Managing insects in field crops

Insect management is an essential component of crop production, as insect damage can lead to significant yield loss or quality penalties.

You should:

• seek out the latest information on insect control, spray thresholds, and insecticide resistance management strategies
• keep fields and surrounding areas free of alternative hosts
• time crops to avoid periods of high insect activity (e.g. helicoverpa is more likely to infest late-planted chickpeas)
• adopt agronomic practices that break insect breeding cycles (e.g. pupae busting)
• regularly check crops for pests and natural enemies
• plan your monitoring around the crop stages most susceptible to insect damage
• spray if economically damaging insect populations are detected
• ensure that spraying equipment is calibrated and in good working order.

Monitoring your crops

Regular scouting for insects takes time. Include insect monitoring in your budget when planning your cropping program.

It may be worthwhile to pay a consultant or adviser who will perform crop monitoring at regular intervals and keep records of insect numbers. Consultants have ready access to chemical information and the choices available. Accredited agronomist training programs for chickpeas, mungbeans and sunflowers are available.

Routine checking allows timely control of insects. It is important to accurately know the type, stage and number of insects and beneficials present in your crop in order to make the correct control decision.

Record keeping

Good record keeping is essential. A record of crop inspections will indicate whether pest numbers are increasing, decreasing or remaining stable, and help to make spray decisions.

Deciding to spray

When making a spray decision, consider:

• numbers of eggs, larvae or nymphs, and adult pests
• size of larvae/nymphs
• position of pest in crop
• predator and parasitoid activity
• presence of secondary insect pests
• spray conditions and drift risk
• crop value and cost: benefit ratio
• insecticide resistance levels in your area.

Spraying is usually only recommended when an economic threshold is reached (the potential crop value saved from damage is more than the cost of application). Thresholds are expressed in numbers of insects per area or plant part.