The host selection for oviposition by Spodoptera frugiperda (J.E. Smith) among corn, millet, cotton and soybean, and its relationship with the biological characteristics were investigated. Free and non-choice tests for oviposition using plots containing five plants each, from each host in plastic greenhouse, resulted in similar oviposition preference among the host plants. In addition, selected biological characteristics of S. frugiperda were determined in the laboratory with larvae feeding on host leaves, and the combination of leaf and cotton boll. Neonate larvae exhibited low success of colonization on cotton boll compared to the leaves of all other hosts. Spodoptera frugiperda fed only on cotton bolls exhibited longer larval and pupal development, and longer adult life span; however with similar egg production. Larvae fed cotton leaves during six days and then transferred to cotton bolls, however, exhibited development and reproduction similar to those reared on corn or only on cotton leaves. Therefore, the variations on immature stages of S. frugiperda were not related with host selection for oviposition which was similar among the studied hosts. Based on our data, the millet as a winter, rotational, and cover crop is a potential host for S. frugiperda, while leaves and cotton bolls were diets of intermediate suitability as compared to corn and soybean leaves.
This research aimed to point out the most suitable trichogrammatid strains to control the soybean looper Pseudoplusia includes Walker. Biological parameters and parasitism ratio of 11 Trichogramma pretiosum Riley, one Trichogramma atopovirilia Oatman & Platner and one Trichogrammatoidea annulata De Santis strains reared on P. includens eggs were evaluated. Among all tested strains/species, T. pretiosum strain RV, collected in Rio Verde, GO, had the fastest development cycle and the highest percentage of parasitism of P. includens eggs. There was no difference in the parasitism and in the number of parasitoid emerged per egg among the tested parasitoid species and strains. Accordingly to the cluster analysis, T. pretiosum strain RV reared on P. includens eggs had the best performance. Considering the higher parasitism rate, shorter biological cycle, higher survival and sex ratio, T. pretiosum strain RV is the most appropriated to be used in field releases aiming at P. includens control.
Este estudo objetivou selecionar as linhagens de tricogramatídeos mais adequadas ao controle da lagarta falsa-medideira, Pseudoplusia includens Walker. Foram avaliados os parâmetros biológicos e a taxa de parasitismo de 11 linhagens de Trichogramma pretiosum Riley, uma linhagem de Trichogramma atopovirilia Oatman & Platner e uma linhagem de Trichogrammatoidea annulata De Santis, criadas em ovos de P. includens. Entre as espécies/linhagens avaliadas, a linhagem T. pretiosum RV, coletada em Rio Verde, GO, apresentou o ciclo de desenvolvimento mais rápido e a maior porcentagem de parasitismo em ovos de P. includens. Não houve diferença no parasitismo e no número de parasitóides emergidos por ovo entre as espécies e linhagens de parasitóides avaliadas. De acordo com a análise de agrupamento (cluster analysis), a linhagem RV criada em ovos de P. includens teve o melhor desempenho. Apresentou maior taxa de parasitismo, menor duração do ciclo biológico, alta sobrevivência e predominância de fêmeas, sendo a mais indicada a ser utilizada em liberações de campo visando ao controle de P. includens.