Occurrence Patterns and Control Methods of the White-Spotted Flower Chafer

The white-spotted flower chafer belongs to the order Coleoptera, family Cetoniidae, and is also known as the white-striped copper flower chafer, white-spotted flower chafer, white-spotted golden chafer, and copper chafer. It is distributed in Northeast China, North China, and the Huang-Huai-Hai region.

When the white-spotted flower chafer damages crops, the market quality is greatly reduced in mild cases, and completely lost in severe cases, bringing relatively serious economic losses to growers.

Hosts Currently, the hosts of the white-spotted flower chafer include corn, sunflower, tomato, watermelon, peach, grape, plum, strawberry, hop, the large composite weed bull thistle, willow, and elm.

Damage characteristics The white-spotted flower chafer mainly causes damage as an adult, with fresh-eating corn suffering the most severe damage, followed by sunflower, willow, and elm. In mid-to-late May, the earliest adults appear and begin feeding on the sap of willow and elm, greatly affecting the growth of young trees and newly transplanted trees. In mid-to-late June, the large composite weed bull thistle begins to bloom, and some white-spotted flower chafers move to the flower buds of bull thistle to suck sap. After entering July, the damage further intensifies. The white-spotted flower chafer begins to damage fresh-eating corn, sunflower, flat peach, plum, grape, watermelon, tomato, and hop. Because fresh-eating corn is mainly composed of sweet and waxy varieties, it suffers the most severe damage, especially early-sown corn. During the grain-filling and milk-ripe stage of corn, the white-spotted flower chafer directly feeds on the milky sap of the corn kernels at the tip of the ear, affecting the growth and development of the ear. On sunflower, it damages the flower disk, causing the disk to rot and reducing yield. Because our division has very little sunflower area, although the damage is severe, no economic loss has yet been caused. However, on some early-maturing aromatic grape varieties, the white-spotted flower chafer bites the fruit into holes and then feeds on the sap; the sap flows onto surrounding unbitten fruit, greatly reducing the market quality of the grapes, and the economic losses to growers are also relatively large.

Morphological characteristics The adult body length is 17-24 mm, width 9-12 mm, oval, with a bronze or copper-green luster, and the body surface is scattered with numerous irregular white felt spots. The front edge of the clypeus is folded upward and tilted, concave in the middle, with borders on both sides, and the outer side slopes downward; the antennae are dark brown; the compound eyes are protruding; the pronotum has irregular white felt spots, and the posterior margin is concave in the middle; between the posterior angle of the pronotum and the anterior margin angle of the elytra there is a very prominent triangular plate, namely the posterior lateral plate of the mesothorax; the elytra are broad, nearly rectangular, covered with coarse punctures, and the white felt spots are mostly in transverse wavy shapes; the pygidium is short and broad, with 3 white felt spots on each side arranged in a triangle; abdominal ventrites 1-5 have white felt spots on both sides; the legs are relatively stout, with white felt spots at the knees; the posterior outer end angle of the hind coxa is sharp; the outer margin of the fore tibia has 3 teeth, and the tip of each tarsus has 2 curved claws. Adults often lay eggs in soil at the junction of manure and soil, and the larvae (white grubs) mostly feed on decaying matter and move with their backs to the ground.

Life habits One generation occurs per year, and the larvae overwinter in compost, decaying matter piles, and soil rich in humus. Adults begin to appear in early May, with the peak occurrence from June to July, when damage is relatively severe, and their numbers gradually decrease in mid-to-late September. Egg laying begins after July, and adults lay eggs in compost, decaying matter piles, and soil rich in humus. The larvae feed on humus and generally do not cause damage. In May of the following year, the overwintering larvae make earthen cells at their living sites and pupate.

Adults are active during the day and have relatively strong flying ability, but they are mostly inactive in the morning and evening or on cloudy days when the temperature is lower, and they have a death-feigning habit, making them easy to catch.

The white-spotted flower chafer has no phototaxis. According to the author's years of statistics on forecast lamps, a large occurrence site of the white-spotted flower chafer was only 20-30 m away from a forecast lamp, but the forecast lamp did not attract a single adult white-spotted flower chafer. Therefore, frequency-vibration insecticidal lamps have no trapping and killing effect on the white-spotted flower chafer.

Adults have a relatively strong chemotaxis. They are attracted to the smell of sugar and wine vinegar.

Control methods 1. Manage farmyard manure well. Because adults have a strong attraction to undecomposed farmyard manure and humus and often lay eggs in them, farmyard manure should be piled centrally and decomposed through high-temperature fermentation to reduce places for adult egg laying and reproduction. 2. Before mid-May, turn over or apply the manure piles, pick up the larvae and pupae of the white-spotted flower chafer, and when necessary spray 50% phoxim emulsifiable concentrate at 1000 times dilution, or 40% dimethoate emulsifiable concentrate at 1000 times dilution, or 80% trichlorfon soluble powder at 1000 times dilution, for concentrated elimination. 3. Based on the characteristic that adults cause damage in groups, manual capture can be adopted in the morning and evening or on cloudy days when the temperature is low, and they can be concentrated and killed. 4. In the early occurrence period of the white-spotted flower chafer, hang narrow-mouth bottles on trees around sunflower, corn, orchard, and other sites. Wine bottles or cleaned waste pesticide bottles can all be used. The hanging height is 1-1.5 m. Put a little fruit flesh or wine vinegar in the bottle, then put in 2-3 white-spotted flower chafers, which can effectively lure other adults into the bottle. 5. Cut watermelon or melon into two halves, leave part of the flesh, and sprinkle a little wine vinegar and dichlorvos or other insecticides on it, which can also effectively trap and kill adults. 6. Mash the adults caught manually and trapped, soak them in water for 2-3 days, filter out the filtrate, dilute it with water, and spray it on the fruit, which can repel adults and prevent them from damaging the fruit. 7. When controlling the white-spotted flower chafer on willow and elm, phoxim emulsifiable concentrate and omethoate emulsifiable concentrate can be mixed and sprayed at double concentration, having contact, systemic, and stomach-poison effects, with relatively obvious control results.