Effects of diatomoceous earth on water content of Sitophilus granarius (L.) (Col., Curculionidae) and its possible use in stored product protection

Increased problems caused by application of chemical pesticides within pest protection has led to the demand for non-polluting, biologically specific active countermeasures. This study aimed to test the possible use of diatom aceous earth against Sitophilus granarius. It will also examine the physiol ogical effects of amorphous diatomaccous earth against this insect. After 2 weeks, 100% mortality was observed of the adults treated with 2 g Fossil S hield((R)) per kilogram wheat, at 11-12% corn moisture content and relative humidity of about 62 +/- 2%. The rise in grain moisture and relative humid ity decreased the effectiveness of the Fossil Shield((R)). It was observed, that the diatomaccous earth reduced the number of adult granary weevils an d increased the mortality rate at development stages, but they did not comp letely prevent the hatching of the next generation. After contact with diat omaceous earth, the individuals of S. granarius had lost weight and reduced their water content, respectively. The adults significantly lost weight an d body water after I day exposure to Fossil Shield((R)). This showed that s ilica dusts break the water barrier of the cuticle. However, it increases t he transpiration rate of water across the cuticle and several insects died through dehydration. At higher relative humidity diatomaceous earth was les s effective toward S. granarius, because there was a lower permeability for water across the cuticle. This delays or rather prevents the drying action of diatomaceous earths. Furthermore, the addition of food affected the eff ectiveness of dusts against S. granarius. A lot of stored product beetles a re able to produce metabolic water in the feed substrates. This ability pro tects them and works contrary to the loss of water.