Organic Pest Management Overview

Hort 390

Fall 2006

Pest Control – As Integrated Systems

• Plan ahead, anticipate, take a design approach to your garden.

• Prevent as many problems as possible, build resilience into the system.

• Monitor plants and pests on a regular basis. Problems that are identified early are easier to solve.

• Use least toxic methods first, to preserve the beneficial insects and microbes as much as possible, and maintain system integrity.

Pest Control Possibilities:

• Systems Approach – prevention/passive

• Systems Approach – moderate

• Systems Approach – active

Note: none of these is a “business as usual but do nothing” approach. Also, they all incorporate aspects of Integrated Pest Management – IPM.

Integrating practices

• Biological Control

• Cultural Control

• Mechanical and Physical Control

• Habitat manipulation

• Use of resistant varieties

• Chemical Control

Derived from Kaolin clay, a natural mineral, forms a barrier film that acts as a broad spectrum crop protectant. It works to control insect pests and disease, protect against sunburn and heat stress. Applied as a water-based slurry before pests arrive.

D.E. is the fossilized shells of tiny water-dwelling organisms called diatoms, with microscopically fine, sharp edges which break the outer protective layer of the insect and desiccate them. Applied as a dust or mixed into a slurry for foliar spraying. Barrier to crawling pests and soft bodied insects, used in the garden and as a stored grain additive. Can be used as a dust on manure for fly control and for intestinal parasite control.

Examples of physical pesticides.

Other barrier methods can protect crops from insects, and provide early season growth enhancement, and some frost protection.

Organic Cropping System in a high tunnel

This is NOT a systems approach

- lacks bio-diversity

- no soil improvement plan

- etc….

Organic vs. conventional fruit production in Italy

Ichneumon wasp

Friends

Two-spotted lady beetle

Syrphid Flies

Green lacewing

Insects in Kansas• The number of species that are “harmful to

our interests” is relatively small.• Many are beneficial.• Most are neutral in their effect on our

welfare.• It is estimated that there are between

15,000 and 20,000 species within Kansas, some of which have never been identified.

• Field guide (“Insects in Kansas”) includes photographs of about 850 species.

Economic loss from pest insects is due to:

• Reduced yields

• Lowered quality of produce

• Increased costs of production and harvesting

• Expenditures for control

Approaches to insect management:

• Be prepared by knowing which insects are likely to show up in each crop.

• Know something about each pest’s life-cycle, when it shows up, where it comes from etc…

• Scout regularly. Every 2 to 3 days is recommended during critical periods. Have a scouting plan (see details later)

Old saying: “The best fertilizer is the footsteps of the farmer.”

Approaches continued:

• Know the critical thresholds for insects that you might find, and how the thresholds might change over time (more critical at different life-cycle stages)

• Use any and all preventative measures that are available and practical. [see later slides]

• When/if using pesticides, use the ones that will have the least impact on you, non-target organisms (honey bees, beneficial insects, neighbors, etc…)

What’s tolerable?

Control applied

Number or damage

level

Threshold

Time

Note: threshold will depend on stage of crop, weather, and has been determined through empirical research and/or modeling.

Injury and treatment thresholds

Injury level• Depends on how much

damage the users will tolerate.

• Economics– How much will it cost to

treat?– Would the losses be

greater than the cost of treating?

Treatment threshold• Control action is taken if

a pest problem is expected to occur, to prevent crop loss or damage. – e.g. weather conditions

indicate a disease outbreak if no action is taken

Preventing pest problems

• Plant selection:– Select variety or crop for location – Chose resistant varieties

• Prepare the site correctly

Cultural control

SanitationDestruction of alternate

hostsHabitat modificationSmother & cover cropsHost resistanceCrop rotation IntercroppingPlanting & harvest datesFlooding

Irrigation and water management

Fertilizers & soil amendments

Mechanical & physical controlSoil tillageMowingMulches, barriersTemperature manipulation,

solarization

Avoidance

Pest populations exist but the impact is avoided through cultural practice

• Fertilization program to promote rapid plant development.

• Not planting in certain areas where pest populations are likely to cause problems.

• Host-free periods.– Crop rotation (e.g. rotate sugarbeets on a 3 to 10 year cycle to

reduce sugarbeet cyst nematode).

– Planting or harvesting date modification (e.g. pink bollworm management).

Tactics for prevention and avoidance strategies may overlap

Two Types of Plant Disease

Abiotic diseases/disorders are caused by noninfectious agents such as weather stress, nutrient deficiency, chemical injury, soil factors…

Biotic diseases/disorders are caused by infectious agents such as fungi, bacteria, viruses, nematodes

Biotic/infectious diseases: Disease triangle

HostSpecies Cultivar Age

Pathogen

fungi bacteria nematodes viruses

EnvironmentTemp, RH, wetness

Infectious agents: pathogens

Viruses

Bacteria

Fungi

Nematodes

most microbes are not pathogens

Alternatives/organic

Biological controlsantagonistic fungi, bacteria

Green manures

Plant growth promoters

Compost teas

Copper, sulfur, potassium bicarbonate http://grant-adams.wsu.edu

Nysaes.cornell.edu

Boost crop vigorIncreased crop vigor will reduce the impact of competition by weeds on yields.

