, IPM is a responsible approach to pest management, combining the maximum use of natural management practices, with chemical control measures only when required.’

Predators control mites in vineyards By David James and Jennifer Whitney

‘A revolution is about to occur in vineyard mite control. Miticides will soon be replaced by two attractive predatory ladies with enormous appetites for the mite pests of grapevine bunch mite, blister mite and rust mite. Doreen (Typhlodromus doreenae) and Victoria (Amblyseius victoriensis) are predatory mites of the Phytoseiidae family and they spearhead the push toward reduced chemical usage in grapevines. Doreen and Victoria are Australian through and through and have been trying to invade inland vineyards to feed on pest mites ever since viticulture began in these areas. However, until now their efforts have been thwarted by a barrage of chemical sprays aimed at vine diseases, insect pests and mites.

Vignerons have done an excellent job in keeping Doreen and Victoria (and no doubt many other useful organisms) out of their vineyards. Everywhere, that is, except the Riverlands in South Australia. Here, viticulturists have opted for the use of inorganic compounds such as sulphur and copper to control diseases such as powdery and downy mildew. They rarely use the newer systemic fungicides which can really spoil a predatory mite’s day. Consequently, Doreen is a full time inhabitant of Riverlands vineyards.

She is able to put up with the regular applications of sulphur and copper and produces populations which can occupy 90% of the leaves in a vineyard. Doreen is fond of feeding on bunch mites and normally if Doreen is present then the bunch mites are scarce or absent. A big attribute of Doreen is that she does not disappear when she eliminates her favourite food.

Unlike a number of other predatory mites used in horticultural crops, Doreen is not dependent on a single food resource for survival. She will also feed on rust and blister mites and when times get really tough will eat pollen, insect eggs and honeydew. Consequently, it is common to find large Doreen populations, but no mite pests on Riverlands grapevines.

Victoria is also a general feeder, but tends to prefer rust and blister mites and therefore complements the bunch mite preference of Doreen. Unlike Doreen, which remains on grapevines throughout the year, Victoria departs with the leaves in autumn and returns early-mid summer. Her return is largely influenced by sprays used. Unlike Doreen, Victoria is susceptible to sulphur.

34 Grape production

The Doreen and Victoria combination generally hits its stride in January and thereafter bunch, blister and rust mites are a rarity in Riverland vineyards. Of course, no one knew Doreen and Victoria were performing such an excellent service until vineyard mite fauna was examined in 1989/90.

Riverlands growers had been applying two to four sulphur sprays a season to control mites, a production cost which was totally unnecessary. Viticulture in the Murrumbidgee Irrigation Area and Sunraysia is characterised by greater inputs of synthetic fungicides which are generally more detrimental to predatory mites than sulphur and copper. Victoria is common in both regions, but does not appear on grapevines until sprays cease.

Doreen has only been recorded once on MIA grapevines. It is likely that Doreen and Victoria could establish that same winning partnership in Sunraysia and the MIA if predator-friendly chemicals were used. Recent studies in Canberra vineyards have shown Doreen is alive and well in this region and clearly must have the ability to survive cold and hot conditions!

Chemical mite control costs the Australian grape industry an estimated $2.8 million per annum. Doreen and Victoria have the potential to remove most of this cost from grape production.

Research is now being directed toward developing and implementing biological control strategies for grapevine mites in all leading viticultural regions of south-eastern Australia. Strategies will be based on the successful Riverlands model either using Doreen and Victoria or other predatory mites already present in the regions.

An important research area is development of a mass rearing technique for Doreen and Victoria. If commercially available, these predators will be rapidly introduced to vineyards without them.

The Doreen and Victoria story is an excellent example of the substantial benefits from basic biological research into previously unstudied systems. Doreen and Victoria and their ilk have the potential to save the viticultural industry millions of dollars in production costs. They will also ensure a less contaminated product and help to clean up the environment.’

