ECOLOGICAL STUDY ON THE COFFEE STEM BORER <I>XYLOT RECHUS QUADRIPES </I>CHEVROLAT (COLEOPTERA: CERAMBYCIDAE) IN NORTHERN THAILAND. III. INVESTIGATION OF ADULT EMERGENCE HOLES

Abstract

Adult emergence holes of coffee stem borer (Xylotrechus quadripes Chevrolat) were investigated in the orchards at Mae Lord, Pang Bong and in the laboratory during the period of 1991 to 1992 in Chiang Mai. The number of emergence holes apparently observed on the tree samples and the position of the holes on coffee stems were recorded and conclusively classified them into the new and old holes.

Among all tree samples, the maximum number of emergence holes observed per tree were 33 at Pang Bong and 12 at Mae Lord. The record also showed the averages of 6.13 and 3.00 holes per tree at Pang Bong and Mae Lord respectively. The emergence holes in both locations frequently occurred on the coffee stems at the heights of 100-150 cm beyound the ground level or about one half to one third toward the apex. Base on the observations, most of the adult borers were emerged in May with the average number per tree of 1.10 at Pang Bong and 0.68 at Mae Lord. At Pang Bong, 47.50% of emergence holes from the total number counted were recorded as the new one. In contrast, slightly high in number of 52.50% were determined at Mae Lord. Furthermore, the record of death plants, primarily due to the attack by stem borers were estimated at 35 and 20% for Pang Bong and Mae Lord respectively.

In the laboratory experiment, the observation on the adult emergence period during 24 hours revealed that the adult emerged during the daytime. The highest frequency of adult emergence was occurred at 10 a.m.