Acute-Contact and Chronic-Systemic In Vivo Bioassays: Regional Monitoring of Susceptibility to Thiamethoxam in Soybean Aphid (Hemiptera: Aphididae) Populations From the North Central United States

The risks associated with soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in the North Central soybean systems has fostered the adoption of prophylactic chemical control practices, such as planting seeds treated with neonicotinoid insecticides, especially thiamethoxam. Consequently, there is a concern that increased selection pressure imposed on the arthropod–pest complex by this insecticide may lead to resistance. Therefore, in vivo bioassays were conducted to determine the susceptibility of soybean aphid to thiamethoxam among North Central U.S. populations. Concentration-mortality data were collected using contact glass-vial and detached-leaf systemic bioassays. The results of these experiments indicate that both bioassays were reliable to detect shifts in susceptibility between different soybean aphid clones. The LC50s of field populations of soybean aphid were significantly different when mortality was recorded in contact and systemic exposure assays. Nevertheless, the magnitude of the resistance ratios was consistent in both methods. In addition, a significant increase in the LC50 and EC50 values was observed among field populations tested in detached-leaf systemic bioassays. These results represent the first extensive efforts to identify the variability in susceptibility of soybean aphid to thiamethoxam in the North Central United States Therefore, our results provide a baseline for future assessment and contribute to a better understanding of the applicability of in vivo bioassays for susceptibility monitoring and resistance detection of soybean aphid to thiamethoxam

Acute-Contact and Chronic-Systemic In Vivo Bioassays: Regional Monitoring of Susceptibility to Thiamethoxam in Soybean Aphid (Hemiptera: Aphididae) Populations From the North Central United States

The risks associated with soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in the North Central soybean systems has fostered the adoption of prophylactic chemical control practices, such as planting seeds treated with neonicotinoid insecticides, especially thiamethoxam. Consequently, there is a concern that increased selection pressure imposed on the arthropod–pest complex by this insecticide may lead to resistance. Therefore, in vivo bioassays were conducted to determine the susceptibility of soybean aphid to thiamethoxam among North Central U.S. populations. Concentration-mortality data were collected using contact glass-vial and detached-leaf systemic bioassays. The results of these experiments indicate that both bioassays were reliable to detect shifts in susceptibility between different soybean aphid clones. The LC50s of field populations of soybean aphid were significantly different when mortality was recorded in contact and systemic exposure assays. Nevertheless, the magnitude of the resistance ratios was consistent in both methods. In addition, a significant increase in the LC50 and EC50 values was observed among field populations tested in detached-leaf systemic bioassays. These results represent the first extensive efforts to identify the variability in susceptibility of soybean aphid to thiamethoxam in the North Central United States Therefore, our results provide a baseline for future assessment and contribute to a better understanding of the applicability of in vivo bioassays for susceptibility monitoring and resistance detection of soybean aphid to thiamethoxam

Suscetibilidade de adultos de \u3ci\u3eBemisia tabaci\u3c/i\u3e biótipo B a inseticidas

A associação de alguns vírus fitopatogênicos com seus vetores pode ou não alterar a ação do controle químico. Este trabalho objetivou avaliar a suscetibilidade de moscas-brancas virulíferas (com aquisição do begomovírus Tomato severe rugose virus, ToSRV) e avirulíferas (sem aquisição do ToSRV) aos principais inseticidas registrados para o seu controle na cultura do tomateiro. Foram realizados ensaios com plantas de tomateiro e discos foliares de feijão- -de-porco. Os tratamentos foram arranjados em esquema fatorial de 7 (seis inseticidas + controle) e de 5 (quatro inseticidas + controle) x 2 [mosca-branca (MB) virulífera (V) ou avirulífera (AV)] e dispostos no delineamento em blocos ao acaso com seis e 25 repetições para o tomateiro e feijão-de-porco, respectivamente. Os inseticidas e concentrações avaliados foram: a) tomateiro: acefato (100 g), clotianidina (20 g), pimetrozina (40 g), piriproxifem (75 mL) e tiametoxam (20 g de i.a./100 L de calda) e diafentiurom (800 g de i.a./300 L de calda); b) feijão-de-porco: acefato (100 g), tiametoxam (20 g), pimetrozina (40 g de i.a./100 L) e diafentiurom (800 g de i.a./300 L de calda). Não houve diferença na suscetibilidade do vetor em razão de sua condição (V ou AV). Os inseticidas diafentiurom (87,68%±4,96) e tiametoxam (43,95%±9,43) proporcionaram maior mortalidade de MB no tomateiro, enquanto no feijão-de-porco diafentiurom (92,01%±2,68) e tiametoxam (86,39%±2,74) apresentaram desempenho similar. Diafentiurom foi o único inseticida que proporcionou controle satisfatório de B. tabaci em ambos os ensaios avaliados. The association between some plant pathogenic viruses and their vectors may or may not alter the action of chemical control. This study aimed at evaluating the susceptibility of viruliferous (transmitter of the begomovirus Tomato severe rugose virus, ToSRV) and aviruliferous (non-transmitter of ToSRV) Bemisia tabaci biotype B to the main insecticides registered to its control in tomato crops. Two sets of experiments were carried out with tomato plants and foliar discs of jack beans. The treatments were schemed in a factorial design of 7 (six insecticides + control) and 5 (four insecticides + control) x 2 [viruliferous (V) or aviruliferous (AV) whiteflies (WF)] and arranged in completely randomized blocks design with six and 25 replications, respectively, for tomato and jack beans. The following insecticides and concentrations were evaluated: a) tomato: acephate (100 g), clothianidin (20 g), pymetrozine (40 g), pyriproxyfen (75 mL) and thiametoxan (20 g of a.i./100 L), and diafenthiuron (800 g of a.i./300 L of solution); b) jack beans: acephate (100 g), thiametoxan (20 g), pymetrozine (40 g of a.i./100 L) and diafenthiuron (800 g of a.i./300 L). The insecticide susceptibility of whiteflies was not altered by their viruliferous condition (V or AV). The insecticides diafenthiuron (87.68%±4.96) and thiametoxam (43.94%±9.43) caused the highest mortality of whiteflies in tomatoes. In jack beans, diafenthiuron (92.01%±2.68) and thiametoxam (86,39%±2,74) caused similar mortality. Among the tested insecticides, diafenthiuron was the only one causing significant mortality of B. tabaci biotype B