Good Fruit and Vegetables. Rural Press. Issue No. 2. (1992).


Botrytis Botrytis is fungal disease that affects many of Australia’s vineyards. Varieties that are prone to botrytis (also known as grey rot) include Semillon, Chardonnay, and Sauvignon blanc.

watery spots

skin splits

dead tissue

soft rot

Grapevine shoots, leaves, flowers and berries can be infected by botrytis.

Steve Warne is a winemaker for De Bortoli Wines in Griffith in the MIA. The De Bortoli family company produces a large range of wines which includes Noble one, a botrytised dessert wine of exceptional quality. Steven was asked about the effect botrytis has on grape production. Following is his comment.

‘Botrytis can have a positive or negative effect on grape production. One of the negative effects is that it reduces grape quality. There are problems in processing with juice stability etc. These can be overcome, but at a cost. On the positive side, an exceptional dessert wine can be produced under the right conditions. The initial infection is produced under conditions of high humidity. If grapes are allowed to dehydrate so that the sugar content increases then noble rot develops. In this area, cloudy foggy mornings followed with clear days produces the right conditions. This varies from area to area with some areas better than others. This may be due to differences in air drainage. Canopy training and other management practices also affect botrytis infections.

There are a number of fungicides that can be used to control botrytis. The main site of infection is the flower. This fungus overwinters in the old dried berries and other vine material. Timing is critical in fungus control. It must be knocked out before flowering.’

36 Grape production

De Bortoli Wines started producing botrytised dessert wines in 1982. It was seen as a marketing opportunity, an industry trailblazer.

The symptoms of infection are easy to see. In the advanced stages a hairy sort of mound covers the fruit. Earlier, grapes are papery, pinkish and easy to break. The fruit used to produce Noble one looks pretty disgusting with mould all over the fruit.’

dried out grapes

dormant fungus (winter)wind

spores (spring)

infection

new shoot

flowerflower

wind

overwintering

dormant fungus (winter)

Life cycle of Botrytis cinerea (bunch rot).


Herbicide resistance management program - It’s your move ‘Herbicide resistance is a major threat facing Australian grain growers. Pressure on growers to rely more heavily on Group A and Group B products will result in increasing discoveries of resistant populations of annual ryegrass, wild oats and broadleaf weeds. However, resistance can be managed and a Grains Research Development Corporation National Extension Program has helped raise national awareness of this problem.

In 1992 State agricultural agencies, Avcare, weed researchers and GRDC put in place a program to address herbicide resistance, a major threat facing Australian grain growers. Projects were funded in Southern Queensland, Northern and Southern NSW, Victoria, Tasmania, South Australia and Western Australia. These projects had the common aim of raising awareness of herbicide resistance and to extend information on how to avoid and manage this problem.

A major feature of the program has been the cooperation and interaction between the coordinators; researchers; advisers from government, private and corporate sectors; the Herbicide Resistance subcommittee of Avcare; key farmers and farmer groups. This cooperation has lead to a greatly improved understanding with both the avoidance and management of herbicide resistance.

A key achievement of the program has been the agreement to make it mandatory for all herbicide labels to include the “mode of action” group for each chemical.

Outputs and activities of the projects include the following:

• WA Herbicide Resistance Reference Manual

• Weed Smart booklet - used in 1993 and 1994

• Tasmanian Herbicide Resistance awareness and management package

• the 1994/95 and 1996 awareness brochures

• articles on resistance in a wide range of weed control charts, books, magazines, etc

• posters

• workshops, seminars, conferences and training programs for farmers and advisers

• packages for advisers and “Farmcare” training providers, , for example, overhead and slide transparencies

• procedure for a field test for resistance

• displays and presentations at major field days, conferences and local programs

• audio-visual using slides for use at major field days and conferences, which has been put onto video for use with smaller groups.

38 Grape production

Has the program made any difference?

