Major Pests and their Control in South Africa: Evolving Agrichemical Practices

Tim G Grout

World Citrus Production 2014/5 x1000 tons

0 5000 10000 15000 20000 25000 30000 35000 40000

Morocco

Indonesia

Pakistan

South Africa

Iran

Italy

Turkey

Egypt

Spain

Mexico

USA

India

Brazil

China

World Citrus Exports 2014/5 (x1000 tons)

0 500 1000 1500 2000 2500 3000 3500 4000

Argentina

Greece

Morocco

Mexico

USA

China

Egypt

Turkey

South Africa

Spain

In 2016 Australia exported 220 000 tons

SA Citrus Market Distribution 2015

USA 4%

South America

UK 10% N Europe 22%

Middle East 21%

Far East 9%

Asia 11%

Australia

Russia 9%

Africa 1%

Canada 3%

Other 3%

S Europe 7%

MPUMALANGA

SWAZILAND

EASTERN CAPE

KWAZULU-NATAL FREE STATE

WESTERN CAPE ATLANTIC OCEAN

INDIAN OCEAN

MOZAMBIQUE

BOTSWANA

NAMIBIA

NORTHERN CAPE

NORTH WEST

ZIMBABWE

GAUTENG

NORTHERN PROVINCE

MPUMALANGA

EASTERN CAPE

KWAZULU-NATAL FREE STATE

LESOTHO

WESTERN CAPE

NORTHERN CAPE

NORTH WEST GAUTENG

LIMPOPO

Citrus Production Regions

Scope of the South African Citrus Industry

South African Citrus Production 2015

Exports 67%

Processed 27%

Local 6%

2013: Total SA research funding = 0.73% of GDP; Agric got 0.06%

Research Funding in South Africa

Government

Business

Foreign

Other

Who funds all research Who pays for Business research

All business research

6%

90%

Citrus Research Overview

• 1907: First official exports of citrus from South Africa to the UK

• 1956: First citrus industry researchers appointed and funded via an export levy

• 2001: Citrus Research International formed and is mostly funded from a levy of US$0.05 per 15 kg export carton collected by the CGA

• CRI’s in-house staffing policy aims to appoint one lead researcher per key research field, with technical support

• CRI forms the core of a group of institutions with a mission to maximise the long-term global competitiveness of southern African citrus growers

Citrus Growers Association Group Structure

River Bioscience Citrus Grower

Development

Company

Cultivar Co.

Citrus Academy

Citrus Growers’ Association

various functions

Citrus growers in South Africa,

(Swaziland and Zimbabwe)

Citrus Research

Trust

CRI XSIT

3

1

1

5

River Bioscience and Xsit

• River Bioscience (www.riverbioscience.co.za) was created as a spin-out company under the CGA to commercialise IP developed by researchers in CRI

• A percentage of profits goes into the Citrus Research Trust

• Most products are biorational: e.g., viruses for lepidoptera, fruit fly bait stations and male annihilation blocks for OFF (Bactrocera dorsalis)

• River Bioscience now also owns Xsit (X Sterile Insect Technique – www.xsit.co.za) another spin-out company for the control of False Codling Moth by releasing irradiated moths

CRI Operational Structure

Citrus Improvement

Scheme

Research Extension

CEO

(Tech Market Access Coord)

CRI Board

Stakeholder representation

(CGA Shareholder)

Biosecurity

Research Operational Structure

Manager: R & T

Portfolio IPM

Portfolio DM

Portfolio Horticulture

Programmes Programmes Programmes

Programmes in Horticulture

• Cultivar evaluation

• Fruit production and quality

• Rind condition

• Cold chain & packaging

Programmes in Disease Management

•Graft transmissible diseases

• Fruit and foliar diseases (with CBS)

• Soil-borne diseases and nematodes

•Postharvest pathology

Programmes in IPM

• False codling moth

• Fruit flies

•Mealybug and other phytosanitary pests

•Non-phytosanitary key pests

•Minor pests and mites

Red Scale: Past to Present

•Aonidiella aurantii

•Key production pest that can kill trees

Red Scale: Important Natural Enemies

• Aphytis africanus parasitoid indigenous, most effective, but cannot be reared

• In 1960s introductions of A. melinus, A. lingnanensis, Comperiella bifasciata, Chilocorus cacti

