Plant & Pest Advisory» All Fruit Articles


As I See It - Heat Event, Sunburn Materials for Apple and Return Bloom

Win Cowgill- County Agricultural Agent

We are expecting extreme temperatures for 2-4 days rising into the 90’s on Wednesday and Thursday and maybe longer.

Mike Farigone, extension educator Cornell warns:

“Be aware of the danger of applying spray materials under hot, slow drying conditions. To limit damage, avoid applying sulfur and any kind of salt, including calcium sprays, until the weather cools a bit. Also limit the number of products, particularly adjuvants (including oil) that you add to the tank at any one time. Prior to this heat would be a good time to test one of the sunburn-preventative materials on a few Honeycrisp, Cameo and other very sunburn-susceptible apple cultivars. Work done in Washington State suggests that (in their dry climate) air temperatures as low as 93 degrees can result in fruit damage as fruit surface temperatures in the sun will be 20+ degrees warmer than air temperatures.”  My guidance is never spray above 85F!

Sunburn Materials

I have used Surround Clay for the past 6 years as a sunburn material on Honeycrisp with good success. We have also evaluated Pure Shade and it has worked well. Pure Shade was purchased by the Surround people.

The secret with these materials is to get them applied prior to the heat events. For Surround apply 50lbs / 100 gallons tree row volume dilute the first application. You then layer it on with subsequent applications at 25lbs/100. It may take 2-3 applications for full coverage.

Surround also has the added benefit of repelling Japanese beetles on Honeycrisp apples and may assist with BMSB as well. We are hand thinning Honeycrisp today at the Rutgers Snyder Farm and then will apply Surround to all Honeycrisp and Cameo apples.

Apple Return Bloom - Ethephon 

Continue your weekly ethephon or NAA sprays but do not apply in the heat due for the next few days. Wait for the temperatures to break. Ethephon applied over 85F or if temps rise above 85F up to 3 days after application can be problematic. Caution: Ethephon applications at high temperatures and high rates can de-fruit trees, Temperatures over 85F can cause severe fruit drop.

See our Fact Sheet on Return Bloom