Effect of Certain Weather Factors and Some Natural Enemies on The Population Densities of Four Piercing-Sucking Insects on The Cotton Crop at Kafr El-Sheikh Governorate

The effect of prevailing weather factors (mean daily of temperature, relative humidity and wind speed) and some natural enemies (six insect predators were recorded; Coccinella undecimpunctata, L.; Scymnus interruptus Goez.; Paederus alfierii Koch, Syrphus spp., Orius spp. and Chrysoperlla carnea (Steph.) on the population densities of the cotton aphid (Aphis gossypii Glover), whitefly (Bemisia tabaci (Genn.), Jassids (Empoasca spp.) and green stink bug (Nezara viridula (L.)), during 2016 to 2017 cotton growing seasons was studied at the Farm of Sakha Agricultural Research Station, Kafr El-Sheikh Governorate. Results revealed that:
1.  The initial infestation cotton aphid on cotton plants appeared in the second week of July of 2016 and 2017 seasons (12^th and 11^th of July of the two seasons, respectively) and had three peaks of population activity of both seasons of the long period of 12^th of July till the 20^th of September of the first season, and 11^th of July till the 26^th of September of the second season. The aphid population density was affected positive significantly (0.498*) in the first season and unsignificantly (0.310) in the second season by the temperature. Whereas, the relative humidity was affected positive unsignificantly in both seasons (0.375 and 0.320), respectively, but the effect by the wind speed was negative and highly significant in the two seasons 2016 and 2017 (-0.582** and 0.710**), respectively. The effect by the insect predators on the population density of A. gossypii were positive and highly significant correlations recorded in both seasons were (0.587** and 0.620**), respectively.
2.  The cotton whitefly began to appear on cotton leaves at 28^th of June of both seasons and had four peaks of population activity of both seasons, of the long period of 28^th of June till the 4^th of October in the first season and 28^th of June till the end of the second season (24^th of October). The whitefly population density was affected positive highly significant (0.727**) in the first season, and unsignificantly (0.383) in the second season by the temperature. Whereas, the relative humidity was affected positive unsignificantly (0.378) in the first season and significant (0.490*) in the second season, but the affected by the wind speed was unsignificantly positive and negative (0.090 and -0.280) in the 2016 and 2017 seasons, respectively. The effect by the insect predators on the population density of B. tabaci were positive and significant correlations recorded in both seasons were (0.505* and 0.470*), respectively.
3.   The cotton jassids began to appear on cotton leaves at 30^th of May and 6^th of June in the two seasons, respectively, and had five peaks of population activity in 2016 season of the long period of 30^th of May till the 27^th of September and six peaks in 2017 season of the long period of 6^th of June till the end of the season (24^th of October). The relationship between the temperature and the population density of this insect was positive and highly significant (0.713**) in the first season, and unsignificant (0.420) in the second season. So, the effect by the relative humidity on the population density of jassids was positive and unsignificant (0.221 and 0.400) in both seasons, respectively. While, the wind speed was positively insignificantly and negatively significantly (0.298 and -0.490*) with insect numbers in 2016 and 2017 seasons, respectively. While the effect  by the insect predators on the population density of Empoasca spp. were positive and significant correlations recorded in both seasons were (0.485* and 0.510*), respectively.
4.                   The green stink bug began to appear on cotton leaves at 14^th and 13^th of June in the 2016 and 2017 seasons, respectively, and had three peaks of both seasons of the long period of 14^th of June till 18^th of October in the first season and 13^th of June till 17^th of October of the second season. The population density of this insect on cotton plants was affected negatively and unsignificantly (-0.086 and 0.180) in both seasons by the temperature, respectively. But, the relative humidity had unsignificantly positive and negative (0.021 and -0.060) in both seasons, respectively. While, the effect of the wind speed was negative and unsignificantly (-0.237 and -0.080) in both seasons, respectively. The population density of N. viridula on cotton plants was affected by the insect predators were positive and significant correlations recorded in both seasons were (0.515* and 0.499*), respectively. Study the effect of abiotic and naturally occurring biotic factors on seasonal population fluctuations of insect pests, this factors to played the main factor in the evolution and distribution of this insect pest.