White cotton-like masses made of flocks of bugs appear on the underside of leaves, stems, flowers, and fruits. Infestations can lead to yellowing and curling of young leaves, stunted growth of plants and early fall of fruits. The bugs excrete honeydew during sap-sucking and this makes the tissues sticky and prone to be colonized by opportunistic bacteria and fungi. Fruits are particularly susceptible to be attacked and may become deformed or completely coated by wax secretions. Ants may be attracted by the honeydew and may spread the pest to other plants. Older leaves are less likely to become deformed or distorted.
Mealybugs are oval, wingless insects found in warm or temperate climates. Their body is protected by a layer of thin mealy wax that gives them a cottony appearance. They insert their long piercing and sucking mouthparts (stylets) into plant tissues and suck the sap out of them. The symptoms are a reaction to the toxic substances that they inject into plants while feeding. The eggs of the mealybug are also laid in the soil. After hatching, nymphs and adults can crawl to neighboring plants. They can also be dispersed over large distances by wind, ants, animals, birds or simply during fieldwork activities such as pruning or harvesting. They have an array of alternative hosts such as eggplant and sweet potato, as well as many weeds. Warm temperatures and dry weather favor their life cycle and the severity of the symptoms.
At the first sign of slight infestation, smear the colonies of mealybugs with a cotton bud imbued with oil or spirit. You can spray the plants with insecticidal soap. Nearby plants should be sprayed with neem oil or pyrethrins in order to prevent the spread of the population. Natural antagonists include the green lacewing, parasitoid wasps, hoverflies, ladybird beetles, mealybug destroyer and the predator butterfly Spalgis epius.
Always consider an integrated approach with preventive measures together with biological treatments if available. Treatments against mealybug are difficult because they are protected from adverse environmental conditions by their waxy layers and fibers. However, foliar spray with solutions based on imidacloprid, acetamiprid and chlorpyrifos can be effective against mealybugs.