Abstract:
The field experiments were conducted to assess susceptibility of seven transgenic varieties of cotton (Aleppo 33; McNair 308; Tashkent 3; McNair 307; McNair 235; TamCot CAMD; McNair 220 As imported varieties and Moubarak93 (conventional cultivar) as local variety to infestation with cotton aphids Aphis gossypii and cotton white fly Bemisia. tabaci. The results indicate that aphid population had three main peaks (1st peak in July, 2nd peak in the 2nd week of August and the 3rd peak was occurred at the last week of August). Aphid population showed high reduction with low average of infestation (17.9-24.0 %) at May and June with Temp. (22.9-25 oc), R. H. (48- 56%) Wind speed (1.8 -2.0m/sec.) and sun shine duration (13.6-14.1 hr and mid of September of cultural season.
The most attractive varieties of transgenic cotton with higher insect population and comparatively susceptible to A. gossypii were Var. Aleppo 33 , var. McNair235 and var. Tash Kent 3 followed by var. McNair 307, whereas the least attractive varieties of cotton and resistant against A.gossypii were var. Tamcot CAMD and var. McNair 220, compared to the conventional variety (Mubarak 93 ) which was the most tolerant to infestation with cotton aphids. There were high significant difference between infestation of transgenic varieties of cotton with A.gossypii .
The population of cotton whitefly, B. tabaci had three main peaks in growing season (July, August and September) with Temp. (26.2-26.6 oc), R. H. (68.3-69.0 %), wind speed (0.77-0.90 m/sec.) and sunshine duration (12.4-13.9 hr), however, the lowest population of whitefly was recorded in May with Temp. 23.0 oc), R.h. (51.7 %), W. speed (1.7 m/sec.) and sunshine duration (13.6 hr). Both A. gossypii and B. tabaci reached peak population in the third and fourth week of August (2013). The local conventional variety (Moubarak 93) was the most tolerant against infestation with A. gossypii and B. tabaci . It was found that the rates of cotton yield were decreased with increasing infestation rates of aphid or white fly. The results of seasonal dynamics are detected several weeks differences in peak and main activity period on the host plants. |
