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District agronomist, Rohan Brill (NSW DPI), has reported slaters attacking a canola crop near Coonamble, in the Central West Slopes and Plains district of New South Wales. The slaters have been identified as the flood bug (Australiodillo bifrons). The flood bug is a native species, approximately 7-8 mm in length and 4 mm wide. They are oval shaped and have a flattened body, with light coloured legs. They have the unusual behaviour of moving in ‘swarms’ which can consist of >100,000 individuals.

Rohan says the slaters have completely chewed the tops of emerging cotyledons; in some cases only the seedling stumps remain. This paddock was not cultivated prior to sowing, and there was some stubble on the soil surface. Large numbers of slaters were observed moving across the paddock. Interestingly, there was no visible feeding damage in an adjacent faba beans crop, despite the presence of a large numbers of slaters. Rohan reported that slaters have also been noticed in surrounding properties.

Slaters can attack broad-acre crops, and in some instances can cause serious damage. In the past, we have received reports of slaters causing damage to cereals, canola, lentils and pastures in New South Wales and Victoria. Feeding results in uneven rasping-type damage that often appears as ‘windows’ of transparent leaf membrane. However, the presence of slaters within a paddock (even in high numbers) does not necessarily mean a pest issue. Slaters typically feed on decaying organic matter and only rarely feed on emerging crop seedlings.

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. Slaters need damp conditions and will die if exposed to open and dry situations.

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. Rohan says an insecticide spray was applied to the affected paddock pre-emergence, and this was only five days before slaters were first observed. There are chemical baits registered for use against slaters in horticulture, and reports suggest some success with chlorpyrifos baits in Western Australia.

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