Direct and indirect influences of intercrops on the coconut defoliator Opisina arenosella

K. S. Shameer,Chandrika Mohan,Ian C. W. Hardy,M. Nasser

doi:10.1007/s10340-017-0904-6

Abstract

Coconut palm (Cocos nucifera) infestation by Opisina arenosella (Lepidoptera: Oecophoridae) in the Indian subcontinent may occur in November to May each year in the same or adjoining areas of plantations. Parasitoids of O. arenosella may also be consistently present at these times. During other periods, pests and/or parasitoids could be maintained on intercrops that are commonly grown throughout the year. Field surveys of 54 intercrop species in Kerala, India, found that O. arenosella attacks banana, but not others, while laboratory screening showed that O. arenosella can mature on jack fruit, cashew and oil palm. Larvae of 20 lepidopteran species found on intercrops were screened for use by Goniozus nephantidis (Hymenoptera: Bethylidae), a larval parasitoid of O. arenosella, which oviposited on two species but its offspring failed to mature. Thirteen intercrop herbivore species were screened for use by Brachymeria nosatoi (Hymenoptera: Chalcididae), a pupal parasitoid of O. arenosella, which completed development on the pyralids Herculia nigrivita, Syllepte derogata and Psara basalis. Further, connectance trophic webs were compiled using prior field records of coconut, 33 species of intercrops, 58 species of lepidopteran herbivores and 29 species of primary parasitoids. Both laboratory and literature evidence suggests that populations of O. arenosella are unlikely to be maintained by feeding on intercrops or strongly influenced by direct competition with other lepidopterans but are likely to be affected by sharing parasitoids. Intercrop herbivores have clear potential for maintaining parasitoids of O. arenosella, and we recommend thirteen plant species as intercrops that should aid in conservation biocontrol.

Highlights

The coconut palm, Cocos nucifera L., is grown in more than 93 countries, in areas totalling 12,479 million Ha, and yields harvest in all seasons
Larvae of 20 lepidopteran species found on intercrops were screened for use by Goniozus nephantidis (Hymenoptera: Bethylidae), a larval parasitoid of O. arenosella, which oviposited on two species but its offspring failed to mature
The most fed on intercrop species were Artocarpus heterophyllus (Jack fruit), Elaeis guineensis (Oil palm) and Anacardium occidentale (Cashew), where feeding rates were approximately 30–45% of those observed on C. nucifera (Coconut) leaves

Summary

Introduction

The coconut palm, Cocos nucifera L., is grown in more than 93 countries, in areas totalling 12,479 million Ha, and yields harvest in all seasons. Mohan et al (2010) reported that the nut yield of infested coconut palms could be reduced by as much as 45.4% in the year following severe pest incidence and that the number of flower bunches and leaves could be reduced by 21 and 13.8%, respectively. Opisina arenosella is reported to infest a number of other species of palms (palmyra palm, Borassus flabellifer Linn., Rao et al 1948; Murthy et al 1995; date palm, Phoenix dactylifera Linn., Butani 1975; Talati and Kapadia 1984; fan palm, Livistona chinensis, wild date palm, Phoenix sylvestris, Talati and Kapadia 1984; talipot palm, Corypha umbraculifera Linn., Talati and Kapadia 1984; Sadakathulla et al 1999)

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