Rain and sun
Berry splitting occurs in some varieties if rain occurs between colour change and harvest.
Sunburn is a problem, particularly in December and January. 'Red Globe' and 'Muscat Gordo' are particularly sensitive.
Can quickly cause considerable damage to young vines. Webbing and excreta may be seen on bunches together with chewed leaf margins. Products containing Bacillus thuringiensis, a naturally occurring bacteria, are organic and target only caterpillars but need to be reapplied every 5-7 days or after rain. Chemical sprays containing spinosad also control caterpillars and have translaminar movement, which means the chemical moves into the leaf, making the active resistant to rain and sunlight once the spray has dried.
These nocturnal pests chew leaves and flower buds. Banding the trunk of the vine with petroleum gel or grease will prevent weevils crawling up to the leaves.
Grapes contain sugars which make them attractive to birds such as silvereyes and rainbow lorikeets. There are no poisons registered for bird control and poisoning native birds is illegal. A wide range of netting is available.
Mediterranean fruit fly (Ceratitis capitata) is a serious horticultural pest in Western Australia. It stings grape berries to lay eggs and the fruit is then inedible.
Baiting and lure-and-kill traps will reduce numbers but netting or bagging of fruit may also be necessary.
For further information on controls read web article Mediterranean fruit fly.