Snail numbers can grow rapidly during wet, moist conditions, and for the first time in more than a decade, orchardists are starting the season with full dams and wet conditions.
This weather pattern is typical of how it used to be 15 years ago, at least in southern Victoria.
With the wet and humid weather come problems that growers haven’t needed to worry about for some time, such as snails.
One of the most common snails in apple orchards is the garden snail. The recent weather has been favourable for snails and their numbers appear to have exploded in some regions.
Life cycle
During summer, snails find shelter on fence posts, orchard floor trash, leaves and weeds, and on tree trunks, tree guards and buildings.
Snails remain dormant (aestivate) during the warmer months—until the ‘rains’ come in autumn/winter.
When the weather becomes cool and wet, snail activity increases as they feed and begin mating.
They lay eggs in the soil. Each snail can lay 300 plus eggs a year, depending on snail species. The eggs hatch and young snails feed through the winter/spring months.
Egg laying continues if conditions remain wet, and juveniles that are feeding will move into the tree canopy, especially if the orchard floor is disturbed by practices such as clearing a herbicide strip.
Damage
When present in very high numbers, snails can feed on fruit, especially the calyx of apples; or on young shoots of newly planted trees.
Control
A key time to control snails by baiting is during the autumn rains (see Table 1 for bait products). This will reduce egg numbers (and the snail population) the following spring.
If in early spring many snails are detected in the orchard, then baiting should commence as soon as possible.
Maintaining or clearing a herbicide strip is a good way to minimise sources of food and shelter. Having a bare herbicide strip also increases the kill when baiting.
When baiting, spread pellets evenly rather than in a concentrated heap or in a pile or narrow band.
Copper acts as a repellent to snails, so sprays as bands targeting trunks can act as a barrier.
Spraying the whole tree can help move snails down to where the bait is at the base of the tree.
For a table of bait products, see Tree Fruit September 2013
