Aggregation pheromones for the management of weevil borers: Possibilities and limitations

The use of pheromone mass trapping of adult sugarcane weevil borer, Rhabdoscelus obscurus, was tested during February-June 1999 in far-north Queensland. Lures used were rhynchophorol/octanol plus ethyl acetate in combination with several 5 cm lengths of split cane. Although traps attracted large numbers of adult borers, treated plots had higher numbers of borers compared to control plots. There were more infested stalks and more damaged internodes in the treated plots than in the control plots at the end of the season, with older internodes being more frequently infested than younger ones. However, there was a negative correlation between numbers of damaged internodes in treated plots and the total number of trapped borers, indicating that massive pheromone trapping of adult borers will result in less damage in cane. During the following season (January-August 2000), pheromone trapping was tested in combination with application of the insecticide Regent® (200 gIL fipronil at 75 g active ingredient per ha), in comparison to fipronil application alone. The data suggest that this combination may result in some level of weevil borer control. However, heavy invasion of rats as well as wind damage compromised the results in some plots. This work looks at the potential of using pheromone trapping in borer management as a part of an overall IPM program, and highlights the limitations of the application of this method of control and the challenges facing weevil borer management. Future research work is also suggested for the management of weevil borers based on our results.