The overall health and vigour of a crop will influence its susceptibility to insect attack, and its ability to compensate for insect damage. Below are some of the crop production factors that can affect plant-insect interactions.
Crop choice and timing
- Rotations may assist with weed management, reducing the potential for green bridges, however some crop rotations can result in a greater incidence of pests for the subsequent crop, especially soil insects and seedling pests such as mites. Crops sown in paddocks previously containing long term pastures are particularly susceptible to pasture pests (e.g. mites, lucerne flea, and soil insects).
- Choose a varieties with inherited disease and pest resistance where agronomically and economically viable
- Seedling vigour and other physiological features such as hard seed coats will help to deter pests.
- Select planting windows to minimise the likelihood of major pests during critical development phases of the crop. If possible, avoid staggered plantings in adjacent fields to minimise the opportunity for pests to move between fields as the crop develops.
Soil preparation and successful crop establishment
- Cultivation or herbicide use during a fallow to eliminate weeds will minimise pest survival opportunities.
- Quick uniform establishment improves a crop’s ability to withstand insect (and pathogen) attack.
- Seedlings suffering from stresses (moisture, temperature or water logging) are often more susceptible to pests
- Appropriate rates of treated seed (seed dressings) may suppress soil insects as well as aphids in the first three weeks
Irrigation and nutrition
- Drought stressed crops are more susceptible to damage and yield penalties, and stressed crops are less able to compensate for damage
- High nitrogen levels in plant tissue can decrease resistance and increase susceptibility to pest attacks (particularly sap-sucking pests), however more research is needed to clarify the relationship between crop nutrition and pests. Most studies assessing the response of aphids and mites to nitrogen fertiliser have documented dramatic expansion in pest numbers with increases in fertiliser rates
- Many insects use weeds as alternate host plants.
- Control weeds in crop but also consider adjacent fields, borders and roadsides where possible.
- Also control volunteers from previous crops
- Diseased plants are unthrifty and susceptible to insect attack.
- Some insects can transmit diseases/viruses.
- Insect damage can expose crops to disease infestations
Hygiene and sanitation
- Some insect pests are moved by machinery (e.g. harvesters), vehicles and people – e.g. on clothing and footwear.
- Practice good farm hygiene to minimise pest movement
- For more information, see farm biosecurity
- Minimise exposure of pesticides to bees and birds. Apply insecticides late in the day when birds and bees have finished feeding
- For more information, see chemical control
- Know how weather affects some pests (e.g. heavy rain may wash some aphids off plants, winds can assist insect migration, some insects reduce feeding at lower temperatures etc)
Preserve beneficial insects
- Tolerate non-economic early season damage
- Minimise early season sprays to conserve beneficials
- Learn how to encourage beneficials into your crops
- Biological formulations such as NPV, Bt and Metarhizium are highly specific and do not harm beneficials.
- Integrate cultural and biological control strategies into the production system where practical.