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Biological aspects and life table of Uroleucon ambrosiae (Thomas, 1878) as a function of temperature

Keywords: insecta , aphids , biology , climatic factors

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The aphid Uroleucon ambrosiae (Thomas) is considered a pest of hidroponically-grown lettuce, but basic and applied information on its control are scarce in Brazil. The aim of this study was to determine the effect of different temperatures on biological aspects and life history of U. ambrosiae (Thomas) developing on hydroponic lettuce (Lactuca sativa L.) crop. Newly emerged nymphs were placed on 4-cm discs of hydroponic lettuce, var. Ver nica, which were maintained on 5-cm Petri dishes, at temperatures of 15, 20 and 25oC and 14 h photophase, and inside a greenhouse, within micro-cages at room temperature. The duration of development in all nymphal stages varied inversely to temperature. Nymphs maintained at 20oC and 25oC, had similar development period. However, at fluctuating greenhouse temperatures (daily mean = 21oC), different results were obtained, which was also true for the pre-reproductive, reproductive and post-reproductive periods. Daily and total fertilities at 20oC were better in comparison to the other treatments. The highest mortality rate of aphids occurred under greenhouse conditions. The production of 1.28 nymphs per female per day, the time needed for the population to double in size (TD=2.77days), and the intrinsic rate of population increase (r m=0.25), were similar for in insects maintained at 20 and 25oC. On the other hand, time interval between generations (T) and the net reproductive rate (Ro) were higher at 20oC. In the greenhouse, even though T was similar to laboratory conditions at 20 and 25oC, the R0, r m and l parameters were lower and TD was higher. Based on biological aspects, fertility and life expectancy tables, constant temperature of 20oC is the most suitable for U. ambrosiae.


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