In recent years, the cotton mealworm, once a minor pest in cotton production, has become one of the most significant threats in many cotton-growing regions. Known also as whitefly or sweet potato whitefly, this pest is scientifically identified as *Bemisia tabaci*. According to the latest findings from the Institute of Plant Protection under the Chinese Academy of Agricultural Sciences, this species, originally from the Mediterranean-Asia Minor region, has become a "super pest" due to its wide range of damage across important crops like cotton, vegetables, and tobacco. It was introduced into China through the importation of plants such as poinsettia. The introduction led to an "asymmetrical mating interaction" between native and invasive whiteflies, which significantly boosted the population of the B-type whiteflies while suppressing the native ones. This shift has resulted in recent outbreaks of tobacco whitefly, causing severe damage.
Adults and nymphs of the cotton mealworm both harm cotton plants, with the nymphs being particularly destructive. The adults have a waxy white coating on their bodies and wings. Nymphs go through five instars, with the first instar being mobile and later stages attaching themselves to the underside of leaves. These pests can produce up to 10 generations per year. In May, they begin to appear in cotton fields, thriving best at temperatures between 20°C and 30°C. By August and September, damage peaks. Initially, only a few insects are found on the upper leaves, but within days, both upper and lower leaves suffer extensive damage. The upper leaves may have 50 to 60 adult and nymphs per leaf, with some areas reaching 2,000 to 3,000 or even 4,000 to 5,000 individuals. After feeding, the leaves show yellow or reddish-brown spots, followed by curling, scorching, and eventual leaf drop. This leads to reduced boll weight and yield losses ranging from 5% to 30%.
To manage this pest effectively, several preventive measures are recommended. First, it's crucial to raise awareness about the threat posed by cotton mealworms. Relevant authorities should issue timely yellow alerts. Agricultural technicians and farmers must remain vigilant, recognizing the serious challenges these pests pose to cotton farming. Early intervention using motorized sprayers should be organized, especially in high-risk areas, and even low-infestation fields require early prevention.
Second, maintaining a clean environment around cotton fields is essential. While cold winters and springs can help suppress whitefly populations, nearby vegetable greenhouses provide shelter for them. Therefore, removing leftover plant debris from greenhouses and weeding cotton fields can reduce the risk of infestation.
Third, chemical control should be applied promptly. Options include 3% Royal Dan wettable powder at 60 grams per acre, or 3% Qi Qiao EC at 50 ml per acre, mixed with 15–30 kg of water for spraying. Alternatively, silver finches (3% acetamiprid wettable powder) diluted 1000–2000 times, or 20% acetamiprid wettable powder at 1500 times, can be used alongside 1.8% abamectin EC at 3000 times. At the early stage of infestation, 25% Buprofimone EC diluted 1000 times is also effective. Timely application of these treatments can help prevent further spread and minimize crop losses.
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