Role of host feeding niches and host refuges in habitat-related behaviour ofHyssopus pallidus(Hymenoptera: Eulophidae), a larval parasitoid of the codling moth

Abstract

AbstractParasitoid fitness depends largely on the capability to locate a host in an ecosystem. A parasitoid of a polyphagous host might not be able to find or to access the host in all its feeding niches. This study evaluated the niche selection ofHyssopus pallidus(Askew), a larval parasitoid ofCydia pomonella(Linnaeus), at the plant level with the goal of assessing its potential for biological control on different fruit crops throughout the plant cycle. Parasitoid behaviour during host location and reproduction rate were investigated on host caterpillars actively feeding on apple, pear, apricot or plum, and on caterpillars diapausing under the bark. Under laboratory conditions, the host searching behaviour ofH. pallidusvaried depending on the fruit species offered and the infestation of the fruits. Parasitoid females searched longer on apples than on other fruit species, and they searched longer on infested than on uninfested apples. Female wasps were able to locate and parasitize host caterpillars under the tree bark, and their behaviour did not vary with host accessibility. The numbers of caterpillars attacked byH. pallidusdepended on the fruit species. The highest numbers of caterpillars were parasitized in apples and apricots. Their accessibility (i.e. position) within the fruit or on the branch did not influence parasitism success. Although hosts were parasitized throughout the season, the best results were achieved with early and late releases. Therefore, the host niche selection behaviour ofH. pallidusmost likely co-evolved with the hostC. pomonellaon apples, which rendersH. pallidusa valuable biocontrol agent for successful release at different times of the season into apple orchards.