May 13, 2012 in Features

Pesticide-free orchard worth additional effort

By The Spokesman-Review
 
Susan Mulvihill photo

These beautiful apple blossoms are a welcome sight in the spring.
(Full-size photo)

Last year, I wrote a column about growing fruit trees organically. In it, I detailed what my husband and I have been doing to grow worm-free apples over the past three years. It generated so much interest that an update is in order.

To recap, we have a small orchard of 20 apple, cherry and plum trees. Growing apples is problematic because they are susceptible to a number of insects and diseases which traditionally are treated through a regular pesticide-spraying routine.

The main insect pest in this region is the apple codling moth, which lays eggs on or near developing apples. The larvae then burrow into the apple and feed off the seeds which are high in protein.

 While we want to be responsible home orchardists by keeping our trees healthy and well cared for, we want to avoid using pesticides.

 Here is how we are achieving that goal and what we have learned:

 While the trees are still dormant, we apply a dormant oil spray to the branches and trunks. This is an organic method that smothers overwintering pest insects and their eggs.

 We also prune the trees to keep them healthy and to open up the canopy to let in light and promote good air circulation.

When the apple trees start blooming, we hang codling moth traps so we can watch for moth activity. The traps contain a pheromone (mating hormone) that attracts the males, which then get caught in the sticky lining of the traps. Once we start catching them, we know it’s time to act. 

We spray all of the foliage with a product called Surround At Home Crop Protectant, which is a powdered form of kaolin clay. It is mixed with water and sprayed onto the trees. The clay forms a film on the leaves and developing apples which deters egg-laying and obstructs any larvae that do hatch. If we get heavy rains during the season, we reapply the spray.

Once the developing apples are the size of a marble, we thin them to about one every 6 inches so the tree does not have too many to sustain. We cover each apple with a small maggot barrier which is a nylon cover that protects the apples from moths and larvae. It’s a tedious job but well worth the effort.

The first year we used the maggot barriers, we didn’t know about using them along with kaolin clay. The results were about a 20 percent success rate of worm-free apples.

The second year, we used the barriers and the kaolin clay and had about an 80 percent success rate.

Last year, we used the maggot barriers and the kaolin clay for most of the apple trees but experimented with using kaolin clay alone on two of the trees. Even without the maggot barriers, we still had a good success rate although it appears the combination of barriers and kaolin clay is the best. That’s our plan for this season.

What new experiments will take place in the Mulvihill orchard this year?

The most annoying insect problem for cherry trees is the cherry fruit fly. They are responsible for those disgusting maggots found inside cherries. This year, we are going to try covering our trees with homemade sacks made from floating row cover material once the small cherries start developing. It is our hope the flies won’t be able to lay their eggs. Stay tuned.

Susan Mulvihill can be reached via email at inthegarden@live.com. Visit her blog at susansinthegarden.blogspot.com for more gardening information, tips and events.


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