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
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
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
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
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.
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)
Relative seasonal abundance of larvae of the false codling moth (Thaumatotibia
leucotreta)
Oviposition
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
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
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