I have to admit it did look a little odd. There, on one end of our orchard, were three cherry trees wrapped with giant white covers that made them look like huge lollipops.
But a few windstorms later, they looked more like a cross between early Halloween decorations and the ghost ship from “Pirates of the Caribbean.” There were more than a few questions from neighbors and passers-by about what we were trying to accomplish.
We have four cherry trees: English Morello and Montmorency pie cherries, and Rainier and Bing sweet cherries. Our goals were to grow our cherries organically and keep the birds from eating the harvest.
The covers would hide our crop from the birds and prevent the cherry fruit fly – the adult of that unappetizing maggot found in unsprayed cherries – from laying eggs.
We ordered 100 feet of floating row cover online from Johnny’s Selected Seeds and made three 30-foot-square covers. We did not cover the Montmorency tree to compare an organic spray control.
Floating row cover is meant to be used on vegetables to provide insect and frost protection. It’s not meant to be put on trees but we thought we’d give it a try.
My husband, Bill, hung sticky traps in the orchard – plastic yellow plates coated with Tanglefoot – so he would know when the cherry fruit flies had arrived. Once we had evidence of that, we covered the trees.
This was no easy task, especially considering the fact that we needed to cover the trees on a windy day. Over the course of the next couple of weeks, there were several windstorms that caused some of the branches to poke through the material.
Bill repaired these holes with duct tape and joked that “I’ll only consider this experiment a failure when I’ve run out of duct tape.” That didn’t take long.
Over time the holes grew larger so he decided to use an organic spray called Bull’s Eye Bioinsecticide on all of the trees. The active ingredient is spinosad, a microbe that is safe for humans and animals but deadly to the fruit flies. He sprayed the trees weekly and more often when it rained.
As the cherries ripened, Bill tied Mylar flash tape to the uncovered Montmorency tree as a deterrent to birds. The flash tape came from Ed Hume Seeds and they recommend only hanging it when you need to protect a crop. If left in place for long periods of time, the birds become accustomed to it.
Here is what happened:
There was no bird damage on the covered trees. But because of the covers, we did not see that aphids and wasps were becoming a problem on the sweet cherry trees. The wasps damaged a lot of the harvest, something we hadn’t anticipated. There weren’t any wasps on the pie cherries so we think it was the sweetness of the Bings and Rainiers that attracted them.
Even with the above problems, we had our best cherry harvest ever and had a minimal amount of worm damage. We feel the spinosad spray routine was more effective than the covers especially since the uncovered – but sprayed – Montmorency tree had very clean fruit. The Mylar flash tape did a good job of keeping birds off the cherries.
It’s possible that an application of dormant oil spray before the trees came out of dormancy would have prevented the aphid problem. And we’re mulling whether we should test a more durable cover for the trees but at this point, the costs seem to outweigh the benefits.