Influência da aplicação de silício na ocorrência de lagartas (Lepidoptera) e de seus inimigos naturais chaves em milho (Zea mays L.) e em girassol (Helianthus annuus L.)

Abstract

The corn fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) and the sunflower caterpillar Chlosyne lacinia saundersii (Doubleday & Hewitson, 1847) are regarded as key pests, respectively, on corn and sunflower crops. In that way, the objectives of the present work were to evaluate the effects of silicon in the occurrence of fall armyworm, of the sunflower caterpillar and of their natural enemies on corn and sunflower. The experiment was conducted in the field in an experimental area intended to the organic cultivation at the UFLA, in the period of February to June of 2008, adopting the randomized block design in a factorial scheme 2 (crops) x 2 (with and without silicon application) and 8 replications. The total number of caterpillars, the parasitism rate and the occurrence of earwigs and ladybugs were evaluated. From the results, one can find that the application of silicon, although don’t having direct effect on the S. frugiperda infestation, affected the development of C. lacinia saundersii, causing a reduction in the number of caterpillars. In relation to the ladybugs, they were found in the two crops, their being significantly higher on sunflower plants. There was no record of parasitized caterpillars, a fact that should be investigated in other research works.