Biological Suppression of Major Mealybug Species on Horticultural Crops in India
Mealybugs, known to be 'hard to kill pests', live in protected areas and most stages in their life cycle are covered in a waxy coating. Several insecticides are found ineffective against mealybugs. Fortunately, mealybugs - being sessile insects - are more amenable to biological control. The exotic parasitoid, Leptomastix dactylopii How., was found to be highly effective in suppressing citrus mealybug, Planococcus citri (Risso.) permanantly on citrus, sapota, guava, pomegranate and coffee. This is one of the recent successes in classical biological control attempts in India. However, the Australian ladybird beetle, Cryptolaemus montrouzieri Muls., often provides spectacular control of heavy infestation of P. citri on acid lime, lemon, sweet orange, pummelo, Crossandra and custard apple. Though Anagyrus dactylopii (How.), is a potential parasitoid of pink hibiscus mealybug, Maconellicoccus hirsutus (Green), on grapes, releases of C. montrouzieri only help in suppression of the pink hibiscus mealybug on grapes, ber, guava, sapota, custard apple, citrus and hibiscus. The encyrtid parasitoid, Tetracnemoidea indica (Ayyar), was able to check the oriental mealybug, Planococcus lilacinus (Ckll.) on acid lime and pomegranate. The predators, C. montrouzieri and Spalgis epeus Westwood, also play a major role in suppression of P. lilacinus on guava, ber, sapota and chow-chow. The local parasitoid, A. dactylopii was seen to play a major role in suppression of spherical mealybug, Nipaecoccus viridis (Maskell) on citrus and jackfruit. Nevertheless, releases of C. montrouzieri are found highly effective in controlling N. viridis on acid lime and pummelo. Similarly release of C. montrouzieri is found to be highly effective in controlling striped mealybug, Ferrisia virgata (Ckll.), on guava, tuberose and Acalypha in 30-40 days of release. A local parasitoid, Aenasius advena Comp., also plays a major role in suppression of F. virgata on guava, mango, guava, hibiscus, fig, citrus, etc. Release of the coccinellid predator, C. montrouzieri, was found very effective in controlling the mango coccid, Rastrococcus iceryoides (Green) on mango and also on the medicinal plant Decalepis hamiltonii. The encyrtid, Praleurocerus viridis (Agarwal), was found very effective in reducing populations of R. iceryoides on guava. Spalgis epeus was found to be the predominant predator of the papaya mealybug, Paracoccus marginatus Williams and de Granara Willink, but releases of the exotic parasitoid, Acerophagus papayae(Noyes&Schauff), only provide excellent control of P. marginatus within 3-4 months of release. The second successful classical biological control attempt on mealybugs in India. The brinjal mealybug, Coccidohystrix insolita (Green), is known to attack brinjal, Coleus, Hibiscus, etc. Cryptolaemus montrouzieri effectively controlled mealybugs on these three crops in 30-40 days of release. Verticillium lecanii Zimm. (Phule bugicide @ 2g/L) is found to be effective in killing the mealybug. Other fungal pathogens, viz., Beauveria bassiana (Bals.) Vuill and Metarhizium anisopliae (Metch.), are also seen to infect mealybugs in rainy season under humid conditions.
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