• Chilocorus nigritus first seen in late 1970s – very effective for high populations

• Insectary production of Aphytis abandoned in 2013 Chilocorus nigritus

Red Scale: Organophosphate Era

• Biological control of red scale was possible in some regions for local market fruit but blemish-free fruit for exports required parathion for thrips and better red scale control

• A single parathion spray in spring allowed natural enemies to recover in summer – some later referred to this as IPM

• Red scale first became resistant to OPs in 1975 in the subtropical areas and horticultural mineral oils (HMOs) were introduced with experience from Israel to save the trees

• 10 years later, OP resistance appeared in the temperate Eastern Cape where oils were more phytotoxic

• Methomyl was sometimes used as a partially effective corrective but oil was mostly used preventively

Red Scale: Conservation of Natural Enemies

• With no effective option to control high scale populations on the fruit late in the season other than C. nigritus beetles, conservation of Aphytis spp. during summer was important

• This meant that chemical control options for citrus thrips needed to be as soft as possible or applied soon after petal fall

• Research on the non-target effects of thripicides on Euseius predatory mites that suppressed thrips started in the early 1990s and expanded to other natural enemies

Grout, T.G. and G.I. Richards. 1992. Experimental and Applied Acarology 15: 199-204.

Red Scale: Insect Growth Regulators

• Sanctions during the 1980s and 90s limited availability of high quality HMOs and local substitutes had an impact on crop or colour when used at high percentages

• When buprofezin plus 0.5% oil was registered for red scale it was welcomed as a means of reducing the risk from oil, but it was not very effective for high populations

• Pyriproxyfen followed as a double or triple spray with 0.3% oil for high populations and was very effective, but expensive

• Pyriproxyfen also resulted in local extinction of ladybird beetles and outbreaks of cottony cushion scale in adjacent orchards

• Inexpensive, generic pyriproxyfen has now resulted in widespread extinction of Chilocorus nigritus

Hattingh, V. and B. Tate. 1995. Bulletin of Entomological Research 85: 489-493.

Grout, T.G. and G.I. Richards. 1991. Journal of Economic Entomology 84: 1802-1805.

Red Scale: Neonicotinoids

• The first neonic to be registered was imidacloprid as a stem treatment or soil drench at 3 g a.i. per tree for control of red scale, triozids and aphids

• This dose also gave suppression of mealybug and thrips

• Fortunately no sprays were registered as these would be very detrimental to predatory beetles

• Acetamiprid stem treatments followed, giving an IPM option for mealybug, but poor spray applications were disastrous

• Clothianidin was registered as a spray and also resulted in mealybug repercussions when the tree framework was not sprayed well – chemical shield effect

Red Scale: Neonicotinoids contd.

• Thiamethoxam was not marketed by Syngenta for citrus due to other competition, but recently some generics are becoming available

• Thiacloprid was registered for citrus thrips as a spray and was not as disruptive as sprays of acetamiprid and clothianidin, but not commonly used due to cost

• Inexpensive generic imidacloprid drench treatments became an insurance policy for growers in the northern regions to prevent red scale repercussions after disruptive thripicides

• Continual use for 20 years has resulted in resistance in red scale populations in the north

Red Scale: Imidacloprid Resistance

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5

10

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40

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50

Control MD (early) MD (Late) Med oil (July) Confidor Oil+MD late

Sundays River, Eastern Cape: Red scale fruit infestation (%) January 2016

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b

c c

c

d

Red Scale: Imidacloprid Resistance

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Control MD (early) MD (Late) Med oil (July) Confidor Oil+MD late

Marble Hall, Limpopo: Red scale fruit infestation January 2016

a

b

c

d d

d

Red Scale: Latest Options

• Spirotetramat (Movento) is registered with 0.3% oil and is a good IPM option but is detrimental to predatory mites

