Importance of Longhorn Stem Borers in Durian and Their Control

Abstract

The studies on the longhorn stem boring beetle in durian were carried out in major planting areas throughout the country during October 2003 to July 2005. Series of experiments including the survey on infestation, infestation behavior, courtship and oviposition behavior, life cycle, and chemical control were conducted. There were more than one species of longhorn beetles, ingested durian but Batocera rufomaculata (De Geer) was the most prevail. Adult are 4-6 cm in length, pronotum with a strong sharply pointed tooth at each side; elytra rough and with small black raised spots near the base, humeral angle bearing a small sharply pointed spine at each side, antennal segments generally rough surface and with spines. This species are black or ferupinous yellow, pronotum with and orange-red spot on each side of median line; scutellum yellow; elytron with medium orange spots scattered towards apex and some small orange spots among the black raised spots at the basal half. Female beetle chews a small tunnel shaped depression in the tree bark and inserts an egg under the bark. After hatching from the egg, the beetle larva initially feeds under the bark. Young larvae begin feeding in the phloem tissue then migrate into the heartwood to pupate. Damage from small larvae was difficult to be assessed, but hole,tunneling, dipping sap, and frass can beobserved on the bark when they grew up. Full grown larva is 8-10 cm in length. Larval and prepupal + pupal stage lasts about 280 and 24-29 days respectively. For insecticide efficacy trial on stage of longhorned beetle, it was found that imidacloprid (Confidor 100SL 10% SL). Acetamiprid (Molan 20% SP), and thiametoxam (Actara 25% WG) at the rates of 30 ml, 30 and 40 g per 20 l of water, respectively, gave the best control of longhorn beetle larvae.