Crop vigor can be enhanced through variety selection and management practices that favor the crop over the weeds.

Favorable variety and hybrid traits to look for include:

Rapid emergence – Planting hybrids/varieties that emerge quickly will give the crop a head start over emerging weeds, helping them to establish and better compete. Quick canopy closure – Once the canopy closes it reduces the amount of light that reaches the soil surface which some small seeded weed seeds need to initiate germination. The faster the canopy closes the more weeds it shuts out. Efficient nutrient scavenging – Logically, crop varieties that are efficient in utilizing nutrients will perform better and they may help prevent weeds from taking up nutrients. Indeterminate growth habit – Because indeterminate crops continue to grow throughout the season, they are less likely to be shaded out by weeds. Drought tolerance – Drought tolerant plants that are better water scavengers will be better equipped to compete with weeds.

Management practices that favor crop vigor over weed vigor:

Appropriate placement and timing of fertilizers for the crop – Banded fertilizer applications applied at times when the crop demands it most will favor the nutrients reaching the target crop instead of feeding the weeds.

Increase plant density or populations – Increasing your planting density will provide quicker canopy closure and deprive weed seeds and seedlings of light.

Early-season weed control – Getting a jump on weed control when the crop is most vulnerable will increase plant health and help the crop compete against future weeds.

Adjust planting dates – By delaying planting until after the first flush of weeds, new weed seedlings can be killed with a light cultivation or flaming. This practice can help deplete the seed bank in the top layer of soil, resulting in reduced competition later in the growing season. This technique is referred to as a false seedbed approach.

Avoid additions to the seedbank; do not let weeds go to seed

Weeds can disperse several hundred to several hundred thousand seeds each year by way of wind, water, animals and humans. The number of seeds produced depends on the weed species and its environment. As you can imagine, if left uncontrolled, weed seed production and subsequent weed infestations could increase exponentially for the years to come.

More information on weed seedbank management can be found in “Managing weed seed banks throughout the growing season” by Adam Davis, in the April 29, 2004 issue of the New Ag Network (http://www.new-ag.msu.edu/issues04/04-29.htm#3).

Increase favorable habitats for weed seed predators

Though we mainly view weeds as a nuisance, there are several animals that use weed seeds as a food source. Mice, insects, worms and birds that are already in your fields are all example of weed seed feeders or “predators.” The exploitation of predator feeding can help reduce the weed seedbank; a tactic that is referred to as conservation biological control. Certain crop management strategies, such as tillage and the use of pesticides, can disrupt the habitat and lifecycles of these creatures, ultimately reducing the weed management benefits realized from predator feeding. To aid in increasing weed seed predator populations consider the following:

Plant cover crops – In addition to suppressing off-season weeds, cover crops can provide weed seed feeders with protection from predators.

Leave border strips around fields – Border strips can serve as overwintering sites and refuges for weed seed predators.

Reduce fall tillage – Reducing fall tillage leaves more weed seeds on the soil surface, where most seed predation occurs. It also increases the persistence of crop residues which provides shelter and refuge to weed seed predators similar to a cover crop.  

General Strategies: Ways to diversify production:

Crop rotation – Certain weeds are often affiliated with certain crops based on their growth habit and management. For example, there is more likely to be a problem controlling weedy grass species in corn than in soybeans. A diverse crop rotation with several different growth habits does not favor the buildup of any one particular weed. Incorporating fall and/or spring seeded cover crops into your rotation can help add diversity.

Variations in postemergence control – Increasing the variety of postemergence control practices used will help suppress a larger spectrum of weeds than relying on one tactic.

Herbicide (organic or non-organic) mode of action rotation – Consistently relying on the same herbicides or organically acceptable compounds for weed control promotes resistance. If even one weed is naturally resistant, the over reliance of that strategy increases the selection pressure on that weed population and can go on to build an entire population of resistant weeds. One way to avoid this pressure is by alternating herbicide modes of action and practices. It is less likely that a weed will be resistant to multiple modes of action.

Tillage and weed control

Pre-plant• Primary tillage

(destroy last year’s weeds)

• Secondary tillage – one or more times (prepare seed bed)

• PLANT

Post-plant• Pre-emergence

culTIvation• Post-emergence shallow

cultivation – usually 1 to 3 times (rotary hoeing, etc)

• Post-emergence cultivation between rows, between plants, etc…(see novel examples in video)

Non-tillage weed control

• Crop rotation – will rotate weeds too• Allelopathic cover crops – rye, oats,

crimson clover, etc….will suppress weed seed germination, establishment

• Mulches – grow in place, or apply later. Depth and timing matter.

