Effects of Spring Imidacloprid Application for White Grub Control on Parasitism of Japanese beetle (Coleoptera: Scarabaeidae) by Tiphia vernalis (Hymenoptera: Tiphiidae)

• Published in: Journal of economic entomology 2003-10, Vol.96 (5), p.1412-1419
• Main Authors: Rogers, Michael E., Potter, Daniel A.
• Format: Article
• Language: English
• Subjects: Animals; application rate; application timing; Biological and medical sciences; biological control agents; Coleoptera; conservation biological control; Control; ECOTOXICOLOGY; Fundamental and applied biological sciences. Psychology; Generalities; host location; host seeking; Hymenoptera - drug effects; imidacloprid; Imidazoles - administration & dosage; Imidazoles - toxicity; insect control; insecticide residues; Insecticides - administration & dosage; Insecticides - toxicity; larvae; lawns and turf; Neonicotinoids; Nitro Compounds; nontarget organisms; parasitism; parasitoid fitness; parasitoids; Pest Control, Biological; Phytopathology. Animal pests. Plant and forest protection; Plants; Popillia japonica; Protozoa. Invertebrates; Seasons; spring; sublethal effects; Tiphiidae; toxicity; Vespidae
• ISSN: 0022-0493; 1938-291X; 0022-0493
• DOI: 10.1603/0022-0493-96.5.1412

Imidacloprid, a relatively long residual neonicotinoid soil insecticide, is often applied to lawns and golf courses in spring for preventive control of root-feeding white grubs. We evaluated effects of such applications on spring parasitism of the overwintered third-instar Japanese beetle, Popillia japonica Newman, by Tiphia vernalis Rohwer, an introduced solitary ectoparasitoid. Natural rates of parasitism on a golf course rough were significantly lower in plots treated with full or one-half label rates of imidacloprid in early May compared with untreated turf. Parasitism also was reduced when female T. vernalis were exposed to imidacloprid residues on turf cores in the laboratory. Such exposures did not affect wasp mortality, longevity, survival, or developmental period of Tiphia larvae feeding on hosts in treated turf. They did, however, reduce wasps’ ability to parasitize hosts in nontreated soil for at least 1−2 wk postexposure. In Y-trail choice tests, wasps that previously had been exposed to treated turf failed to respond normally to host frass trails in the soil. Female wasps did not avoid imidacloprid residues, imidacloprid-treated host frass, or host grubs that had previously been exposed to treated soil. This study indicates that applying imidacloprid in early spring can interfere with biological control by T. vernalis, whereas postponing preventive grub treatments until June or July, after the wasps’ flight period, will help to conserve T. vernalis populations.