The Role of the Palm Weevil, Rhynchophorus palmarum, as a Vector of Red Ring Disease of Coconuts. I. Results of Preliminary Investigations1

Abstract

The incidence of red ring disease was found to be highly correlated with the seasonal abundance of the palm weevil, Rhynchophorus palmarum (L.) Adult insects became contaminated with fragments of diseased tissue containing large numbers of nematodes after visiting diseased palms. The main source of contamination appeared to be the frass in tunnels excavated by the larvae during feeding, but adult weevils also became contaminated by bodily contact with diseased tissue and after walking through suspensions of worms in “pockets” in diseased palms. Internal contamination of the gut and body cavity also occurred following the feeding of insects on infected tissue. Virgin insects were found to be contaminated both externally and internally prior to emergence from their cocoons. The numbers of nematodes picked up by adult weevils was found to vary with the source of contamination, the density, stage, and activity of the worms present, and the age and feeding history of the insect. Longevity of the nematodes on the body surface of the insect varied between 2-6 days and was as long as 10 days in the gut and body cavity. External and internal contamination of the field population was found to be 38.5% and 9.8%, respectively. The incidence of red ring disease was significantly reduced following the application of endrin for palm weevil control.