Banana weevil borer control in south-eastern Queensland

Abstract

Banana weevil borer Cosmopolites sordidus (Germar) is the main insect pest of bananas in south-eastern Queensland and northern New South Wales. Four trials were conducted over 3 years to test current and new pesticides and 2 species of entomopathogenic nematode Heterorhabditis zealandica Poinar (strain 327) and Steinernemu carpocapsae (Weiser) (strain BW), in growers' plantations at Yandina and Wamuran. Nematodes were applied in a thickened aqueous solution into 200 mm deep incisions in the residual rhizomes of harvested plants usually at bimonthly intervals from November to May. The treatments were not effective possibly because of early nematode mortality caused by free water in the spike holes and/or because of the need for more frequent application. More than 1 or 2 applications a year, however, would probably be uneconomic. Prothiophos (5 g a.i./stool) was the most effective of the currently registered pesticides and bifenthrin (0.25 g a.i./stool) consistently effective among the new pesticides. Both were significantly better than all other treatments on most occasions. Efficacy was assessed using pseudostem traps (to assess beetle activity) and a sliced peripheral cut to the side of the rhizome (to assess damage by larvae). Monitoring of populations and damage by these techniques will promote the most effective and minimal use of pesticide treatments. Average beetle catches of 2 per trap and damage ratings of 2 are proposed as action thresholds for south-eastern Queensland.