Following a cool spring, hot humid weather has moved into our area. The warm weather is pushing degree day accumulations forward, but overall we are still behind the normal through May 25.
Tender Fruit and Fresh Grape
Frost damage to Peaches
Frost damage is becoming more apparent in tender fruit orchards within the last week. The extent of damage varies from “natural thinning” to considerable damage, depending on the location, variety and stage of development. In some instances the damage is more severe then originally predicted, likely a result of colder than expected temperatures, and the cumulative effect of multiple frost events. It is still too early to know the full impact of the frost on yields as frost may impact fruit set, fruit drop and potentially cause fruit russetting. Overall, apricots have the greatest levels of frost damage, however in some areas, yields of peaches/nectarines, cherries, and plums are also affected. Fresh grapes had not broken bud when the frost occurred, and as a result we are expecting minimal frost injury to the crop.
In Niagara, apricots are post shuck split. Peaches and nectarines are at the shuck to shuck split stage of development. Yellow plums are at shuck split, and blue plums are starting shuck split. Pears are after fruit set. Tart cherries are at fruit set. Fresh grapes range from 5 to 15 cm of growth.
In southwestern Ontario, apricots are at shuck split. Peaches range from shuck to shuck split and pears are at fruit set. Tart cherries are at fruit set.
Pear Thinning and Size Enhancement
Applications of 6-BA (active ingredient in Cilis Plus and MaxCel) can be applied now for size enhancement and at 5-14 mm diameter for fruitlet thinning. The MaxCel and Cilis Plus labels are slightly different from each other for pear thinning and size enhancement.
- With MaxCel for fruitlet thinning, sizing and enhanced return bloom, apply 50-200 ppm at 8-14 mm fruitlet diameter and do not apply more than twice per season.
- With Cilis Plus for fruit size enhancement, apply 2-4 applications of 10-50 ppm starting at petal fall continuing at 3-to10-day intervals. For fruitlet thinning apply 1-2 applications of 50-200 ppm at 5-10 mm in fruitlet diameter.
The risk for fire blight has been extremely high with wet weather and open blooms. Growers continue to protect remaining blossoms. Thrips numbers are increasing in orchards and pose a problem especially in nectarines. The wet weather has also been conducive to black knot infections in tart cherry and plum. The selection of pesticides for this disease is relative limited. Plum curculio emergence has started but rains have delayed sprays. In orchards where these are a problem, insecticides that control both curculio and oriental fruit moth will be applied. Black aphids are present in high numbers in peach and nectarine orchards this year. They are not usually a problem in peaches. Pear psylla numbers are increasing and the first generation emergence was extended due to warm weather followed by cold. Growers are targeting multiple insect pests in tender fruit in the next few sprays.
Winter was relatively mild and with the exception of some cultivars (Cab Franc or Cab Sauv) there appears to be minimal winter injury. Where winter injury did occur, it was likely related to the sudden drop in temperatures that occurred around November 11 when some late harvesting varieties had yet to acclimate.
The recent onset of warmer temperatures in the past week have made it easier to see that overall most varieties made it through the spring frosts with minimal damage.
Vitis vinifera cultivars in Niagara range from 5 to 10 cm of growth with clusters apparent on varieties like Chardonnay. See this chart from MSU for grape growth stages.
Phomopsis infections are favoured by rainy weather and lesions are being detected on the first few leaves already. Growers typically rely on protectant products at the stage of growth; however the heavy rains have washed off protectants so growers will have to try to get in to protect foliage as soon as the wet front passes. There are challenges with using the new formulations of captan that have 55 day re-entry periods. This basically eliminates them as an option in wine grape production at the time. Flea beetles have been detected in many vineyards in Niagara this spring. This is unusual as they are not generally considered a major pest. Growers are monitoring vineyards and spot sprays. may be required.