Hibiscus Pink Mealybug

📖 Description

Hibiscus Pink Mealybug (Maconellicoccus hirsutus — the Pink Hibiscus Mealybug) is one of the most serious sap-sucking pests of hibiscus (Hibiscus rosa-sinensis — one of India’s most popular urban and landscape ornamental plants) and okra (Abelmoschus esculentus — bhendi, one of India’s most important vegetable crops) across the Indian subcontinent and worldwide. Particularly severe in urban and landscape plantings of hibiscus throughout India (hibiscus is among the most widely planted ornamentals in Indian gardens — used for the flowers which are offered in Hindu worship, used for hair care, and used to make hibiscus tea; hibiscus is the national flower of Malaysia and a popular ornamental across tropical Asia). The pest is also a major pest of okra in India — India is the world’s largest producer of okra (over 6 million tonnes annually from over 530,000 hectares), and M. hirsutus causes 50-80% yield loss in severely affected okra crops. The pest is unusual among landscape ornamental pests because (a) it is highly polyphagous — populations build up on hibiscus, okra, cotton, cocoa, citrus, grapevine, mulberry, and over 300 other plant species, allowing rapid and damaging infestations on a wide range of crops, (b) the mealybug causes characteristic ‘bunchy top’ or ‘leaf bunching’ symptoms — caused by toxic saliva (diagnostic for this species — leaves and shoots at the growing tip become distorted, crinkled and bunched together; distinct from other mealybug species which cause general yellowing and stunting), (c) the mealybug characteristically feeds on tender shoots and flower buds — directly reducing flowering and ornamental value of hibiscus (the colourful flowers are the ornamental feature), (d) the pest has 12-15 overlapping generations per year allowing rapid population buildup, with each female laying 200-400 eggs in loose cottony ovisacs, (e) the mealybug characteristically hides in leaf axils and flower buds where the waxy covering makes them difficult to wet with contact insecticides — making infestations difficult to control with conventional insecticide sprays, and (f) the mealybug is a major invasive species — has spread rapidly across the Caribbean, Central America, South America, Africa, and Southeast Asia in the last 30 years, causing severe damage to hibiscus, okra, cotton and other crops (the pest is native to South Asia but has invaded many other tropical regions). IPM with clean planting material, weekly plant inspection for ‘bunchy top’ symptoms, biological control (Cryptolaemus montrouzieri ladybird beetles — the mealybug destroyer, highly effective; Anagyrus kamali parasitoid — specific to M. hirsutus, highly effective; Verticillium fungus; conservation of native predatory bugs, lacewings, and ladybirds), neem-based sprays (with surfactant to break down the waxy covering), need-based insecticide rotation (Buprofezin — insect growth regulator effective against nymphs, safe to predators), pruning of infested shoots, ant control, and weed host management provides effective control. The pest is a particular concern for Indian urban horticulture and okra growers because (i) hibiscus is one of the most widely planted ornamentals in Indian gardens and the flowers are used in Hindu worship — any widespread outbreak would affect urban aesthetics and religious practices, (ii) the colourful flowers are the ornamental feature — mealybug damage to flower buds directly reduces the show, (iii) the mealybug is a major pest of okra — India’s most important vegetable crop, causing 50-80% yield loss in severely affected crops, (iv) the mealybug’s waxy covering and hidden feeding in leaf axils and flower buds make control difficult with conventional insecticide sprays, and (v) the mealybug has spread to many other tropical countries — making it a quarantine concern in international trade.