The influence of food on Copidosoma koehleri (Hymenoptera: Encyrtidae), and the use of flowering plants as a habitat management tool to enhance biological control of potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae).
Laboratory and field experiments were conducted to determine the effect of food availability on C. koehleri fecundity and longevity, to assess a number of candidate plants for their floral resource potential, and to test, under field conditions, whether growing nectar-producing plants around a potato crop can increase the mortality caused by C. koehleri. In laboratory experiments, unfed females achieved only 59% of their potential fecundity, as ovipositing declined significantly after 3 days and no female lived for >6 days. The total number of eggs laid by fed C. koehleri females was not significantly impaired by a 5-day period of host unavailability, which was another potential benefit to supplying non-host food to this parasitoid. Access to flowering plants of dill [Anethum graveolens], borage [Borago officinalis] or coriander [Coriandrum sativum] led to mean life-spans of >9.8 days, which was significantly greater than those observed for corresponding treatments with access to these plant species without flowers. In field cage experiments, rates of P. operculella parasitism were higher when C. koehleri had access to a food source than when caged without food. In further field trials to investigate the effects of habitat management, parasitism rates were greatest in P. operculella larvae recovered from potato tubers close to flowering plants. It is concluded that there may be value in providing non-host foods to C. koehleri by deploying flowering plants in a habitat management strategy.