Influence of Decis spraying on the community structure and species composition of beetles (Insecta: Coleoptera) on a potato field

The researches were carried out on a potato field in the vicinities of Omgovitchy village (53°06'04"N and 27°40'35"E, about 20 km to the E of Slutzk, Minsk District, Belarus), in June-October, 1998. On 29* of June, half of the field (28 ha) was treated with Decis insecticide (0.3 kg /ha) to control Colorado beetle's larvae population. And on the other half of the field the beetle's larvae were collected manually. For the collection of the beetles plastic pitfall traps (volume 200 ml, diameter 72 mm) were used filled with a formalin solution (4 %). 10 traps were placed in each plot in line. After 10-12 days the traps were inspected. Representatives of 120 species of beetles from 14 families were collected in the entire field. In the treated plot about 1919 specimen (10 families, 74 species) were collected. In the control plot 2636 specimen (13 families, 93 species) was found. Beetle activity in the experimental plot was reduced after Decis spraying and it was restored only at the end of August. The application of Decis did not influence the zoogeographical structure of beetle community. We found the reduction of species number and number of the recedent and subrecendent species. The number of saprophagous species and percentage of specimens had decreased in the treated plot. The percentage of necrophagous specimens had increased.