Implementation of a risk assessment program to forecast greyback canegrub damage in Mulgrave sugarcane fields

Abstract

RISK ASSESSMENT OF damage caused by the greyback canegrub, Dermolepida albohirtum, was implemented in the Mulgrave sugarcane growing region of Far North Queensland. Twenty growers participated in a ‘GrubPlan’ Integrated Pest Management (IPM) program where the risk of potential greyback infestation on selected fields on their farms was assessed. This was based on monitoring grub numbers and damage levels in 2008 to predict grub densities in 2009 using previously developed prediction models. Growers were advised whether or not to treat these fields according to the predicted level of risk, and the majority of growers accepted our recommendations. The same fields were sampled again in 2009 to validate predictions. Data showed a significant reduction in grub numbers where growers applied a chemical treatment following our recommendations. Grub numbers did increase in fields that were not treated; however, where growers were advised to refrain from treatment, grub numbers were still well below economic levels. We also validated two types of prediction models that are currently available: 1) a discriminant model, which predicts the likelihood of grub densities being either low, medium or high, and 2) a regression model, which predicts actual grub number/plant in the following year. Results showed that the discrimination model was more reliable, while more work is needed to improve the regression model. This study demonstrates the feasibility of implementing a risk assessment program to enable strategic application of insecticides and to encourage growers to embrace a proactive approach towards grub management. The success of this project confirms the value of BSES extension programs and demonstrates the importance of research-based extension in pest management.