Highly polyphagous invasive rugose spiraling whitefly (RSW), Aleurodicus rugioperculatus Martin was recorded on coconut at Pollachi, Tamil Nadu in 2016 by scientists from ICAR-NBAIR, Bengaluru. Subsequently, the pest rapidly spread to coconut growing districts of entire South India. It was later found to be feeding on banana, sapota, maize, oil palm, mango,cashew and many other ornamental plants. Recently, its occurrence was reported in Goa, Assam, West Bengal, Maharashtra and Gujarat. Nymphs and adults of this whitefly damage the plants by sucking the plant sap, especially from under surface of the leaves. Adults produce prodigious quantities of honeydew which in turn gets darkened by the development of sooty mold on the upper surface of leaves. The characteristic concentric waxy spiraling symptoms are noticed on several parts of the host plants. The hybrid and dwarf varieties of coconut like Chowghat orange dwarf, Malayan orange dwarf and Ganga bondam are preferred by the RSW.
Failure of chemical pesticides
Alarmed by the invasion of a pest unknown to them, farmers resorted to spraying of chemical pesticides to control RSW. But the efforts were in vain as the chemicals turned out to be a temporary fix and moreover, other ill effects like environmental pollution, killing of natural enemies and health risks to the people involved in spraying operations made the insecticide application a risky business apart from being uneconomical.
Biological control as an effective and sustainable solution
Explorations were carried out so that biological control of the pest could be accomplished through naturally occurring insect predators and parasitoids which are economically feasible, ecologically compatible and environmentally benign. Among natural enemies encountered, two aphelinid parasitoids, Encarsia guadeloupae and E. dispersa were found to have colonized the RSW and naturally suppressing the pest. The dominant parasitoid was found to be E. guadeloupae as it recorded natural parasitism of 56-82% while E. dispersa recorded 5-10%. Apart from these parasitoids, Dichochrysa astur, Jauravia pallidula, Cheilomenes sexmaculata and Cybocephalus sp. were also observed to be feeding on RSW.
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