Slaters

Agronomist, Ben Cordes (Tyler’s Hardware & Rural Supplies), has reported finding slaters causing some damage to a chickpea crop near Rupanyup, in the Wimmera district of Victoria. The slaters have ringbarked the stems of several plants just above the soil surface. In many cases, the stems have been completely severed. Over the past five years we have received numerous reports of slaters causing damage to broad-acre crops. There appears to be a correlation with minimum tillage and stubble retention. Stubble provides a cool, moist refuge that facilitates survival and population development. Crumbly clay soil surfaces and cracking clays also seem to favour the survival of slaters.

Slaters have a hard skeleton on the outside of their bodies and many pairs of jointed legs. Slater damage is often in the form of uneven rasping that can appear as ‘windows’ of transparent leaf membrane. One particular species, the flood bug (Australiodillo bifrons), is known to be a significant pest of cereal crops in northern New South Wales. The slater species observed by Ben is not the flood bug, but is a species that may be more closely related to the commonly found introduced garden slater, Porcellio scaber.

The presence of slaters, even in high numbers, in a paddock does not always mean there is a pest issue because slaters typically feed on decaying organic matter. Feeding on emerging crop seedlings is rare. It is unclear why slaters suddenly prefer to eat plant seedlings rather than organic matter.

There are no insecticides registered against slaters in broad-acre crops, and reports indicate they are difficult to control with foliar sprays of synthetic pyrethroids and organophosphates applied to control other pests (even when applied at very high rates). Insecticides are probably ineffective because slaters hide under cover and thus avoid contact with insecticide sprays. There are chemical baits registered for use against slaters in horticulture, and reports suggest some success with cracked wheat baits treated with chlorpyrifos in Western Australia. The level of trash cover, amount of plant material present and time of bait or spray application will affect the level of control achieved.