Loss factors on maize cultivars on late planting - DOI: 10.4025/actasciagron.v26i2.1891

Este trabalho objetivou estudar os fatores de perdas incluindo insetos-praga e seus inimigos naturais, em 49 cultivares de milho em cultivo na época da safrinha de 5/02 a 11/09/1999, em Coimbra, MG. Para estudo das perdas, utilizou-se tabela de vida de cultura. A produtividade média foi alta (3386,59kg/ha). As cultivares mais produtivas foram: CO 34, Mitla 9742, XB 7012, HTEP 22, P 30F80, Hata 2025 e XB 7070. A perda acumulativa total, considerando a média de todas as cultivares, foi de 33,92%. O componente de produção no qual ocorreu maior perda foi o grão, seguido pelo óvulo, plantas e espigas. O componente crítico de perdas foi o grão. O fator-chave de perdas foi o ataque de Sitophilus zeamais (Coleoptera: Curculionidae) aos grãos seguido pelo ataque de Helicoverpa zea (Lepidoptera: Noctuidae). As cultivares com menores perdas por S. zeamais foram: Agromen 3150, CO 32, HTEP 22, Dina 1000, C 855, P 3027 e CO 9560. As cultivares com menores perdas por H. zea foram: AG 9010, XL 357, HTP 02, Agromen 3100, CO 9560 e P 30F80. As cultivares HTEP 22 e P30F80 estiveram entre as mais produtivas e menos atacadas por S. zeamais e H. zea, respectivamente. Os insetos-praga com maiores densidades no dossel das plantas foram: Dalbulus maidis (Homoptera: Cicadellidae), adultos de Diabrotica speciosa (Coleoptera: Chrysomelidae) e lagartas de Spodoptera frugiperda (Lepidoptera: Noctuidae). O inimigo natural mais abundante foi o predador Doru luteipes (Dermaptera: Forficulidae) cujas densidades foram semelhantes entre as diversas cultivaresThis work was carried out to study the loss factors and densities of insect pests and natural enemies on 49 maize cultivars on late planting (02-05-1999 to 09-11-1999) in Coimbra, Minas Gerais State, Brazil. To study the losses it was used the crop life table. The average yield was high (3386.59kg/ha). The most productive cultivars were CO 34, Mitla 9742, XB 7012, HTEP 22, P 30F80, Hata 2025, and XB 7070. The total cumulative loss was 33.92%. The production component in which happened larger loss was the grain, followed by the ovules, plants, and ears. The critical component of losses was the grain. The key-factor of losses in the grains was the attack of Sitophilus zeamais (Coleoptera: Curculionidae) followed by the attack of Helicoverpa zea (Lepidoptera: Noctuidae). Agromen 3150, CO 32, HTEP 22, Dina 1000, C 855, P 3027 and CO 9560 were the cultivars less attacked by S. zeamais, while AG 9010, XL 357, HTP 02, Agromen 3100, CO 9560 and P 30F80 were less damaged by H. zea. The cultivars HTEP 22 and P30F80 were the most productive among the cultivars and less damaged by S. zeamais and H. zea, respectively. The insect-pests with highest densities on the canopies on the plant were Dalbulus maidis (Homoptera: Cicadellidae), Diabrotica speciosa adults (Coleoptera: Chrysomelidae) and Spodoptera frugiperda larvae (Lepidoptera: Noctuidae). The most abundant natural enemy was the predator Doru luteipes (Dermaptera: Forficulidae). The densities of these insects were similar among the cultivar