ECOLOGICAL FACTORS AFFECTING THE POPULATION ACTIVITY OF SAP-SUCKING PESTS INHABITING COTTON FIELDS IN THREE DIFFERENT AGRO-ECOSYSTEMS

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Abdallah¹, Y.E.Y. and S.M.O. Kelany¹

Abstract

          The present investigation was carried out at three different agro-ecosystems namely; Qalyubyia, Sharkia and Dakahlia during 1999 and 2000 cotton growing seasons. Obtained results revealed that for T. urticae, two peaks characterized each district in the two seasons. The two peaks occurred during May in the 2000 season, while the 1^st took place in May and the 2^nd in July in the 1999 season. A. gossypii (Clover) had two main periods of activity at all locations. The 1^st period occurred during April-May and the 2^nd was during August-September in 2000 and in 1999, the same trend was observed in Qalyubyia only. In Sharkia and Dakahlia another peak was formed during July. The population of B. tabaci (Genn.) nymphs at all tested agro-ecosystems was relatively high in 1999 compared to 2000, except during July at Sharkia where the highest peak occurred. T. urticae was highly affected by minimum temperature during both seasons (1999 & 2000) and the effect was sometimes negative and sometimes positive in the three governorates. Maximum temperature had a significant and positive effect in Qalyubyia and Dakahlia. The only significant effect for relative humidity was at Sharkia during the second season. All tested weather factors had no significant effect on the activity of A. gossypii  population. The relationship between minimum temperature and the population of B. tabaci nymphs was significant and positive in all governorates but it varied according to the season. This positive effect could be explained as that factor was around the optimum for B. tabaci activity. The monthly averages for this factor ranged between 19.1-24.4°C during May-September 1999 and 21.0-25.5°C during the same period in 2000 and this was the highest among the three governorates. Relative humidity had a significant and negative effect at Sharkia Governorate only during 2000
season.