Insecticide susceptibility of Euschistus heros (Heteroptera: Pentatomidae) in Brazil.

Euschistus heros (F.) (Heteroptera: Pentatomidae) is the most prevalent stink bug pest in Brazil, and populations can be difficult to manage using organophosphates or endosulfan. Because E. heros is difficult to rear in the laboratory, no baseline insecticide susceptibility data have been published. Therefore, we conducted dose-mortality studies using field-collected insects, and, using the results from the dose-mortality studies, we surveyed susceptibility to acephate, methamidophos, and endosulfan in populations from southern and central Brazil. In addition, esterase activity was evaluated among populations as these enzymes have been related to organophosphate resistance. Finally, newer chemistries were evaluated for E. heros population management in small-plot field studies. In the dose-mortality bioassays, variation in susceptibility to methamidophos and endosulfan among populations was significant, but the variation in susceptibility to acephate was not. The population from Londrina (at the Embrapa Soybean Research Station, northern Parana state) was among the most susceptible, whereas the population from Pedrinhas Paulista (southwestern Sao Paulo state) was among the least susceptible. Significant variation among populations was observed in esterase activity with the population from Pedrinhas Paulista having the highest esterase levels and the population from Londrina having among the lowest levels. To survey populations, we used the dose-mortality data for the Londrina population (because it was, consistently, one of the most susceptible populations) to estimate the insecticide concentration that killed 99% of the population (LC99). The corresponding doses were 5.9 microg (AI) of acephate adult(-1), 0.7 microg (AI) methamidophos adult(-1), and 1,600 microg (AI) endosulfan adult(-1). The survey data confirmed the data from the dose-mortality bioassays in that the population from Pedrinhas Paulista was identified as one of the least susceptible and the population from Londrina was one of the most susceptible. The field tests confirmed that older chemistries provided minimal control (< 50% control), whereas the products containing mixtures of pyrethroids and neonicotinoids provided better control (> 60%).

Insecticide resistance to endosulfan, monocrotophos and metamidophos in the neotropical brown stink bug, Euschistus heros (F. ) / Resistência do percevejo marrom Euschistus heros (F. ) aos inseticidas endosulfan, monocrotofós e metamidofós

As populações do percevejo marrom, Euschistus heros (F.), são normalmente controladas com inseticidas fosforados e ciclodienos (endossulfam). A ocorrência de casos de insucesso de E. heros, o percevejo mais comum nas regiões produtoras de soja do Paraná, São Paulo e da Região Central do Brasil, tem levado à investigação da resistência a esses inseticidas. Com essa finalidade foi avaliada a suscetibilidade de adultos provenientes de campos de soja, aos inseticidas endossulfam, monocrotofós e metamidofós. A população mais suscetível aos três inseticidas foi coletada em Londrina. A população mais resistente ao endossulfam (TR= 8,7) e ao metamidofós (TR= 2,7) foi proveniente de Pedrinhas Paulista (SP); para monocrotofós a população mais resistente foi coletada em Centenário do Sul (PR) (TR= 3,1). Percevejos E. heros provenientes de Toledo (PR) apresentaram níveis de suscetibilidade ao metamidofós comparáveis aos de Londrina (PR).

The Neotropical brown stink bug, Euschistus heros (F.), is usually controlled by organophosphate (OP) and cyclodiene (endosulfan) insecticides. Some unsuccessful control cases lead us to search for resistance to these insecticides in E. heros, the most common stink bug in the soybean growing regions of Paraná State, São Paulo State and Central Region of Brazil. Bioassays were performed with endosulfan, monocrotophos and metamidophos against adults. The most susceptible population was found in Londrina. Populations from Pedrinhas Paulista (SP) showed the highest resistance ratio (RR) to endosulfan (RR= 8.7) and metamidophos (RR=2.7); resistance to monocrotophos was detected on bugs from Centenário do Sul (PR) (RR= 3.1). Stink bugs collected from Toledo (PR), showed susceptibility to metamidophos comparable to those from Londrina.