Tuesday, February 24, 2015

Apple and Pear Scab

I'm almost to a point where I think that our nice weather is going to stick around for a while. The Old Farmer's Almanac winter forecast for our area has been spot-on, and their long range outlook is equally favorable. My peas are in the ground, and although I haven't seen any sprouts yet, it's still a little bit early for that.

UC IPM Illustration of the scab life cycle.
So now, in addition to getting my seeds organized and started, I need to be mindful of the fruit trees and their needs. The bees are out and about already, and they're absolutely loving our plum tree which is now in full bloom. I don't recall it ever being so fragrant in February before!

One of the problems we have here is scab on our apple and pear trees. It's common everywhere, but our cool, wet springs are absolutely perfect growing conditions for the fungi that cause these ailments. Apple scab is an infection caused by a fungus called Venturia inequalis, whereas the Pear scab is an infection caused by a close relative, V. pirina. The infections, even though they appear symptomatically similar and are also managed in essentially the same ways, are different and cannot spread interchangeably between the two types of trees.

The fungi overwinter on the ground in the leaf and fruit debris from the trees until the following spring rains come and spread the spores. If the temperatures are right (between 55 and 75 degrees F) the spores will germinate quickly in the spring. Cleaning up and removing the fallen leaves and fruit is one of the most important things you can do to manage scab in existing orchards, and in many cases can significantly reduce the severity of an infection, year over year. If you are putting in new trees, planting resistant varieties will also help.

We have a couple of trees this year where there are some dead leaves and fruit are still stubbornly stuck to the branches on which they grew. I'm going to need to figure out a way to knock those down so I can get rid of them before the new leaves start to open. Once an infection takes hold, you cannot get rid of it- you can only do damage control for the rest of the season. It can cause a significant loss of fruit if the infection is severe, so catching it early and being vigilant in your management program is key.

I'm also researching spray options this year, which I don't normally do. Historically, warm and wet conditions here in the Spring means we're going to have all sorts of fungal issues to contend with, so I'm definitely interested in preventing whatever I possibly can.There are a lot of choices out there, from hard-hitting chemical concoctions, to more gentle "home remedies" that may or may not work. Keep an eye out for that, in the next couple of weeks.

What about you? Have you had any experience with apple or pear scab?

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