Publication 360, Fruit Production Recommendations: Preventing Heat Stress and Fruit Sunburn on Apple and Pear Trees


Pub 360: Fruit Production Recommendations > Chapter 9, Other Pests and Disorders > Preventing Heat Stress and Fruit Sunburn on Apple and Pear Trees

Excerpt from Publication 360, Fruit Production Recommendations 2010-11,
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Preventing heat stress and fruit sunburn on apple and pear trees

Surround WP Crop Protectant is highly refined kaolin clay. Applied to the tree canopy, it forms a microscopic particle film that protects both leaves and fruit from high UV light and heat, which can slow the photosynthetic rate in a tree canopy.

The benefits of using Surround WP on young apple and pear trees during their establishment include:

  • greater net accumulation of carbon from photosynthesis
  • enhanced fruit bud initiation
  • increased trunk diameter
  • increased shoot growth

In established orchards, trees treated with Surround have healthier foliage through to leaf drop. Plant dormancy is not affected. Fruit finish and marketable yield are improved on several cultivars.

To prevent heat stress, make two applications of Surround WP, 7 days apart, using 50 kg/ha. Begin spraying before heat stress is likely to occur. Continue applications at 7-14 day intervals at a reduced rate of 25 kg/ha to maintain even coverage. .

Surround WP is made of an inert, non-reactive grade of kaolin that is not absorbed by plant tissues. The kaolin is food grade quality and approved by both the PMRA and EPA. Surround WP is OMRI listed, highly refined and suitable for reduced risk programs.

Precautions when using Surround

  • Do not mix Surround with spreaders, stickers or anti-foaming agents.
  • Do not spray when bees are active.
  • In orchards treated with Surround, monitor fruit maturity carefully and use starch iodine tests in the last two weeks of crop development.

In orchards treated with Surround, monitor fruit maturity carefully and use starch iodine tests in the last two weeks of crop development.

For information on using Surround to suppress crop pests, see notes on Biopesticides and reduced risk products for insect control; Kaolin Clay (Surround WP).


For more information:
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Author: OMAFRA Staff
Creation Date: 05 July 2007
Last Reviewed: 15 July 2010