The 2021 Honeycrisp Playbook:  Apogee (Prohexadione calcium) at Pink for Bitter Pit Suppression.

Daniel Donahue, CCE-ENYCHP, Hudson Valley New York

"Effective Bitter Pit suppression in Honeycrisp involves the deployment of a number of tactics over the course of the growing season, there is no silver bullet, no trick play to save the game, think of it like following a playbook in football, three yards and a cloud of dust."

•  For BP suppression, Apogee should be applied to mature bearing tall spindle Honeycrisp (HC) at pink stage at a rate of 6 oz./A. Cover the foliage well.  Apply at full or late pink, not early pink.  Use a water conditioner, "hard" water deactivates Apogee.

• New for 2021:  Temperature at application and during the 8-hours post is a critical factor.  Prohexadione calcium (Apogee, Kudo) are plant growth regulators and require metabolic activity within the plant for uptake and metabolism.  Temperatures below the mid-60's are questionable for an application timed at pink.  Delay your application until temperatures are warm enough for up to eight hours post.  In the Lower Hudson Valley that may be next Saturday or Sunday, and later than that as you move north.  Of course, the forecast could (will) change.

• New for 2021:  Reviewing our 5-years of data in ENY and 2-years statewide, its clear that Honeycrisp bitter pit management recommendations need to take the rootstock into account.  Our detailed survey data from ENY 2016-2018 clearly demonstrates that HC fruit produced on the B.9 rootstock will have on average substantially less bitter pit (11%) than fruit produced on the M.9 clones ( 25%), M.26 (  30%) after 120 days of regular storage.  In a 2020 trial, after 74 days of regular storage, G.41 expressed 22% BP vs 10% for M.9.  Our team found substantial variability between blocks by site, region, and year, which is one reason why BP prediction and mitigation have been such a challenge over the last, say, 150 years?.  For 2021, I am recommending not to include B.9 Honeycrisp blocks in your pink Apogee program. For BP suppression.  B.9 HC fruit already have a low probability of BP symptom expression, and the low-vigor characteristics of the combination result in a tree that can have trouble filling its allotted space.  Prohexadione calcium formulations (Apogee, Kudos) applied at pink will suppress vegetative growth to some degree, so if not needed, don't use it.

• To avoid aggravating BP in Honeycrisp, do not use Apogee (prohexadione calcium) for vegetative growth reduction post-bloom as is generally recommended.  Our data shows that in 2 years out of 3, "conventional" Apogee use significantly aggravated BP.  Contrary to commonly held belief, our data over three years indicates that the reduction of vegetative growth achieved by Apogee is not correlated with a reduction of BP incidence. 

•  If fire blight is a problem, there are real benefits to using Apogee to suppress shoot infections, in this case, you must pick your poison as they say.  However, the single pink application timing on its own will help suppress FB infections.  Follow an aggressive blossom blight protection program, use the NEWA models and deploy other tools such as ASR materials to help.  Specifically for HC, reserve post-pink Prohexadione calcium applications as an FB suppression measure of last resort.  For example, if you have cankers from prior seasons, or active shoot blight infections, or perhaps concern over hail damage prior to terminal shoot set.

• Can I include foliar calcium in my Apogee tank mix?  Generally not because calcium in solution (i.e. hard water) will deactivate the Prohexadione calcium.  However, there is an exception!  The Agro-K company produces a foliar calcium product Sysstem-CAL™ which has been tested and shown to be compatible with Prohexadione calcium formulations (Apogee, Kudos) in tank-mix combinations.  Follow the link here for more details.  I will be discussing foliar calcium applications in the next installment of the 2021 Honeycrisp Playbook. 

• Leave a trellis panel unsprayed as a control.  Sample 100 apples from the control trees, and 100 apples from the treated trees, and hold in regular storage for 60 days.  If you really want to push the envelope, pre-condition at 50F for 7 days as pre-conditioning aggravates bitter pit.  Taking a sample like this is necessary for accurate on-farm evaluation.  This is also true of your calcium applications.  BP evaluations by "eyeball" at harvest, on-the-tree or in-the-bin, or even off the packing line are not reliable due to sampling bias and the fact that BP symptoms will visibly express at different timings depending on the year, site, and rootstock. 

• A single application of Prohexadione calcium (Apogee, Kudos) at pink will result in a degree of vegetative growth reduction.  Therefore, do not apply Apogee at pink for BP suppression to young-bearing orchards that haven't filled their allotted space.  Use  POMA,  Sysstem-CAL , CorClear, or a similar foliar calcium program in young bearing orchards. 

• You must have the NYSDEC 2EE label in your possession to use Apogee at pink for BP suppression.  A copy of the NYS 2EE label can be found here.  Search the NYSPAD database by product name:  Apogee. 

• Want to know more?  Read this article from the March 2019 issue of CCE-ENYCHP Tree Fruit News, or contact Dan Donahue, CCE-ENYCHP Regional Tree Fruit Specialist at 518-322-7812 or djd13@cornell.edu.