Impact of Some Abiotic Factors on Population Fluctuation of Whitefly, Bemisia Tabaci ( Genn.) and Pod Borer, Helicoverpa Armigera (Hübner) Infesting Two Tomato Varieties

Abstract

Weather factors plays a critical role in the population fluctuation of certain insects infesting tomato in field. Whitefly, Bemisia tabaci ( Genn.) ( Homoptera : Alyrodidae ) , pod borer, Helicoverpa armigera (Lepidoptera: Noctuidae) infesting tomato foliage and fruits and considered the most serious pests infesting tomato plantation all over the world. This research was conducted to study the effect of air temperatures , relative humidity and dew point on population fluctuation of Bemisia tabaci and Helicoverpa armigera, eggs and larvae at different examination dates. The field experiment were carried out in a private farm of Elghaba village , Abukabier district , Sharkia governorate, along two successive summer plantations 2014 and 2015. Experimental area was planted with tomato , Lycopersicon esculentum ( Mill.) Super Strain B (SSB) and Castle rock (CR) varieties. The obtained results show that there were significant differences and positive correlation between air temperature , relative humidity & dew point and eggs and larvae number of Bemisia tabaci and Helicoverpa armigera along the two successive seasons (2014 and 2015). Air temperature , relative humidity and dew point affect egg and larvae numbers of both studied insects by 16.7 to 82.6 % and 1.2 to 69.8% during 2014 and 2015,respectively. Bemisia tabaci recorded three peaks on castle rock ( CR ) and super strain B ( SSB ) recorded ( 30,300 and 140 eggs/ ten leaves ) and (40, 32 and 20 eggs/ ten leaves ) at 13 th May , 10 th and 30 th June , while H. armigera recorded one peak on both varieties during 10 th June 2014 recorded 107 and 32 eggs/ ten leaves , respectively on CR and SSB. Also, the results indicated that B. tabaci and H. armigera larvae population during 2014 summer season recorded three peaks on CR and SSB , during 20 th May, 10 th June and 6 th July 2014 . At 2015 summer season the results revealed that population fluctuation of B. tabaci and H. armigera eggs recorded one peak on both varieties , expect B. tabaci egg on CR which recorded two peaks ( 15, 3 egg / 10 leaves ) at 13 th May and 3 rd June. Regarding to larvae population of B. tabaci on SSB , there were three peaks , but larvae population of B. tabaci on CR , H. armigera on SSB and CR recorded two peaks.