• Flame weeding – but not in a high-mulch environment.

• Mow weeds, graze, etc…..

Chemical Weed Control

Pre-plant options

• Check publications to see what is allowed for vegetable crop of interest. Must be listed on the label to be legal.

• Organic options include corn gluten, but must be from non-GMO corn.

Post-plant options• Again, check publications

to see what is registered for each crop.

Post Emergence options• Herbicides may affect

some species and not others, or be general (like glyphosate)

• Organic non-specific herbicide is vinegar.

Biological Weed Control

• Principle is that an insect or disease selectively targets a “weed” without endangering non-target plants.

• Insects released to control weeds include natural enemies of musk thistle and St. Johnswort. Have kept these weeds at reduced levels, but has not resulted in elimination.

• Under development (mycoherbicides)

Timing as a form of weed control

• Tillage, then repeat at critical intervals• Tillage, then kill subsequent weeds without

tillage (flame or herbicide) to create a “stale seed-bed.”

• Cultivate at night? No light to stimulate germination of new seeds (but no sunlight to kill cultivated weeds either).

• Plant later than your neighbors…soil is warmer, crop comes up quicker than the weeds, easier to control the weeds.

Weed-free threshold concept

• Control early weeds

• Usually if the weeds are controlled for the first 6 to 8 weeks; the later weeds don’t matter (except if there is a crop quality problem, harvesting problem, or aesthetic issue).

Strategy vs. Tactic

• from the Dictionary of Sustainable Management• http://www.sustainabilitydictionary.com/s/strategic_plan.php

• STRATEGIC PLAN• A complex and ongoing process of organizational

change which establishes a context for accomplishing goals, and provides a framework and direction to achieve an organization's desired future. A strategic plan differs from a business plan in that it focuses more on the overall organizational development and not, specifically, on financial models, investment, and budgets.

strategic

Programs, goals, and projects of great importance

tactical

The lowest level of military operations, the view from the trenches and the foxholes. Tactical decisions are those made by the commanders on the spot, on the front lines. Most miniature games are tactical or grand-tactical in nature. The opposite of tactical is strategic.

.

http://vvvvvv.od.ua/term/term/tactical/page/0/

Pest Control Possibilities:

• Systems Approach – prevention/passive

• Systems Approach – moderate

• Systems Approach – active

Planning ahead is strategic.

The practices you choose are your tactics.

Pest Control Possibilities: Insects

• Systems Approach – prevention/passive

- resistant/tolerant crops, attract beneficial insects to area

• Systems Approach – moderate

- row cover/barrier, clay film barrier, diatomaceous earth, vacuum or hand pick, sticky traps, pheremones (distruptants and traps).

• Systems Approach – active

- botanical pesticides (pyrethrum, sabadilla, neem, rotenone), microbial pesticides (Nolo bait for grasshoppers, Bt for various larvae.

Pest Control Possibilities: Diseases

• Systems Approach – prevention/passive- grow species that aren’t affected in our

climate, live with it, rotation, compost and soil improvement for root diseases.

• Systems Approach – moderate- sanitation (residue management,

pruning), choose specific varieties for disease resistance, disease free seeds and plants.

• Systems Approach – active- sulfur, horticultural oils, baking soda

(sodium bicarbonate), potassium bicarbonate, compost tea foliar spray (still experimental, E. coli concerns?).

Pest Control Possibilities- Weeds:

• Systems Approach – prevention/passive- high planting density, leafy crops to

shade weeds, targeted irrigation, rotation• Systems Approach – moderate

-pre-plant tillage, lots of mulch, landscape fabric, hand weeding

• Systems Approach – active- corn gluten pre-emergence, flame

weeding, between row cultivation, soaps as post-emergence, livestock grazing

Diagnosing the problem

• Caused by a pest

• Caused by weather

(frost, hail, wind)

• Caused by nutrition deficiency

• Caused by machinery, inadequate irrigation

Seedling wilting from fungi, primarily weather-related

Mower damage

Importance of identification

• Many symptoms look similar.• Presence of a pest doesn’t

mean it caused the damage.• Not all damage needs to be

treated (thresholds). • Pests may no longer be

present.• Pest may be difficult to find

(especially soil-borne pathogens/ nematodes).

• Symptoms may be caused by improper cultural practices.

Stink bug damage

Below-ground damage

from root-knot nematode

Katydid damage

Importance of pest identification

• Proper identification is essential for choosing the right control actions.

• Requires identifying:– Pest organisms– Beneficial organisms– Population levels

• Requires correlating pests to damage.

Big-eyed bug (beneficial insect)

False chinch bug (sporadic, minor pest)

Lygus bug (major pest)

Herbicide damage vs. grub damage

“Stump the Chump”

• Come to class on Thursday to play!

• Bring samples if you want.