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Cord Association Of Fungi With Dead Nzinga Palmivora Wilson (Homoptera: Cicadellidae) In Coconut Plots In Ghana

Nzinga palmivora is one of the putative vectors of the Cape St. Paul Wilt Disease of coconut in Ghana. During a study to determine the seasonal population dynamics of the insect on coconut palms in the field, many of the insects were found dead and covered with fungal mycelia at one location. To investigate the role of the colonizing fungi in the death of the insects, two treatments of crude inocula, prepared from dead insects ground in sterile distilled water, were used to treat live insects in fyltis sleeve cages built around leaflets of coconut fronds. Insects treated with sterile distilled water (sdH2O) alone, served as the control. The insects treated with the crude inocula showed higher mortality compared with the control (p<0.001). The crude inocula also had adverse effect on oviposition, hatching of eggs into nymphs and the emergence of adults from nymphs. Fungal isolations from dead insects revealed apparently a total of 24 colonizing species of fungi. The most frequently associated fungus with dead insects after surface sterilization was a species of Penicillium (tagged as P. sp. 1). This was followed by Pestalotiopsis sp. and Cladosporium herbarum. The surface unsterilized dead insects yielded certain of these fungi more frequently than sterilized ones, besides several other species of fungi. Among the fungal isolates, the only known entomopathogen was Verticillium sp., however, it was isolated from only 2% of the dead insects studied and this may not account for the insect mortality encountered in the field, due to its low frequency of occurrence.  The implications of these findings and future direction of the study are discussed.

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