Control of tortoise back leaf beetle

Ipomoea aquatica and sweet potato leaf are the main vegetable varieties in summer. Recently, many vegetable farmers have reported that a small beetle has occurred in large numbers on these two kinds of vegetables. It bites the leaves and causes cuts and holes, causing disaster. After investigation, it was found that the insect belongs to the small or brown tortoiseshell of sweet potato in the group of tortoiseshell.

Sweet potato small tortoise shell and sweet potato brown tortoise shell shape is very similar, adult body length about 5 mm, hemispherical (often mistaken for ladybug farmers), body color is mostly yellow-green to green, and with metallic luster. The pronotum and the two elytra extend outward into a "turtle" shape, and the extension part has a reticulate pattern. Mouth chewing, black. Antennas light green, 11 nodes. Its larva body is green, long elliptic, body back middle unripe protuberant line, body all round unripe thorn, thorn 16 pair. The eggs are scattered near the veins, about 1 mm long, oblong, green. The pupa is flat rectangular, light green, large prothorax, surrounded by small spines, the head hidden under it, 1~5 abdominal segments on both sides of a flat large spinous process, pupa tail often adhere to the back of the leaf.

The insect mainly feeds on the leaves of Convolvulaceae plants such as Ipomoea aquatica and Ipomoea batatas. It occurs about 5~6 generations a year in Guangdong. Adults overwinter under weeds, dead leaves, soil cracks or stone cracks, and begin to feed actively in warm spring (temperature about 14℃). The main period of occurrence is between spring and summer and before mid-autumn. Due to its ability to fly and spread, the adult has a long life span, a long spawning period, a large number of eggs, eggs and young larvae scattered and unnoticeable, vegetable farmers neglect to guard against. In addition, in recent years, many places have continuous cropping of Ipomoea aquatica and sweet potato leaves, which provide rich food for them. Especially in May to June of each year, seasonal rainfall and typhoon influence period can not spray control pests, often resulting in a large number of occurrences, even outbreaks.

The following measures should be taken to control the beetle: (1) Clean the fields after harvesting the leaves of water spinach and sweet potato, and eradicate the weeds (especially the weeds of Convolvulaceae such as morning glory) in the fields to eliminate the overwintering insect sources. (2) Learn to identify various insect states, pay attention to observing and monitoring insect conditions, and take measures to eliminate the main force during the peak period of the first and second generations in May and June. (3) The insect is sensitive to pesticides, so low toxicity and low residue pesticides should be selected, and low concentration spraying should be used as far as possible. The selected pesticide varieties are: Aribax (4.5% EC) 3000~4000 times, trichlorfon (90% crystal) 1000 times, Nongster (40% EC) 2000~3000 times, Saifong (20% EC) 5000~6000 times. (4) Because water spinach and sweet potato leaves are harvested continuously in spring and summer, it is suggested to spray after each harvest to ensure a safe interval of more than 7 days. It is better to spray at dusk.