Management of Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) on corn, Zea mays L.: basis for populational evaluation and biological control using the egg parasitoid Trichogramma atopovirilia Oatman &Platner, 1983 (Hymenoptera: Trichogrammatidae). / Manejo de Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) em milho, Zea mays L.: bases para avaliação populacional e controle biológico utilizando o parasitóide de ovos Trichogramma atopovirilia Oatman &Platner, 1983 (Hymenoptera:Trichogrammatidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The objectives of this research were the improvement of cross-section Spodoptera frugiperda using pheromone traps to verify the capacity of dispersion of Trichogramma atopovirilia as an agent for biological pest control as well as evaluating the attractiveness of Amaranthus sp. to T. atopovirilia females. To improve cross-section of S. frugiperda, the studies were carried out in two commercial corn field plantations, one made up of 36,3 ha (called MIP and with 30 points of sampling) and another of 10 ha (called conventional and with 10 points of sampling). In these fields pheromone traps were randomly displaced (ratio of 1 trap/ha). The evaluations were realized twice a week during the whole plant development, considering : number of male adults collected by the traps, insect injury to plants, egg masses and larval densities (small, medium and large). The numbers of adults collected were correlated to the insect injury, egg masses and larval density. The larval occurrence did not show difference between areas and sampling points. The injury levels, egg masses and small larva densities did not show correlation to adult caught by traps. There was significant correlation between large larvae (4th and 5th instars) and the number of plants showing whorl holes and/or destroyed ones. There were no correlations observed among adults caught by traps and insect infestation or injury, so demonstrating that larvae should be counted for timing pest control. The capacity of dispersion of T. atopovirilia was studied in 3 distinct phases of corn plant development, when they had 4 to 6 leaves, 8 to 10 leaves and tassel. In each stage was applied an artificial infestation with egg masses (<24 h) of S. frugiperda on plants located 6 to 24 m from a parasitoid release point. Right after this artificial infestation, was applied only one parasitoid adult release to each distinct corn plant phase , always early in the morning or late in the afternoon. The parasite contamination was allowed during 48 h and then the egg masses were retrieved and taken into a climatic chamber until emerging adulthood. The results showed that plants affected the parasitoid dispersal. The egg masses placed farthest from the release point were parasited only during the 4 to 6-leaf stage. In the others stages, only egg masses next to the release point were parasited. The attractiveness of four species of Amaranthus (A. retroflexus, A. viridis, A. hybridus and A. spinosus) to the females of T. atopovirilia was evaluated by a Petersons olfactometer. These plants were evaluated in both vegetative and reproductive stages. Complete randomized procedure was adopted with 40 replications (considering one insect/replication) and each insect was observed during 600 seconds. The most attractive species were A. viridis and A. retroflexus during vegetative and reproductive stage, respectively. When plants were tested simultaneously, the species did not show attractive properties to the parasitoids. These results suggest the viability of the use of these plants or its derivatives to change host habitat and parasite increase for biological control in integrated pest management.

ASSUNTO(S)

amostragem olfatômetro chemical signal. interação trófica sinais químicos. comportamento de forrageamento foraging behavior olfactometer trophic interactions sampling (cross-section)

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