Carrington Research Extension Center


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Hungry Caterpillars, Borers and Fungi


We went from deep snow to warm temperatures quite quickly this spring which made pruning dormant wood a challenge.  I know from experience that I need to prune in this order: Currants (because their buds break so early), Haskaps (because they bloom so early), Juneberries (early bloom), Cherries/Apples, grapes (okay to prune as buds as well so you can see what’s alive) and then plums after bloom.  But honestly, the project has become so big after all these years, that I just do the best I can.

I’ve received questions about ‘webs in trees.’ These are tent caterpillars.  The eggs are those hard, foamy black masses that you find on branches as you prune. Then the caterpillars hatch out and become eating machines.  Trees can handle some defoliation – they’ll just grow the next set of leaves out after the caterpillars pupate into moths. But it looks bad and adds a little stress to the tree.  Just take a stick, or your gloved hand, and pull down the web nest in the evening.  Pesticides are not necessary!  But you if you have to, try a pyrethrin or Bt product.

Tent caterpillars.

I was told they would come and they have:  Currant borers.  We’ve had them several years now and their numbers built up because, for a while, I thought the funny growth was the remnant of winter injury. The insect likes all colors and types of currant and gooseberry. If you have slow, puny leaf growth with what looks like ‘all flowers, or all fruit’ on the canes, cut it out now at the base and burn it or discard it in your trash.  I decided to do a big cleanup in the older plants this year.

Currant Borer in the cane in April.

Currant borer exit hole in mid-June.

Years of effort and ignorance. Removed all canes older than one year.

And just for fun (there are a lot of other beautiful, fun things here too like birds and bees and flowers!):  Fairy rings!  We have lots of them, probably due to all the old shrubs removed 10 years ago. Below is a picture of 2 small ones growing near each other.  If you look at the CREC in satellite map view, you can see several big ones on the west end of the orchard!  They never cause grass death here and I never see mushrooms. They just make me happy.

Fairy rings.

Enjoy this stretch of cool weather which makes our spring flowers last longer.

Kathy Wiederholt
Fruit Project Manager

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