Validity of several factors in insecticide effects assessment in control of Ceuthorrhynchus spp. on rapeseed | Validnost nekoliko parametara u oceni efekata insekticida u suzbijanju Ceuthorrhynchus spp. na uljanoj repici

Central European countries with long history of rapeseed growing, have many data on pests biology and control, as well as on consequences of insecticide application in this crop. However, there is little data of this kind for our production conditions, and usually they do not refer to Ceuthorrhynchus spp. Therefore, the aim of the study was to determine optimal timing for insecticide application and to evaluate insecticide efficacy in control of the mentioned species while accounting for different methods for monitoring and evaluation of attack level. Trials were conducted in 2011, according to OEPP methods, at localities Budisava and Kać. The applied products were based on chlorpyrifos /250 g/+beta-cifluthrin /12 g/l/ - (0.75 and 1 l/ha), chlorpyrifos /400 g/l/+bifenthrin /20 g/l/ - (0.75 l/ha) and deltamethrin /25 g/l/ - (0.3 l/ha). Assessments of insecticide efficacy were done according to the following data: number of adults/plant before and after treatment, number of infested plants and number of larvae/plant. At Budisava locality products based on chlorpyrifos+beta-cifluthrin (1 l/ha), chlorpyrifos+bifenthrin and deltamethrin significantly reduced the number of infested plants compared to the check plot. Product based on chlorpyrifos+beta-cifluthrin applied at higher rate of 1 l/ha, significantly reduced the number of infested plants compared to the rate of 0.75 l/ha. Percentage of infested plants after insecticide application was 48-76%, and 93.7% in the check plot. All tested insecticides provided significant reduction in the number of larvae/plant compared to the check plot. Average number of larvae/plant in insecticide treatments was 0.9-3.6, and 10.4 in non-treated check plot. At locality of Kać insecticide treatments significantly reduced the percent-age of infested plants and number of larvae/plant compared to the check plot. The percentage of infested plants after insecticide application was 38.7-52.5%, and 96.2% in the check plot. The average number of larvae/plant in insecticide treatments was 0.7-1.7, and 8.3 in non-treated check plot.