The coordinators are confidant that the answer is “yes”. Most grain growers are now aware of herbicide resistance as a potential problem on their farms.

Good understanding however, about how to avoid, delay or manage resistance is mostly confines to those farmers who have recognised the problem on their own farm or nearby. Such farmers are proving that resistant weed populations can be managed in a manner that improves the prospects of profitable production. This is only being achieved where farmers are prepared to reduce reliance on the highly effective Group A and B products to use a wide range of methods to control crop weeds such as annual ryegrass, wild oats and Indian Hedge mustard. The awareness and understanding of those advising farmers has improved significantly over the three years of the program (1993–1996).

With increasing economic burdens and in some cases falling herbicide prices growers are going to be under more and more pressure to rely heavily on Group A and Group B products for weed control in intensive grain growing areas. The potential for resistance in broadleaf weeds to Group B products is of major concern to the coordinators and resistance researchers and highlights the need for continued research and extension effort on the prevention and management of resistance weeds.’

Cooperative Research Centre for Weed Management Systems. Research highlights. Weed Watch. Issue number 3. March – June 1996. Cooperative Research Centres Program. Australia.

Weevil causes destruction on Paterson’s curse ‘The last issue of Weed Watch reported that Paterson’s curse root-crown weevil Mogulones larvatus, first released by CSIRO Entomology researchers, were developing in large numbers at a release site near Yanco. Since that time the weevils have undergone a further generation with devastating results. On an organic farm the weevils have killed all plants within a 200 m radius of the release point (an estimated 150 000 plants). This has occurred in the absence of plant competition and isolated pockets of healthy plants that have not been so heavily hit prove the damage can be attributed to the weevil.

Such damage levels are much higher than those ever recorded in the native range and beyond the expectations for the project personnel. This holds well for the next biological agent redistribution workshop due to be held at Yanco next autumn. If such attack levels continue to spread and start to appear elsewhere at other younger release sites we may be seeing the start of something big! An interesting observation is that the biggest plants died first. This site will be closely monitored in future seasons and will be used as the main harvesting site for further distributions throughout NSW.’

Cooperative Research Centre for Weed Management Systems. Research highlights. Weed Watch. Issue number 3. March – June 1996. Cooperative Research Centres Program. Australia.


Suggested answers Suggested answers The life and times of phylloxera 1 Vineyards that are most at risk: have young vines; are located in an

area where phylloxera has been a pest in the past, for example Rutherglen and Geelong; grows European vines (Vitus vinifera) on their own roots; has unrestricted access by machinery, equipment and vine material.

2 Vineyards at least risk: are located in an area free of the pest (SA and WA); have vines grown in sandy soils; are well established; and have vines grafted onto a phylloxera resistant rootstock.

Control of phylloxera 1 a) This is a quarantine area. No cuttings, no grapes, no vine

material of any sort may be taken into the Hunter without written permission by NSW Agriculture.

b) This is a declared phylloxera area. No vine material may be taken out of the area.

2 Movement of material out of infected areas and into phylloxera free regions is restricted preventing the spread of phylloxera.

Black spot

The grapevine looks as if it might be infected by black spot. There are black spots on the grapes. At this stage there are no black spots on the leaves, these may develop later.

Downy mildew 1 In winter, downy mildew lies dormant as spores in the soil and on

dead leaves. Rain and temperatures of at least 10°C produce spores underneath the grape leaves. Warm and wet conditions with high humidity spreads disease to leaves in the canopy. Leaves, with spores, fall to the ground in late autumn and winter and the cycle begins again.

2 Good canopy management would improve air circulation and therefore dry out the leaves and reduce humidity. Some vineyards use fungicides to prevent disease. Using overhead sprinklers should be avoided when infection is likely.

40 Grape production

Powdery mildew 1 Infected grapevines would yield much less since there is poor berry

set. Table grape production would suffer because damaged berries are poor quality.

