As we move through pink and bloom in most parts of the state, many of the decisions we make in apple orchards can affect fruit quality at harvest and even influence next year’s crop. Early-season sprays are not only about protecting foliage and fruitlets; they also play an important role in managing fruit size, bitter pit, vegetative growth, fruit finish, and return bloom.
Calcium starts early, not late
When growers think about bitter pit management, calcium often comes to mind as a late-season program. In reality, early-season calcium sprays are highly important, especially for cultivars such as Honeycrisp, Golden Delicious, and York Imperial that are prone to bitter pit and cork spot. A seasonal target of 4 to 14 lb of actual calcium per acre is recommended, which is roughly equivalent to 15 to 50 lb of calcium chloride per acre, or about 2 to 8 lb per cover spray depending on the program. Calcium sprays that begin around pink are usually more effective than waiting until later in the season.
Boron supports both fruit set and calcium movement
In most programs, 0.5 to 1 lb of actual boron per acre is sufficient, which is about 2.5 to 5 lb of Solubor per acre. This can be applied at pink, at bloom, or about 7 to 10 days after petal fall. Boron can be included with calcium chloride in the spray tank, but one important point is to avoid pre-mixing Solubor and calcium chloride together in a small volume of water before adding them to the main tank. They should be added separately.
Prohexadione-calcium is more than a growth regulator
Prohexadione-calcium products such as Kudos and Apogee can be very useful when applied early, particularly at pink. Most growers think of these products mainly for shoot growth control, but early applications can also help reduce bitter pit and suppress blossom blight and later shoot blight development. In vigorous blocks, that combination of benefits can make prohexadione-calcium one of the most valuable early-season materials.
The standard rate highlighted in your handouts is 6 oz per acre. Performance can drop when spray water is alkaline or contains high levels of calcium carbonate, so hard water should be conditioned with ammonium sulfate. A surfactant can improve uptake, although some combinations may foam and require an anti-foam material. One important limitation is compatibility: prohexadione-calcium should not be tank-mixed with calcium or boron. It should also be kept in mind that prohexadione-calcium is not a substitute for calcium sprays.
Urea can help when fruit set or fruit size is at risk
Foliar urea remains a useful tool early in the season, particularly when growers are trying to promote cell division and improve fruit sizing. It is especially valuable in Gala and in situations where king blooms have been damaged by frost, since the loss of king fruit can shift the crop toward smaller fruit. Applications at bloom at 3 lb per 100 gal, followed by petal fall and first cover applications at 5 to 6 lb per 100 gal, can help support fruit set and early fruit growth.
There is another benefit at bloom: foliar urea can help extend the effective pollination period. That said, foliar nitrogen should not be viewed as a substitute for a sound ground nitrogen program, because it does not move down into woody tissues the same way soil-applied nitrogen contributes to whole-tree reserves. Its role is more immediate and is mainly tied to fruit set and sizing.
Fruit finish problems begin soon after bloom
For Golden Delicious and Gala, fruit finish issues such as russeting and scarf skin are often tied to humid conditions during the first 30 to 40 days of fruit development. Where these problems are common, GA₄₊₇ products such as ProVide 10SG or Novagib 10L can be useful. The handouts recommend 2 to 4 sprays beginning at petal fall and repeating at 7- to 10-day intervals. This is one of those programs where timing is much more important than waiting until symptoms are visible, because by then the damage to fruit finish has already started.
Young trees need a different mindset
For second- and third-leaf trees, the goal is often not crop retention but defruiting, so the tree can put more energy into canopy and framework development. There are several approaches, including blossom thinning with lime sulfur plus oil during bloom and post-bloom thinning with 6-BA or NAA plus carbaryl at petal fall and again at 6 to 12 mm fruit size. Ethephon plus carbaryl plus oil can also work at 10 to 15 mm, but this mix should be avoided on weaker or medium-vigor cultivars on dwarfing rootstocks because of the risk of excessive growth suppression.
Defruiting young apple trees using blossom thinning with lime sulfur and oil (left) and post-bloom chemical thinners (right).
