Effects of leaf litter removal on Cameraria ohridella Deschka and Dimic (Lepidoptera Gracillariidae) and their parasitoids

Published source details Grabenweger G. (2002) Auswirkungen der Falllaubentfernung auf Cameraria ohridella Deschka und Dimic (Lepidoptera, Gracillariidae) und ihre Parasitoiden. Mitteilungen der Deutschen Gesellschaft für allgemeine und angewandte Entomologie, 13, 141-143.
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Summary

The removal of dry leaves in autumn is supposed to reduce infestation of horse chestnut trees Aesculus hippocastanum by the invasive leaf miner moth Cameraria ohridella, but numbers of beneficial parasitoids attacking the leaf miner may also be reduced by leaf removal. Parasitoids, mostly belonging to the wasp family Eulophidae, and leaf miners both hatch from the old leaves in spring. Over two years the effects of leaf removal at different times of the year on leaf miner density and parasitism rates were studied near Vienna, Niederösterreich, Austria.

Although the horse chestnut is not native to Austria, this species of leaf miner also attacks tree species in the genus Acer, and alien invasive species of leaf miner have a negative impact on native trees in other parts of the world, causing premature leaf drop in Canadian birches Betula spp. for example.

In 1998 and 1999 at five sites south of Vienna the three treatments 1) leaf removal in autumn, 2) leaf removal in spring (after the majority of parasitoids hatched), and 3) control, no leaf removal, were conducted at spatially separated horse chestnut populations. In the following two springs (1999 and 2000), infestation density (number of mines per leaf) in the first generation of moths and the percentage of leaf mines that produced parasitoids were evaluated.

Leaf removal in spring and autumn resulted in significantly lower leaf mine densities than in control trees across all five sites. The timing of leaf removal did not affect parasitism of the first generation of C.ohridella. Differences in infestation densities between the five sites were attributed to the degree of accuracy in leaf removal and spatial isolation of treated and untreated trees.

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