Relationship between the population density of silver leaf whitefly Bemesla argentifolii bellows and perring, and the spread of squash leaf curl virus,slcv, on squash leaves in Egypt

This study was carried out to classify the natural infestation of the whitefly and associated virus infection ratio on squash leaves. The first appearance of the whitefly on summer plantation occurred during the late of April 2004 with low adult number and then gradually increased to reach the highest level of infestation during the mid of July of the same season and during early of August for nymphal stages , the same trend of population was recorded in 2005 summer season but with different numbers recording the peak of abundance during the last week of August for adult stage and during the early of the same month for nymphal stages population. The regular inspection of squash leaves revealed that the early infestation of whitefly on squash leaves during Nili plantation was determined during the late of April 2004 and continuously increased till reaching to their maximum population level during mid of both July and August for adult stages. The population of whitefly nymphal stage was slightly lower than that of adult recording the peak of abundance during early of August. During 2005 Nili cultivation season, the adult and nymphal infestation of whitefly was obviously denoted that the population was in a gradually increased reaching to their highest level during late of August. The virus infection ratio in this study during Nili plantation was recorded the highest ratio during early and mid of August 2004 and late of August 2005.The regular inspection of squash plantations during the different sowing times through the experiment revealed that the following periods Summer 2004, summer 2005 and summer 2006 were the preferable time for growing the population of the whitefly nymphs but the Nili 2004 and Nili 2005 were the lowest period for harboring the nymph population. From the obtained results there were very highly significant differences between the time of planting and the infestation of insect nymphal stages.