Współwystępowanie nicieni owadobójczych i szkodników drzew w zbiorowiskach leśnych w północnej Polsce

Repeating outbreaks of the Scots pine pests, effecting in stands damages, are the most important problems of forest protection. In extreme cases they pose a real threat to the stability of stands. Naturally occurring entomopathogenic nematodes are important regulatory factors in insect populations. Many species are employed as biological agents to control the insect pests. The objectives of this research was to describe the influence of potential forest pests on occurrence and abundance of entomopathogenic nematodes. Entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) were studied in woodland soils in northern Poland. Soil samples were collected from 2010 to 2015 from coniferous forests with abundant suitable insect hosts: the beetle grubs of Melolontha melolontha L. living in the soil (Coleoptera: Scarabaeidae) and foliage feeders Diprionidae spp. (Hymenoptera) and the caterpillar of Dendrolimus pini L., Panolis flammea Den. et Schiff. and Bupalus piniarius L. butterflies. Nematodes occurred in all type of forest and 171 soil samples were taken from 40 localities. Each study plot was approximately 100 m2 and 20 cm deep; 50 individual samples were taken using Egner’s stick, making the bulk sample approximately 600 cm3 in volume. The presence of entomopathogenic nematodes in the soil samples were determined using a standard Galleria mellonella baiting technique. Entomopathogenic nematodes were isolated from 52 soil samples (30,4%). Three species of the genus Steinernema (Steinernema feltiae, S. affine, S. silvaticum) and anyone of the genus Heterorhabditis were recorded. S. feltiae was the most common species and distinguished by the largest ecological flexibility especially to hosts. The largest number of S. feltiae samples was isolated in the places of butterfly outbreak P. flammea and also in the places of mass occurrence of beetle grubs of M. melolontha. In the feeding places of beetle of Scarabaeidae a high share of S. affine was noted too. The more rarely noted was S. silvaticum especially in outbreak of Diprionidae spp. The most abundance of entomopathogenic nematodes community was 140 000 ind./m2 in sites with M. melolontha grubs.