Effect of Planting Dates on Major Insect Pests and Yield of Watermelon Seeds (Citrullus lanatus.) in Kafr El - Sheikh Governorate

Abstract

Bemisia tabaci (Genn.) Aphid, Aphis gossypii Glover Jassid. Empoasca decipiens (Paoli) Armyworm, Spodoptera littoralis (Boisd) the natural enemies predators, Coccinella undecimpunctata Chrysoperla carnea and yield. The effect of four planting dates of watermelon to produce the (Citrullus lanatus) seeds during summer plantation in both seasons 2011 & 2012 (April,1 st , April, 15 th , May, 1 st , and May, 15 th) by the levels of infestation with four pests, whitefly, Bemisia tabaci (Genn.), aphid, Aphis gossypii Glover, jassid , Empoa-scadecipiens (Paoli) and armyworm, Spodoptera littoralis (Boisd) in addition the natural enemies two predators Coccinella undecimpunctata Reiche and Chrysoperla carnea Stephens. The yield of this plants, were weighted during two successive seasons (2011 and 2012). The degree of infestation ofB. tabaci, A. gossypii, E. decipiens and S. littoralis increased significantly by delaying sowing date, while watermelon plants cultivated in the earliest planting date (April, 1 st and April, 15 th) which were attacked by the lowest numbers and gave highest weight of watermelon seeds, the plants of the latest sowing date (May, 1 st and May, 15 th) harboured more insects infestation with lowest weight of watermelon seeds. Statistical analysis for the effect of the two selected predators factors C. undecimpunctata and C. carnea on the population density of B. tabaci,A. gossypii and E. decipiens during both seasons. gave significant positive effects of C. undecimpunctata and C. carnea on the seasonal fluctuations of B. tabaci nymph and A. gossypiiin both seasons. The combined effect (explained variance (E.V) of these natural enemies factors showed that B. tabaciand A. gossypii these factors were responsible as a group for 99 % and 99% effects throughout both seasons, respectively. The results revealed insignificant positive effects of C. undecimpunctata and C. carnea on the seasonal fluctuations of E. decipiens individual in both seasons. The combined effect explained variance (E.V) of these predators factors on B. tabaci nymph showed that these factors were responsible as a group for 40 % and 37 % effects throughout both seasons, respectively. Therefore, it was concluded that, the planting date was effective on the rate of insect infestation and watermelon seeds yield. Recommendation: The first and second planting dates (April 1st and April, 15th) were effective on the rate of insect infestation and increases yield of watermelon.