2 Susceptible vines can be sprayed with sulfur or other chemicals to prevent powdery mildew. Powdery mildew prefers low light conditions so an open canopy is part of a prevention plan.

3 A spraying program would begin just before budburst and continue until berry set. This is when the environmental conditions are most likely to be ideal.

Agricultural activities 1 There are many affects that farming can have on the environment.

• Harvesting and haymaking reduce the nutrient levels in the soil if crops aren’t fertilised. Soil pH may be reduced also making the soil more acid.

• Cultivating paddocks may lead to a decline in soil structure. Soil organism activity may decrease, especially if soil conditions change greatly, for example pH.

• Land has been cleared for cropping and grazing. This reduces the variety of living things that live there (loss of biodiversity). A reduction in trees greatly increases the risk of the watertable rising, producing saline conditions.

2 Some chemicals may: accumulate in soil and water; adversely affect birds, fish and bees.

Mite research 1 Population dynamics refers to the way mite numbers alter over time

due to a number of influences, for example climate, season, other organisms, food availability.

2 Encouraging predator mites to naturally control the pest mite population would be a form of biological control. Predator mites could be bred in the laboratory and introduced into vineyards.

3 Research at different vineyards over many years gives us more accurate and representative data. A comparison of pest and predator mite populations over time can lead to valid conclusions about how the populations of each mite affect each other.

Chemical control of mites 1 They matched the timing of spraying with population changes.

Information about spraying programs tells the researchers what chemical affects which mite.


2 The bioassay technique tells researchers how much of a particular chemical kills how many mites.

3 Information from the field gives researchers an idea of how things are working in the field. Bioassay is an accurate measure done under laboratory conditions.

4 Seasonal conditions, climate, stage of the vines, presence of other food sources, presence of predators are some of the things that may affect mite populations.


The research was carried out over many growing seasons in different areas. Aspects of climate, for example, rainfall and temperature and the presence (or absence) of mite species would have been taken into consideration.


Integrated pest management means that a range of pest control strategies should be used. For example; planting a range of crops, allowing poultry to forage and sheep to graze, encouraging predators and rotating chemicals.

Insect pests

Control method Example

Cultural control remove weeds, canopy management

Natural control predators (spiders, lady bird, shield bug) and parasites (Trichogramma, parasitic wasp)

Chemical control chlorpryifos, carbaryl, methidathion, winter oil, maldison

Biological control Bacillus thuringiensis

42 Grape production

Chemical control – herbicides • Some chemicals are toxic to humans and other animals.

• Some chemicals may kill crop and pasture plants as well.

• Not using enough may mean that many weeds survive and farmers may need to respray.

• Chemicals may leave residues or run off into water courses.

• Weeds may more easily become resistant to chemicals.

• Wildlife and livestock may be affected.

Herbicides in the vineyard

(dead) (dead) (dead)(healthy) (healthy)

weed seeds

Mechanical/cultural control Advantages Disadvantages

• non toxic • soil structure declines

• leaves no residues • plough pans may form

• existing machinery can be used • high labour input

• digs up all weeds • cultivating crop plants must be avoided

• don’t need spraying equipment • weeds with deep taproots are hard to kill in this way

• don’t need chemical safety gear • high fuel costs


Cover crops 1 • Cover crops can improve soil structure especially if they are

deep rooting perennials, for example lucerne.

• Legumes may provide additional nutrients to the soil.

• Produce additional to grapes can be sold or used from the vineyard if, for example, the cover crop is baled for hay.

• Weed populations can be managed.

• Cover crops reduce the risk of erosion.

• Vigorously growing vines need nutrients which they have to compete for with surrounding plants, for example cover crops.

• Cover crops may compete more successfully for water than newly established vines especially in a dry season.

• Pests such as Rutherglen bug breed in cover crops and weeds to then infect grapevines.

