The efficacy of some biological and chemical insecticides against the diamondback moth, Plutella xylostella (L.) (Lepidoptera, Plutellidae).

The diamondback moth, Plutella xylostella (L.) (Lepidoptera, Plutellidae), is the most important pest of crucifers such as common cabbage, cauliflower and rapeseed in central parts of Iran. To struggle for control of this pest farmers use chemical pesticides more than 12 times in a crop cycle in Isfahan province (central Iran); such the overuse of pesticides, however, not only is useless in control of P. xylostella, but it also destroy the natural check of the pest by its parasitoids. The present study aimed to study the efficacy of three biological insecticides [Antario 32K‎ض (Bt ssp. kurstaki; 32000 IU/mg; Russell IPM, UK), Belthirul‎ض (Bt ssp. kurstaki PB 54 Strain; 32000 IU/mg; Probelte, Madrid, Spain) and Biolep‎ض (Bt ssp. Kurstaki; 108 cells/ml; Tabiatgera, Karaj, Iran)], two registered chemical insecticides [Avaunt‎ض (indoxacarb SC 150) and Consalt‎ض (hexaflumuron EC 10%)] and a new insecticide Atabron‎ض (chlorfluazuron SC 10%) against P. xylostella in Isfahan province. A field experiment was established using nine different pesticide treatments [Antario 32K‎ض (‎1 kg/ha), Belthirul‎ض (‎1 kg/ha), Biolep‎ض (‎2 kg/ha), Avaunt‎ض (‎0.25 lit/ha), Consalt‎ض (‎1 lit/ha), Atabron‎ض (‎0.5, 0.75 and 1 lit/ha) and control (water)] in plots of 50 m2 at a 2.5 ha cauliflower farm, which was heavily infested to P. xylostella, in Falavarjan county (southwestern Isfahan) during autumn 2011. The treatments were replicated four times in a randomized complete block design. The live P. xylostella larvae were recorded on 5 cauliflower plants in each plot the day before the pesticide spraying and once again 5 days after the application. The data was corrected using Henderson-Tilton's formula and differences in the percentage mortality between treatments were analyzed using logistic analysis of deviance (binomial error) in R 2.10.0. There was a significant difference between the tested insecticides for their effects on P. xylostella mortality; such that the best efficacy in causing P. xylostella larval mortality was obtained by Atabron‎ض [‎1 lit/ha] and Belthirul‎ض with the percentage mortality of 60.8 and 58.8, respectively. Other treatments were categorized in one statistical group; the mortalities caused by Biolep‎ض (‎47.1%), Antario 32K‎ض (‎41.2%), Avaunt‎ض (‎37.3%), Consalt‎ض (‎27.5%), Atabron‎ض [‎0.75 lit/ha] (15.7%) and Atabron‎ض [‎0.5 lit/ha] (11.8%) were not significantly different. Given the present study's findings and the bio-safety risk of using chemical pesticides, Belthirul‎ض (‎1 kg/ha) can be recommended as a component of sustainable management strategies of P. xylostella in Isfahan province. Key words: diamondback moth, Isfahan, insecticide, Bt, field : Abstract