Control of aggregated populations of the eye fly Siphunculina funicola (diptera: chloropidae) using pyrethroid aerosols.

Three commercially available insecticide aerosol compositions containing cyphenothrin, imiprothrin, cypermethrin, d-tetramethrin and permethrin, in various combinations and concentrations were evaluated for control of the oriental eye flies Siphunculina funicola (de Meijere) from their aggregation substrates in two villages in the Chon Buri Province, Thailand. Each aerosol produced almost complete kill of eye flies on most of the treated substrates. Time to reoccupation of each treated substrate was determined at 24, 48 and 72 hours post-treatment. All 3 aerosol preparations killed eye flies on most of the treated substrates and kept most of the substrates free of eye flies for at least 48-72 hours. The effectiveness and longevity of the aerosols varied depending on the type and location of the substrate. Smooth, hairy and polished substrates did not intercept sufficient insecticide; therefore providing low residual activity compared to porous and coated surfaces. Aerosols applied to substrates located at higher levels gave good initial kill, but reoccupation of these substrates by flies occurred relatively quickly (within 24-48 hours) following treatment. Attempts should be made to discharge aerosol flumes closer than 1 m from the aggregation substrates.

Effect of Bt-cotton on chrysopids, ladybird beetles and their prey: aphids and whiteflies.

The effect of Bt-cotton, i.e. genetically modified cotton that contain genes expressing delta-endotoxin, on aphid, whitefly, chrysopid and coccinellid populations was determined with a two-year field study at a cotton farm near Marble Hall, South Africa. Although Bt-cotton is lepidopteran specific, non-lepidopteran arthropod populations may be indirectly influenced by the endotoxin. Abundance of aphid, whitefly, chrysopid and coccinellid populations and predator-prey interactions were used as measures to determine possible effects on the populations under investigation. The cultivation of Bt-cotton had no effect on aphid, whitefly, chrysopid or coccinellid abundance. Positive density dependent interactions occurred between aphids and coccinellids which were not influenced by Bt-cotton. A significant relationship between whitefly and coccinellid abundance, i.e. predator-prey reaction, occurred in the control and sprayed non-Bt cotton fields but was absent from the Bt-cotton fields.

Toxicity of insecticides to Toxorhynchites splendens and three vector mosquitos and their sublethal effect on biocontrol potential of the predator.

Toxicity of six larvicides ie fenthion, temephos, malathion, deltamethrin, alphamethrin (Fendona), OMS 3031 and five adulticides ie malathion, fenitrothion, propoxur, deltamethrin, permethrin to Aedes aegypti, Culex quiquefasciatus, Anopheles stephensi and the predator, Toxorhynchites splendens was studied for evaluating safety margin. Concentrations of alphamethrin that killed 50% larvae of T. splendens were 53 and 12 times more than that which killed Cx. quinquefasciatus and Ae. aegypti. In case of deltamethrin, concentrations required to kill 50% larvae of T. splendens were 14 and 5 times more than that required against other two species. Other larvicides tested were equally toxic to both T. splendens and vector mosquitos. There was no significant difference in the toxicity of larvicides to T. splendens and An. stephensi. Deltamethrin was 25-132 times less toxic to adults of T. splendens in comparison to vector mosquitos. For other adulticides the range was 1-10. Immature developmental time of T. splendens was not affected by any of the insecticides tested. However, predation rate was lowered when larvae of Ae. aegypti previously exposed to fenthion and temephos were offered. Whereas, alphamethrin and OMS 3031 did not affect the feeding rate of the predator. There was a significant reduction in the pupal weight and pupation as a result of the predator feeding on the insecticide treated prey. There was a significant negative relationship between rate of pupation and dosage. The present study indicates that synthetic pyrethroids owing to their higher safety margin can be used in an integrated vector management program.