Repellent Effect of Alphacypermethrin-Treated Netting Against <I>Bemisia tabaci</I> (Hemiptera: Aleyrodidae)

Abstract

For > 20 yr, Bemisia tabaci Gennadius persists as a begomovirus vector and is a serious problem in tomato production in many parts of the world. In tropical countries, the use of netting to protect horticultural crops has proven to be an effective and sustainable tool against Lepidoptera but not against small insects. This study evaluated the repellent effect of AgroNet 0.9T, a 0.9-mm pore diameter and 40-mesh size netting treated with alphacypermethrin insecticide against B. tabaci. This pyrethroid insecticide is known to have toxic and repellent effects against mosquitoes and has been used for treatment of mosquito nets. Two nontreated netting materials were used as control: AgroNet 0.9NT with 0.9-mm pore diameter and 40-mesh size and AgroNet 0.4NT with 0.4-mm pore diameter and 80-mesh size. The behavior of B. tabaci and its parasitoid Encarsia formosa Gahan as they progressed through the treated netting was studied in the laboratory in choice and no-choice tests. The development of wild B. tabaci population on tomato plants protected by the same nets was followed in two field trials implemented in Njoro, Kenya. Results obtained with the no-choice tests showed a significant reduction of movement on the treated net with 40-mesh (19%) compared with nontreated netting (35 and 46% with 80- and 40-mesh, respectively). The mortality of B. tabaci was significantly higher (two-fold) in the test tube containing only the treated netting compared with the nontreated one. The repellent effect of the treated netting was also demonstrated against E. formosa, but it did not have this toxic effect. Unlike for B. tabaci, the treated and nontreated nets appeared to have a similar repellent effect on E. formosa in the choice test, which suggests a learning behavior of the parasitoid. In both field tests, B. tabaci population was significantly lower on tomato protected by the treated net compared with the same nontreated net. However there was no significant difference in B. tabaci population between the treated 0.9-pore diameter and the nontreated 0.4-pore diameter. We discussed these findings and their implications for the use of repellent netting in integrated pest management in horticulture and more specifically in vegetable production.

Naturally occurring bioactive compounds from four repellent essential oils against Bemisia tabaci whiteflies

“…showed that a net treated with alpha‐cypermethrin blocked the pest Myzus persicae on cabbage crops in field conditions because of the irritant and repellent effects of this chemical. Moreover, a net treated with alpha‐cypermethrin was shown to reduce the whitefly net‐crossing rate and improve tomato crop protection as compared with untreated netting . However, there are also approaches other than applying chemicals on nets to repel whiteflies, e.g.…”

“…For each product, each concentration was replicated 6 times simultaneously. The number of whiteflies and their status (alive or dead) were recorded for each tube after 4 h to establish the whitefly net‐crossing rate and the mortality . Then, dead and live whiteflies that had crossed through the net after the 4 h were separately placed on tomato leaves ( Solanum lycopersicum L.) and placed on agar gel (1%) in a petri dish.…”

“…A combination between a large‐mesh screen and a repellent or irritant product could be a solution. New compounds now have to be found because of pest resistance to pyrethroids and the low repellent and toxic effects of these chemicals on whiteflies …”

Control of insect vectors and plant viruses in protected crops by novel pyrethroid-treated nets

“…Our results also agree with the findings on A. proletella survival in cabbage field experiments using deltamethrin‐impregnated nets as a fence . Recently, promising results have been obtained with the pyrethroid alpha‐cypermethrin against whiteflies . The size of the mesh and the chemical compound appear to be major factors in the production of effective LLITNs, and dicofol‐impregnated nets controlled injurious mites in eggplants, even though their size was smaller than that of whiteflies .…”

Compatibilidad de Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) y Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), importantes enemigos naturales de la mosca blanca Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) en cultivos hortícolas, con nuevas barreras físicas selectivas y modernos plaguicidas

“…La efectividad de este tipo de mallas en control de B. tabaci viene determinada tanto por el tamaño de poro, como por el tipo de insecticida empleado (Dader et al, 2014;Martin et al, 2014). Actualmente hay disponibles dos tipos de mallas tratadas con insecticidas: las más convencionales, que son pulverizadas o sumergidas en las soluciones insecticidas, y las más modernas, denominadas mallas insecticidas de larga duración (Long Lasting Insecticidal Nets: LLINs), las cuales llevan incorporado el tratamiento insecticida en el momento de su fabricación, lo que alarga notablemente su efecto al degradarse menos el insecticida con la luz (Martin et al, 2007).…”