Thrips are major agricultural pests throughout much of the United States. More information is needed about sampling methods, management practices, and insecticide susceptibility to help better control this pest. A two year survey was conducted to determine the species present in southeast Virginia and the population characteristics of those species. Thrips were monitored using yellow sticky traps. Tobacco thrips, Frankliniella fusca, were the most abundant species. In general thrips populations began to build up beginning in April, peaked in August, and then started to decline. Differences in this trend were observed between species. A study was conducted in seedling soybean to evaluate the within-plant location of thrips, whether a plant subsample could be used for thrips monitoring, and to determine the thrips species complex present. Soybean thrips, Neohydatothrips variabilis, were the most prominent species present. The greatest density of thrips larvae was located in the terminal bud of the seedling and suggests that immature thrips aggregate. Neither of the proposed subsamples of plant material explained the variability in immature thrips numbers and at this time we recommend whole-plant sampling for obtaining the most accurate estimate of thrips populations in seedling soybean. Tobacco thrips, F. fusca, as well as a complex of other thrips species attack cotton and peanut seedlings and can cause significant yield loss to these crops in the mid-Atlantic U.S. Experiments were conducted in these two crops to assess the efficacy of a novel diamide insecticide cyantraniliprole applied as a liquid in-furrow at planting and post-plant emergence broadcast spray treatment to control thrips. In both cropping systems cyantraniliprole significantly reduced the number of immature thrips and reduced thrips feeding injury to the plants. In several instances cyantraniliprole treatments resulted in increased yield as compared to the non-insecticide treated control and yields which were statistically similar to those obtained with standard thrips control insecticides. Laboratory bioassays were conducted to evaluate the toxicity (LC50 values) of cyantraniliprole and two conventional insecticides against F. fusca adults. Results of these assays were inconclusive. At times F. fusca adults were susceptible to the insecticides, but the results could not be replicated consistently. / Master of Science

O controle de Spodoptera frugiperda (J. E. Smith) tem sido realizado principalmente pelo uso de inseticidas químicos e plantas geneticamente modificadas que expressam toxinas de Bacillus thuringiensis Berliner (Bt) no Brasil. Casos de evolução da resistência no campo a estes agentes de controle têm sido uma das grandes ameaças para programas de MIP. Inseticidas diamidas ainda representam uma importante opção para o manejo de S. frugiperda; sendo assim, estudos que fomentem a implementação de estratégias pró-ativas de manejo da resistência são fundamentais para a manutenção da eficácia deste grupo químico no controle de S. frugiperda. Os objetivos da presente tese foram: (i) Monitorar a resistência de S. frugiperda a inseticidas diamidas no Brasil, utilizando métodos genotípico e fenotípico; (ii) Selecionar em laboratório uma linhagem de S. frugiperda resistente a inseticidas diamidas e caracterizar as bases genéticas da resistência; e (iii) Investigar os mecanismos associados à resistência de S. frugiperda a inseticidas diamidas. O método de F2 \"screen\" foi utilizada para o monitoramento genotípico da resistência de S. frugiperda ao inseticida chlorantraniliprole, sendo testadas 817 isolinhas provenientes de 14 populações brasileiras de S. frugiperda entre os anos agrícolas 2016 e 2017. Dentre as populações testadas, foi verificada uma variação de 0,0030 a 0,0781 na frequência de alelos que conferem resistência a chlorantraniliprole, com média geral de 0,0217. No monitoramento fenotípico, foram testadas ≈ 70 populações de S. frugiperda coletadas das principais regiões produtoras de milho durante os anos agrícolas 2016, 2017 e 2018. A sobrevivência larval para o inseticida chlorantraniliprole variou de 0,00 a 32,08% na concentração diagnóstica de 0,505 µg de chlorantraniliprole cm-2. Para o inseticida flubendiamide, as sobrevivências variaram de 0,00 a 46,25% na concentração diagnóstica de 2,842 µg de flubendiamide cm-2. Populações de S. frugiperda da Bahia, Mato Grosso, Mato Grosso do Sul e Goiás apresentaram as menores suscetibilidades a chlorantraniliprole e flubendiamide. Os valores de CL50 das linhagens suscetível (Sus) e resistente a chlorantraniliprole (Chlorant-R) foram 0,011 e 2,610 µg i.a.cm-2, respectivamente, com razão de resistência (RR) de ≈ 240 vezes. A herança da resistência de S. frugiperda a chlrontraniliprole foi caracterizada como autossômica, incompletamente recessiva e monogênica. A linhagem resistente a