It is common to have fruit set in newly planted and young apple trees. However, cropping young trees can negatively affect the goal of filling in the space within the first 3 years after planting and will result in stunted tree growth. Here are a couple of alternatives to remove blossom and fruitlets from young apple trees.

1) Lime Sulfur (LS) at bloom will reduce fruit set on young or newly planted orchards. LS can be applied at 4-10% (v/v) when used alone, or at 1.5 to 2% (v/v) when combined with oil. Option for oil include: fish oil at 2% (v/v), dormant petroleum oil at 1%, or summer oil at 1 to 1.5% v/v. Research shows that using LS+oil is more effective than using just LS. *Currently, LS does not have a label in WI for blossom thinning*.

2) Another option to remove blossoms in young trees during bloom would be to use ATS (Ammonium Thiosulfate) applied at 2 gallons per 100 gallons at 100 gallons solution per acre (do not mix with oil). LS is a more effective bloom thinner than ATS, but LS works as a thinner by temporarily inhibiting photosynthesis which is harder on new trees with less foliage than in mature trees, LS can also cause apple leaf burn.

Avoid use of LS and ATS when a high temperature is forecast to exceed 80°F within 24 hours. The potential for injury is greater under slow drying conditions (low light, high humidity). Avoid spraying under these conditions. Tender foliage that grew under cool, cloudy, damp conditions will be more likely to show symptoms.

3) At petal fall apply Sevin+MaxCel (2 pints Sevin plus 4 pints MaxCel per 100 gallons) and a second application when fruitlets are 8-10 mm will thin all fruitlets with minimal stress to new trees. Another alternative is to use 2 sprays of Sevin+NAA (2 pints Sevin plus 15 ppm NAA) the first at petal fall followed by another spray at 8-10 mm. NAA is a more aggressive thinner than MaxCel and Sevin, so do not apply if high temperatures are forecasted (>85°F) as some leaf drop could happen.

4) Hand thinning is always an alternative if there aren’t many blossoms but be careful to only remove flowers and not the actively growing terminal shoot.

This article was posted in Apples and tagged Apples.