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IPMG wraps up ten years of research

­­IPMG members

Figure 1: Participants at the Albany workshop in Western Australia in July. From left: Matt Armstrong (ITC); Bob Edwards (GSL); Hans Blom (Timbercorp); Svetlana Micic (DAFWA: Department of Agriculture and Food WA); Robert Archibald (Murdoch University); Wendy Bradshaw (South Coast NRM); Justine Edwards (GSL); Sally Black (Timbercorp); Chris Szota (ex GSL); Melissa Gordon (ex Timbercorp); Allie Munelli (AFRC: Albany Forest Research Centre); Euc Asada (AFRC); Mal Parker (GSL); Peter Wood (DAFWA).

Mamoru Matsuki
Department of Agriculture, Western Australia

The Industry Pest Management Group is in the process of being restructured and has been holding "wrap-up" workshops in the Green Triangle and Western Australia to pull together all aspects of the main IPMG activities over the past ten years.  Twenty-three industry representatives attended either of two workshops that were held in Hamilton (Victoria) and Penola (South Australia) on 25th and 26th June. Participating companies included Integrated Tree Cropping (ITC), Great Southern Limited (GSL) and Timbercorp.  Western Australian workshops were held in Bunbury and Albany on the 6th and 7th of July.  These were well attended by interested industry partners including 11 people from Great Southern Timber Holding and WA Plantation Resources (Bunbury workshop) and 16 people from ITC, GSL, Albany Forest Research Centre, Timbercorp, South Coast Natural Resource Management, Department of Agriculture and Food (Western Australia), and Plantall Ltd. (Albany workshop; Fig 1).

Each workshop covered all main aspects of IPMG activities in the past ten years.  Results of IPMG research projects were summarised in presentations; follow-up discussions identified the strengths and key missing links in IPMG research.  Each workshop was divided into four sections that included a presentation followed by general discussions:

1)  Summary of the goal and conceptual structure of IPMG research.  Participants in all workshops agreed that the goal of IPMG research has been to ascertain whether or not damage by insects causes economic loss due to reduced harvest volume.  Figure 2 shows the summary diagram of IPMG research projects.  You may view this in more detail in slide 1 of the power point presentation (click here to download pdf of a summarised powerpoint presentation).



Figure 2: Interactions between insect abundance, tree damage, tree growth and harvest volume are never simple (click for larger image).

2)  Relationships between: (i) abundance of insects and damage levels; (ii) damage levels and tree growth; (iii) tree growth and harvest volume.  IPMG has four insect exclusion trials that have been carried through to harvest.  The trials started when the trees were 3 years old and ended when the trees were harvested (10 - 12 years old).   Insects were excluded from when the trees were 3 yr old (at the beginning of the trial) to when the trees were 5.5 years old.  There was no statistically significant difference in harvest volume between the control and insect exclusion treatments.  Results of other short term studies by IPMG also indicated that insect damage does not necessarily result in reduced growth of trees.

3)  Key insect pests in blue gum plantations: (i) how to group insects based on how they feed; (ii) seasonal pattern of abundance; and (iii) factors affecting the seasonal pattern of abundance (see slides 2-10 of summarised powerpoint presentation).

4)  Pest management: (i) risk assessment; (ii) population assessment; (iii) options for control; (iv) biological control; and (v) how to develop and write effective pest management plans (see slides 11-19 of summarised powerpoint presentation).

The issue of biological control in blue gum plantations was a hot topic for discussion.  When blue gum plantations were newly established in Western Australia, there was an idyllic "honeymoon period" during which there were very few insects in the plantations and very little insect-related damage.  However, within a few years a small number of pest species started causing severe and extensive damage. More recently, most severe damage caused by insects is found in small patches or in areas where blue gum plantations have been newly established.  What caused this pattern of deterioration and amelioration in the severity and extent of insect damage to plantations?  In recent years insecticide spraying in post-establishment plantations has been reduced to nearly zero in Western Australia, so reduced insect damage can not be attributed to the use of insecticide.  The solution appears to have been biological.  In the last ten years more than 150 species of herbivorous insects have been recorded on blue gum in WA.  Of those, only about ten species are considered to be pests and more than 65 are considered to be natural enemies of the pest species.  Furthermore, over twenty species of insectivorous birds have been recorded in blue gum plantations in Western Australia.  It appears that increased diversity of insect herbivores and their natural enemies in blue gum plantations may have resulted in reduced occurrence of severe and extensive damage by insect pests.  This conjecture is consistent with observations from overseas where a small number of insect pests cause extremely severe damage in eucalypt plantations.  In such plantations, diversity of insect herbivores and their natural enemies are very low.

The final activity in the workshop was a "hypothetical".  Participants were asked to come up with a brief management plan for an unknown insect (introduced accidentally from overseas) that has been found to be causing severe damage in plantations.  The participants used their knowledge and understanding gained from the workshop to suggest an outline of a management plan.

Biobuzz issue nine, August 2009