What are the control methods for citrus flat-headed borer?

The citrus flat-headed borer has one generation per year in the Chenggu area, overwintering as larvae of various instars inside the branches and trunks of citrus trees. In late March, the larvae bore into the xylem and begin to pupate; mid-to-late April is the peak pupation period, with the pupal stage lasting about 25 days. Early May is the peak emergence period for adults, and mid-May is the peak period for adults to emerge from their holes. The emerged adults feed on a small amount of citrus leaves to supplement their nutrition, then mate and lay eggs. The edges of the damaged citrus leaves form small notches, but the damage to the leaves is not significant. Adults exhibit death-feigning behavior; once shaken, they fall to the ground and pretend to be dead. Late May to early June is the peak egg-laying period. Eggs are mostly laid among the moss and lichen on the branches and under rough cracked bark. The eggs are scattered, generally only 1 to 2 eggs per spot, with 3 to 5 in some cases, and they may overlap. July is the peak hatching period. After hatching, the larvae bore into the bark to cause damage, and a sputum-like gum foam appears at the damaged site, commonly known as "spitting foam" by local people.

Adult-stage control: After the citrus flat-headed borer pupates within the xylem of the trunk and chews through the bark to crawl out (emerge from its hole), it can then mate and lay eggs. Its emergence from holes is quite concentrated, and newly emerged adults have relatively weak resistance. Seizing this critical period to poison and kill the emerged adults, spray the branches and trunks with 5% DDT emulsifiable concentrate. The spraying height should ideally reach the parts of the branches and trunks with moss, lichen and cracked peeling bark, which both saves costs and achieves a control effect of over 90%. DDT is not only effective in directly poisoning adults, but may also have a repellent effect in preventing adults from laying eggs.

Larval-stage control: The sputum-like gum foam "spitting foam" phenomenon at the larval damage sites is another critical period for controlling the flat-headed borer. Applying a diluted solution of 1059 mixed with water (1:1) and 80% dichlorvos mixed with water (1:3) to the spitting foam sites gives very good control results. From late June to August, when gum foam holes are found on citrus trunks, scrape off the gum foam and a thin layer of bark with a knife (about the size of a 5-fen coin is sufficient), then apply the pesticide.

In addition, doing a good job of clearing the orchard before April, thoroughly scraping off the moss, lichen and peeling bark on citrus trees, can improve the effectiveness of branch and trunk spraying and eliminate egg-laying sites for the flat-headed borer.