EFFICIENCY OF TRISSOLCUS-BASALIS (HYMENOPTERA, SCELIONIDAE) AS AN EGGPARASITOID OF NEZARA-VIRIDULA (HETEROPTERA, PENTATOMIDAE) IN CENTRAL ITALY

The natural control exerted by Trissolcus basalis (Wollaston), a solit ary egg parasitoid of Nezara viridula (L.), in soybean fields in centr al Italy over 6 yr has been assessed. T. basalis was the only egg para sitoid attacking N. viridula egg masses. In total, 260 N. viridula egg masses were collected. Of these, 105 contained at least 1 egg parasit ized by T. besalis. Approximately 20% of egg masses were parasitized d uring the first 2 yr (1986 and 1987), increasing to 50% in the followi ng years (1988, 1990, 1991, and 1992). Parasitism efficiency (the perc entage, of eggs parasitized over the total egg masses discovered) was approximate to 65% in 1986 and 1987, significantly less than in 1988 a nd 1990 (approximate to 92%). The impact of the parasitoid on the N. v iridula population was low, <13%, for the first 2 yr, and much higher, approximate to 40%, in the following years.