2 In most areas, the advantages outweigh the disadvantages for growing a cover crop between the rows of grapevines. The improved soil fertility (nutrients and structure) in addition to reduced soil erosion make cover crops an attractive soil management strategy.

Biological control 1 Advantages of biological control agents:

do not leave residues in soil, water and produce

are not toxic

do not need to be continually applied

do not require spraying equipment

do not require safety gear

can be used to grow organic produce.

2 Disadvantages of biological control agents:

may not be native to Australia, and therefore may interfere with the natural balance

may not survive conditions in the field

may be costly to introduce into the area.

3 Biological control agents are chosen carefully and trialled in quarantine facilities over many years before they can be released. Non-chemical control must be an advantage in environmental and economical terms.

44 Grape production

Exercises – Part 3 Exercises – Part3 Exercises 3.1 to 3.4 Name: _________________________________

Exercise 3.1: Bunch rot

Read the information about Botrytis in the Additional resources section and use this to help you answer the following questions.

1 Describe how botrytis infections affect grape production.

_____________________________________________________

_____________________________________________________

_____________________________________________________

2 Outline the life cycle of botrytis.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

3 Explain how environmental conditions affect botrytis infections.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

4 Outline management strategies you would recommend for the control of botrytis. Is timing important? Why? Why not?

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________


Exercise 3.2: Mites

The research carried out at Yanco Agricultural Institute by Dr David James and Jennifer Whitney is just one of many projects designed to improve agricultural productivity in Australia.

Refer to the interview transcript and the newspaper article in the Additional resources section for background information to answer the questions that follow.

1 The damage caused by mites in vineyards varies depending on the species of mite and the grapevine variety. Buds can be killed, the growth of new shoots can be greatly affected, leaves can fall prematurely and bunches of grapes can be scarred.

Explain how integrated pest management can be used in vineyards in Australia.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

2 Evaluate integrated pest management as a strategy in Australian vineyards.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

46 Grape production

Exercise 3.3: Resistance

You will have read about the problems of resistance to chemicals by both pests and weeds. It is a major concern not only in Australia, but overseas as well.

The Herbicide Resistance Management Program is described in an article in the Additional resources section. Educational materials have been produced for farmers as part of the program. These are in the form of brochures, information sheets, booklets and leaflets. During your course you have collected many of these from various sources such as NSW Agriculture, your local stock and station agent, field day displays, etc.

In this exercise you will be designing educational materials in a format similar to these. Features you may consider including are: large bold headings, eyecatching layout, use of colour, diagrams, photographs, small amounts of concise information.

• Use information from your lesson notes and other sources to produce a handout on chemical resistance that is suitable for farmers in your area.

• Choose a format that you like such as a poster or pamphlet.

• You must use your own paper or cardboard.

• Include information that will answer the questions that farmers ask about resistance to chemicals:

– What is resistance?

– How can I identify resistant populations?

– Why is resistance to chemicals a problem?

– How can resistance to chemicals be prevented?


Exercise 3.4: Interference

The growth and development of crops and pastures may be interfered with in various ways such as competition, allelopathy, changes to the environment, and plants as hosts.

1 Briefly describe how competition affects plant production.

______________________________________________________

______________________________________________________

______________________________________________________

2 Outline what is meant by the term allelopathy and describe how it interferes with plant growth and development.

______________________________________________________

______________________________________________________

3 Growing agricultural plants can modify the environment. Describe another way that farming practices interfere with plant productivity.

______________________________________________________

______________________________________________________

4 Rutherglen bugs live and breed in plants such as capeweed. These bugs are pests of grapevines. Explain how these plant hosts interfere with plant production.

______________________________________________________

______________________________________________________

5 Outline a weed management plan that you think would contribute to sustainable long term productivity.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

48 Grape production

Documents

Grape production - lrrpublic.cli.det.nsw.edu.aulrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/hsc_agriculture/... · Part 3: Pests and diseases of grapes ... that interfere with