An Overview of Control Strategies of Economically Important Stink bugs

(Heteroptera) and Tortricidae Moths Occurring on Litchis in South Africa

P. S. Schoeman

Introduction

• Three main pest complexes

• Stink bugs (Heteroptera) early season

• Litchi and false codling moths (Tortricidae) mid season

• Fruit flies late season

Description of the problem

• Stink bugs, tortricids and fruit flies are very polyphagous and are also major pests of macadamia, avocado, mango, guava, citrus etc.

• These pests can migrate between various hosts. Cultivating susceptible hosts in close proximity to each other invariably result in higher incidence of insect damage

• Pesticides currently registered have relatively short residual actions

• Important – pest complexes are indigenous

Philosophy regarding management of pests and related R&D

• Two clear options

– Study pest related problems on each crop individually.

– Study the problem holistically over all main subtropical crops.

Questions – where do we start ? And how do we use limited manpower optimally?

Work plan

• Optimal usage of manpower – Formed a stink bug working group that deals with

entomological issues (Subtrop, ARC, various Universities & consultants)

– Delegation of tasks

– Peer review and funding of planned projects

– Regular planning and feedback sessions (meetings are held on a rotational basis in main subtropical production areas of South Africa)

– Invitation of selected international experts

Stink bug working group

Work plan

• Research program – Study damage profiles of pests on respective crops

– Devise monitoring schemes for most important pest insects (Pheromones in collaboration with Tshwane University of Technology)

– Train growers as well as farm workers on a country wide basis in collaboration with Subtrop

– Investigate alternative management techniques focussing on the optimisation of the biological control component(s)

– Insect population modelling (forecasting) - Reduce the usage of broad spectrum insecticides

– Area wide management programs

Training

2012

Schalk Schoeman

ARC-ITSC

Macadamia scouting

Training manuals

Coconut bug on litchis

Damage (mature fruit)

Effect of stink bugs on post harvest quality and shelve life?

Relative seasonal abundance 2009

0

10

20

30

40

50

60

70

80

O O N N N D D

% F

ruit

in

fste

d w

ith

P.

wayi

Onderberg damage (area with few alternative commercial host plants)

2008 Number

of infected

fruit (%)

Number of

fruit

examined

2009

Number of

infected

fruit (%)

Number of

fruit

examined

Farm 1 10 (6.62) 151 24 (12) 200

Farm 2 7 (4.67) 150 22 (11) 200

Farm 3 0 70 15 (7.5) 200

Farm 4 12 (6) 200

Mean damage

(±SD)

3.76 ± 3.4 9.13 ± 2.84

t value 2.28

P value 0.07

Nelspruit damage (area with a number of commercial host plants)

2008 Number of

infected fruit

(%)

Number of

fruit examined

2009 Number of

infected fruit

(%)

Number of

fruit examined

Farm 1 278 (39.6) 308 230 (48.42) 475

Farm 2 7 (7) 100 128 (41.56) 308

Farm 3 71 (67.72) 105 95 (48.72) 195

Farm 4 51 (50.5) 101

Total 407 (66.29) 614 453 (46.32) 978

Effect of early (21 August) spray (Cypermetrhin 200g/L EC) on the percentage coconut bug infested prematurely aborted fruit as well as

final yield of mature litchi trees (cv. Mauritius)

Percentage prematurely

aborted fruit infested by

P. wayi ± SD

Mean final

yield/tree (kg) ±

SD

Cypermethrin

200g/L @

20ml/100L

23.43a ± 11.5

Control 54.28b ± 9.48

T value 5.823

P = 0.0043

Df 4

Effect of early (21 August) spray (Cypermetrhin 200g/L EC) on the percentage coconut bug infested prematurely aborted fruit as well as

final yield of mature litchi trees (cv. Mauritius)

