Effects of protect-it on efficacy of Anisopteromalus calandrae (Hymenoptera : Pteromalidae) parasitizing rice weevils (Coleoptera : Curculionidae) inwheat

Citation
J. Perez-mendoza et al., Effects of protect-it on efficacy of Anisopteromalus calandrae (Hymenoptera : Pteromalidae) parasitizing rice weevils (Coleoptera : Curculionidae) inwheat, ENV ENTOMOL, 28(3), 1999, pp. 529-534
Citations number
26
Categorie Soggetti
Entomology/Pest Control
Journal title
ENVIRONMENTAL ENTOMOLOGY
ISSN journal
0046225X → ACNP
Volume
28
Issue
3
Year of publication
1999
Pages
529 - 534
Database
ISI
SICI code
0046-225X(199906)28:3<529:EOPOEO>2.0.ZU;2-6
Abstract
The parasitoid Anisopteromalus calandrae (Howard) was: very sensitive to di rect contact with Protect-It, an inert dust formulation containing 90% diat omaceous earth and 10% silica aerogel. LT(50)s at room temperature and humi dity were 49 min (95% CL = 48-51) and 72 min (95% CL = 69-74) for males and females, respectively, in petri dishes containing 7.5 mg dust per square c entimeter. Under the same conditions, adults of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), a host of A. calandrae, were much less sensitive. Mortality of S. oryzae after a 24-h contact period was 50% for females and 62% for males. When tested in no-choice laboratory bioassa ys at 27 degrees C, label rates of Protect-It (200 and 400 ppm) dusted onto hard red winter wheat, Triticum aestivum, L. (13.9% moisture content) that was infested with immature rice weevils reduced the longevity of parent A. calandrae females and significantly reduced parasitization of the weevils at 3 tested humidities, 43, 60, and 75% RH. Parasitoid progeny production w as also significantly reduced. At 75% RH, 92.8 +/- 2.9 parasitoid progeny w ere produced in untreated wheat compared with 12.6 +/- 2.6 progeny in the t reated wheat. Sex ratio of parasitoid progeny was not significantly affecte d by the dust treatments at any relative humidity. In two-choice tests in d ivided petri dish arenas, single A. calandrae females showed a strong avoid ance of Protect-It-treated wheat and a significant preference for parasitiz ing weevils in untreated wheat. How ever, significantly more parasitoid pro geny were produced in dishes in which one-half contained Protect-It-treated wheat and the other half contained untreated wheat compared with dishes in which both halves of the divided dishes held untreated wheat. Reasons for the Protect-It-stimulated oviposition response by A. calandrae are not know n, but may be related to stress induced by the dust. In separate tests, the re was no significant difference in emergence of weevils from treated or un treated a heat, regardless of the weevil age at time of dusting, or the rel ative humidity at which the dusted wheat was maintained. Our studies provid e evidence that any natural control of pest insects exerted by local popula tions of parasitoids, or enhanced biological control by augmentative releas es of parasitoids, would be adversely affected. by the use of Protect-It or other diatomaceous earth products on stored grain.