Locusts can be readily controlled with insecticides if treated at the right time with appropriate application methods.
The most appropriate application methods for locusts vary with the locusts' life stage and behaviour.
Bands of small hoppers (nymphs) are the best targets for ground spraying using agricultural chemicals. Australian plague locusts and migratory locusts readily form hopper bands, which can be best seen in the early morning and late afternoon from the air or from raised areas. Spur-throated locusts are also easiest to kill when in the hopper stage.
Large hopper bands can be sprayed with boom sprays. Isolated and small areas can be sprayed using misting machines or knapsack sprayers.
There is no licence required if you are controlling locusts on your own property using insecticides from ground spraying equipment.
When using insecticides, it is essential that you read and follow the entire insecticide label.Although all bands are worthy of control, the best results are achieved if control is undertaken when hoppers are in the smallest area.
Factors influencing the movement of hopper bands and the effectiveness of control include:
- Density - hoppers at densities below 30 square metres move very little and don't form bands.
- Weather - spraying in the late afternoon is most effective, as hoppers tend to spread out during the day. Strong winds may cause hoppers to shelter in cracks in the ground or behind windbreaks.
- Cover - dense, high pasture or crops should not be sprayed in still conditions, as wind turbulence is needed for spray penetration of the foliage.
Hoppers die after contact with, or ingestion of, treated vegetation. This may be 2-48 hours after spraying. Follow-up treatments may be necessary for up to two weeks after spraying, as several waves of bands will hatch from one egg bed.
Once locusts have fledged or are 'flying', aerial spraying of agricultural chemicals is the only efficient method of control.
Aerial spraying should be undertaken by a licensed aerial distribution contractor and the pilot in command of aircraft must hold a current pilot chemical rating licence.
Agricultural chemicals applied to control locusts must be approved for use by the Australian Pesticides and Veterinary Medicines Authority (APVMA). You can check on registered products and permits granted for control of locusts by consulting the APVMA website.
Landholders should be aware that there are different chemicals used to control each species of locusts. Landholders should consult their local agronomist for the best options for their crops.
Managing chemical residues
Agricultural chemicals used to control locusts have the potential to cause unacceptable residues in grazing livestock and in some crops which could cause problems in export commodities.
Withholding periods must be observed to avoid residue issues. The actual withholding period which applies to a treatment, may differ depending on the chemical product and active constituent in the product used. Information on withholding periods will appear as an instruction on the chemical label.
Graziers should also check which chemical products have been applied and observe relevant export intervals (EI). It is essential that all relevant EIs have been observed before selling stock for slaughter especially where meat may be destined for an overseas market. (See SAFEMEAT link below for more information.)