THE EFFECTS OF ORGANIC AND CONVENTIONAL FARMING METHODS ON PLANT BUG DENSITIES (HEMIPTERA, HETEROPTERA) WITHIN WINTER-WHEAT FIELDS

An understanding of the mechanisms responsible for direct and indirect effects of pesticides on Heteroptera were studied by comparing densit ies within fields of winter wheat on organically and conventionally ma naged farms. Weed and insect densities were estimated in 56 fields in 1990 and 62 in 1991. Four out of five of the heteropteran groups studi ed were more numerous within organic fields in both years, however dif ferences were statistically significant in only one out of 10 comparis ons. Differences in agricultural practices between the two farming reg imes are given as possible reasons for the densities observed.