Abstract
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. Verônica, 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.
Highlights
Lettuce (Lactuca sativa L.) is one of the most common and found vegetables in Brazilian homesScientia Agricola, v.60, n.4, p.657-662, Oct./Dec. 2003(Darold et al, 1993)
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
Summary
Lettuce (Lactuca sativa L.) is one of the most common and found vegetables in Brazilian homesScientia Agricola, v.60, n.4, p.657-662, Oct./Dec. 2003(Darold et al, 1993). This insect is an important vector of the lettuce mosaic virus, and cause qualitative damage, because excretes and deposit the “honeydew” over the leaves, which encourages the development of the sooty mold, and undervaluate the product. Highest population densities for this aphid in the hydroponic lettuce condition occurbetween 16.4 and 19.2oC (Auad et al, 2002). Negative correlation between temperature and relative humidity and population density of U. compositae (Theobald) was verified by Akashe et al (1995). This fact indicates that investigating the interaction between temperature and development rate of aphids is essential to understand their population dynamics (Liu & Meng, 2000)
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