Monday, December 3, 2012

Cape lilac caterpillar control using least toxic methods

 Cape Lilac/White cedar Caterpillar

Cape lilacs are a beautiful, tough deciduous tree that grows fairly commonly around Perth as a woody weed. Parrots often disperse the seed and the trees have become increasingly important food sources for the endangered forest red-tailed black cockatoos that are now having to include urban trees of the Swan Coastal Plain in their diets as more of their forest habitats are destroyed. Tony Cavanagh.

One drawback of the cape lilac is that they have their very own pest species, the cape lilac moth (Lepoctneria reducta) which lays hundreds of eggs, usually around autumn. Once the larvae form they invade homes, garages and sheds and crawl everywhere, horrifying and disgusting people that encounter them. The initial response of many people at this stage is to want to remove the tree or use highly toxic pesticides to control the pests. A single tree may have hundreds of caterpillars; these creatures crawl up the tree in the evening to feed and then retreat down to ground level to hide out during the day. It is this habit of climbing back down which gives us the opportunity for the least toxic way of trapping them.
Tie a piece of hessian or other thick soft material around the trunk of the tree. As the caterpillras crawl down the tree they will gather among the cloth to hide from the heat and light of the day. Simply gather up the cloth after sunrise and shake it over a tub of soapy water, maybe stirring it to ensure the caterpillars sink. Repeat the process for a few mornings and numbers will be rapidly reduced. Keep an eye on the tree's pest numbers from time to time by shining a torch into the canopy to see if there are problematic amounts present.

There are pictures here of all the life stages of Lepoctneria reducta, as cleverly compiled by these people at the Butterfly House. Thanks.

Hairy caterpillars are hard to control with sprays as the hairs protect them. Natural predators can be encouraged to help reduce numbers of cape lilac caterpillars. Paper wasps can control larvae, as can micro bats. 
Microbats live throughout the Perth region, living in holes in trees, under bark and in some wooden houses where there are good gaps. You can also build and instal a bat box. has some designs and info on bats.  This page from Perth Zoo also has some good information about Perth's micro bats. 
Cape lilac trees are a fantastic shade tree and it is quite easy to keep the numbers of cape lilac moth under control by using some simple measures that need no poisonous pesticides. Any tree that can help support the red-tailed blackcockatoos are pretty important too.

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