• Sulfoxaflor was recently registered for mealybug and gives some red scale suppression

• My personal research showed that mating disruption can maintain low populations of red scale, but not high populations

Citrus Thrips: Past to Present

• Scirtothrips aurantii •Primary cosmetic pest that is key

to an IPM approach •Natural enemies include

predatory mites, predatory thrips, predatory bugs and a parasitoid •Resistance management essential

Citrus Thrips: Biology

• Will pupate under calyx or in cracks in the bark, so only approximately 50% drop to the ground – unlike Pezothrips kellyanus

• Natural enemies on the ground and fungal pathogens therefore have limited impact

• Can cause damage for 12 weeks after petal fall, although first 8 wk worst

• Closely linked with growth flush: extra autumn flush is problematic

Citrus Thrips: Control Approaches

• Historically, two different approaches • Georgala: Long-residual spray at petal fall • Bedford & Kamburov: multiple, shorter residual sprays, on

spring flush and after petal fall

• Georgala first used temephos to provide control for 8 wk but soft scale pest resurgence was extreme. Replaced with pyrethroids combined with OPs, these later gave way to fipronil and chlorfenapyr

• B&K opted for OP at petal fall followed by tartar emetic bait which sometimes also used preblossom to reduce populations

• Although red scale resistant to OPs they were still used for thrips so this maintained selection pressure for red scale resistance

Citrus Thrips: Control contd.

• Multiple sprays of tartar emetic plus sugar resulted in resistance so that now this can only be used once per season

• Pyrethroid resistance similar with cross-resistance to carbamates such as formetanate and methiocarb

• Abamectin plus oil is relied on heavily as an IPM-compatible option and has been used for 20 years

• Spinosad gave similar control to an OP, with few repercussions but Dow replaced this with spinetoram which causes mealybug if used too late after petal fall

• Still waiting for new options like cyantraniliprole (Exirel) to be registered but IPM profile looks good

Grout, T.G., P.R. Stephen and N.J.S. la Croix. 1996. African Entomology 4: 15-20.

Managing Citrus Psylla and African Huanglongbing (HLB)

• Trioza erytreae is usually found above 500 m altitude in the tropics and subtropics but can be found near the coast in cooler regions • It cannot survive low RH% and high temperatures •African HLB or greening disease also cannot

tolerate high temperatures and inoculum can be reduced by pruning • Young trees must be protected with systemic

chemicals and inoculum continually removed

Managing Citrus Psylla and African Huanglongbing (HLB) contd.

•African HLB caused citrus production to stop in certain areas before Carel Buitendag developed his technique in the 1980s for applying monocrotophos or methamidophos directly to the stem of young trees •Acetamiprid now applied in the same way to

stems and imidacloprid drench also used but we need alternatives •Residual control is often better with soil or stem-

applied systemics than spraying, e.g. spirotetramat

Fruit Fly Management

• The South African citrus industry was very progressive with the development and use of protein baits for fruit fly control from 1958 while more disruptive cover sprays were used for many years in other crops

• Ceratitis capitata and C. rosa Natal fruit fly are the primary pests and both can be monitored and controlled in the same way

• Malathion or trichlorfon were OP toxicants commonly used in baits but now spinosad in GF120 bait is being used

Fruit Fly Management contd.

• Biorational control options are also used such as bait stations with a pyrethroid toxicant (400/ha), male annihilation and SIT in regions where Medfly comprises >95% of the flies

• The arrival of Bactrocera dorsalis (OFF) in the northern parts has led to the use of MAT blocks (12/ha) impregnated with methyl eugenol and malathion, or Static spinosad being used in addition to the protein baits for females

• C. rosa was recently split into C. rosa and C. quilicii suited to hot and cooler areas

False Codling Moth: Economical Pest

• Thaumatotibia leucotreta was for many years not considered an economic pest and removal and destruction of dropped fruit once a week was adequate for control

• When introduced to the navel production area around Citrusdal in the Western Cape it started causing significant losses, perhaps because the dry summers were bad for the egg parasitoid

