Biology and control of the dubas bug, Ommatissus binotatus lybicus de Berg. (Homoptera, Tropiduchidae), infesting date palms in Iraq

Abstract

The dubas bug, Ommatissus binotatus lybicus de Berg, is a serious pest of the date palm (Phoenix dactylifera) in Iraq, where there are two generations a year. Both nymphs and adults, which are described, suck the sap from the date palm. Repeated heavy infestations cause the weakening and death of some of the palms.The eggs are laid on all the green parts of the palm except the fruits, the majority on the leaflets, especially the upper surface. They are distributed evenly on the four aspects of the date palms, but unevenly on the frond rows, the second and fourth oldest rows having the majority of the eggs in the overwintering and summer generations, respectively. Deposition of eggs of the overwintering generation began in the second week of November and hatching started during the first week of April, the nymphal period lasting 47 days and the adults surviving for 15 days. Eggs of the summer generation were deposited from the second week of June, and hatching started in the first week of August, the nymphal period lasting 50 days and the adults surviving for 13 days. There are five nymphal instars.The nymphs excreted droplets of honeydew, and both nymphs and adults prefer the shady parts of the date palm. In order to escape the severe heat of the summer days, the nymphs and adults of the overwintering generation migrated towards the bases of the new fronds. The sex ratio was nearly 1:1, and the mean number of eggs laid per female was 106. The mortality rate for a constant population level was 98·11 per cent.The eggs were parasitised by a small Chalcidoid. The larvae of the lace wing Chrysopa carnea Steph. and the adults of Coccinella septempunctata L., C. undecimpunctata L., and Chilocorus bipustulatus (L.) preyed upon the nymphs and adults.In tests with inseeticidal sprays containing 240 g. active ingredient per 100 gal. applied at the rate of 1½ gal. per palm against adults and nymphs, DDT and malathion were equally effective, but Dipterex was less so. Similar concentrations of mixtures of malathion with heptachlor and DDT with diazinon were also effective.