Early season apple disease activity

Due to other pressing commitments this year, some of my updates and bud development stages may be delayed. Every orchardist should be aware of ongoing developments in their own orchard and protect or react accordingly.  The updates for the Winchester area are based on the AREC's NEWA weather station as they have been since 2017. This resource and other NEWA stations in Virginia are available publicly, and all growers and advisers should be using them in their disease management decisions. 

Tight cluster stage on Red Delicious at Virginia Tech AREC, Winchester. Note the small mummified blossom next to the developing flower cluster. These and dead twigs are a common source for spores of fruit rot and frogeye leaf spot fungi.

Apple scab outlook: At Winchester on Sunday March 22, we are seeing tight cluster stage on Red Delicious and other advanced cultivars. Because of potential for fruit russet, this stage is too late for application of copper sprays to fresh market fruit, and another protectant fungicide should be used ahead of infection. With green tip set at March 7, the apple scab program on our AREC NEWA station indicates that 17% of the scab ascospores have matured, and many would be ready for a potential infection period with combined wetting over the next several days or later in the week. This is a high level of ascospore maturity for the first infection period of the year and could result in heavy primary infection on the large susceptible target. 

Where there is concern that scab infection may have occurred without any fungicide protection, it would be prudent to mix Vangard (cyprodinil) with a protectant to improve post-infection control. Dodine (Syllit) is another early season option where scab may be the only apple disease of concern up to pink stage. Do not use Syllit after pink stage. 

Expect powdery mildew and rust activity soon in orchards prone to these disease problems. 

For the Roanoke area and areas east of the Blue Ridge, please check NEWA stations in your region, adjust your green tip stage setting and hit 'calculate' to predict scab status in your area. Generally, these areas have higher percent ascospore maturity and had their first infection period last week if green tip was present by March 1. The Gadino Cellars NEWA station in Rappahannock County indicates that scab infection could have occurred as early as March 2-3 if green tip was present by March 1.