Seasonal variation of white grubs population (Melolontha kraatzi persica R.) at natural forest and reforestations in Neka region

Feeding behavior of white grubs (Melolontha kraatzi persica R.) in soil causes damages on weeds, natural regeneration and various trees. This research studies the density of white grubs in different plantations of Alder (Alnus subcordata C. A. Mey.), Oak (Quercus castaneifolia C. A. Mey.), Maple (Acer velutinum Bioss.) and Cypress (Cupressus sempervirens var. horozontalis) with the adjacent mixed broad leaved stand in Darabkola, east of Mazindaran province in the Caspian region. To determine the seasonal variation of density, twenty samples were taken for each season. First, at each treatment one-1 ha sample plot was selected and then ten-0.01 ha circular sample plots random-systematically were established. Samples were taken from the depth of 30 cm and small white grubs were extracted using Berlese funnels and were counted by binocular. Various parameters of the stands and soils were recorded in each plot. This study showed that the mean annual density of white grubs in the Cypress plantation was the least, whereas in the Maple reforestation, it was the highest. The differences of density among other treatments were not statistically significant. However the population density of Melolontha kraatzi persica in this region was not significant regarding to a serious drawback to the stands. The analysis of PCA showed that the parameters of the density of white grubs, number of trees, number of vegetation cover, relative light intensity (as an indicator for soil heat) and moisture content of soil take an important role in seasonal differences of white grubs in each treatment.