Adequação alimentar de forrageiras para afídeos-praga de gramíneas

Abstract

The forages, Brachiaria decumbens (Stapf), Cynodon dactylon (L.) and Pennisetum purpureum (Schumach) are prominent species on pasture production in Brasil, being researched in the Centro Nacional de Pesquisa em Gado de Leite (EMBRAPA/CNPGL), where plant breeding are conducted. The present study aimed to verify food adequacy for aphid species, Sipha flava (Forbes, 1884), Hysteroneura setariae (Thomas, 1878), Rhopalosiphum padi (Linnaeus, 1758) and Rhopalosiphum maidis (Fitch, 1856), with forages plants. A biology essay was conducted with the aphids, using development and reproduction parameters, and a free-choice essay. Nymphs emerged within 24 hours, of each aphid species were reared in plastic container filled with agar (1%) and a leaf disk of forage species and then kept on climate chamber. All aphid species were capable of complete their life cycle at the three forage grasses tested, however, variation on evaluated parameters indicates higher adequacy of some of the forage plants and aphids. The forage P. purpureum provided better conditions for aphid development. The specie B. decumbens had lower adequacy to S. flava, the plant C. dactylon had lower adequacy to R. maidis, H. setariae e R. padi. The aphid R. padi showed the higher development capacity on every forage specie offered. At the preference essay, after 1 hour, S. flava prefered B. decumbens instead of C. dactylon, as P. purpureum did not differed significally from other. After 24 hours, S. flava did not show preference for any forage offered. The aphids R. padi, R. maidis and H. setariae prefered B. decumbens already at first hour, however there was no difference between P. purpureum and C. dactylon. After 24 hours the preference for P. purpureum was significantly more than C. dactylon, while the preference for B. decumbens continued significantly higher than other. The results show that the forage grasses has different adequacy for each aphid species and these insects have choice mechanisms, however these relations need more studies