Study presents a classification model for predicting the occurrence of mass damage in young forest plantations caused by insect pests on roots belonging to Melolontha genus. Logistic regression model was built on the basis of 10 taxation features describing 177 young stands. Habitat fertility, occurrence of Scots pine and European beech, and weed infestation of the habitat are the most significant features that influence mass occurrence of cockchafer larvae acting as insect pests on roots in plantations.
Number of Melolontha grubs in forest soils reforested with Scots pine (Lubartów A, LA, Lubartow B, LB) and those in post agricultural soils afforested with this species (Swierczyna, SW) were assessed before (autumn 2011, spring 2012) and one year after (2013) planting. At the same time, mortality of seedlings was evaluated on both study sites. Pine sawdust was mixed with soil in rows (treatment T1) or applied under seedling roots just before planting in April 2012 (treatment T2). In May 2013, seedling mortality varied significantly, from 27.5% in LB to 51.0% in LA, whereas the differences between the treatments were not significant. The mean number of Melolontha grubs decreased from 35/0.15 m3 of soil in autumn 2011 to 3/0.15 m3 in spring 2012 and in spring 2013. The differences depended on the site, treatment and grubs spatial distribution in soil. Addition of sawdust did not influence either seedlings, or insects mortality. T2 was more beneficial for Scots pine seedlings growing on agricultural soils, while treatment T1 – for those on forest soils. On the other hand, pine sawdust applied under roots of the seedlings seemed to attract Melolontha spp. grubs.