Terrie Greco, B.A.; HLT Dip.

When I was a child I found great pleasure in holding what I considered to be a fragile yet comical creature in my hand – the caterpillar.  Over the years, I came to realize that caterpillars are programmed for plant destruction. It’s a survival strategy to which allows them to develop into the adult stage as a moth or butterfly and reproduce.

The caterpillars I find most intriguing are categorized as ‘the social caterpillars’ – (see link below for an explanation).  They are the:

• Eastern Tent Caterpillar            Malacosoma americanum
• Forest Tent Caterpillar               Malacosoma disstria 
• Fall Webworm Caterpillar         Hyphantria cunea

Both Eastern and Forest Tent caterpillars emerge mid-late May from over wintering egg masses found on twigs.  Eastern Tent caterpillars will attack crabapples, apples, and cherry trees.  Forest Tent caterpillar prefers maples, oaks and birch as host plants.  Fall Webworm larva emerge in  late August from eggs laid on the undersides of leaves – this pest infests numerous fruit tree species along with elm and willow species.

Defoliation can be severe, and if repeated, can result in the death of the tree.  Treatment with Bt (Bacillus thuringiensis) – a natural and safe bacterium – is the best known solution.  It has proven over the years to be user-friendly, efficient and safe.  One important thing:  Bt is much more effective when the larva is small.

Why is Bt more effective on younger larva?  

• Bt bacterium produces a crystalline protein toxin that kills the single layer of cells lining a caterpillar gut
• Cells in the younger larva  are not multiplying and dividing as rapidly as in older larva – therefore the older larva can effectively ‘heal’ the gut wall and survive the effects of Bt.  COOL!
• If Bt has not been effective for you in the past – you probably applied it too late!

Pruning out egg masses and opening webs to natural predators are easy ways to check an infestation before it’s too late – remember folks – effective treatment means catching things early!

This link describes the safety of the product Bt.

http://www.youtube.com/watch?v=7TTS80xyw4A

 Excellent instructions and information on the use and application of Bt(Bacillus thuringiensis)

http://www.agf.gov.bc.ca/pesticides/infosheets/bt.pdf

Oh, and don’t forget to check out the following Web site for more info: http://www.bugwood.org/