Side‐effects of cowpea treatment with botanical insecticides on two parasitoids of Callosobruchus maculatus

Abstract

Studies on the protective effect of botanical products against pest insects have infrequently been extended to side‐effects on natural enemies. Indirect effects of botanicals on the storability of seeds could occur through their possible negative impact on biological control agents. Four plant powders and six plant oils with a known effect on the cowpea beetle Callosobruchus maculatus (Fabr.) (Coleoptera: Bruchidae) were investigated for their effect on the beetles’ egg parasitoid Uscana lariophaga (Steffan) (Hymenoptera: Trichogrammatidae) and the larval parasitoid Dinarmus basalis (Rondani) (Hymenoptera: Pteromalidae). All treatments caused a decrease in parasitisation by U. lariophaga, and developing parasitoids of this species were affected by powders of Nicotiana tabacum (L.) and Tephrosia vogelii (Hook. f). In a two‐choice situation using a linear olfactometer, U. lariophaga was repelled by most of the oils. In a no‐choice situation, parasitisation by D. basalis was hampered by treatment with plant powders, but eggs that were laid developed normally. In a Y‐tube olfactometer, this parasitoid did not discriminate between odours of untreated and plant‐powder‐treated beans. The powders of N. tabacum and T. vogelii had stronger negative effects on the two parasitoids than the powders of Azadirachta indica (Juss.) or Blumea aurita (DC). In samples collected from untreated traditional storage facilities, subsequently treated with plant powders in the laboratory, none of the treatments could prevent the increase in beetle numbers. At 24 days after treatment, most beetles had emerged from beans treated with powders of N. tabacum and T. vogelii. Parasitoids were affected by the botanical insecticides tested here, but the powders of A. indica and B. aurita may be compatible with biological control by D. basalis.

Evaluation of the Efficacy of Plant Powders, Cow Dung Ash and Malathion Dust against Callosobruchus Chinensis L. (Coleoptera: Bruchidae) On Chickpea in Jole Andegna: Southern Ethiopia

“…The effect of the ash is caused by a mechanical rather than by a chemical action. The ash hinders adult movement and thus hampers oviposition (Boeke et al, 2003). The applied ash does not only hamper beetle movement, but it can also do physical damage to the adult beetles.…”

Toxicity and repellent effects of some botanical insecticides on the egg-larval parasitoid Chelonus oculator Panzer (Hymenoptera: Braconidae)

“…In their studies Satti et al (2010) and Mandal (2011) reported that azadirachtin has a repellent effect. Boeke et al (2003) found that in the choice test with Y tube, oil of the Azadirachta indica (Meliaceae) has displayed a repellent effect on the parasitoid Uscana lariophaga Steffan (Hymenoptera: Trichogrammatidae). A similar result was obtained for B. hebetor (Raguraman and Singh, 1998).…”

Applied evolutionary ecology of insects of the subfamily Bruchinae (Coleoptera: Chrysomelidae)

“…I suggest an endosymbiotic bacterium, Wolbachia, from bean beetle pests and its functional relation with the host (Kondo et al, 2002) may be applied to biological control of stored product pests. When the above-mentioned multiple methods are used in combination, the possibility of one agent negating the other must be taken into account (e.g., Boeke et al, 2003).…”