IPM Guidelines For Grains

Soybean – northern region

This page includes information specific to the northern soybean production region.

Insect pest risk

High risk Reduced risk Low risk
Helicoverpa 
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.
Podsucking bugs
  • Sequential plantings of summer legumes (podsucking bug populations will move progressively from earlier to later plantings, eventually building to very high levels).
  • Small stressed crops (set fewer pods and suffer more seed damage in % terms for a given bug population). Bug thresholds in such crops are lower.
 Late soybean plantings (greater risk of podsucking bugs invading crops from earlier soybean plantings).
SLW (silverleaf whitefly) 
  • Sequential soybean plantings.
  • Planting soybean in close proximity to earlier maturing SLW hosts (e.g. cucurbits, cotton).
  • Late soybean plantings in high SLW risk regions.
  • Spraying caterpillars with non selective pesticides in the vegetative stages may flare SLW.
  • Planting soybean in non-cotton growing regions.
  • Spraying podsucking bugs with SPs during early podfill (SLW should be on the wane in soybeans and the crop is less attractive to helicoverpa).
Other pests
  • Planting close to lucerne increases the risk of lucerne crown borer.
  • Early spraying for podsucking bugs with SPs (at flowering) increases the risk of flaring SLW and helicoverpa.
  • Slugs can be a problem in high rainfall areas with no-till retained stubble.
  • Low plant density – increased risk of lodging if infested with lucerne crown borer.
  • Water stressed plants are more attractive to soybean moth.
  • Soybean moth activity is often higher in soybeans in close proximity to trees.
  • Water-stress in crops increases the risk of grass blue butterfly larvae attacking plant terminals in preference to leaves.
 Plant crops away from sugar cane (host of red shouldered leaf beetle (monolepta) larvae).

Pest incidence

Major pests of soybeans are in bold.

Pest Crop stage
Emergence Vegetative Flowering Podding Podfill
Red­shouldered leaf beetle Present Damaging
Silverleaf whitefly Present Present Damaging
Aphids Present Damaging Damaging
Mirids Present Damaging Damaging
Soybean moth Present Damaging Damaging
Loopers Damaging Damaging Damaging
Legume webspinner Damaging Damaging Damaging
Grass blue butterfly Damaging Damaging Damaging
Mites Damaging Damaging Damaging
Lucerne crown borer Present Present Damaging Damaging
Cluster caterpillar Present Damaging Damaging Damaging
Helicoverpa Damaging Damaging Damaging Damaging
Podsucking bugs 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:
    • Bacillus thuringiensis (Bt) is effective against loopers (under 12 mm).
    • NPV is most effective against helicoverpa larvae (less than 7 mm long).
  • 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.

More information:

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