The development of resistance in stored-grain insects to organophosphate insecticides registered for use as grain protectants has led, in the USA, to a search for newer diatomite formulations which might replace conventional chemicals. Insect0 is a new diatomaceous earth which was registered by the United States Environmental Protection Agency in June, 1984, for application to grain at 0.5-1.0 g/kg and to empty grain stores at 5 g/m’. Despite the ability to effect reasonably good control against a series of insect pests (see above), small scale trials with Insecto-treated wheat (lots of 109 kg) stored in metal bins showed that significant numbers of live adult R. dominica and S. oryzae were continually found in samples collected for up to 250 d after insects were introduced to the grain. These observations were contrary to laboratory data which demonstrated that these species exhibited 100% mortality when exposed for seven days to wheat treated with 0.05% Insecto. The authors, who also obtained excellent control when the adults were
exposed to treated plywood, postulated that the reduced mortality in the small bins may have been due to poor distribution of the dust throughout the grain bulk, allowing insects to survive in areas of low dust concentration. However, the grain sustained sufficient damage to warrant downgrading in terms of the US Federal Grain Inspection Standard, so that further improvement in control must be achieved if the treatment is to become commercially viable.
The development of resistance in stored-grain insects to organophosphate insecticides registered for use as grain protectants has led, in the USA, to a search for newer diatomite formulations which might replace conventional chemicals. Insect0 is a new diatomaceous earth which was registered by the United States Environmental Protection Agency in June, 1984, for application to grain at 0.5-1.0 g/kg and to empty grain stores at 5 g/m’. Despite the ability to effect reasonably good control against a series of insect pests (see above), small scale trials with Insecto-treated wheat (lots of 109 kg) stored in metal bins showed that significant numbers of live adult R. dominica and S. oryzae were continually found in samples collected for up to 250 d after insects were introduced to the grain. These observations were contrary to laboratory data which demonstrated that these species exhibited 100% mortality when exposed for seven days to wheat treated with 0.05% Insecto. The authors, who also obtained excellent control when the adults wereexposed to treated plywood, postulated that the reduced mortality in the small bins may have been due to poor distribution of the dust throughout the grain bulk, allowing insects to survive in areas of low dust concentration. However, the grain sustained sufficient damage to warrant downgrading in terms of the US Federal Grain Inspection Standard, so that further improvement in control must be achieved if the treatment is to become commercially viable.
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