Podsucking bugs

Podsucking bugs* (green vegetable bug, redbanded shield bug, brown bean bugs, brown shield bug) in summer pulses (soybean, mungbean, navy bean, adzuki bean)

  Pre-plant Seedling/Vegetative Budding/ Flowering Podset Podfill Podripening/Harvest
Find insects and damage

GVB nymphs

GVB nymphs

Sequential plantings of summer legumes  allow podsucking bugs to move progressively from early to later plantings – building to very high levels in later plantings. No damage unless very high populations (>10 adults per m2). No damage unless populations are high. Damage will not be visible during podset.Look for egg rafts and clusters of nymphs Critical stage for bug damage.

  • Deformed & shrivelled seed
  • Reduced yield
Crops still at risk until pods are dry.

  • Blemished seed is difficult to grade out and results in downgrades in quality.
  • Deformed & shrivelled seed
  • Damaged seed is  also prone to weathering.
Monitoring Check for overwintering adults in preceding season’s crop and weed hosts Monitor

  • Use a beat sheet twice weekly early to mid-morning
  • Take 5 samples within 20 m radius
  • Repeat at 6 random sites as nymphs tend to be clumped.
  • Look for egg rafts on plants, and beneficial insects.
  • Bugs can be found basking in the sun in the top of the canopy early in the day.
Pods most at risk are those containing well developed seed
Beneficials A number of beneficals attack pod sucking bugs but rarely regulate populations.

  • Trissolcus wasps parasitize bug eggs
  • Trichopoda flies parasitize GVB adults & large nymphs.
  • Bug nymphs are attacked by ants, spiders and predatory bugs
Cultural control
  • Avoid sequential plantings.
  • Plant away from other hosts e.g. cotton, tomatoes, pecans
  • Eradicate weed hosts e.g. cruciferous weeds prior to planting
  • Minimise overwintering hosts
  • Late summer plantings are at greater risk than spring planted crops, particularly in southern Qld and in NSW.
Set harvester up to screen out damaged seeds
Thresholds Familiarise yourself with bug thresholds. High numbers of young nymphs inflict very little if any damage until podfill. Thresholds are based on seed quality, are typically low (<1bug/m2), and are expressed in green vegetable bug equivalents (GVBEQ). Other podsucking species are converted to GVBEQ and totalled.

  • Maximum seed damage limits are usually 2%
  • Threshold ranges from 0.3-0.8 GVB/m2 depending on crop size (seeds/m2).

Podsucking bug threshold at podfill (GVB/m2) = number of seeds per square metre*0.25/1000. The more seeds a crop sets, the higher the bug threshold as damage penalties are based on % seed damage.

Pod-sucking bug thresholds can be determined with economic threshold calculators

Pesticides
  • Delay spraying until podfill, as no selective options are available
  • Unless very high numbers, spraying before podfill has no economic benefit.
  • At flowering and early pod-set, many immature bugs are in the egg stage – not controlled by insecticide
  • Delay control to conserve beneficials that attack  podsuckers, helicoverpa, mites and whitefly.

The addition of 0.5% salt (Na/Cl) to tank mixes of deltamethrin will control 60% of red banded shield bugs which are not controlled with the chemical alone.

Control at early to mid-podfill. Go at early podfill if high populations (>4 adults/m2)Soft options for sucking pests are limited If high sustained bug pressure, a late spray may be necessary.Observe pesticide withholding periods
Multi-pest considerations To reduce the risk of flaring silverleaf whitefly, mites and helicoverpa, delay spraying for podsucking bugs until early podfill. The addition of 0.5% salt reduces the need for full rates of insecticides and is less damaging on beneficials
Communicate and discuss management of pod sucking bugs Agronomists and growers can discuss:

  • Control of  weeds
  • Crop selection – avoiding other  hosts in close poximity
  • Planting dates and sequential plantings to minimise incidence of bugs
  • Monitoring methods and frequency – also monitor for other pests at the same time
  • Chemical control options and the use of salt adjuvant to reduce chemical rates/cost
  • Spray management plans with neighbours and consultants – Area Wide Management

Industry publications provide up to date information about regional pest issues

*Podsucking bug species: Green vegetable bug (GVB) Nezara viridula, redbanded shield bug Piezodorus oceanicus, brown bean bugs Melanacanthus and Riptortus sp., brown shield bug Dictyotus caenosus.

Further information

  • Certified Mungbean agronomy course – Pulse Australia
  • DAF Queensland