By Kathryn Carter
Table of Contents
Weather
Rainfall continues to be higher then average in Niagara in May, with the current monthly precipitation totals for May at 40 mm for Vineland, 28.6 mm for Harrow and 36 mm for Belleville. Rainy weather is making it difficult to plant and cultivate in orchards and vineyards.
Temperatures have fluctuated widely this week, reaching highs of 30 °C resulting in accelerated crop development, followed by temperatures around 10 °C that slowed development. Windy conditions have also made spray applications challenging
The forecast is for more rain on Saturday and Sunday and temperatures ranging from 10 to 18°C.
Tender fruit
Bloom is complete for most tender fruit crops. Activities in the orchard include planting, pruning, cultivating, planting cover crops and crop protection sprays.
Crop Development
Pears (left) and peaches (right) in Lincoln, May 21, 2026
Peach Fruit Growth and Development
Peach growth throughout the season follows a double-sigmoid curve pattern known as the double-sigmoid curve, which can be divided into three main stages or phases.
Stage 1 -Starts after full bloom and continues until approximately 30 days post bloom. During this time there is extensive cell division and cell expansion, rapid shoot and leaf development and the pit begins to form. During this stage of development it is important to avoid water stress and ensure trees have adequate nutrients to support growth and development.
Stage 2 – This phase typically occurs 38 to 66 days after bloom, and is associated with reduced fruit growth and pit hardening.
Stage 3- This phase starts 4 to 6 weeks prior to harvest, and is marked by rapid cell expansion, increasing fruit size and fruit ripening.
The timing and duration of each of these phases depends on environmental conditions as well as the genetic makeup of the cultivar.
At present, peaches are in Stage 1 of development. Temperatures during this period -from bloom to approximately 30 days after bloom-play a significant role in determining both harvest timing and fruit sizing. Warmer temperatures during this time will hasten fruit development resulting in an earlier harvest and increased tendency for smaller fruit size. During cool springs, fruit develop more slowly resulting in larger sized fruit.
Pear fruitlet thinning
Some pear blocks can struggle to set adequate levels of fruit. It is best to assess fruit set before applying chemical thinners, especially when conditions have been cool and/or wet during bloom. The response of pears to chemical thinners under Ontario conditions has been inconsistent from year to year. It is recommended to trial chemical thinning on a limited scale within pear orchards, allowing thinning responses to be assessed in relation to tree vigour, cultivar characteristics, and target fruit size.
- When using chemical thinners complete coverage is essential for good results.
- The optimal timing for thinning pears with MaxCel is when fruitlets are 8-14 mm in diameter. Early treatments tend to be more effective.
- Brevis (metamitron) is a new chemical thinner that is registered for use from late petal fall until 16-18 mm, it inhibits photosynthesis, reducing carbohydrate production in the trees, causing trees to abort excess fruitlets.
- Avoid applying to trees less than 4 years old. Young trees are more sensitive to thinning.
- Do not add any adjuvants that increase droplet spreading or penetration.
- Do not spray on wet leaves.
- Apply when air temperatures are between 10°C and 29°C and delay application if temperature will exceed 29°C within five days of application.
- Avoid drift to plum and cherry trees as it may scorch the leaves.
- DO NOT apply to trees that are under stress or have poor tree health.
- DO NOT apply if rain is forecast the same day as application
- Summer oils, adjuvants and some oil-based crop protection products, SDHI fungicides and other products in the spray program (e.g., amino acids) may increase thinning effect of Brevis.
For additional information on pear thinning refer to OMAFA crop hub or Thinning of tree fruit | ontario.ca.
Grapes
Crop Development
Timpson table grape buds (Left), Reisling (right) grape buds, Lincoln, May 21, 2026
Activities in vineyards include removing kicker canes, cultivating and seeding cover crops and crop protection.