This page includes information specific to the northern soybean production region.
Insect pest risk
|High risk||Reduced risk||Low risk|
|Use of non selective pesticides (e.g. synthetic pyrethroids & carbamates) in vegetative stages increases the risk of subsequent helicoverpa, mite and whitefly outbreaks in the more critical flowering/podding stages.||Water-stress in crops increases the risk of helicoverpa feeding on plant terminals in preference to leaves.|
|Late soybean plantings (greater risk of podsucking bugs invading crops from earlier soybean plantings).|
|SLW (silverleaf whitefly)|
|Plant crops away from sugar cane (host of red shouldered leaf beetle (monolepta) larvae).|
Major pests of soybeans are in bold.
|Redshouldered leaf beetle||Present||Damaging|
|Grass blue butterfly||Damaging||Damaging||Damaging|
|Lucerne crown borer||Present||Present||Damaging||Damaging|
|Present||Present in crop but generally not damaging|
|Damaging||Crop susceptible to damage and loss|
Soybean leaves are more attractive to foliage-feeding pests than most other summer pulses, but most defoliators are relatively minor pests. However, some, like soybean moth and grass blue butterfly occasionally occur in very high numbers and inflict significant damage. Refer to the defoliation thresholds for the different pests. Note that the helicoverpa threshold in vegetative soybeans is based on damage to the plant’s axilliary buds which are the precursors to the floral buds, and that damage by more than 6 helicoverpa/m2 can be severe.
Soybean crops are most attractive to pests from flowering onwards. Mirids are often present but crops can tolerate up to 5 mirids/m2 with no yield loss. Flowering/podding crops are also attractive to helicoverpa – thresholds typically range from 1-2/m2. Podsucking bugs have a major impact on seed quality and must be controlled if culinary bean specifications are to be achieved, i.e. <3% seed damage (see quality thresholds).
Compensation in soybean
Soybean crops are very tolerant of insect damage at many stages of crop development. Noticeable damage (particularly leaf damage) does not necessarily translate to yield loss.
- Soybean can tolerate up to 33% leaf loss (if terminal and auxiliary buds are not attacked) without yield loss but their ability to compensate for pest damage decreases as pods develop
- Soybean set a large number of reserve pods and compensate for insect damage at early podding by diverting energy into reserve pods. If developing seeds are damaged, the plant diverts more energy to undamaged seeds, making these bigger and heavier.
- Crops are better able to compensate for early rather than late pod damage, however where water is limited, significant early damage may delay or stagger podding with subsequent yield and quality losses.
Key IPM strategies
- Tolerate early damage. Minimise early season sprays to conserve beneficials.
- Use biopesticides in vegetative soybeans prior to flowering to preserve beneficials:
- The addition of a 0.5% salt (NaCl) adjuvant to some chemicals applied at a reduced rate (targeting podsucking bugs) can still control pests satisfactory. This strategy may reduce the impact on beneficials, but may also reduce residual efficacy.
- Use selective insecticides such as indoxacarb to control helicoverpa in flowering and podding crops to preserve natural enemies and reduce the risk of flaring whitefly and mites.
- Where pest invade from adjacent field (e.g. monolepta beetles and aphids), consider spraying only the borders and not the whole field
- Resistance to synthetic pyrethroids and carbamates is present in H.armigera
- Natural host plant resistance: in cotton, narrow leafed and smooth leafed (less hairy) cultivars are less attractive to SLW. However, other pests such as aphids preferred the smooth-leafed varieties.
- Ready reckoner for helicoverpa in soybean
- Economic threshold calculator for podsucking bugs
- DAF website
- GRDC Grownotes
- Enhancing host plant resistance of Australian cotton varieties. The Australian Cottongrower, January-February 2002.