Control measures against Cameraria ohridella
A paper presented at the International Symposium on Plant Health in Urban Horticulture, 2000-05-22/25, in Braunschweig, Germany, reviews the existing control measures against Cameraria ohridella (EPPO Alert list). The main constraint is that horse chestnut trees are mainly grown in urban environment.
Cultural methods: Sufficient irrigation and nutrition of the trees are important factors to ensure good tree vitality. Removal by burning or composting of dead leaves which contain overwintering pupae efficiently reduces the first generation of the moth the following spring. It is recognized that removal of dead leaves is difficult in large parks or in forest areas.
Chemical methods: Tree injections with systemic insecticides were tried but appeared difficult in practice (irregular penetration of the product, phytoxicity of solvent). Insect growth regulators (triflumuron, diflubenzuron) appear more effective and practicable. For example, effective control has been achieved in Austria with diflubenzuron at a concentration of 0.04 %, with one treatment per year applied during the flight period of the first generation (mid or end of April). Although effective, chemical control is generally not regarded as appropriate in the long term.
Biological control: Studies done in Austria have identified 22 parasitoids on C. ohridella. The most abundant species were Pnigalio agraules and Minotetrastichus frontalis. However, the rate of parasitism was very low (5 to 20 %). Further investigations are being made in other European countries on parasitoid species, mass rearing or parasitoids, identification of the possible area of origin of C. ohridella (it is speculated that it may originate from America or the Far East). The sex pheromone of C. ohridella has been identified and produced, and studies are continuing on how to use it for monitoring and control.
Finally, the author stressed the need for international cooperation on an integrated pest management system for urban areas.
Sources
Lethmayer, C. (2000) Control measures against the horse chestnut leafminer, Cameraria ohridella.
Mitteilungen aus der Biologischen Bundesanstalt für Land- und Forstwirtschaft, no. 370, 256-255.