Abstract:
Helicoverpa armigera (Hub), Jacobiasca lybica (de Berge),
Bemisia tabaci (Genn.) and Aphis gossypii (Glover) were the major
cotton insect pests in the Gezira Scheme. Those insect pests were
affected by various factors and independent variables most important
of which are the weather conditions, the other crops and the pesticides
used in the area. Detailed data concerning these factors have been
compiled in this work during the period of 1970 to 2003 and were
subjected to statistical analysis. The results of this study are intended
hopefully to be utilized in forecasting the seasonal severity of these
pests.
The following are the important significant correlations: A
positive and highly significant correlation is recorded between the
African Bollworm (ABW) H. armigera and the maximum temperature
during the period August – October, mean average temperature during
September – January and mean relative humidity (RH) during Sept. –
Jan.
A positive and highly significant correlation of Jassid was
detected between jassid numbers and mean maximum temperature
during September–January and mean average temperature of July-
February. Moreover, a negative but significant correlation was shown
between jassid numbers and the number of insecticide sprays per
iv
season, the cotton post-sowing rainfall and the total rainfall of the
season. Lastly, a significantly positive correlation was detected when
jassid numbers were correlated with the areas under groundnut of the
same season.
White fly (B. tabaci) numbers showed a positive and highly
significant correlation with the annual areas grown with cotton,
number of sprays/season, both mean average temperature and RH
during Aug – Oct., cotton pre-sowing rains, post-sowing rains and
total annual rains.
Only two significant relationships between aphid (A. gossypii)
and the independent variables were recorded. The first one is the
positive and highly significant correlation with the annual areas under
vegetables. The other one is the positive and significant correlation
with the mean minimum temperature during the period Aug – Oct.
