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Competition behavior involving agricultural pest species has long been viewed as a powerful selective force that drives ecological and phenotypic diversity. In this context, a Game Theory-based approach may be useful to describe the decision-making dilemma of a competitor with impacts to guarantee its superiority in terms of ecological dominance or sharing of the food resource with its competitor. In an attempt to elucidate the consequences of competitive dynamics for the ecological dominance of these species in refuge areas of Bt cotton, we conducted a study that was divided into two parts. The first study consisted of an evaluation of interactions involving Spodoptera frugiperda (JE Smith, 1797) and Helicoverpa armigera (Hübner, 1808) on non-Bt cotton plants in a field trial. In the second study, we explored the data matrix collected in the field to parameterize a model of Cellular Automata (CA) with update rules inspired by Game Theory. Computer simulations were analyzed in hypothetical scenarios involving the application (or not) of insecticides in the refuge areas in combination with the resistance factor of one or both pest species to the insecticides used in the refuge areas. H. armigera had superior competitive performance in relation to S. frugiperda only at high densities. According to the density-mediated shift in dominance of the species, the resistance of S. frugiperda to insecticides is seen as a risk factor for the production of susceptible individuals of H. armigera on a large scale in the refuge areas. Additionally, S. frugiperda insecticide resistance may potentially impact the resistance evolution of the H. armigera population to Bt cotton. Thus, ecological dominance could diverge by the presence of a resistance allele to insecticides with interspecific competition perhaps subordinate to evolutionary processes.

ABSTRACT: Vatiga illudens is a pest of economic importance for the cultivation of cassava. Knowing the time of incidence of this insect in combination with environmental factors enables control strategies. The objective of this study was to determine the population dynamics of V. illudens in cassava cultivars and the correlation of these insects for climatic factors in Dourados, Mato Grosso do Sul. Four cultivars of cassava were evaluated: Kiriris, N-25, IAC 90 and Fécula Branca. Population assessment of the lace bug was conducted over 18 months observing 2 crop cycles. Fortnightly, they were randomly sampled four central plants of each plot and five leaves from the middle third of each plant, quantifying the number of nymphs and adults per leaf. Twenty months after planting cassava, two central rows of each plot were harvested and measured productivity in kg ha-1. The experimental design was randomized blocks with four treatments and two replications. The peak population of nymphs and adults for the first crop cycle occurred during the months from March to May. For the second cycle, these population indices happened in the months from January to April. Cultivar Kiriris showed the highest mean number of nymphs and adults per leaf cassava and cultivar IAC 90, the lowest number of insects. There was a negative correlation between the population of adult insects and root yield. The maximum, mean and minimum temperatures affected the population of nymphs V. illudens. These results are fundamental to define management strategies for control of lace bug.

A cultura do algodão (Gossypium hirsutum L.) é hospedeira de um complexo de pragas que pode ocasionar danos às raízes, caule, folhas, botões florais, flores, maçãs, sementes e fibras. Este trabalho objetivou avaliar por meio da alimentação com folhas de algodoeiro geneticamente modificadas resistentes a lepidópteros, à sobrevivência e desenvolvimento de lagartas de Spodoptera frugiperda e Chrysodeixis includens. Os experimentos foram conduzidos no Laboratório de Entomologia Aplicada da Universidade Federal da Grande Dourados, Dourados, Mato Grosso do Sul, no período de 05 de janeiro (preparo dos vasos) a 23 de junho de 2012 (algodoeiros em fim de ciclo, com 154 dias após a emergência). As plantas foram cultivadas em casa de vegetação, enquanto os biotestes de sobrevivência e desenvolvimento de lagartas foram conduzidos em laboratório. Os estudos foram constituídos de: A – oferta de folhas de algodoeiro Coker TwinLink® e Cooker não modificada a lagartas de S. frugiperda; B – oferta de folhas de algodoeiro Coker TwinLink® e Cooker não modificada a lagartas de C. includens; C – oferta de folhas de algodoeiro PHY 440 WS Widestrike®, FM 975 WS Widestrike® e FM 933 não modificado a lagartas de S. frugiperda; D – oferta de folhas de algodoeiro PHY 440 WS Widestrike®, FM 975 WS Widestrike® e FM 933 não modificado a lagartas de C. includens. Compilando as informações do presente estudo, observamos que o algodoeiro Coker TwinLink® permitiu menores valores percentuais de sobrevivência de lagartas neonatas de C. includens se comparada à S. frugiperda. As linhagens de algodoeiros resistentes a lepidópteros interferem de forma negativa na sobrevivência e desenvolvimento de lagartas de S. frugiperda e C. includens, quando comparadas às linhagens não modificadas. Dependendo da linhagem, do evento geneticamente modificado e da praga, é necessário controle complementar. Palavras-chave: Programa de melhoramento. Resistência de plantas. Proteínas.

As espécies de Trichogramma constituem um importante grupo de parasitóides que atacam, principalmente, ovos de lepidópteros. A qualidade e o desempenho desse inimigo natural podem ser influenciados por alguns fatores, como hospedeiro alternativo utilizado nas criações massais, temperatura e diferenças de fotoperíodo. Nesse sentido, o objetivo desse trabalho foi avaliar o número de ovos parasitados, % de fêmeas que parasitaram, % emergência, razão sexual e número de indivíduos de Trichogramma galloi Zucchi em os ovos de Diatraea saccharalis (Fabricius), na presença e ausência de luminosidade. O delineamento experimental utilizado foi inteiramente casualizado com dois tratamentos (claro e escuro) com 60 repetições, cada uma dessas foi constituída por 40 ovos de D. saccharalis que foram colocados em tubo de vidro com uma fêmea de T. galloi com 24 horas de idade, previamente alimentadas com mel. O experimento foi conduzido à 25º C ± 2º C e 70 ± 10% umidade relativa. Em cada um dos tratamentos, o parasitoide foi removido após 12 horas. O maior número de ovos parasitados (12,9) e % de fêmeas que parasitaram (83,3%) foi observado no período com luz. Em relação à emergência, razão sexual e número de indivíduos por ovo, não houve diferença estatística. Os resultados demonstraram que a presença de luminosidade é essencial para esse agente de controle biológico. Influence of Photoperiod on Parasitism of Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) on Eggs of Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae) Abstract. Trichogramma species are an important group of parasitoids that attack especially lepidopteran eggs. The quality and performance of this natural enemy may be influenced by factors such as alternative host used in the massal rearing, and differences in the temperature and photoperiod. Based on this, this study aimed to evaluate the number of parasitized eggs, % of females that parasitized, % emergence, sex ratio and number of individuals of Trichogramma galloi Zucchi per egg of Diatraea saccharalis (Fabricius) in the presence and absence of light. The experimental design was completely randomized with two treatments (light and dark) and 60 replications, being each experimental unit composed by 40 eggs of D. saccharalis which were placed in a glass tube with one female of T. galloi with age of 24 hours, previously fed with honey. The experiment was carried out at 25 ± 2 °C and 70 ± 10% relative humidity. In each one of the treatments, the parasitoid was removed from the tube after 12 hours. The highest number of parasitized eggs (12.9) and % of females that parasitized (83.3%) was observed during the period with light. For the emergence, sex ratio and number of individuals per egg, there was no statistical difference. The results showed that the presence of light is essential for this biological control agent.