ABSTRACT
The first detection of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Brazil pointed to a gloomy future for South American agriculture in the 2012/2013 harvest, and insecticide sales increased exponentially during 2013 and 2014. However, after this outbreak, the population of this insect returned to manageable levels. This study documents data on H. armigera moth collection using light traps during the outbreak in two locations: (a) western region of the state of Bahia, including population levels of H. armigera and main noctuid pests during the big outbreak (February and March 2013); (b) Federal District, including monthly data for five growing seasons (July 2012-June 2017). During the outbreak, an average of 527.3 moths were collected per trap (cotton crop, March) in the western region of Bahia each night, while the maximum average in the Federal District was 75.4 moths (January). The number of moths decreased in the following growing seasons, and in October 2016, the maximum number was 2.8 moths per trap. Aspects related to the variations of H. armigera and Helicoverpa zea (Boddie) populations, including the study of phenology and relationship with climatic factors and Oceanic Niño Index, were analyzed and discussed. All aspects are approached to contribute to the management of lepidopteran pests, especially H. armigera, in the productive systems of the Brazilian Cerrado.
Subject(s)
Agriculture , Moths , Animals , Brazil , Pest Control , Population Density , SeasonsABSTRACT
The identification of factors responsible for the population dynamics is fundamental for pest management, since losses can reach 18% of annual production. Besides regular seasonal environmental factors and crop managements, additional supra-annual meteorological phenomena can also affect population dynamics, although its relevance has been rarely investigated. Among crop pests, Spodoptera stands out due to its worldwide distribution, high degree of polyphagy, thus causing damages in several crops in the world. Aiming to distinguish the relevance of different factors shaping population dynamics of Spodoptera in an ecosystem constituted of dry and rainy seasons, the current study used circular statistics to identify phenological patterns and test if its population fluctuation is driven by El Niño-Southern Oscillation (ENSO) effect, seasonal meteorological parameters, and/or host plant availability. Samplings were done in an intercropping system, in the Brazilian Savanna, during the new moon cycles between July/2013 and June/2016. Species were recorded all year round, but demonstrated differently non-uniform distribution, being concentrated in different seasons of the year. Population fluctuations were mostly affected by the ENSO intensity, despite the contrasting seasonal meteorological variation or host plant availability in a 400-m radius. Studies involving the observation of supra-annual phenomena, although rare, reach similar conclusions in relation to Neotropical insect fauna. Therefore, it is paramount to have long-term sampling studies to obtain a more precise response of the pest populations towards the agroecosystem conditions.
Subject(s)
El Nino-Southern Oscillation , Seasons , Spodoptera , Animals , Brazil , Crops, Agricultural/parasitology , Grassland , Population DynamicsABSTRACT
ABSTRACT: Natural biological control is one of the major causes responsible for reduction of pest population in agricultural ecosystem. However, natural biological control importance is usually minimized by not being estimated. This study reports the occurrence of Campoletis sonorensis (Cameron, 1886) (Hymenoptera: Ichneumonidae), Archytas marmoratus (Townsend, 1915) and Archytas incertus (Macquart, 1851) (Diptera: Tachinidae) associated with Helicoverpa armigera (Hübner, 1809) (Lepidoptera: Noctuidae). The rate of larval parasitism was up to 41% in structured refuge areas of cotton, without chemical control with insecticides. This study strengthens our knowledge relating to parasitoids associated with natural control of H. armigera in the American continent. In addition, it documents the rule that structured refuge areas could play as a source of natural enemies, besides their contribution to production of non-selective populations to Bt technology.
RESUMO: O controle biológico natural é um dos principais componentes responsáveis pela redução populacional de pragas em agroecossistemas. Entretanto, a importância do controle biológico natural, usualmente, é minimizada devido não ser estimada. Este estudo documenta a ocorrência de Campoletis sonorensis (Cameron, 1886) (Hymenoptera: Ichneumonidae), Archytas marmoratus (Townsend, 1915) e Archytas incertus (Macquart, 1851) (Diptera: Tachinidae) associados a Helicoverpa armigera (Hübner, 1809) (Lepidoptera: Noctuidae). A taxa de parasitismo larval foi superior a 41% em áreas de refúgio estruturado de algodão, sem uso de inseticidas químicos. Este estudo fortalece o conhecimento relacionado com os parasitoides associados ao controle natural de H. armigera no Continente Americano. Adicionalmente, documenta o efeito que áreas de refúgio estruturado podem desempenhar como fonte de inimigos naturais, além da sua contribuição para produzir insetos não expostos à tecnologia Bt.
