Assessing Fruit Set - Use a Knife!

Another year with spring frosts in the southwest gave us a challenging thinning season, and uncertainty at this time about how much crop is set. Sepal closure shortly after petal fall is the first indication of set. Growth of fruitlets over a few days usually indicate if the thinners worked, or whether more applications are necessary. We are now approaching the June drop, which will hopefully result in enough drop to minimize the hand thinning time required.

Remember that seeds control fruit growth from now on, and the more seeds that are set, the larger and faster the fruit will grow. Take a knife and slice across some fruitlets to count how many seeds are set. Most apples can have up to 10 seeds, and our goal should be to set 8-10 of those in each apple.

Some interesting research is being done in Michigan to count seeds in Honeycrisp apples. It seems that some Honeycrisp may have more than 10 seeds, often at 12 - 14! This may explain the large fruit size, but more important, this may contribute to the problem of biennial bloom, and to the bitter pit problem. Keep an eye on this - and cut some of your own to see how our Honeycrisp (and other cultivars) compare.