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Linking the leaf beetle IPM program with health surveillance

The leaf beetle IPM (Integrated Pest Management) monitoring program has been operating for the past 20 years. Over this time the eucalypt plantation estate has aged and expanded. This has highlighted the importance of a targeted program that effectively monitors those plantations most at risk. For the past 2 years we have investigated the effectiveness of our monitoring program by conducting intensive defoliation surveys. These surveys have shown that our control operations are successful at limiting moderate and severe defoliation in high population areas, indicating our IPM program is effective.

Throughout summer, leaf beetle larvae hatch, feed and grow, before pupating in the soil and emerging as adult beetles late in the season. The forest health surveys have shown us that it is this second generation of adult beetles that is responsible for most of the moderate and severe damage observed throughout the estate. Most of this leaf beetle defoliation occurs in high-elevation (>500 m) plantations. We are collaborating with the University of Tasmania to get a better understanding of why such site differences occur.

Traditionally, leaf beetle management has focussed on younger plantations 2 to 6 years old, due to the belief that this is when trees are most vulnerable, particularly in plantations managed for solid wood where leaf-beetle defoliation that coincides with crown removal during pruning could result in significant growth reduction. However, the health surveillance results showed that the majority of plantations that suffered moderate or severe defoliation were older than those normally included in the IPM monitoring program. All previous modelling of impact has focussed on young plantations, so we are developing methods to monitor older plantations, and collaborating with CSIRO and the CRC for Forestry to model defoliation impacts in older plantations so as to better focus management efforts.

Forest health surveillance needs to be linked to operational pest management to evaluate the effectiveness of the surveillance, but this is rarely done anywhere in the world.  It is an approach that will give us a much clearer understanding of how to optimise management of leaf beetles.


Karl Wotherspoon
Leonie Jordan

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