Publication 360, Fruit Production Recommendations:
Plum Calendar - Notes on plums

Extract of Publication 360, Fruit Production Recommendations, 2010-11,
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Table of Contents

1. Notes on Plums
• Heat spot
• Thinning plums
2. Other Plum Calendar Sections
   • Dormant (before bud break)
   • Green tip (just as buds are bursting)
   • Popcorn (when blossoms show white)
   • Bloom
   • Shuck (when most of the shucks are off)
   • First cover (12 days after Shuck)
   • Second cover
   • Prepick
   • Special sprays (when monitoring indicates the need)
   • Postharvest fruit treatment
3. Other Information on Plums
   • Notes on Tender Fruit Insects & Diseases
   • Table 7-10. Products Used on Plums
   • Table 7-11. Activity of Fungicides on Stone Fruit Diseases
   • Tender Fruit Nutrition
4. Plum Calendar (PDF 103 KB)
5. Chapter 7 - Tender Fruit Calendar PDF 401 KB
6. Related Links

High temperatures may cause purplish spots on plum and prune fruits that exude clear gum. These spots develop about 5-8 days after a period of hot weather. Summer cover crops and mulch help to reduce this physiological condition.

To reduce this disorder on prunes, spray with 4 kg of calcium chloride in 1,000 L of water during the period from early July to mid-August. Apply three sprays, 10-12 days apart. See notes on Calcium (Ca) for plums.

Thinning Plums

In recent years, the market demand for larger fruit has placed more importance on fruit thinning, pruning and irrigation. Japanese plums require systematic fruit thinning; otherwise fruit size will be small and biennial cropping will ensue. European plums grown for fresh market also require thinning in the years of heavy fruit set. Inadequate fruit thinning results in production of under-sized plums and, at times, fruit ripening on overloaded trees will be delayed. Irrigation is important to obtain large-sized fruit. See notes on irrigation under Thinning Peaches. Start thinning near the end of June drop in early to mid-June when it can be determined which fruit will abort and fall on their own. Thinning at early fruit development has more benefits than late thinning.

Fruit size thinning is preferred to conventional space thinning. Size thinning selectively removes small, weak, blemished or diseased fruit regardless of spacing of the fruits on the branches. The end result should be proper sizing of the fruit remaining on the tree.

Related Links

• Integrated Pest Management (IPM)
• Pesticide Application and Safety
• Pesticide Companies and Agents
• Search the PMRA website
• Ontario Minor Use Program
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 360: Fruit Production Recommendations