Biological control
Since all of our pest snails and slugs are introduced, there are limited agents that control them in Western Australia. This partly explains why they are such pests. Some predatory beetles and lizards feed on them, but birds and rats are the most effective.
Ducks, chickens or guinea fowl can provide effective, long-term control in orchards, vineyards and gardens and the biggest problem in using birds is protecting them from foxes. A safe, fox-proof roost to house the birds overnight is essential. They should be released from this pen one hour or more after sunrise and returned at least one hour before sunset, when fox activity is lower — but foxes can be active at all times, especially if human activity is low. Keeping vegetation low will also make it difficult for foxes to stalk their prey. For high-value crops, fox-proof fencing may be a commercially viable option.
You should provide an alternative pen, away from plants, so that the birds are not nearby during pesticide applications for other pests, and can be kept off the treated area for the full withholding period. Some common insecticides are particularly toxic to birds — notably, diazinon, azinphos-ethyl and azinphos-methyl.
As it is not necessary for birds to be present all year round for snail control, they fit in well with a system of production, growth and harvesting.
Ducks, especially khaki campbell or indian runner varieties, are usually considered the best birds for snail control. Ducks need to be in a flock to operate efficiently. A flock of two dozen can service an area as large as 20 hectares. Once snail numbers have been reduced, the ducks may stop actively hunting for them. Also, ducks are likely to spend most of their time on or near the dam unless it is inaccessible to them.
Chickens may not forage as widely as ducks, but they can provide good control of snails and many insect pests as well as controlling weeds. However, they can damage fruit and should be moved when it starts to ripen. Chicken numbers should be managed so that they don’t remove enough vegetation to create dust when scratching around, which favours a build up of pest plant mites on orchard trees.
Guinea fowl are mainly used for insect control and it is not known how effective they are in controlling snails. They are less liable to damage fruit than chickens but are strong fliers and can be difficult to contain. Guinea fowl leave the flock to nest on the ground which makes them very susceptible to fox predation.