Avaliação da suscetibilidade e resposta comportamental de populações de traça-das-crucíferas Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) a inseticidas

Abstract

Considered as the main pest of brassica crops, Plutella xylostella (L.) has its damage action potentiated in tropical conditions, given the climatic conditions that are highly favorable for its development. Synthetic insecticides are the main control tool. However, the crucifer's moth has developed high levels of resistance for all classes of insecticides. The objective of this research was to verify the susceptibility of diamondback moth populations to Brilhante® (Metylcarbamate oxine, Premio® (Chlorantraniliprole) and Dipel® (Bacillus thuringiensis var. Kurstaki) insecticides, as well as to investigate their behavioral response when in contact with the evaluated pesticides. Populations of diamondback moth from the municipalities of Camocim de São Félix - PE, Lajedo - PE, Sairé - PE, Bezerros - PE, Venda Nova do Imigrante - ES, Viçosa - MG (Laboratory) and Recife - PE (Laboratory) were studied. The experiments focused on larval susceptibility of the pest by ingestion of cabbage discs treated with insecticides. The parameters of the behavioral activity (walking distance, walking time, mean velocity, number of stops and rest time) were evaluated in the populations of Camocim de São Félix - PE, Sairé - PE, Lajedo - PE, Recife - PE and Viçosa - MG. Surfaces treated and untreated with neurotoxic insecticides (Methylcarbamate and Chlorantraniliprole) were used. Resistance ratios for insecticides were found by dividing the LD50 of the population assessed by the LD50 of the most susceptible population. Mortality data were submitted to Probit analysis. The suitability of the Probit analysis model for all the populations tested for the insecticides Chlorantraniliprole and B. thuringiensis was checked. However, it was verified that the model was not adequate for the field populations of Camocim de São Félix, Sairé, Lajedo and Bezerros when the Brilhante® (methylcarbamate oxine) insecticide was tested due to the low mortality caused by the insecticides in these populations. The population of Camocim de São Félix - PE, presented the highest Resistance Ratio (322.5 times) when compared to the population of Viçosa - MG for the insecticide Premio® (Chlorantraniliprole) at LD50. Field populations in the Agreste region of Pernambuco presented the highest LD50. Similar results were observed for the insecticide Dipel ® (Bacillus Thuringiensis var. Kurstaki), the population of Recife - PE being the most susceptible. Again, the population of Camocim de São Félix - PE followed by the population of Sairé showed the highest LD50s and the highest Resistance Ratios (4.26 and 2.59 times). In relation to the insecticide Brilhante®, it was verified that the population of Recife - PE (LD50 = 8.34 mL L-1) was more resistant than the population of Viçosa - MG (LD50 = 3.19 mL L-1). For the results of the behavioral parameters, it was verified that all the populations of diamondback moth evaluated had behavioral changes when exposed to the area treated with the insecticides. Thus, it was verified that the field populations of the insect pest presented significant levels of resistance for the insecticides Premio®, Brilhante® and Dipel®, in addition to changes in behavioral parameters that contribute to the reduction of insecticides efficacy.