Tree Fruit Newsletter — May 22, 2024

In this newsletter:

  • Highmoor Farm Bud Stages
  • Chemical Thinning at Early Fruit Set of Apple and Pear
  • Starting Calcium Sprays
  • Orchard Observations

Highmoor Farm Bud Stages

McIntosh apples – full bloom and just starting petal fall
Honeycrisp apples – full bloom
Pears – petal fall
Sweet and sour cherries – a mix of petal fall and jacket stage
Peaches and Plums –petal fall
Apricots – fruit set

Chemical Thinning at Early Fruit Set of Apple and Pear

Fruit set is when the majority of chemical thinning is normally done, but warm weather is needed for the thinners to be effective. When deciding when to apply thinners, apply thinner when the high temperature is expected to be above 70 °F, if possible. The forecast shows sevaral days of warm weather so timing the spray for optimum weather looks possible in the next few days for both petal fall thinning and at early fruit set. Cool weather is forecasted for Monday when it would be better to postpone the application till the return of high temps above 70 °F.

I suspect most of us have trees with more blossoms than usual because of last year’s light crop load. This excess bloom combined with favorable pollination means aggressive thinning will be needed in order to get the crop load down to where it needs to be for good fruit size and for return bloom.

For variety specific thinning info, check out the New England Tree Fruit Guide:
Chemicals for Apple Thinning | New England Tree Fruit Management Guide (

Start Calcium Sprays at Petal Fall on Honeycrisp

Honeycrisp develops bitter pit in cold storage despite repeated foliar calcium applications. For this variety, it is suggested to start foliar calcium sprays at petal fall to increase the final calcium concentration in the fruit. Many products are available, but the ones with higher concentrations of calcium generally work better. The ones formulated without calcium chloride are less likely to russet fruit, but are less effective at preventing bitter pit.

Orchard Observations

A few tree deaths have occurred in one of my young orchard blocks. They started to leaf out, but died suddenly, so I suspect it’s a problem in the roots. Last year’s excess soil moisture may have been too much for sensitive rootstocks such as G.11.

I am seeing a lot of flowers on one-year-old shoots. These are located laterally along the shoot and have a later bloom date than the spurs and terminal blooms. This makes them a fire blight risk. Varieties that have this problem are Gala, Honeycrisp, Golden Delicious and others, but not McIntosh.

Brown rot on blossoms, shoots and fruit has shown up in our apricot block which was in bloom before the first fungicide spray. Frequent rains during bloom this year may mean more brown rot on the highly susceptible cherries and apricots. There’s no sign of it in the peaches or plums.


Renae Moran
UMaine Cooperative Extension Tree Fruits Program
University of Maine Cooperative Extension
PO Box 179
Monmouth, ME 04259
(207) 933-2100

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