ABSTRACT
ABSTRACT: Given the increasing importance of Elaphria agrotina (Guenée) (Lepidoptera: Noctuidae) in corn crops, especially in the Brazilian Savannah biome, the present research aimed to study its development and survival on Greene's and Poitout & Bues's artificial diets (25±1°C, 70±10% relative humidity [RH] and 12h photophase). Poitout & Bues's diet was more suitable than Greene's diet, providing higher survival percent (77.51% vs. 5.57%), lower development time (49.81 days vs. 55.24 days) and higher fecundity (167.65 vs. 84.9 eggs), respectively. All the caterpillars reared on Poitout & Bues's diet passed through six instars, while almost half of the larvae reared on Greene's diet went through one less instar stage. Regarding the main reproductive parameters, higher average time of generation (T) and lower values of net rates of reproduction (Ro), and increased (rm) intrinsic and finite reason of increase (λ), were observed for larvae reared on Greene's diet. Results presented in this study indicated that Poitout & Bues's diet is more suitable for maintenance of colonies of E. agrotina as compared to Greene's diet.
RESUMO: Com a crescente importância de Elaphria agrotina (Guenée) (Lepidoptera: Noctuidae) em cultivos de milho, especialmente no Bioma Cerrado, o presente trabalho objetivou comparar o seu desenvolvimento e sobrevivência em dieta artificial de Greene e Poitout & Bues (25±1ºC, 70±10% umidade relativa [UR] e fotofase de 12h). A dieta de Poitout & Bues foi mais adequada que a dieta de Grenne, proporcionando maior sobrevivência (77.51% e 5.57%), menor tempo de desenvolvimento (49.81 dias e 55.24 dias) e maior fecundidade (167.65 ovos e 84.9 ovos), respectivamente. Todas as lagartas alimentadas com dieta de Poitout & Bues passaram por seis instares, enquanto que praticamente metade das provenientes da dieta de Greene passou por um instar a menos. Lagartas alimentadas com dieta de Greene, apresentaram maior valor do tempo médio de cada geração (T) e menores valores das taxas líquida de reprodução (Ro), intrínseca de aumento (rm) e razão finita diária de aumento (λ). Os resultados deste estudo indicam a recomendação da dieta de Poitout & Bues para manutenção de colônias e criação massal de E. agrotina quando comparada com a dieta de Greene.
ABSTRACT
Abstract Chrysodeixis includens (Walker, [1858]) is currently the main plusiine pest in the Americas, not only because of the damage caused to soybean, but also with several crop species in a broad geographical range. However, its population dynamics is still poorly understood, despite outbreak records that are common across different locations in the Americas. The current study aimed at identifying phenological patterns of C. includens emphasizing its differences among the three years of sampling effort in an intercropping area of the Brazilian Savanna. Thereafter, we tested whether the El Niño size effect, meteorological factors, or soybean, corn and wheat cycles, are better predictors of its monthly abundance. The insects were collected with a light trap during five consecutive nights (repetitions) during 35 new moons. In total, 2026 specimens were collected in all months of the year although not consecutively. Across each year, monthly abundance of C. includens was non-uniform, characterized by sharp population peaks concentrated in the rainy season. These peaks varied from January until March, depending on the year sampled. We found that the local soybean cycle and El Niño effect to significantly influence the species abundance across the entire period of study. These results aid in understanding the species population dynamics and its status as a pest, providing evidence of factors that determine its phenological patterns. Although it presents a very defined phenology, the population dynamics of C. includens varies significantly between years and locations, which demonstrates the importance and need to monitor local populations of larvae and adults for its management.
ABSTRACT
ABSTRACT:The present research updates the systematic position and nomenclature of Lepidoptera associated with soybean crops in Argentina, Brazil, Chile and Uruguay. Scientific literature lists 69 species of Lepidoptera feeding on soybean plants. These species are representatives of the Superfamilies Noctuoidea(31),Pyraloidea(13), Hesperioidea(12), Tortricoidea(5), Geometroidea(5), and Bombycoidea(3). Diversity of Lepidoptera associated to crop, injury in different parts of the plant, and changes in species composition are discussed considering the changes in plant disease management, introduction of plants expressing Bt proteins, and the recent introduction of Helicoverpa armigera(Hübner) as a new crop pest.
RESUMO:O presente estudo atualiza a posição sistemática e a nomenclatura dos lepidópteros associados com a cultura da soja na Argentina, Brasil, Chile e Uruguai. A literatura científica relaciona 69 espécies de Lepidoptera cujas larvas se alimentam de soja. As espécies incluem representantes das Superfamílias Noctuoidea(31),Pyraloidea(13), Hesperioidea(12), Tortricoidea(5), Geometroidea(5), and Bombycoidea(3). A diversidade dos lepidópteros associados com a cultura, as injúrias em diferentes partes da planta e alterações na composição das espécies são discutidas considerando mudanças no manejo de doenças da cultura, a introdução de plantas expressando proteínas Bt e a recente introdução de Helicoverpa armigera(Hübner) como uma nova praga da soja.