• Hofmeyr registered IGRs for the control of eggs on the fruit and developed a trap threshold to determine when it was economical to spray

False Codling Moth: Phytosanitary Threat

• The USA demanded a 22 d cold treatment at -0.6°C for FCM and other new markets copied their lead

• Exports of infested peppers to the EU from other African countries also increased the awareness of the pest there which recently led to them drawing up a pest risk assessment

• Our action threshold was therefore discarded and we now must have zero tolerance for FCM: this is not sustainable for biocontrol

• No single treatment gives more than 80% mortality so a sequential combination of different approaches is used where SIT is not available

False Codling Moth: Control Options

• Fortunately Moore commercialised a granulovirus for the control of FCM at about the same time we lost the MRLs for the IGRs

• Mating disruption is best used in the summer months when the pheromone is more volatile

• Egg parasitoids are commercially available for release and late in the season methoxyfenozide or chlorantraniliprole can be applied

• Weekly removal of dropped or infested fruit is still critical

• Area-wide control with SIT is now happening in two regions and is very effective

Moore, S.D., D.A. Hendry and G.I. Richards. 2011. BioControl 56: 341-352.

FCM: Commercial SIT Experience (Xsit)

0.92

0.77

0.30

0.16

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

wild 2010-11 wild 2011-12 wild 2012-13 wild 2013-14

Average wild FCM per trap per week during weeks 36 to 4

Citrus Black Spot – Phyllosticta citricarpa

• Historically it was considered a minor cosmetic pest and fruit was often exported with one or two spots

• EU requirements now force growers to have a zero tolerance and apply at least 4 sprays per season

• Government inspectors have to clear orchards for export • Unless the fruit is going to Canada, 2 sprays usually contain

mancozeb which is detrimental to predatory mites • The result has been that areas like the Eastern Cape,

where predatory mites were suppressing thrips populations soon after petal fall, have now had to resort to harsh thripicides as used in the subtropical region

• Once again, phytosanitary requirements have been detrimental to IPM

MRLs and Spray Practices

• CRI and CGA jointly publish a list of MRLs and PHIs applicable to export markets twice a year

• No attempt is made to pander to individual supermarkets: that is left to export agents and growers themselves

• In some cases old products are used when there is no fruit on the tree or where residues will be below LoD.

• Most PHIs are based on 1X or 2X concentrations

• Concentrations >2X have not been used since OP resistance in red scale due to concern for greater impact against natural enemies: breakdown curves unknown

Spray Volumes

• Most sprays of citrus in South Africa are applied as 1X and in order to control phytosanitary pests on fruit inside the canopy, high volumes are used

• To control sessile FCM eggs and CBS lesions on the back of fruit, or indigenous mealybug species on the tree trunk, penetration of the canopy must be very good

• Spray volumes may be as high as 10 000 to 15 000 L/ha

• Hand pruning of trees allows for better penetration of canopies and lower spray volumes

Future Challenges of Citrus Under Net

• Obvious reasons for net are hail and sunburn but reduction in wind damage is also a benefit

• Increasingly being installed to improve fruit set and fruit size in seedless cultivars, e.g. Midknight

• Nets are providing some surprises:

• More water use because leaves photosynthesise more hours per day

• Colour develops more slowly where nights are cold because warmer under nets

• Mealybug repercussions – predator confusion

• Chemical residues last longer – less wash off

Biosecurity

• We recently created a biosecurity position within CRI in order to increase awareness and bring threats to the attention of our DAFF

• We try to do proactive research on likely invasives before they arrive, e.g. I developed a cold treatment for OFF in Kenya and a colleague is learning to control Diaphorina citri in Mauritius

• D. citri and Asian HLB are our biggest threats: the vector is currently in Tanzania and the disease in Ethiopia

• We will be encouraging the covering of all citrus nurseries with insect-proof net

Grout, T.G. et al. 2011. Journal of Economic Entomology 104: 1180-1188.

Thank You

Any Questions?

My thanks to CAL for inviting me to give this talk and to Peter Stephen of CRI for some of the photos