Spraying
At present the strategic use of insecticides is the only economic method of control. Outbreaks can be prevented by spraying the early instars before they disperse from the hatching site. It is vitally important that control is carried out within three weeks of emergence; early detection and control is therefore the key to success.
Aerial application of insecticide is not generally economic but may be necessary to remove infestations from valuable crops or large favourable breeding areas. Aerial spraying organised jointly by affected landholders will minimize costs and simplify treatment of ridges that overlap property boundaries.
Spraying is most effective on newly-emerged hoppers at the hatching sites before they begin dispersing. As hatching can occur over several weeks, it is necessary to monitor likely areas from early September and spot treat as required. Look at areas where there was bare ground during the previous summer, around isolated trees, on sandy ridges and north-facing slopes.
Remember you are looking for tiny grasshoppers (smaller than a match head) which are almost black in colour (see Figure 6). Their presence can be indicated by damage to capeweed flowers, which are a favoured food at this stage.
Spraying is best carried out first thing in the morning on a day that promises to be warm to hot. This will ensure that the chemical is on the ground for a full day while the grasshoppers are active. The recommended chemicals break down rapidly and may be ineffective if left on the ground overnight.
When using a ULV mister, never allow swath widths to be greater than 50 metres as this will result in poorly treated bands in which the grasshoppers will survive.
