Elm Leaf Beetle Infestation: Non-chemical control
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Emerging immature beetles post-winter hibernation.
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Adult Elm Leaf Beetle feeding on leaves creating punctures that lead to the skeletonisation of leaves.
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Heavy infestations can cause extensive skeletonisation which decreases the trees’ capacity to photosynthesise. Although a healthy Elm tree can survive an initial attack, constant subsequent attacks in one season and over repeated years can lead to tree death.
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Tree banding was one method employed to decrease the ELB population. In this picture, the tape has trapped larvae, immature adults, and full adults.
Elm Leaf Beetle Infestation: Non-chemical control
The invasive and non-native Elm Leaf Beetle (ELB) (Xanthogaleruca luteola) was discovered infesting over a dozen European Elm Trees at a property on the Monaro Plains of NSW. ELBs and their larvae skeletonise and puncture leaves (pictured above). In dense populations this leaf damage can dramatically reduce the trees' capacity to photosynthesise and cause trees to defoliate. Multiple attacks, especially recurring attacks in the same season can ultimately lead to tree death.
The purpose of our work at this property was to dramatically reduce or eradicate the ELB population using organic methods not requiring insecticides. The conventional control method involves using insecticides classed as Neonicotinoids which are well documented to be detrimental to the environment, insects, birds, lizards, amphibians, and fish. This classification of insecticide has been linked to the decline in bee, bird, & aquatic life across Europe and has been banned in many countries (https://sophiespatch.com.au/2017/08/28/elm-leaf-beetle/) (https://www.eea.europa.eu/highlights/neonicotinoid-pesticides-are-a-huge).
Control methods included; banding with tape, and application of horticultural glue, with both tape and glue being replaced for maximum effectiveness each week. Elm suckers were removed to clean-up the area and to decrease habitat for larvae and hibernating adults. Biological controls were introduced and encouraged; plantings of lavender and other flowers nearby the trees were undergone to create habitat for beneficial insects such as lacewing and lady beetles. Lace Wing larvae were purchased and released periodically. The trees were given a little assistance with a nutritious boost to the soil surrounding them; beneficial mycorrhizae fungi were added, and an active vermiculture tea was applied.
The ELB population was dramatically reduced, the trees are now thriving, and we had a “Darwin” moment whereby we identified a new biological control that was previously unknown (a native beetle was observed predating upon the ELB, previous research had not identified any native enemies to the ELB in Australia, so we were VERY excited).