Percentage prematurely

aborted fruit infested by

P. wayi ± SD

Mean final

yield/tree (kg) ±

SD

Cypermethrin

200g/L @

20ml/100L

23.43a ± 11.5 126.66a ± 43.01

Control 54.28b ± 9.48 142.98a ± 23.72

T value 5.823 0.743

P = 0.0043 0.478

Df 4 8

Coconut bug on avocados

Relative seasonal abundance

Coconut bug on macadamias

Husk damage Kernel damage

Relative seasonal abundance of the coconut bug

0

10

20

30

40

50

60

70

80

o o n n n n n d d d d j j j j j f f f f m m m m

Nu

mb

er

of

dam

age

d f

ruit

/5 t

ree

s

Litchis

Integration of control options for major subtropical crops

0

10

20

30

40

50

60

70

80

o o n n n n n d d d d j j j j j f f f f m m m m

Nu

mb

er

of

dam

age

d f

ruit

/5 t

ree

s

Macadamia Litchis

Integration of control options for major subtropical crops

0

20

40

60

80

100

120

140

o o n n n n n d d d d j j j j j f f f f m m m m

Nu

mb

er

of

dam

age

d f

ruit

/5 t

ree

s

Avocado Macadamia Litchis

Integration of control options for major subtropical crops

Relative seasonal abundance of B. natalicola

0

10

20

30

40

50

60

70

n d j j f m m a a m m j j j j a s s o o n n d d j j f f m m a a m m j j j j a a s o

Nu

mb

er o

f in

se

cts/1

0 t

re

es

Nymphs Adults2010 2011 2012

Proposed spraying dates

Proposed spraying dates

Proposed spraying dates

Proposed spraying dates

Proposed spraying dates

Control options for stink bugs

• Classical biological control options limited as most pests are indigenous

• Optimisation of beneficial insects by reducing chemical sprays, investigating refugia and by increasing functional biodiversity of plants and weeds in orchards

• Chemical control currently largely based on synthetic pyrethroids although softer products have recently been registered.

Litchi moth (Cryptophlebia peltastica)

Control methods

• Chemical (Synthetic pyrethroids, IGR’s)

• Pheromone - attract and kill products

• Mating disruption

• Monitoring

• Inundative releases of natural enemies

Relative seasonal abundance of litchi moth

0

5

10

15

20

25

30

35

40

Oct Oct Nov Nov Nov Nov Dec Dec Dec Dec jan

Perc

en

tag

e e

gg

s a

nd

larv

ae

reco

vere

d

0

2

4

6

8

10

12

14

16

18

Fru

it m

ass (

g)

Eggs Larvae Fruit mass (g)

False codling moth on avocados

Relative seasonal abundance of larvae of the false codling moth (Thaumatotibia

leucotreta)

Oviposition

Tortricids on macadamias

Relationship between pheromone trap catches and various nut borer stages

Regression coefficient (r2)

Eggs Larvae Damage

Ne

lsp

ruit

Eggs

Larvae 0.372

Damage 0.864 0.399

Moths 0.588 0.277 0.47

Frie

de

nh

eim

Eggs

Larvae -0.453

Damage 0.676 -0.421

Moths -0.641 0.451 -0.488

Relative seasonal abundance of nut borer moths in relation to damage - Nelspruit

Conclusions

• Control actions applied against one pest, invariably affects other pests

• A number of environmentally friendly options exist for tortricid moth control but most control programs against stinkbugs still use synthetic pyrethroids.

• Stinkbugs are fussy feeders and move from crop to crop. Factors affecting migration must be studied.

• Chemical treatment against key pest(s) (heteropterans) – prophylactic. Must move towards more informed decision making.

• Chemical usage should be more target specific eg. Pymetrozine

• Use of GIS to manage and interfere with migration patterns of indigenous heteropterans

• Quick communication between research, extension and growers. Current website initiative is a start but significant expansions are still required

Acknowledgements

• ARC-ITSC for funding

• Subtrop SALGA, SAMAC & SAAGA for funding

• Subtrop staff for frienship and assistance

• Everyone from the stink bug working group

• Participating growers

• Chemical companies