Control Methods for the Boxwood Narrow Jewel Beetle

Large-leaf boxwood (Euonymus japonicus) is a tree species widely used for landscaping. In recent years in the Nantong area, large-leaf boxwood has been found to die off, initially in scattered patches and gradually developing into large areas of dieback. Breaking off dead trees at the root collar revealed insect-bored tunnels. Observation showed this to be damage by the narrow jewel beetle.

The large-leaf boxwood narrow jewel beetle belongs to the order Coleoptera, family Buprestidae, genus Agrilus. This insect's larvae bore into and feed on the stems of large-leaf boxwood, weakening the plants until they die.

I. Morphological Characteristics

Adult: body length 5-7 mm, compactly built, head and thorax dark brown, elytra bronze-colored, with a relatively wide oblique black patch in the posterior middle. The top of the head differs between male and female: the male's is blue, the female's brown. Larva: known as the "flat-headed borer." Mature larva body length 10-13 mm, flat and bead-shaped, milky white. Prothorax broad and flat. Thorax legless, the mesothoracic spiracle larger than the abdominal spiracles, crescent-shaped. The head-thorax dorsal plate has brown stripes, and the end of the abdominal segment bears a pair of small brown tail pincers. Pupa: spindle-shaped, initially milky white, turning black before eclosion, length 6-8 mm. Egg: white, spherical, diameter 1 mm.

II. Living Habits and Life History

One generation occurs each year, overwintering as larvae. Overwintering larvae become active from late February to April of the following year, pupate in May, and emerge as adults in June. Adults are rarely seen on large-leaf boxwood. In the morning and evening, adults rest on the undersides of leaves and branches of other surrounding plants; they have a feigning-death habit and slight phototaxis. Late June is the peak period of adult activity, and noon each day is the peak time of the day's adult activity, when they feed on tender leaves and mate. Adults emerge female first, then male. Larvae appear in July, and by early August some larvae have already bored into nests in the xylem, overwintering with their bodies folded. Eggs are laid around late June, in cracks in the stem bark, and hatch in late June and early July. After hatching, larvae bore upward in a spiral pattern beneath the stem bark; the frass is not expelled and appears brown. By late July, 3-5 larvae are present beneath the damaged bark within the stem, and the plant shows pale leaf color and wilting; in severe cases the plant dies. In early to mid-May of the following year, larvae begin to pupate, taking about 8 days to become initial pupae and 13 days to emerge as adults.

III. Control

(1) Strengthen management: in winter, remove plants that have died or become severely wilted after being bored by larvae, and destroy them by soaking in water, deep burial, or burning. (2) Based on the adults' daytime activity, seize the opportunity in mid-to-late June to spray insecticides such as dimethoate or deltamethrin on the trees, flowers, and grasses around the plants to kill the adults. (3) Dig out larvae. When larvae have just entered the xylem, the bark can be shaved off with a knife and the small larvae dug out. (4) Inject insecticide into the insect holes and seal the openings with thin mud. (5) For plants that have not died but are beginning to wilt, apply a systemic insecticide at their roots.