How to safely compost Cameraria ohridella‐infested horse chestnut leaf litter on private compost heaps

Abstract

Abstract: The horse chestnut leafminer Cameraria ohridella (Lep., Gracillariidae) is a recently introduced invasive pest, which frequently defoliates horse chestnut trees Aesculus hippocastanum already in summer. Currently, the removal of leaf litter, in which pupae of C. ohridella hibernate, is the only effective short‐term control measure available. In the past the deposition of pest‐infested litter on private compost heaps was dissuaded because of the risk of leafminer emergence in the following spring. Thus, the aim of this study was to test safe ways to compost pest‐infested horse chestnut leaf litter on small heaps so that private gardeners can save the costs for leaf disposal. The number of C. ohridella adults emerging from heaps covered with either soil or uninfested foliage was reduced by 96% compared with controls. Only single leafminers emerged from the top covered heaps and there was no difference between the use of soil or uninfested foliage as cover. However, cover did not prevent the emergence of a few leafminers over the sides of the heaps. Overall, we conclude that it is relatively safe to compost C. ohridella‐infested A. hippocastanum leaf litter on small compost heaps provided they are properly covered.