In Brazil, the caterpillar Helicoverpa armigera (Hübner) is a key economic pest of soybean, from seedling emergence to the reproductive stage. Control of this pest has relied on foliar insecticide sprays, and the use of insect-resistant cultivars. Characterization of the efficacy of insecticides that can be used for seed treatment, as a complement or alternative control for this pest, is needed for the production sector. The study objective was to evaluate the insecticidal potential of diamides for control of H. armigera larvae, when applied to soybean seeds. The effects of seed treatment with cyantraniliprole or chlorantraniliprole on 1st-and 3rd-instar H. armigera larvae, in both conventional and in "Bt soybean" (Cry1Ac), were evaluated under laboratory conditions. Two infestations were carried out at 8, 13 and 21 days after plant emergence, to determine the leaf area consumed, and mortality of larvae. The insecticides cyantraniliprole and chlorantraniliprole, used at rate of 60 and 62.5 g a.i./100 kg seeds, respectively, have potential for the control of 1st-instar H. armigera larvae up until at 13 days after the emergence of soybeans plants. The Cry1Ac protein controlled both 1st-and 3rd-instar H. armigera larvae at least until 21 days after plants emergence.

Helicoverpa armigera (Hübner) (Lep.: Noctuidae) has established itself as a soybean pest in southern Brazil; however, as a polyphagous species, the caterpillar has been found in other economically important crops and even uncultivated plants. The nutritional value of host plants as food sources influences biological performance, which can interfere with population dynamics and pest management. In this sense, an experiment was carried out to assess the effect of different foods on biological aspects and larval consumption. Eight plant species were evaluated, including cultivated plants, ground cover plants, and weeds. Soybean, where caterpillars acquired greater importance as a pest, was considered the standard food. The plants were grown in pots in a greenhouse, and the leaves were harvested to feed the larvae as they hatched. The findings show that H. armigera larvae fed on canola or radish leaves exhibit biological performance comparable to that fed on soybean. The larvae did not survive when fed ryegrass, horseweed, corn, or wheat.

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