By Kathryn Carter, Dr. Wendy McFadden-Smith and Amanda Green, OMAFRA
The hot weather has continued to push degree day accumulations (GDD) forward and as of June 29, 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 784 GDD, Lakeshore Rd 740 GDD and Beamsville 743 GDD which put us on par to 2018 with respect to degree day accumulations (Ontario Tender Fruit Growers, 2020).
Despite the small amount of precipitation, we received this weekend, soils are very dry and irrigation has started in some crops.
Tender Fruit and Fresh Grape
In Niagara pears are 32 mm, plums are 21 mm and nectarines are 30 mm. Sweet cherry harvest has begun and tart cherries are15 mm.
Fruit thinning continues in orchards. Frost damage is apparent in many areas with reduced crop and some russeting and warty nectarines (Figure 1)
Fire blight continues to show up in pears with the driving rains spreading bacteria from bloom infections. Growers should wait until terminal growth ceases to remove blighted shoots or at least wait until a period of hot, dry weather to do so.
Hot, dry conditions may result in movement of plant bug species from row middle ground cover into the canopies of stone fruit. Avoid travel through orchards if plant bugs are a problem in your blocks. Foliar bacterial spot infections are present in peach, nectarine, apricot and plum blocks. The only treatment available is copper. The best timing for copper applications is before a forecast rain to protect from new infections. Refer to the ON Fruit post at https://onfruit.ca/2020/06/15/see-spots-run-bacterial-spot-and-peach-scab-season-is-here/ for more information.
Spotted wing drosophila has been detected in all counties where it is being monitored. Refer to ON Fruit for details: https://onfruit.ca/2020/06/26/spotted-wing-drosophila-update-june-20-27-2020/. In cherries, products that are active against both spotted wing drosophila and cherry fruit fly should be used. Weekly counts are posted on the blog. Oblique banded leafroller trap counts indicate the need for sprays in tart cherries and pears where this insect has been a problem. In pears, a product with activity vs both OBLR and pear psylla is recommended. Tart cherries are also very susceptible to cherry leaf spot and powdery mildew.
Precipitation has been very low and soils are very dry. Irrigation for tender fruit is important in increasing fruit size, especially in long periods of dry conditions. Adequate moisture is also needed to enhance fruit bud development for next years crop. Although it may be tempting to focus only on mature fruiting trees, instead of non-producing trees, research has shown extensive benefits to irrigating young trees. Irrigating young trees results in the development of larger trees with greater fruiting wood structure and, earlier fruiting potential.
There are three stages of development for peaches: Phase 1-cell division, Phase 2-Pit Hardening (where there is little increase in fruit size), Phase 3- cell expansion (resulting in a large increase in fruit size). The key times for irrigating peaches are during cell division (from bloom to 30 days after bloom) and during cell expansion (approximately 2–4 weeks before harvest). The most accurate method of determining irrigation needs is to use soil moisture probes (see How to Get the Most Crop Per Drop). For more Information irrigation fruit trees stay tuned for our next ON Fruit post.
Vitis vinifera cultivars are finishing bloom. Vineyard planting is continuing and shoot thinning shoot positioning is ongoing. The vines are very vigorous in some vineyards this year and we are seeing laterals breaking a lot earlier and more vigorously than normal. Bud break was very late this year due to 2 weeks of record breaking cold weather during the first few weeks of May. This was followed by warm to very warm temperatures lasting about a week beginning May 23 (high 20s to low 30’s) and a lot of moisture in the soil, which created perfect conditions for vine growth. It was a relatively mild winter, and vines may have been pruned a little hard as a result, which also may have contributed to the increased vigour. With last year’s moderate crop, flower cluster initiation may have been reduced, resulting in less competition for resources, and increased vigour- resulting in more laterals breaking.
Powdery and downy mildew and black rot have been found on grape foliage and downy mildew was found on flower clusters pre-bloom. We are into the peak period for fruit infections by all of these diseases plus bunch rot. Leaf removal with air pulse technology has been shown to remove flower cap debris as well as thin the canopy around clusters both of which reduce Botrytis infections. Grape mealybug populations are in adult and egg cluster stage of development. In blocks where mealybug is present and grapevine leafroll virus is confirmed, a Movento spray applied around fruit set is the optimum timing. Refer to https://onfruit.ca/2020/06/26/grape-mealybug-development-update-june-23-2020/ for more information.