THE ENTOMOPARASITIC NEMATODE SPECIES STEI NERNEMA-FELTIAE (NEMATODA, STEINERNEMATIDAE) AS A MORTALITY FACTOR OF THE SPRUCE WEBWORM CEPHALCIA-ABIETIS (HYMENOPTERA, PAMPHILIIDAE)

The entomoparasitic nematode Steinernema feltiae Filipjev 1934 can be regarded as an important antagonist of Cephalcia abietis (Linnaeus 175 8.) larvae in soil. Its potential of propagation is high, due to the f act that one generation develops within 21 days at 15 degrees C, thus allowing several generations a year. Eonymphs, pronymphs, pupae as wel l as preadults were infested. A positively host density related parsit ization has been observed. The highest rates of parasitization by nema todes were found in a year of a Cephalcia mass outbreak with a total r ate of 32.23% from V till X. The parasite preferred pupae or preadults and the dropping larvae entering the soil as being shown by laborator y experiments. This corresponds with peak rates of parasitization foun d in the field in V and X.