Ethological aspects of Helicoverpa armigera in the reproductive phase of cotton

Pest behavior studies are important to inform the periods when the pest is more exposed to pesticide. This study aimed to evaluate the movement and feeding of Helicoverpa armigera larvae in the first three instars during the reproductive phase of cotton. First, larval behavior was evaluated with a completely randomized design in a 3 × 5 factorial design with eight replications. The treatments were the instars versus behaviors (crawling, resting, waving, eating and dropping-off). In addition, another 3 × 6 factorial design with eight replications was performed to evaluate the plant region most preferred by the caterpillars. The treatments were the instars versus six parts of the plant (abaxial surface, adaxial surface, on floral bud, internal surface of bract, petiole, and terminal growth). Then, the period of the day when caterpillars are more active was also evaluated by a 3 × 2 factorial essay. The treatments were the instars versus periods of the day. Eating and resting are the most frequent behaviors for all instars. The plant regions preferred by the caterpillars for crawling are on the floral bud and the adaxial face of the leaf. There is no preferred period of the day for eating, resting, waving or dropping-off. Caterpillars (until the third instar) prefer to walk in the morning and other behaviors can occur at any period. Therefore, sprays should preferably occur in the morning, and the insecticide drops/spray should reach the flower buds and the adaxial surface of the leaves to contaminate the larvae.

Economic survey to support control decision for old world bollworm on processing tomatoes

Helicoverpa armigera (Hübner) regularly requires quick deployment of control practices due to its potential of causing yield loss of processing tomatoes. The monitoring of H. armigera adults using stick traps lured with sex pheromone was correlated to egg densities, larvae, and percentage of damaged fruits, aiming to subsidize control decisions only using the number of males caught in the traps since surveying pest stages or damaged fruits is laborious and costly. Surveys were carried out on 11 tomato fields (ca. 80 to 120 hectares each) for processing during the 2015 and 2016 crop seasons. The survey was initiated at the flowering stage with traps set up along the field borders 100 m distant each. Evaluations of adult male capture in the traps were conducted twice a week for 14 and 10 weeks during the 2015 and 2016 seasons, respectively. Simultaneously, 70 tomato plants were fully inspected for eggs, larvae, and damaged fruits per area using a rate of 10 plants per point of trap setting in each area. Overall capture of male moths correlated to subsequent eggs, larvae, and damaged fruits. Based on the outcome of the regression analysis between male moths captured and percentage of damaged fruits, the control decision is suggested when three to six male moths are captured per trap during one week. The monitoring of adults using pheromone traps help deploy chemical or biological control methods to restrain H. armigera population reaching economic threshold levels.

Economic survey to support control decision for old world bollworm on processing tomatoes

Helicoverpa armigera (Hübner) regularly requires quick deployment of control practices due to its potential of causing yield loss of processing tomatoes. The monitoring of H. armigera adults using stick traps lured with sex pheromone was correlated to egg densities, larvae, and percentage of damaged fruits, aiming to subsidize control decisions only using the number of males caught in the traps since surveying pest stages or damaged fruits is laborious and costly. Surveys were carried out on 11 tomato fields (ca. 80 to 120 hectares each) for processing during the 2015 and 2016 crop seasons. The survey was initiated at the flowering stage with traps set up along the field borders 100 m distant each. Evaluations of adult male capture in the traps were conducted twice a week for 14 and 10 weeks during the 2015 and 2016 seasons, respectively. Simultaneously, 70 tomato plants were fully inspected for eggs, larvae, and damaged fruits per area using a rate of 10 plants per point of trap setting in each area. Overall capture of male moths correlated to subsequent eggs, larvae, and damaged fruits. Based on the outcome of the regression analysis between male moths captured and percentage of damaged fruits, the control decision is suggested when three to six male moths are captured per trap during one week. The monitoring of adults using pheromone traps help deploy chemical or biological control methods to restrain H. armigera population reaching economic threshold levels.(AU)

Danos da lagarta Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) em plântulas de soja / Damage caused by caterpillar of Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) to soybean seedlings

A soja está sujeita ao ataque da lagarta Helicoverpa armigera durante todo seu ciclo. Quando na fase inicial, pode comprometer o estabelecimento da cultura no campo. Esse estudo teve por objetivo avaliar os danos da lagarta em plântulas de soja, para isso, utilizou-se o delineamento experimental em blocos casualizados com cinco repetições. Os tratamentos foram cinco níveis de infestação: 0, 7, 14, 21 e 28 lagartas m-2. A infestação ocorreu no estádio fenológico cotiledonar (VC) utilizando lagartas de quinto ínstar, e, durante três dias, foram avaliados os danos causados nas hastes, cotilédones e folhas unifolioladas. Já ao final do experimento avaliou-se a altura de plantas, a biomassa e o estande final. Houve danos nas três estruturas vegetativas avaliadas e, em geral, o aumento da população do inseto promoveu aumento no nível de danos, reduzindo o estande, a altura e a biomassa das plântulas de soja. Conclui-se que a lagarta H. armigera causa danos severos às plântulas de soja, o que pode afetar o estabelecimento inicial da cultura.

Soybean plants are susceptible to the attack of Helicoverpa armigera caterpillars throughout their cycle, including during early developmental stages, which can compromise their settling in the field. This study aimed to assess the damage caused by caterpillars to soybean seedlings. A randomized block design with five replicates was used and the treatments consisted of five levels of infestation: 0, 7, 14, 21 and 28 caterpillars/m-2. The infestation occurred in the cotyledon stage (VC), using fifth instar caterpillars. For three days, all damage caused to the stem, cotyledon, and unifoliates was evaluated. By the end of the experiment, seedling height, biomass, and the final stand value were determined. Damage was observed in the three vegetative structures and, in general, increase in insect population promoted higher levels of damage, reducing stand, height, and biomass of seedlings significantly. Thus, H. armigera caterpillars cause severe damage to soybean seedlings, which may affect their early establishment.

