Viticulture
During spring and summer large numbers of locusts can occur in the agricultural regions of Western Australia, and generally start flying in late September. Due to the high value of vineyards, landowners should act immediately if a swarm of locusts arrive.
Landholders are responsible for the control of locust infestations that are causing damage on their own properties.
Over a period of two to three weeks, locusts can fly up to 200km. Damage to vineyards is erratic in that locusts will fly over some vineyards and then land and feed on others. Although grapevines do not appear to be a favoured host plant, extensive damage may occur, particularly on boundary rows, when large numbers of insects are present. Damage to vineyards can be extensive with adult locusts stripping vines of leaves in hours.
Newly planted vines are more likely to be killed than mature vines. They have little carbohydrate reserves in their stem and root systems. If a significant proportion of the leaves are eaten, particularly if the locust attack occurs in early spring, the young vines are likely to die.
If the leaves of mature vines are eaten the vine will usually recover. If damage occurs early in the season, yields will be decreased and fruit quality may suffer. These vines should however produce normally the following year.
Where insecticide treatment is considered necessary, it is likely that treatment will not be 100% effective and that repeat treatments may be required.
Management options
- Where locusts fly into an area, damage can be very swift and severe and it may not be possible to effectively protect the vines. Any decision to treat in these circumstances must be made on commercial grounds. Treatment of locusts will need to be within hours of them arriving, which means frequent monitoring from early September onwards.
- Control in vineyards should be initiated as soon as any hopper damage becomes evident. The cost of control is almost certain to be less than the cost of even minor locust damage.
- In areas containing high locust egg numbers, consideration should be given to postponing any new vine plantings until the following year.
- Locust hatchings are not likely to be in vineyards more than one year old. Treating areas of high locust concentration in adjoining pasture paddocks before they attack vines is likely to be more effective. Where immature hoppers are invading vineyards from adjacent pastures, an insecticide barrier should be applied across the line of advance.
- Where damage to vines is likely to result from nymphs originating near the vineyard, spraying with insecticides registered for locust control in vines should be effective (refer to Grape vines in Australian plague locust control: horticultural crops).
- Do not spray chemicals which have no registration to control locusts on vines; observe withholding periods and read the label carefully. Grape growers should seek advice from their chosen winemaker regarding the suitability of insecticides to use on their vines.
- Grape growers and winemakers who are exporting wine should refer their enquiries to the Australian Wine Research Institute.