Sunday, June 5, 2016

Precision chemical apple thinning in MA 2016

Well here we are, post petal-fall/fruit set/approaching 3/4 inch diameter apples, and indeed there has been lots of cold damage to tree fruit here in Massachusetts. No peaches (Happy Valentine's Day) and apples were looking pretty bad (early April freeze) until we finally got out of bloom and saw some fruit setting and sizing. It's not all pretty though, apple orchards in eastern MA generally have fared better than those in the Connecticut/Pioneer Valley. Fruit set has depended a lot on variety (Macoun looks good, McIntosh intermediate, Cortland not so good, Honeycrisp, well, it depends) and site (obviously). Return bloom was probably not going to be great either given the heavy apple crop last year. When all is said and done, I predict some orchards will have less than 25% of an average crop, some will have greater than 75%, some will be in the middle at 50%. There will be apples, the price will be good, so it will be a good year to have apples (if you have them). Sometimes years with short crops turn out to be more profitable for some. The cup is half full at least.

So, despite my usual reluctance to measure fruit as they grow per the Precision chemical Thinning Protocol/predicting fruit set (PTP), and with a little prompting from Poliana Francescatto at Cornell, I went whole hog and set up 7 demonstrations across 3 different orchards (TFF, CSO, and SHO) and 3 different varieties (McIntosh, Gala, and Honeycrisp). But, I cheated a bit, by reducing the number of flower/fruit spurs used to 10 per tree (vs. 15 per the PTP) in 2 orchards (TFF and CSO), and just 5 spurs per tree in one orchard (SHO). All my results are published here.

Some comments on the process and results:

  • These were generally nice tall-spindle trees, therefore I felt that using 10 (or as few as 5?) spurs per tree was representative. Wonder if using 10 trees by 5 spurs per tree would be easier and quicker to find numbered spurs within tree? They can be hard to find when foliage fills in.
  • Those little string tags blow around and get tangled in other spurs, sometimes making it difficult to figure out which spur was being used. I have used flagging tape in the past, would
    probably go back to that. (Or something even better? Suggestions?)
  • I did not number the individual fruits. After all measurements were taken, the fruits were sorted largest to smallest within each spur, the assumption being the largest fruits remained the largest upon subsequent measurements (ditto for the smallest). Data would have to be sorted in the XLS spreadsheet, there is a little trick to it. (Thanks Poli!) Seems to work OK, but going to add to potential error.
  • It may be easy to overestimate the potential crop based on counting flower clusters. I suspect there are many flowers on 1-year-old wood which are not likely to set, yet it can be difficult to discount those.
  • Wish there were an easier way to measure fruitlets: do we need to measure to nearest 0.1 mm? Can a template be used to quickly size the fruitlets to the nearest 1 mm (vs. using calipers)?
  • It appeared initially, despite expected spur leaf and bud damage from the April freeze, that trees were going to overset actually. Hence, chemical thinner applications commenced, up to 3 applications, and appear to have worked quite well. We will count the fruit on each tree upon final set to see if the PTP worked or not?

I will try to update once final set is counted...