What are the control methods for tortoise beetle

Water spinach, sweet potato leaves and others are the main vegetable varieties for bridging the summer slack season. Recently, many vegetable growers have reported that a small beetle is occurring in large numbers on these two vegetables, biting the leaves and causing notches and holes, leading to disastrous damage. Investigation found that this insect belongs to the tortoise beetle group, specifically the sweet potato small tortoise beetle or the sweet potato brown tortoise beetle.

The sweet potato small tortoise beetle and the sweet potato brown tortoise beetle are very similar in morphology. The adult is about 5 mm long, hemispherical in shape (often mistaken by farmers for a ladybug), and mostly yellow-green to blue-green in body color with a metallic sheen. The pronotum and the margins of the two elytra extend outward to form a "tortoise" shape, and the extended parts have a reticulated pattern. The mouthparts are chewing type and black. The antennae are light green, with 11 segments. Its larva is green, long oval in shape, with a raised line running down the middle of the back and spines around the body, with 16 pairs of spines. Eggs are laid scattered near the leaf veins, about 1 mm long, long oval in shape, and green. The pupa is flat and rectangular, light green, with a large pronotum and small spines around it, the head hidden beneath it; the sides of abdominal segments 1 to 5 each have one flat, large spinous process, and the tail of the pupa is often attached to the underside of the leaf.

This insect mainly feeds on the leaves of Convolvulaceae plants such as water spinach and sweet potato. In Guangdong, it has about 5 to 6 generations per year. Adults overwinter under weeds, dead leaves, in soil cracks or rock crevices, and begin activity and feeding when spring warms up (at about 14°C). The period from the turn of spring and summer, through summer, to before mid-autumn is the main period of occurrence and damage. Because this insect has a certain ability to fly and spread, adults live a long time, the egg-laying period is long, and the number of eggs laid is large, while the eggs and young larvae are scattered and inconspicuous, vegetable growers neglect prevention. In addition, in recent years many places have grown water spinach and sweet potato leaves in large continuous cropping, providing it with abundant food. Especially during the seasonal rainfall and typhoon rain periods from May to June each year, when pesticides cannot be sprayed to control the pest, it often causes massive occurrence and can even break out into disaster.

The following measures should be taken to control tortoise beetles: (1) After harvesting water spinach and sweet potato leaves, clean up the field and eradicate weeds at the field edges (especially Convolvulaceae weeds such as morning glory) to eliminate overwintering sources of the insect. (2) Learn to recognize its various life stages, pay attention to observing and monitoring the pest situation, and grasp the opportunity during the peak occurrence of the first and second generations in May to June to take measures to eliminate the main force. (3) This insect is relatively sensitive to insecticides, so low-toxicity and low-residue insecticides should be selected, and spraying at low concentrations should be used as much as possible. The pesticide varieties available for selection include: Aruibao (4.5% emulsifiable concentrate) at 3000 to 4000 times, trichlorfon (90% crystal) at 1000 times, Nongsite (40% emulsifiable concentrate) at 2000 to 3000 times, and Saichongte (20% emulsifiable concentrate) at 5000 to 6000 times. (4) Since water spinach and sweet potato leaves are vegetables harvested continuously in spring and summer, it is recommended to spray after each harvest to ensure a safe interval of more than 7 days. Spraying at dusk gives better results.