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apple scab control

May 16, 2011

For those of you with apple trees who would like to protect from apple scab by using a fungicide please read the following. In order to minimize fungicide use, it is ideal to know exactly when to spray so that overspraying does not take place.

Timing of spray is part of a practice known as Integrated Pest Management, or IPM.  The goal of IPM is to reduce or eliminate fungicide use by combining cultural practices (cleaning up plant material under trees, proper pruning, etc) along with proper  monitoring for pest problems.  Pesticide sprays are used in IPM only when necessary, and there are  conventional or organic spray options that tree owners can choose from.

According to Jeffrey Johnson, arborist with the MN Landscape Arboretum,  we are at  the threshold for when protectant cover sprays should start to be applied for apple scab.  A protectant fungicide should be sprayed ASAP to thoroughly cover the foliage and emerging flowers of susceptible apple trees.   Only a fungicide and NOT any insecticide should be sprayed pre-bloom or during bloom.  Never use an all-purpose fruit spray (one that includes an insecticide) during bloom as this will kill pollinators and other beneficial insects.  A follow-up spray in 7 to 10 days is also advised. 

 Captan is the most widely available product although there are other fungicides registered for this use. An organic option would be lime-sulfur.

 At or just after petal fall apple growers may choose to apply a broad spectrum insecticide with a fungicide, but NOT before.  A spray with Sevin (Carbaryl) should be avoided at that time unless extreme thinning of fruit is desired.  A general home orchard spray will contain a fungicide and insecticide to control Apple Scab, Cedar Apple Rust, Plum Curculio, Green Fruitworm and Codling Moth.  Thorough coverage of foliage and fruit (pea size at petal fall) should be applied at that time. If you are only spraying to control apple scab, you just need the fungicide application and not the insecticide.

 To read more on the subject please go to:

Integrated Pest Management for Home Apple Growers:

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