Studies on the Bionomics and Local Distribution of Some Lace Bugs in Thailand VI. Dulinius conchatus Distant (Hemiptera : Tingidae)

Abstract

The morinda lace bug (MLB), Dulinius conchatus Distant is a major pest of the various plants in the family Rubiaceae. The feeding of adults and nymphs causes scattered of a white patches or spots easily seen from the upper surface of leaves, because the chlorophyll is destroyed from the leaf tissue. Apart from this symptom, the nymphs also excrete black liquid dots scattered on the underside of leaves. Life history of the MLB was studied in detail under laboratory condition. It was reared on the Indian mulberry leaf, Morinda citrifolia Linn. The results revealed that the eggs were laid singly or in groups in the plant tissue at the midrib and other veins on the underside of leaves. The incubation period of egg averaged 9.22±0.29 days. Nymphs were found congregated on ventral surface of the leaves. The five nymphal instars averaged 2.01±0.01, 1.28±0.05, 1.55± 0.08, 1.83±0.03 and 2.95±0.04 days, respectively. The mean duration of the five successive instars were 9.62±0.10 day. The developmental period from egg to adult were 18.84±0.37 days, and the life spans of male and female averaged 47.67 and 37.40 days respectively. Female laid an average of 177.40 eggs. The MLB can be found in all parts of Thailand where Morinda Plants are grown. Four species of the host plants found during surveys from June 1988 to June 1990 were Morinda citrifolia linn, M. coreia Harm., M. elliptica Rid1. and Paederia linearis Hook. f.