Slaters

Agronomist, Ben Cordes (Tyler’s Hardware & Rural Supplies), has reported finding slaters causing some damage to an early flowering lentil crop north of Rupanyup, in the Wimmera district of Victoria. Both juvenile and adult slaters were observed and have ringbarked the stems of some plants across a 2-3 ha area. Plants have begun to turn yellow, however given that only odd plants are affected Ben does not expect a significant impact on crop yield. The paddock contains a large amount of barley stubble, and the highest numbers of slaters were found under clumps of stubble that had built up under the air seeder. In these areas, up to 20 slaters were found in a 10 cm x 10 cm area. 

Over the past five years we have received an increasing number of reports of slaters causing damage to broad-acre crops. There appears to be a strong 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.

Contrary to common belief, slaters are crustaceans, not insects. They have a hard skeleton on the outside of their bodies and many pairs of jointed legs. One particular species, the flood bug (Australiodillo bifrons), is known to be a significant pest of cereal crops in northern New South Wales. Slater damage is often in the form of uneven rasping that can appear as ‘windows’ of transparent leaf membrane. 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.

There are no insecticides registered against slaters in broad-acre crops, and reports indicate they are relatively unaffected by foliar sprays of both synthetic pyrethroids and organophosphates applied to control other crop establishment pests, even when applied at very high rates. Ben says this paddock had a pre-sowing application of an organophosphate, and an application of synthetic pyrethroid in early August, but these have not prevented the problem. 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 chlorpyrifos baits in Western Australia.