The Spring Assessing Method of the Threat of Melolontha spp. grubs for Scots Pine Plantations

Hanna Szmidla,Miłosz Tkaczyk,Zbigniew Sierota,Monika Małecka,Grzegorz Tarwacki

doi:10.3390/f10050399

Hanna Szmidla, Miłosz Tkaczyk + Show 3 more

Open Access

https://doi.org/10.3390/f10050399

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Abstract

Root-feeding Melolonthinae larvae are a forest pest species in Europe that can exert serious damage. In Poland, they are classified as the most dangerous pest on land dedicated to afforestation and the most serious threat to natural regeneration in the stands. This study was performed in three forest districts in east Poland (Lubartów, Marcule, and Wyszków forest districts) in mixed conifer forests, where the presence of Melolontha spp. grubs was evaluated in autumn and spring of 2012 to 2017, respectively. In spring 2012, 2014, and 2016, consecutively ‘small sawdust pits’ in rows between seedlings were prepared, and in adjacent inter-rows similar control pits without sawdust were marked. In spring and autumn of the following year, sawdust and soil from both types of pits were sieved and Melolonthinae larvae were counted and compared. More grubs were found in sawdust pits in spring than in autumn. In Marcule Forest District (FD) (2014), more grubs were found in inter-rows than in rows with seedlings, when compared to grubs detected using the traditional method of “autumn large pits assessment”, recommended by Polish forest rules. The Melolonthinae population size and location of grubs were related to the weather conditions in the evaluated periods, as well. We conclude that to properly assess the cockchafer threat, it is necessary to perform spring assessment and to search in inter-rows. This could be recommended for decisions on control.

Highlights

Root-feeding insects are key components of many terrestrial ecosystems
Experimental plots were located in three forest districts (FD): Lubartów
In the Wyszków Forest District (FD), cockchafer grubs were significantly more common in spring 2017 in small pits with sawdust than in pits without sawdust (p-value = 0.031). These results suggest that it is important to perform spring assessment in sawdust pits in all forest districts

Summary

Introduction

The detrimental effect of below ground insect herbivory in agricultural and forest ecosystems is widely appreciated, because root-damaging pests cause great economic losses [1,2]. Among the many insects that have substantial impacts on forest management in European countries, the genus of Melolontha spp. The cockchafer genus, Melolontha spp., is estimated to have been a pest on 200,000 hectares, mainly in Central Europe, over the past 20 years [3,4,5]. In Poland, the most important species are Melolontha melolontha L. (forest cockchafer) [6,7,8] These species occur at varied frequency throughout the country, but are commonly found in the central and southeastern parts of Poland. In certain regions in Poland, the high population density of Melolontha spp. grubs makes reforestation or afforestation impossible

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