Suscetibilidade de adultos de \u3ci\u3eBemisia tabaci\u3c/i\u3e biótipo B a inseticidas

A associação de alguns vírus fitopatogênicos com seus vetores pode ou não alterar a ação do controle químico. Este trabalho objetivou avaliar a suscetibilidade de moscas-brancas virulíferas (com aquisição do begomovírus Tomato severe rugose virus, ToSRV) e avirulíferas (sem aquisição do ToSRV) aos principais inseticidas registrados para o seu controle na cultura do tomateiro. Foram realizados ensaios com plantas de tomateiro e discos foliares de feijão- -de-porco. Os tratamentos foram arranjados em esquema fatorial de 7 (seis inseticidas + controle) e de 5 (quatro inseticidas + controle) x 2 [mosca-branca (MB) virulífera (V) ou avirulífera (AV)] e dispostos no delineamento em blocos ao acaso com seis e 25 repetições para o tomateiro e feijão-de-porco, respectivamente. Os inseticidas e concentrações avaliados foram: a) tomateiro: acefato (100 g), clotianidina (20 g), pimetrozina (40 g), piriproxifem (75 mL) e tiametoxam (20 g de i.a./100 L de calda) e diafentiurom (800 g de i.a./300 L de calda); b) feijão-de-porco: acefato (100 g), tiametoxam (20 g), pimetrozina (40 g de i.a./100 L) e diafentiurom (800 g de i.a./300 L de calda). Não houve diferença na suscetibilidade do vetor em razão de sua condição (V ou AV). Os inseticidas diafentiurom (87,68%±4,96) e tiametoxam (43,95%±9,43) proporcionaram maior mortalidade de MB no tomateiro, enquanto no feijão-de-porco diafentiurom (92,01%±2,68) e tiametoxam (86,39%±2,74) apresentaram desempenho similar. Diafentiurom foi o único inseticida que proporcionou controle satisfatório de B. tabaci em ambos os ensaios avaliados. The association between some plant pathogenic viruses and their vectors may or may not alter the action of chemical control. This study aimed at evaluating the susceptibility of viruliferous (transmitter of the begomovirus Tomato severe rugose virus, ToSRV) and aviruliferous (non-transmitter of ToSRV) Bemisia tabaci biotype B to the main insecticides registered to its control in tomato crops. Two sets of experiments were carried out with tomato plants and foliar discs of jack beans. The treatments were schemed in a factorial design of 7 (six insecticides + control) and 5 (four insecticides + control) x 2 [viruliferous (V) or aviruliferous (AV) whiteflies (WF)] and arranged in completely randomized blocks design with six and 25 replications, respectively, for tomato and jack beans. The following insecticides and concentrations were evaluated: a) tomato: acephate (100 g), clothianidin (20 g), pymetrozine (40 g), pyriproxyfen (75 mL) and thiametoxan (20 g of a.i./100 L), and diafenthiuron (800 g of a.i./300 L of solution); b) jack beans: acephate (100 g), thiametoxan (20 g), pymetrozine (40 g of a.i./100 L) and diafenthiuron (800 g of a.i./300 L). The insecticide susceptibility of whiteflies was not altered by their viruliferous condition (V or AV). The insecticides diafenthiuron (87.68%±4.96) and thiametoxam (43.94%±9.43) caused the highest mortality of whiteflies in tomatoes. In jack beans, diafenthiuron (92.01%±2.68) and thiametoxam (86,39%±2,74) caused similar mortality. Among the tested insecticides, diafenthiuron was the only one causing significant mortality of B. tabaci biotype B

Acute-Contact and Chronic-Systemic In Vivo Bioassays: Regional Monitoring of Susceptibility to Thiamethoxam in Soybean Aphid (Hemiptera: Aphididae) Populations From the North Central United States

The risks associated with soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in the North Central soybean systems has fostered the adoption of prophylactic chemical control practices, such as planting seeds treated with neonicotinoid insecticides, especially thiamethoxam. Consequently, there is a concern that increased selection pressure imposed on the arthropod–pest complex by this insecticide may lead to resistance. Therefore, in vivo bioassays were conducted to determine the susceptibility of soybean aphid to thiamethoxam among North Central U.S. populations. Concentration-mortality data were collected using contact glass-vial and detached-leaf systemic bioassays. The results of these experiments indicate that both bioassays were reliable to detect shifts in susceptibility between different soybean aphid clones. The LC50s of field populations of soybean aphid were significantly different when mortality was recorded in contact and systemic exposure assays. Nevertheless, the magnitude of the resistance ratios was consistent in both methods. In addition, a significant increase in the LC50 and EC50 values was observed among field populations tested in detached-leaf systemic bioassays. These results represent the first extensive efforts to identify the variability in susceptibility of soybean aphid to thiamethoxam in the North Central United States Therefore, our results provide a baseline for future assessment and contribute to a better understanding of the applicability of in vivo bioassays for susceptibility monitoring and resistance detection of soybean aphid to thiamethoxam