Abstract
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 (12th and 11th of July of the two seasons, respectively) and had three peaks of population activity of both seasons of the long period of 12th of July till the 20th of September of the first season, and 11th of July till the 26th 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 28th of June of both seasons and had four peaks of population activity of both seasons, of the long period of 28th of June till the 4th of October in the first season and 28th of June till the end of the second season (24th 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 30th of May and 6th of June in the two seasons, respectively, and had five peaks of population activity in 2016 season of the long period of 30th of May till the 27th of September and six peaks in 2017 season of the long period of 6th of June till the end of the season (24th 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 14th and 13th of June in the 2016 and 2017 seasons, respectively, and had three peaks of both seasons of the long period of 14th of June till 18th of October in the first season and 13th of June till 17th 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.
Highlights
Insect pests one of the major limiting factors in cotton production
The information about the Effect of Certain Weather Factors and Some Natural Enemies on The Population Densities of Four Piercing-Sucking Inse1ct0s 3 behavior and abundance of the piercing- sucking pests on cotton as affected by changes in the environmental weather factors and natural enemies are required to facilitate the prediction of their population density which may help to reduce the amount of the used insecticides for their control
This study aimed to evaluate the effect of three prevailing weather factors and some natural enemies on the population density of the four piercing- sucking pests during the two successive cotton growing seasons, 2016 and 2017
Summary
Insect pests one of the major limiting factors in cotton production. Cotton plants are subjected to attack by a wide range of insect pests throughout growing stages until near maturity. The most serious damage to cotton is a result of honey dew excreted by certain sucking insects which makes the lint sticky, resulting in difficulties in the ginning and spinning process (Perkins, 1987; Anonymous, 1989 and Hassanein et al, 1995). Chemical control of these insects is expensive and environmentally disruptive and largely ineffective. This study aimed to evaluate the effect of three prevailing weather factors (mean daily of temperature, relative humidity and wind speed) and some natural enemies (six insect predators) on the population density of the four piercing- sucking pests during the two successive cotton growing seasons, 2016 and 2017
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