Cockchafer Melolontha Hippocastani Research Articles

Aerial Spraying of Neemazal®-T/S Against the Forest Cockchafer (Melolontha hippocastani, Col.: Scarabaeidae) in South-West Germany: The Effects of Two Field Trials Performed in 2007 and 2008 on Local Populations

The forest cockchafer Melolontha hippocastani is a serious forest pest whose infestation levels have been increasing in South-West Germany since the mid-1980 s. During the past 25 years several control measures have been taken to manage its populations. In 2007 and 2008, 122 and 73 hectares of forest stands comprising of deciduous trees were sprayed with NeemAzal®-T/S (1% azadirachtin A) by helicopter, respectively. Here we summarize the results of the accompanying research with the aim to evaluate the efficacy of NeemAzal®-T/S in the control of M. hippocastani populations under field conditions. As expected from azadirachtin’s mode of action, no immediate mortality occurred but maturation feeding and oogenesis was interrupted. It appeared that precise timing of the application is a crucial issue regarding the level of its effect on the population density. In 2007, the first application was performed in good synchrony with the climax of female emergence from the soil, resulting in a remarkable decline of the population density in the next generation of beetles in 2011. In 2008, our data suggest that maturation feeding and oogenesis had already been completed when the agent was sprayed. Hence, no significant decline of the population density could be registered in 2012. Practicability of the use of NeemAzal®-T/S against M. hippocastani in forests is discussed.

Effects of NeemAzal®-T/S in the burying beetle Nicrophorus vespilloides (Coleoptera: Silphidae) via food chain

In times of mass occurrence, massive numbers of the outbreaking species serve as food sources not only to predators and parasitoids but also to scavengers and decomposers. One example benefiting from this process is the necrophagous guild, which depends on a carcass for nutrition and reproduction. A well-known outbreaking insect is the forest cockchafer Melolontha hippocastani F. It inhabits woodlands on sandy soils, the same habitat as Nicrophorus vespilloides Herbst—a common burying beetle feeding on a variety of animal carcass. In this regard, N. vespilloides may come in contact with plant protective agents applied to control M. hippocastani populations. In a laboratory trial, we studied sublethal effects of NeemAzal®-T/S on the reproductive output of female N. vespilloides. They were previously fed with cockchafers, which in turn had been fed with neem-treated leaves. It was shown that female beetles fed with ‘treated’ cockchafers were negatively affected in carcass burying behavior and egg-laying. Furthermore, reduction in larval hatching and survival during the parental feeding phase caused further diminution of the reproductive output. On the other hand, neither impacts on mean larval weights nor morphological malformations in N. vespilloides were observed. Transferability of the results into the field is discussed.