The present study aimed to evaluate changes in the locomotor activity of diamondback moth (Plutella xylostella) populations exposed to surfaces treated with the insecticide chlorantraniliprole under laboratory conditions. Diamondback moth populations from municipalities incorrectly using the insecticide [Camocim de São Félix, PE (CSF); Sairé, PE (SR); and Lajedo, PE (LJ)] and two laboratory populations from Recife, PE (RCF), and Viçosa, MG (VÇS) were exposed to dry insecticide residues in increasing concentrations. The following behavioral parameters of the populations were analyzed: walking time (WT), mean walking speed (MWS), and rest time (RT). Regarding RT, the SR and CSF populations demonstrated a behavior of irritability and increased WT with increased exposure concentration. The RCF population presented a contrasting response. The MWS values in the SR and CSF populations showed a decreasing trend with increased exposure concentration. The LJ and RCF populations showed no changes in terms of MWS. The RT values in the SR population decreased with increased insecticide concentration. In general, the SR and CSF populations presented a behavioral pattern different from that of laboratory populations. The changes in locomotor activity observed may result in lower control efficacy of the insecticide due to repellency or escape of insects. Regarding the effect of insecticide concentrations used in the populations, a defined pattern was not observed, and the effect alternated between an increase, a decrease, and an undefined pattern for the variables studied.

Plutella xylostella cause severe damage on cruciferous plants all over the world. Farmers in several regions of Brazil report increasing inefficiency of chemical control, even when using high insecticide concentrations. We evaluate here the susceptibility of brazilian diamondback moth populations to the Premio® (Chlorantraniliprole), Dipel® (Bacillus thuringiensis var. kurstaki) and Lannate® BR (Oxime Methylcarbamate) insecticides, frequently used in Brazil. Susceptibility bioassays with five field-collected and two laboratory diamondback moth populations were conducted with increasing concentrations of insecticides up to ten times above the recommended concentration. Extremely high and region-dependent resistances were found in field populations against Chlorantraniliprole and B. thuringiensis, with Resistance Ratios up to 370.0 times for the Camocim de São Felix population. For Oxime Methylcarbamate, we were not able to do Probit analyses for the field populations because of very low mortality rates. Laboratory populations showed resistance to the three tested insecticides with all LC50 concentrations exceeding the recommended doses by at least 3 times. Our results show strong and variable resistance to the three tested insecticides according to the region of origin. To maintain efficient pest control in a large country like Brazil, local levels of resistance need therefore to be monitored by the authorities and reassessment and adjustments of regional doses of insecticides should be implemented as a public policy, to prevent massive spread of insecticides in the field, as well as increases in cases of resistance.

Os insetos herbívoros tem desenvolvido uma série de respostas comportamentais para os inseticidas utilizados nos sistemas agrícolas. O presente estudo teve por objetivo averiguar alterações comportamentais de populações de traça-das-crucíferas expostas a áreas tratadas com o inseticida Metilcarbamato de oxina. Populações de Plutella xylostella provenientes dos municípios de Camocim de São Félix–PE (CSF), Sairé–PE (SR), Lajedo–PE (LJ) eduas populações de laboratório: Recife–PE (RCF) e Viçosa–MG (VÇS) foram expostas a resíduos secos do inseticida, em doses crescentes. Estas populações tiveram os parâmetros comportamentais analisados (Distância de caminhamento (DC),Tempo de caminhamento (DC), Velocidade Média (VM), Número de paradas (NP) e Tempo de Repouso (TR)). Em relação a DC, as populações de SR, CSF, LJ e VÇS não apresentaram padrão claro de redução ou aumento da DC. A população de RCF não apresentou alteração da DC e diferiu estatisticamente entre áreas estudadas. Em relação ao parâmetro TC, a população de SR apresentou aumento deste parâmetro, RCF diminuiu e as demais populações não demonstraram padrão definido. Para o Parâmetro VM, se verificou redução desta nas populações de SR e CSF, e aumento da VM na população de RCF. Para a variável do TR, as populações de LJ, VSÇ e CSF não apresentaram padrão definido, logo, a população do RCF aumentou e SR reduziu tal parâmetro. As alterações resultantes das respostas comportamentais dos insetos a áreas tratadas com inseticidas contribuem para uma menor eficácia de controle desempenhada pelos inseticidas, uma vez que estes vãos se exporem menos a concentrações letais.