In recent years, cotton mealworms—previously considered a minor threat to cotton production—have become one of the most serious pests in many cotton-growing regions. Also known as whiteflies, these pests have caused significant damage due to their rapid reproduction and invasive nature. According to the latest research from the Institute of Plant Protection under the Chinese Academy of Agricultural Sciences, the Bemisia tabaci species responsible for damaging crops like cotton, vegetables, and tobacco is originally a type B variant from the Mediterranean-Asia Minor region. This pest has been labeled a "super pest" by the global scientific community. It was introduced into China through the importation of ornamental plants such as poinsettias. A key factor in its spread was an "asymmetrical mating interaction" between the imported B-type whiteflies and the native whitefly populations. This led to a sharp increase in the B-type population while suppressing the indigenous species. As a result, the more harmful B-type whiteflies have taken over, leading to outbreaks of tobacco whitefly in recent years.
Both adult and nymph stages of the cotton mealworm can damage cotton plants, with nymphs being particularly destructive. Adults have a waxy, white coating on their bodies and wings, while nymphs go through five instars. The first instar is mobile, but later stages remain fixed on the underside of leaves. These pests can complete up to 10 generations per year. Cotton seedlings typically begin infesting fields in May, with optimal temperatures ranging from 20 to 30°C. The peak of damage occurs between August and September. Initially, only a few insects are found on the upper leaves, but within days, both upper and lower leaves become heavily infested. The upper leaves may contain 50 to 60 adults and nymphs per leaf, with some areas having up to 2,000 to 3,000 individuals. After feeding, the leaves show yellow or reddish-brown spots, and the edges and entire leaves begin to curl and scorch. This leads to premature dropping of bolls, reducing boll weight and ultimately decreasing yield by 5% to 30%.
To manage this pest effectively, several preventive measures are recommended. First, it's crucial to raise awareness about the severity of cotton mealworm infestations. Relevant authorities should issue timely yellow alerts, and agricultural technicians and farmers must stay vigilant. Early-stage spraying using motorized sprayers should be organized, and even low-infestation areas need early prevention.
Second, maintaining a clean environment around cotton fields is essential. While winter and spring frosts can help control the population, nearby vegetable greenhouses provide shelter for the pests. Therefore, removing leftover plant debris and weeds from greenhouses and fields can significantly reduce the insect source.
Third, chemical control should be implemented promptly. Recommended 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, 1000–2000 times dilution of silver finches (3% acetamiprid wettable powder) or 1500 times dilution of 20% acetamiprid wettable powder can be used. Mixing with 1.8% abamectin EC at 3000 times dilution is also effective. At the early stage of infestation, 25% Buprofimone EC diluted 1000 times can be applied. Timely and targeted application is key to preventing widespread damage.
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