Enhance Cropping Of Apple After Cold Injury. Cornell & Michigan Studies.

To enhance apple cropping after cold injury this season, consider pre-bloom foliar sprays, which may accelerate recovery of damaged vascular tissue and increase fruit set.

Two studies have shown good results in supporting crop development after a freeze event.

Below you’ll find two studies (PDF Stover et al. 1999), which was conducted by Cornell faculty, including Hudson Valley Research Laboratory staff, initiated to determine if pre-bloom sprays of B, Zn, and urea would enhance cropping of apple (Malus ×domestica Borkh.) after cold injury. Abstract results and link to full reports below.

Abstract.  Study 1: Following a very severe winter that caused visible damage to vascular tissue, ‘Empire’ at both sites cropped more heavily following all treatments that included both B and Zn; such treatments increased cropload by an average of 22% and 35% at the two test sites.

Despite a mild winter preceding the 1995 season, pre-bloom nutrient treatments again increased cropping of ‘Empire’. In 1996, treatments included a control and a single foliar treatment (B + Zn-EDTA at half-inch-green followed by B, Zn-EDTA, and urea at pink) on ‘McIntosh’ and ‘Empire’ at seven orchard sites. Treatment enhanced cropping in ‘McIntosh’ at three of the seven sites, but there was no effect on ‘Empire’.

Factors influencing differences in response were not apparent from this study, although a complex of factors may be involved. Data for all years indicated that prebloom nutrients did not enhance spur leaf development or fruit set; such treatments probably enhance cropping by increasing retention of flower buds that would otherwise abscise before anthesis.

Where cropping was increased, mean fruit weight was not reduced at P≤ 0.05 but fruit weight was significantly less at P ≤ 0.10 in 1995.

Chemical names used: boron (Solubor, disodium octaborate tetrahydrate); zinc (Zn-EDTA, zinc chelate).

Stover et al. 1999 B-Z apple spray for cold injury (1)

Mineral-Nutrition-as-a-Factor-in-Cold-Tolerance-of-Apple-Trees

An alternative approach would employ the use of plant growth regulators in studies deminstrated by Michigan State. The products used in the studie were Promalin (Valent) or Perlan (Fine Americas),  essentially the same product from two different manufactures.

Promalin/Perlan are recommended to be used at 1 pint per acre.

In addition to setting fruit in frosty conditions, Promalin/Perlan may provide:

• Increase of cell division, fruit weight, apple typiness, fruitset and the start the thinning process.