Effects of Protect-It on Efficacy ofAnisopteromalus calandrae(Hymenoptera: Pteromalidae) Parasitizing Rice Weevils (Coleoptera: Curculionidae) in Wheat

Abstract

The parasitoid Anisopteromalus calandrae (Howard) was very sensitive to direct contact with Protect-It, an inert dust formulation containing 90% diatomaceous earth and 10% silica aerogel. LT 50 s at room temperature and humidity were 49 min (95% CL ϭ 48 Ð51) and 72 min (95% CL ϭ 69 Ð74) for males and females, respectively, in petri dishes containing 2.5 mg dust per square centimeter. 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 bioassays at 27ЊC, 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 signiÞcantly reduced parasitization of the weevils at 3 tested humidities, 43, 60, and 75% RH. Parasitoid progeny production was also signiÞcantly reduced. At 75% RH, 92.8 Ϯ 2.9 parasitoid progeny were produced in untreated wheat compared with 12.6 Ϯ 2.6 progeny in the treated wheat. Sex ratio of parasitoid progeny was not signiÞcantly affected by the dust treatments at any relative humidity. In two-choice tests in divided petri dish arenas, single A. calandrae females showed a strong avoidance of Protect-It-treated wheat and a signiÞcant preference for parasitizing weevils in untreated wheat. However, signiÞcantly more parasitoid progeny 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 known, but may be related to stress induced by the dust. In separate tests, there was no signiÞcant difference in emergence of weevils from treated or untreated wheat, regardless of the weevil age at time of dusting, or the relative humidity at which the dusted wheat was maintained. Our studies provide evidence that any natural control of pest insects exerted by local populations of parasitoids, or enhanced biological control by augmentative releases of parasitoids, would be adversely affected by the use of Protect-It or other diatomaceous earth products on stored grain.

Efficacy of Diatomaceous Earth to Control Internal Infestations of Rice Weevil and Maize Weevil (Coleoptera: Curculionidae)

“…Although neither the wheat nor the corn used in this study was actually equilibrated to the desired moisture content, results from other studies using saturated salt solutions have documented consistent inverse relationship between RH and mortality of insects exposed on DEtreated grains (Perez-Mendoza et al 1999, Arthur 2002. Reductions in efÞcacy of DE on corn compared with wheat have been made by Subramanyam et al (1994) and by Subramanyam and Roesli (2000) in reference to unpublished data, and they state that the differences in lipid and starch content of corn may be responsible for the loss of activity.…”

Control of Stored-Product Beetles with Combinations of Protein-Rich Pea Flour and Parasitoids

“…For example, diatomaceous earth is more toxic to A. calandrae than to S. oryzae (Perez-Mendoza et al 1999). By direct contact, diatomaceous earth takes Ͼ1 h to kill 50% of A. calandrae, but it takes 24 h to kill 50% of its host, S. oryzae (Perez-Mendoza et al 1999). In contrast, our studies demonstrated that protein-rich pea ßour and parasitoids were compatible for reducing populations of S. oryzae and C. ferrugineus.…”

Granary Trial of Protein-Enriched Pea Flour for the Control of Three Stored-Product Insects in Barley

“…Unlike diatomaceous earth (Korunic et al 1998, Fields andKorunic 2000), pea protein ßour did not reduce bulk density. Also, most grain protectants harm parasitoids (Perez-Mendoza et al 1999). Protein-enriched pea ßour is not toxic to Anisopteromalus calandrae (Howard), an ectoparasitoid of several stored-product insects, and Cephalonomia waterstoni (Gahan), an ectoparasitoid of C. ferrugineus (Hou et al 2002).…”