How to control the box tree moth? Pest control methods for garden ornamental trees
Distribution and damage The box tree moth Diaphania perspectalis Walker, also known as the boxwood black-edged pyralid moth, belongs to the order Lepidoptera, family Pyralidae. It is distributed nationwide. The larvae damage large-leaved boxwood, boxwood (Buxus sinica), Lushan boxwood, common boxwood, Korean boxwood, Japanese boxwood, holly and Euonymus, etc. This pest occurs suddenly; in mild cases it affects normal growth, and in severe cases the leaves wither and drop, leaving bare branches and causing young plants to die.
Morphological characteristics The adult is about 23 mm long, with a wingspan of about 48 mm. Apart from the dark brown broad bands on the costal, outer and inner margins of the forewings and the outer margin of the hindwings, most of the body is covered with white scales with a purplish-red sheen. In the broad band on the costal margin of the forewing there is 1 crescent-shaped white spot. The male moth has a black hair tuft at the end of the abdomen and is relatively slender; the female moth has no hair tuft at the end of the abdomen and is relatively stout. The egg is oblong, flat, neatly arranged, and not easy to find. When mature, the larva is about 40 mm long, with a black head and a yellow-green thorax and abdomen. The dorsal midline is dark green, with yellow-green and blue-gray transverse bands on both sides, and each segment has distinct black wart-like protuberances bearing setae. The pupa is spindle-shaped, with 8 anal spines arranged in a row, their tips curled into hooks.
Life habits In the Nanchong area of Sichuan, 5 generations occur a year; in Shanghai, Jiangsu and Zhejiang, 3 generations a year; and in North China, 2 generations a year, all overwintering as larvae in webbed leaves. In North China, the overwintering larvae become active and cause damage from mid-March to early April the following year, with the peak in early May; in mid-May they pupate in the webbed leaves, and the pupal stage lasts about 9 days. The adults have weak phototaxis, hide by day and emerge at night, and the female moth lays eggs on the underside of leaves; the egg stage is about 7 days. The larva has 6 instars in total. In the Shanghai area, the larval damage periods are: the first generation from early May to early June, the second generation from early July to early August, and the third generation from late July to late September; the second-generation larvae occur most commonly and cause serious damage. If control is not timely, the leaves are eaten bare and the plants turn yellow and wither. In late September the larvae spin webs and bind leaves into a nest, in which they make a thin cocoon and overwinter; natural enemies include the ichneumon wasp, ants, egg parasitoid wasps, etc.
Integrated control
(1) Manual control In combination with maintenance and management, manually remove the webbed larval nests in a timely manner to kill the larvae or pupae.
(2) Trapping and killing adults During the adult stage, use black light traps to kill them.
(3) Chemical control When the infestation is severe, spray 5% Nomolt (hexaflumuron) emulsifiable concentrate or 10% Trebon suspension concentrate at 2000 times dilution for control, to reduce the population and lessen the damage. Strengthen pest monitoring; it is best to spray in the evening, when the effect is better.