Influência da temperatura no desenvolvimento de Rhopalosiphum maidis (Fitch, 1856) (Hemiptera: Aphididae) em condições de laboratório

Abstract

The aphid Rhopalosiphum maidis (Fitch) has been found in all the development stages of corn and in most towns of Minas Gerais state, Brazil, and its importance has increased mainly in areas where the "fall" corn is grown. Therefore, it was aimed to investigate the influence of temperature upon some biological features of the nymphal and adult stage at different temperatures under laboratory conditions. The trials were conducted in climatized chamber at 15, 18, 21, 24, 27 and 30 ± 1ºC, RH of 70 ± 10% and 12-hour photophase in the Insect Biology Laboratory of the Entomology Department of the Universidade Federal de Lavras - UFLA, MG, Brazil, in a completely randomized design with five replicates with eight specimens each. A positive correlation among all the developmental stages and the fecundity of R. maidis with temperature was found, except between 24 to 27ºC, where a reduction in fecundity occured, noticing a higher relationship biologic cycle/fecundity at the temperature of 24ºC. It was observed that the duration of the nymphal stage was of 13.3, 10.7, 6.7, 4.5, 4.7 and 4.5 days to 15, 18, 21, 24, 27 and 30ºC, respectively, finding a linear decrease in all instars in terms of the increase of temperature in the range of 15 to 24ºC. Above that temperature there was a trend of stabilizing the development velocity. The reproductive period was of 28 days at 15 and 18ºC, became stable between 21 and 27ºC with a duration close to 12 days whereas at 30ºC, there was a reduction to five days. The biological cycle at 15ºC was of 52 days, decreasing about six days with the increase to 18ºC. The greatest reduction was found between 18 and 21ºC, recording a 18-day decrease.