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Effect of three planting dates of onion plants (November, 15 th , December, 15 th , and January, 15 th) on levels of infestation by thrips, Thrips tabaci Lindeman and on its yield, were studied during two successive seasons (2013/14 and 2014/15) at El-Beheira Governorate, Egypt. The degree of infestation with thrips increased significantly by delaying planting date, as onion plants cultivated in the earliest planting date (November, 15 th) were attacked by the fewest numbers with highest weight of onion bulbs, while the plants of the latest planting date (January, 15 th) were more liable to insects infestation with lowest weight of onion bulbs. The population density and life stage composition of T. tabaci populations were determined in the two consecutive seasons and in the three planting dates. The intra-plant distribution of thrips was studied and a clear pattern in the diel periodicity of the intra-plant distribution of T. tabaci, was noticed in that the adults tended to be located higher on the plant during the hottest periods of the afternoon. The vast majority of nymphs occupied the basal half of the leaves and remained there throughout the day. The effect of thrips damage on onion yield was studied and the mean percentages of yield losses in onion bulb as a result of thrips damage during two successive seasons ranging from 26.17 % to 42.39 % in different planting dates in the 1 st season. In the 2 nd season loss in bulb yield recorded 20.45, 30.85 and 35.23 % in the 1 st , 2 nd and 3 rd planting date, respectively. Statistical analysis of correlation coefficient values showed that the effect of climatic factors on the population density of T. tabaci wasn't differed according to planting date during two studied seasons. The population density of onion thrips correlated positively with minimum, mean, maximum temperature, mean of wind speed and negatively correlated with average relative humidity.

Potato (Solanum tuberosum L.) is an economically important vegetable crop all over the world. The piercing sucking insect pests are serious pests threatening potato plantations in many countries. The present investigation contributes to the knowledge in the susceptibility of certain potato cultivars to infestation with these insects in Beheira Governorate, Egypt. Five global potato cultivars currently used in Egypt's potato production were evaluated through two successive seasons (summer plantations) in field experiments for their susceptibility to sucking insect infestation. The experiment was designed in a completely randomized block design and all data were analyzed using the SAS® program. None of the tested potato cultivars was immune or highly resistant to the tested insect pests. The cultivars Banba and Diamante were found quite resistance to piercing sucking insect pests. The cultivar Herms was found as moderately susceptible while Spunta and Cara were found to be the most susceptible cultivars. The green lacewing, Chrysoperla carnea; seven-spotted lady beetle, Coccinella septempunctata; eleven spotted lady beetle, Coccinella undecimpunctata and the pirate bug, Orius sp are the most important predators which associated with the sucking insects pests on the potato cultivars.

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