Danos da lagarta Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) em plântulas de soja / Damage caused by caterpillar of Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) to soybean seedlings

A soja está sujeita ao ataque da lagarta Helicoverpa armigera durante todo seu ciclo. Quando na fase inicial, pode comprometer o estabelecimento da cultura no campo. Esse estudo teve por objetivo avaliar os danos da lagarta em plântulas de soja, para isso, utilizou-se o delineamento experimental em blocos casualizados com cinco repetições. Os tratamentos foram cinco níveis de infestação: 0, 7, 14, 21 e 28 lagartas m-2. A infestação ocorreu no estádio fenológico cotiledonar (VC) utilizando lagartas de quinto ínstar, e, durante três dias, foram avaliados os danos causados nas hastes, cotilédones e folhas unifolioladas. Já ao final do experimento avaliou-se a altura de plantas, a biomassa e o estande final. Houve danos nas três estruturas vegetativas avaliadas e, em geral, o aumento da população do inseto promoveu aumento no nível de danos, reduzindo o estande, a altura e a biomassa das plântulas de soja. Conclui-se que a lagarta H. armigera causa danos severos às plântulas de soja, o que pode afetar o estabelecimento inicial da cultura.(AU)

Soybean plants are susceptible to the attack of Helicoverpa armigera caterpillars throughout their cycle, including during early developmental stages, which can compromise their settling in the field. This study aimed to assess the damage caused by caterpillars to soybean seedlings. A randomized block design with five replicates was used and the treatments consisted of five levels of infestation: 0, 7, 14, 21 and 28 caterpillars/m-2. The infestation occurred in the cotyledon stage (VC), using fifth instar caterpillars. For three days, all damage caused to the stem, cotyledon, and unifoliates was evaluated. By the end of the experiment, seedling height, biomass, and the final stand value were determined. Damage was observed in the three vegetative structures and, in general, increase in insect population promoted higher levels of damage, reducing stand, height, and biomass of seedlings significantly. Thus, H. armigera caterpillars cause severe damage to soybean seedlings, which may affect their early establishment.(AU)

DESEMPENHO BIOLÓGICO EM FUNÇÃO DO ALIMENTO E SENSIBILIDADE A INSETICIDAS EM TRATAMENTO DE SEMENTES DE SOJA DA LAGARTA Helicoverpa armigera

H. armigera (Lepidoptera: Noctuidae: Heliothinae) é uma espécie extremamente polífaga, que pode causar danos a diferentes culturas de importância econômica. Na cultura da soja, pode ser tanto praga inicial, atacando cotilédones, brotos e folhas, como, mais tarde, consumir legumes e sementes. Conhecimentos sobre o desempenho biológico da espécie em diferentes plantas hospedeiras e a eficiência do tratamento de sementes com inseticidas e de genótipos Bt são importantes com vistas ao manejo dessa praga, na cultura da soja. Objetivou-se avaliar a influência do alimento (espécies vegetais) consumido pela forma jovem em atributos biológicos de lagartas e de pupas e o potencial de inseticidas aplicados em tratamento de sementes e da proteína Cry 1Ac para controle da praga, em soja. Foram conduzidos quatro experimentos em câmara climatizada (25 ± 2 ºC; 60 ± 10% UR; 12 h de fotofase) no laboratório de entomologia da Faculdade de Agronomia e Medicina Veterinária, da Universidade de Passo Fundo, em Passo Fundo, RS. Constatou-se que o alimento influencia na sobrevivência, na duração, no número de ínstares e consumo da fase larval de H. armigera. Lagartas neonatas e lagartas de 3º- 4ºínstar apresentam, respectivamente, sensibilidade ao inseticida clorantraniliprole em tratamento de sementes (62,5 mL/100 kg) até 13 dias e 8 dias, após a emergência das plantas de soja. Lagartas de ambos tamanhos apresentam sensibilidade à proteína Cry 1Ac pelo menos até 21 dias após a emergência das plantas de soja Bt.

H. armigera (Lepidoptera: Noctuidae: Heliothinae) is an extremely polyphagous species, which can cause damage to various crops of economic importance. In soybean, can be both initial pest, attacking cotyledons, shoots and leaves, as, later consume vegetables and seeds. Knowledge of the biological performance of the species in different host plants and the efficiency of seed treatment with insecticides and Bt genotypes are important with a view to the management of this pest, in soybean crop. The objective of this study was to evaluate the influence of food (plant species) consumed by young form in biological attributes of caterpillars and pupae and the potential of insecticides applied in seed treatment and protein Cry 1AC for pest control in soybeans. Four experiments were conducted in climatic chamber (25 ± 2°C; 60 ± 10% RH, 12h photoperiod)in entomology laboratory of the Faculdade de Agronomia e Medicina Veterinária, da Universidade de Passo Fundo, Passo Fundo, RS. It was found that food influences on survival, the duration, and the number of instars and consumption of the larval stage of H. armigera. Neonate caterpillars and 3rd- 4th instar caterpillars present, respectively, sensitivity clorantraniliprole insecticide for seed treatment (62,5 mL/100 kg) up to 13 days and 8 days after emergence of soybean plants. Caterpillar of both sizes feature sensitivity to the protein Cry 1Ac at least until 21 days after the emergence of Bt soybean plants.