Identification and control methods of the tea shot-hole borer

The adult and larval stages of the tea shot-hole borer both bore into the branches and trunks of lychee and longan, with branches 1-2 cm in diameter being the most heavily affected, and numerous nearly circular small entrance holes visible on the exterior. If an affected branch is cut open, several nearly ring-shaped horizontal small galleries will be found in the xylem, and dark brown beetles smaller than a grain of rice, or milky white legless larvae and pupae, are commonly seen. Because the transport of water and nutrients in the affected branches is blocked, the trees weaken in vigor and often produce dead branches and broken branches, and entire young trees have even been found killed by the damage. In recent years the tea shot-hole borer has been found in all major lychee and longan producing areas of China, with occurrence and damage being more severe in Zhongshan, Dongguan, Shenzhen, Maoming and other places in Guangdong. It has also been found in India, the Philippines, Sri Lanka and many other countries in Southeast Asia. In addition to lychee and longan, it can also damage tea, cacao, coffee, rubber, camphor trees, willow trees and other economic forest trees.

Morphological characteristics The tea shot-hole borer belongs to the order Coleoptera, family Scolytidae. The adult is small, only 1.3-2.4 mm long, dark brown, and cylindrical. The head extends into a short snout shape, and the antennae are geniculate with the tips swollen into a ball shape, which is an important external feature of this insect. The thoracic notum and elytra are densely covered with punctures and fine hairs. The male adult is smaller in body size and lighter in body color. The egg is white and oval, about 0.6 mm long. The larva is milky white and legless, and the mature larva is about 2.4 mm long. The pupa is milky white to yellowish brown, 1.2-2.4 mm long. Life history and main habits Near Guangzhou, the tea shot-hole borer has 6 generations per year, and because the adults live relatively long, the generations overlap. It mainly overwinters as adults in the galleries it has bored, begins activity when the weather warms in the following spring, and constructs new galleries. This insect lives a concealed life and also lays eggs in the galleries; in its entire life it only goes out for brief activity on sunny afternoons during the adult dispersal period, so chemical control is difficult to achieve effectively. The degree of damage to the host is closely related to variety, tree age, tree vigor and management level: Sanyuehong, Huaizhi and others are rarely damaged, while trees that are old, poorly managed and weak in vigor are severely damaged. The degree of damage is negatively correlated with the water potential of the tree. Control methods should be based on strengthening orchard cultivation management, reasonably increasing nitrogen fertilizer application, enhancing tree vigor and raising the water potential of the tree, combined with thoroughly pruning out infested branches after fruit harvest and during winter orchard cleaning, and collecting dead branches and broken branches in the orchard to burn together in a centralized manner. When necessary, field surveys and observations can be strengthened, and during the period when adults go out and disperse, sprays such as 90% batan wettable powder, 80% dichlorvos emulsifiable concentrate, 50% fenitrothion emulsifiable concentrate at 1000 times dilution, or 40% isocarbophos at 800 times dilution can be applied.