chlorantraniliprole apresentou moderada resistência cruzada para cyantraniliprole (RR ≈ 27 vezes) e muito alta para flubendiamide (RR > 42000 vezes). A pré-exposição a diferentes sinergistas inibidores de enzimas de detoxificação não aumentou significativamente a suscetibilidade larval, sugerindo que a resistência metabólica não está envolvida na resistência de S. frugiperda a diamidas. Mediante sequenciamento da região C-terminal dos receptores de rianodina (RyR) nos domínios II a IV, foi detectada a mutação I4734M que foi recentemente descrita como um dos mecanismos de resistência devido à alteração no alvo de ação de inseticidas diamidas em outras pragas de Lepidoptera. Os resultados obtidos no presente trabalho servirão para a implementação de estratégias efetivas de manejo da resistência para preservar a vida útil de diamidas para o manejo de S. frugiperda no Brasil. / The control of Spodoptera frugiperda (J. E. Smith) has been performed mainly by the use of insecticides and genetically modified plants expressing Bacillus thuringiensis Berliner (Bt) toxins in Brazil. Field-evolved resistance to these control agents represents a major threat in IPM programs. Diamide insecticides represent an important tool for managing S. frugiperda; therefore, studies that promote proactive resistance management strategies are important to prolong the lifetime of this chemical group to control S. frugiperda. The goals of this dissertation were: (i) To monitor S. frugiperda resistance to diamide insecticides in Brazil, using genotypic and phenotypic methods; (ii) To select a resistant strain of S. frugiperda to diamide insecticides under laboratory conditions and to characterize the genetic basis of resistance; and (iii) to investigate the resistance mechanisms of S. frugiperda to diamides insecticides. The F2 screen method was used to genotypic monitoring of S. frugiperda resistance to chlorantraniliprole resistance by testing 817 isofamilies from 14 Brazilian populations of S. frugiperda collected in 2016 and 2017 crop seasons. Among the populations tested, resistance allelic frequency to chlorantraniliprole ranged from 0.0030 to 0.0781, with overall average of 0.0217. In the phenotypic monitoring, we monitored ≈ 70 populations of S. frugiperda collected from major maize-growing regions during the crop seasons 2016, 2017 and 2018. The larval survival for chlorantraniliprole insecticide ranged from 0.00 to 32.08% at diagnostic concetration of 0.505 µg chlorantraniliprole cm-2 and 0.00 to 46.25% for flubendiamide at diagnostic concentration of 2.842 µg flubendiamide cm-2. Populations of S. frugiperda from Bahia, Mato Grosso, Mato Grosso do Sul and Goiás showed the lowest susceptibilities to chlorantraniliprole and flubendiamide. The LC50 values of the susceptible (Sus) and chlorantraniliprole-resistant (Chlorant-R) strains were 0.011 and 2.610 µg i.a. cm-2, respectively, with a resistance ratio (RR) of ≈ 240-fold. The inheritance of chlorantraniliprole resistance in S. frugiperda was characterized as autosomal, incompletely recessive and monogenic. The chlorantraniliprole-resistant strain showed moderate cross-resistance to cyantraniliprole (RR ≈ 27-fold) and high cross-resistance to flubendiamide (RR > 42,000-fold). Pre-exposure to different synergists known to inhibit detoxification enzymes did not result in significantly increased larval toxicity, suggesting a minor role of metabolic resistance. Sequencing of the FAW ryanodine receptor (RyR) C-terminal domains II to VI revealed a SNP, resulting in a I4734M mutation recently described to confer target-site resistance to diamides in lepidopteran pests. The results obtained herein will help for the implementation of effective resistance management strategies to preserve the lifetime of diamides to manage S. frugiperda in Brazil.

This research investigated the phenology of the striped flea beetle (Phyllotreta striolata (Fabricius) (SFB) and crucifer flea beetle (Phyllotreta cruciferae (Goeze)) (CFB), and examined the efficacy and the persistence of biological activity of the reduced-risk insecticides cyantraniliprole, clothianidin, and thiamethoxam applied as seed treatments to spring canola. Yellow sticky cards were placed around field perimeters in order to assess if CFB and SFB have synchronous phenology. It was found that CFB and SFB have largely asynchronous populations in southern Ontario. In laboratory bioassays, while flea beetle control with cyantraniliprole was comparable to that provided by thiamethoxam or clothianidin at the cotyledon stage, control did not persist through the 1st and 2nd leaf stages. Thiamethoxam and clothianidin both provided moderate control of flea beetles in both 1st and 2nd leaves. Field studies suggested that cyantraniliprole may offer control of flea beetles comparable to that provided by thiamethoxam and clothianidin. / E.I. DuPont Canada Co.