Different responses of a solitary (Meteorus pulchricornis) and a gregarious (Cotesia kariyai) endoparasitoid to four insecticides in the host Pseudaletia separata

Abstract

One of the major challenges in implementing integrated pest management (IPM) strategies has been the integration of biological and chemical control. Although biological control offers environmentally friendly and sustainable solutions to a variety of insect pest problems, plant protection is hard to perform without any chemical control. The use of insecticides with low toxicity to native natural enemies, such as parasitoids, has been advocated to enhance the compatibility of the two control methods. Moreover, the use of beneficial natural enemies decreases the frequency of insecticide spraying. 1)The combination of parasitoids as a natural enemy and insecticides is the most effective method for controlling populations of the cruciferous crop pest, the diamondback moth (DBM) (Plutella xylostella (L.), Lepidoptera: Plutellide) and suppressing the development of insecticide resistance. [2][3][4][5] It is important to evaluate the effect of an insecticide on the development of parasitoid larvae by the combined application of parasitoids and insecticides. Such an approach determines the suitability of an insecticide while taking advantage of natural enemies, and is particularly important for determining the most suitable timing for the mass release of parasitoids 6) or spraying insecticides.It is generally considered that insecticides suppress the activities of natural insect enemies strongly in fields where insecticides are sprayed frequently. 7) There have been many reports about the effects of insecticides on the behavioral activities of parasitoids [8][9][10][11] ; however, these reports are restricted to investigating the adult stage of parasitoids, and few reports have investigated the effect of insecticide on a parasitoid egg This study clarified the difference in sensitivity of lepidopteran host larvae parasitized by a gregarious endoparasitoid Cotesia kariyai and a solitary endoparasitoid Meteorus pulchricornis to four insecticides, fenitrothion, cypermethrin, pyriproxyfen and pyridalyl, along with the growth and development of each parasitoid. It is well known that the physiological state of the host is regulated by endoparasitoid after parasitization. It was predicted from our previous report that the detoxification ability of the parasitized hosts was changed by parasitization. The effect of four insecticides on the growth and development of two parasitoids was examined with LD 50 or LD 95 values of unparasitized hosts. Fenitrothion and cypermethrin had an effect on the growth and development of host larvae parasitized by C. kariyai, but in M. pulchricornis caused low mortality on day 3 and later after parasitization. Pyriproxyfen had no effect on the growth and development of C. kariyai, but inhibited the adult eclosion of M. pulchricornis even when the parasitized hosts were treated with 50 ppm (less than LD 10 to unparasitized hosts). Paraffin sections revealed developmental malformations in the abdomen during the pupal stage of M. pulchricornis endoparasitoid. Pyridalyl had a strong effect on larval e...

Effects of pyriproxyfen on wild populations of the housefly, Musca domestica, and compatibility with its principal parasitoids

“…Thus, at this point we can only speculate that perhaps the juvenile hormone receptors of the fly have a greater binding affinity for PPF than those of the parasitoids. Third, the parasitoids may be able to detoxify and sequester PPF …”

“…Third, the parasitoids may be able to detoxify and sequester PPF. 38,39 In light of the observation that parasitoids are negatively affected by PPF, we asked whether parasitoids can discriminate between PPF-treated and untreated hosts. When introduced into an arena with three hosts reared in medium containing 0, 60 or 600 mg kg -1 PPF, the first choice of pupae by M. raptor and S. cameroni was distributed more or less evenly among the treatments (Table 8).…”

Qualitative and quantitative determinations of pyridalyl and metabolites in excrement of two representative Lepidoptera pests

“…Pyridalyl is a new pesticide, [1][2][3][4][5][6][7] and its target enzyme, which was conrmed to be different from reported ones, is regarded as the source of its specic insecticidal activity for Lepidoptera pests. 3,[8][9][10][11][12] Generally, pesticides interact with the target enzyme in the metabolic organ, and certain physiological functions of pests are thus inhibited. 13,14 In this sense, metabolites of pyridalyl in Lepidoptera pests, as well as their metabolic pathways, would be helpful for nding out the target enzyme.…”