Tender fruit and Grape update-July 8,2020

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

Weather

The hot weather has continued to push degree day accumulations (GDD) forward and as of July 5, 2020 the GDD from this year are now ahead of last year’s growing degree day accumulations. The GDD accumulations for 2020 (base 5 °C) for the Niagara Parkway South area are 916 GDD (same as the average), Lakeshore Rd 878 GDD (12 more than the average) and Beamsville 883 GDD (2 less than the average) (Ontario Tender Fruit Growers, 2020).

Soils are very dry and irrigation has started in some orchards and vineyards.

Tender Fruit and Fresh Grape

Crop Development:

In Niagara fruit diameters are as follows: pears ~ 32-40 mm, plums ~26 mm, peaches ~ 36-40 mm and nectarines~ 30 mm.  Sweet cherry harvest has begun and tart cherries are ~20 mm. 

Fruit thinning continues in orchards. Summer pruning is ongoing in some pear orchards.  Surprisingly enough, there are still few rat tail blooms (pear blossoms) in some pear orchards. Sweet cherry harvest is ongoing. Ethrel is being applied to tart cherries. Be cautious about applying full rates of Ethrel in hot temperatures. MSU has reported seeing damage with full rates of ethephon used in hot weather. Tart cherry harvest is expected to start around mid July.

Diseases/Pest Management

Once terminal bud has set fire blight infections can be removed from pear trees with obvious infections.

The hot dry sunny conditions of the past week have not been particularly conducive to disease development.  However, this weather may result in movement of plant bug and mite species from row middle ground cover into the canopies of stone fruit. Second generation Oriental fruit moth flight should occur this week.

Spotted wing drosophila has been detected in all counties where it is being monitored, although counts are lower that last year.  SWD prefer more moderate temperatures, below 30C.  However, they are still present and can cause injury to fruit once it starts to colour.  

Irrigation

Precipitation has been very low and soils are very dry. Irrigation for tender fruit is important in increasing fruit size, and ensuring fruit bud development for next years crop.  Remember to irrigate young trees.

As we are moving closer toward harvest it is important to be aware that irrigation water can contain pathogens, or microorganisms that cause illness or death in humans.  If contaminated water comes in direct contact with fruit, there is a risk that these pathogens may be transferred to the produce. Food safety programs often include the requirement of assessing the quality of your irrigation water.  Taking water samples at your pumping location for microbial testing is a good way to get a better understanding of your water quality. For more information on water quality testing refer to Irrigation Water Quality and Mitigating Food Safety Risks.

Wine Grapes

Crop Development

Vitis vinifera cultivars continuing to grow. Shoot thinning and positioning is ongoing and leaf removal has started. We are starting to see some symptoms of drought with warm temperatures and continued dry weather. Symptoms of water stress in grapes include reduction in shoot growth, tendrils drying up, drooping leaves, leaf bleaching and leaf senescence. Refer to How Grapevines respond to water stress to see examples of symptoms of drought stressed vines.

Pest management

Fruit are susceptible to powdery mildew, downy mildew and black rot until 4 weeks post-bloom.  Make sure fruit are protected with a locally systemic product in anticipation of rainfall called over the weekend.  Grape mealybugs are primarily at the egg cluster stage.  Movento treatment should be applied now if there are new egg clusters present and grapevine leafroll virus has been detected.  Japanese beetles have started to emerge and feed on young leaves.  Second generation grape berry moth emergence started recently and sprays should be applied if mating disruption has not been applied.

Traditional Leaf removal

Traditional leaf removal involves the removal of leaf blades, petioles and lateral shoots from the fruiting zone between fruit set to veraison. Leaves are removed manually or using mechanized leaf removal equipment. Traditional leaf removal is used to improve the canopy microclimate of the fruiting zone to enhance berry quality and decrease disease incidence. For additional information on leaf removal refer to The fundamentals of fruit zone leaf removal.