A completion study on Ommatissus lybicus Bergerin (1930) (Hem: Tropiduchidae).

Dubas bug, Ommatissus lybicus, is one of the key pests of date palm in Iran. Chemical control is the most conventional control method in the pest outbreak regions. The aim of this investigation was study the biology of this pest in different ecological situation again to review the past findings and to examine the probable occurred changes. For this purpose a completely infested date palm grove without any spray was chosen in Kerman, Bushehr and Khozestan provinces. The seasonal fluctuations in the population of nymph and adult of O. lybicus and their natural enemies were studied. Eggs laying behavior of O. lybicus and the seasonal fluctuations in the population of eggs were studied on shoots and the spadix (the fruit stalk). Dynamic behavior of nymphs was investigated at different times of day. This study was conducted for two years in 2011 and 2012. The results showed that O. lybicus has two generations in Kerman, Bushehr and Khuzestan provinces but the population of the second generation was very low in Bushehr. The results revealed that, the nymphs emerge in winter generation varies depending on weather conditions from the first half of March in Bushehr to late April in Khozestan. The nymphs emerge in summer generation was begun from late July to early September. Adults were emerged from mid-May in winter generation in three provinces. The peak occurred in mid-June. The correlation study between the population of natural enemies of the order Diptera, Hymenoptera and Coccinellidae and nymphs and adults of O. lybicus revealed that there was a direct correlation between the population of nymphs and three orders of natural enemies in both years but any correlation was not observed with adult population. The results of egg distribution show they do not lay their eggs on fruits and spadix but they lay their eggs on the upper and lower surface and axis of leaflets. Maximum hatching rate was estimated 90.91 and 91.18 in the first and second generation in Kerman province, respectively while it was 63.96 and 74.29 in winter and summer generation in Bushehr province respectively. Counting Eggs showed that highest rate of eggs was laid on the upper surface of leaflets in both generations so that, the eggs percentage was 65.69%, 9.63% and 28.62% on the upper, lower and axis of leaflets, respectively. The egg laying percentage was 52.9% and 47.09% on young and old leaves, respectively so pruning of old or lower leaves is recommended. The nymphs are hiding during the heat of the day between the bases of the new fronds, Palm trunk fiber and on shoots in both generations. Spot spraying is recommended for high density of nymph controlling on single tree and city garden (like Bam) at this time. It is important in pest management program to pay attention that O. lybicus overwintering in nymph and adult beside egg in Bushehr. Key words: Ommatissus libicus, biology, seasonal fluctuations in the population