Field Investigations on the Interrelationships of the Big-Headed Ant, the Gray Pineapple Mealybug, and Pineapple Mealybug Wilt Disease in Hawaii

摘要

The population density of the big-headed ant was higher during the second (ratoon) crop than during the first crop of pineapple at both Poamoho and Molokai. At Poamoho, no mealybug wilt plants were found in plots where ants had been controlled, while the number of such plants increased sharply during the second crop in plots where ants were not controlled. The incidence of mealybug wilt was higher at the edges of plots than toward the middle reflecting the greater abundance of ants and mealybugs on the margins on the plots. Wilt spread in a contagious manner with the number of diseased plants increasing at a logrithmic rate over time. The coefficient of correlation between the number of ants caught in pitfall traps and the percentage of mealybug infested plants was very high (r = 0.97). Infestation of the Molokai experimental planting by big-headed ants started at the edges of plantings adjacent to abandoned fields and waste areas. Invasion progressed slowly, and two and one half years elapsed before all plots had become infested. Ant and mealybug populations in infested plots increased gradually and appeared to be strongly influenced by the phenology of the pineapple plants during the first fruit crop. Unusually heavy rainfall during March and April 1979 may have caused the dramatic reduction in ant populations observed then. Highest ant population levels occured about three years after planting when all untreated plots became nearly uniformly infested. Pest management strategies for pineapple ants and mealybugs are discussed, and it is suggested that a program of ant surveillance using bait stakes, coupled with treatment of field margins and adjacent infested old fields or uncultivated areas when ants are discovered, can prevent migration of these pests into plantation fields.