Tender fruit and Grape update-July 27,2020

By Kathryn Carter, Dr. Wendy McFadden-Smith and Amanda Green, OMAFRA

Weather

The hot weather has continued to push degree day accumulations (GDD) forward. The GDD accumulations as of July 27, 2020 (base 5 °C) for the Niagara Parkway South area are 1319 GDD, Lakeshore Rd 1289 GDD and Beamsville 1292 GDD which are ahead of 2019 (Ontario Tender Fruit Growers, 2020).

Rainfall for July has been low (Figure 1) however some areas have received much needed rain in the past week. Irrigation is still being used in some orchards and vineyards. Eastern Ontario has been experiencing extremely low levels of precipitation.

Tender Fruit and Fresh Grape

Crop Development:

In Niagara fruit diameters are as follows: peaches/nectarines ~60-70 mm, plums ~45-55 mm, pears ~ 65 mm. Growers are continuing to thin peaches and nectarines.

Apricot and sweet cherry harvest are complete. Harvest is wrapping up for tart cherries this week. Harvest continues for plums, nectarines and peaches. Sovereign Coronation grapes reached veraison in Niagara-on-the-Lake on July 25^th.

Diseases/Pest Management

It is a good time to collect soil and leaf samples for tissue sampling in tree fruit. Peach varieties being harvested include Harrow Diamond, Harrow Dawn and Garnett beauty. Shiro plum harvest has also started. Split pits are a problem in some early varieties.

Bacterial spot is showing up on susceptible varieties (Figure 1). Post harvest control of cherry leaf spot is crucial for cold hardiness and tree survival in both sweet and tart cherries.  Japanese beetle has defoliated young leaves on blue plums and some orchards are also suffering from a severe infestation of Two spotted spider mite and plum rust mite.   Fire blight strikes in pears are very apparent in many orchards, but growers should wait until shoot growth stops before removing affected limbs and insure that cuts are minimum 20 cm away from visible symptoms.  Black knot infections from last year have developed especially in blue plum blocks. 

With thunderstorms and the potential for hail in the forecast it is important to remember that any type of injury to fruit (insect hail etc.) may increase the risk of brown rot.

Wine Grapes

Crop Development

Shoot positioning and hedging is being completed in vineyards.

Pest management

Grapes are at cluster closure with tight clustered varieties very tight already.  Veraison should start in the next week or two. Veraison is a good time to conduct petiole sampling for nutrient analysis.

While dry weather has not favoured downy mildew, powdery mildew has been a problem, particularly in Chardonnay.  Potato leafhoppers have been a challenge to control this year with many vineyards applying insecticides to manage them.  Reddened or curled leaves apparent at this time are not due to virus diseases.  Symptoms of grapevine leafroll and red blotch virus will start to become apparent as vines go into veraison in the next week or two. 

Japanese beetles and their feeding damage are apparent in many vineyards. For more information on Japanese Beetles in vineyards see Ontario CropIPM. Grape Flea beetle feeding is apparent in some young vineyards (Figure 2).

Michigan State University is holding a series of Webinars for grape growers this week. The seminars cover a variety of topics including late season disease management, vineyard canopy management at veraison, late season weed management, insect pests, and grape rootstocks for more information or to register visit MSU viticulture field day.