General observations from MSU Apple Maturity Lab for 2018
Some apple varieties are ripening earlier than expected.
Honeycrisp, and in some cases Gala, are ripening well ahead of the expected harvest date based on bloom date predictions for western and southeastern Michigan. However, color has been slow to develop. With more moderate temperatures and cooler nights expected in the coming days, color development should improve. Harvest these particular cultivars for air and controlled atmosphere (CA) storage as soon as fruit quality parameters meet market demands. Spot-pick for immediate marketing.
Fortunately, fruit firmness is fair to good this year, so fruit condition does not seem to be a worry at this time. Interestingly, McIntosh is on a normal schedule of maturation and should be ready for harvest in the next week or two in southern and mid-Michigan, depending on site and strain.
Cracking has been seen on some Honeycrisp samples, so be aware of this defect, which can get worse if there are substantial additional rains (Note that hurricane Gordon just came ashore in Mississippi and may bring rainfall and cloudy skies in the days to come.). Decay can be a problem for cracked fruit in storage, so discard these fruit if they are destined for longer-term storage.
Variable ethylene is also very noticeable in Gala and Honeycrisp. Those fruit with high ethylene have been seen to have a high starch index (greater starch to sugar conversion) and a more yellow background color. This means that some fruit are much more mature than others on the tree. If harvested together, the more mature fruit will not store well. The implication is that multiple harvests may be needed to minimize variation in fruit maturity to optimize fruit storage potential.