by Leslie Cox; Monday, July 29, 2013

I know, I know. We always seem to be harping on the bad news. Is our morbid side the predominant trait in our character make-up? Don’t know. But I do know that when we get a pest bug showing up and doing major damage in our garden I want to know as much about it as possible. Knowledge helps in planning one’s defences. Ask any general.

So, as it happens, John and I were talking about the forest tent caterpillars again last night. Truthfully, we did talk about a good news item first…how much we enjoyed our horticultural society’s Summer Potluck Picnic that very afternoon. Lots of good food, great…as in really great…music from The Cogs and enjoying the company of our gardening friends. So perhaps our morbid sides are not quite so forefront.

But we are concerned about the possibility we may have another large infestation of these caterpillars again next year. John just informed me he has been pruning out a number of egg masses from the branches of our Amelachier x grandiflora ‘Princess Diana’ (serviceberry).

Which reminds me, I should get the ladder out and check for any on my climbing roses up on the roof lattice over my porch. Remember: these caterpillars favour fruit trees and roses, along with their preferred host – deciduous trees such as alder, willow, birch, etc.

So I asked John if he thought my idea of spraying our trees and shrubs with dormant oil spray this winter would stop the tent caterpillar larvae from emerging in the spring. His response was he did not think it would be a blanket solution because how were we going to reach the very tops of all of our trees? Good point.

Top of the tree canopy is where many of the female moths lay their eggs. Even reaching the egg masses I spotted in the high branches of our variegated elderberry, Sambucus nigra ‘Marginata’ are going to be a challenge to reach given its 20+ ft (7.2 m) height. How were we going to get to the top of the birch tree at almost double that height? We need a cherry picker.

But that will not happen. With a garden as intensely planted as ours, there is absolutely no way we could get a cherry picker into our back yard without trampling a lot of plants.

All this talk about the tent caterpillars really has John reliving the nightmare of our Viburnum leaf beetle (Pyrrhalta viburni) years that resulted in the ultimate removal of our treasured Viburnum opulus ‘Roseum’. Since then, all subsequent pests that enter our garden, such as the daylily gall midge (Contarinia quinquenotata), have a tendency to trigger John’s nightmare and get him revved up.

I try to calm him down because first off, none of the tent caterpillar species are considered especially harmful as they will not usually kill the trees. Granted, their defoliation of the leaves looks horrifically unsightly in the garden but with only one generation a year, the trees and shrubs have a chance to recover before the end of the season. Not like what happens to the viburnums with their specific leaf beetle pest. (I really must get the information about this dastardly beetle posted on my website for you. Soon!)

Okay…I admit I came across some reports in my research of detrimental tent caterpillar damage but those were rare occurrences. Definitely not the norm.

Second good bit of news about tent caterpillars is that even though there may be back-to-back infestations in the same area over a two year period, the numbers will drop off for the next eight to ten years. Large infestation cycles have been pretty much following a ten year pattern.

I do have to admit that my one bit of pessimism towards the forest tent caterpillar (Malacosoma disstria) is that you do not know you have an infestation until the substantially large larvae start to descend from the tree tops where they have been feasting since birth.

You see, there are no tell-tale silky tents to give them away. The western tent caterpillar in our area, Malacosoma californicum pluviale, always shows off its presence with their tents predominantly displayed at the tips of the branches. The forest tent caterpillar on the other hand just forms a silken mat flat along a branch way up high…right where it would be hard to spot if you were not looking specifically for it. And I will be next year. The binoculars are going to be in play lots during my searches next spring.

I know it is hard to look on the bright side of things when all you are seeing is lots of evidence the “nightmare” is going to continue next year in your garden. But the glass is still half full when you factor in all the birds that will be back. I love my birds!