April 2016 Northern Grapes Project News You Can Use – Itasca Grape

News You Can Use

Itasca – New White Grape from the University of Minnesota

April 2016

Itasca grape.

Photo: David Hansen

The University of Minnesota recently released its fifth cold-hardy wine grape, named ‘Itasca.’ Itasca arose from a 2002 cross made by Peter Hemstad between Frontenac gris and MN 1243, and was identified in 2009 as an elite seedling.

Matthew Clark, assistant professor and grape breeder at the University of Minnesota, said “Itasca offers many benefits to wine grape growers over some of the currently available varieties. This is because it has much lower total acidity, disease resistance, phylloxera resistance, and can withstand cold temperatures. It appears to be even more cold-hardy than Frontenac. Itasca berries and wine are flavorful with notes of melon, pear, quince, and minerality.”

Data provided by Clark show that at harvest, titratable acidity in Itasca averages close to 10 g/L, while La Crescent is 14.5 g/L and Frontenac gris is 15.5 g/L. After the Polar Vortex winter of 2014, Itasca had over 60% primary bud survival, while other white cultivars had less (Frontenac gris, 20%: Frontenac blanc, 35%; La Crescent, 30%).

Licensed nurseries will begin selling Itasca in 2017.

Below are links to other articles and videos about Itasca.

University of Minnesota press release: http://discover.umn.edu/news/food-agriculture/university-minnesota-releases-its-latest-cold-hardy-wine-grape

CBS Minnesota: http://minnesota.cbslocal.com/2016/04/04/u-of-m-white-wine-grape/

Wines and Vines article: http://www.winesandvines.com/template.cfm?section=news&content=167366

The Northern Grapes Project is funded by the USDA’s Specialty Crops Research Initiative Program of the National Institute for Food and Agriculture, Project #2011-51181-30850

Chrislyn A. Particka, PhD

Extension Support Specialist

Cornell University

School of Integrative Plant Science, Horticulture Section

630 W. North Street

Geneva, NY 14456



Recent cold and potential damage, plus apple scab management.

By Terence Bradshaw

11 April 2016

If it weren’t for that warm spell, everything would be all right. Orchards around Vermont are largely at the ‘advanced silver tip’ bud stage and have been since the first of April, with tighter buds on Honeycrisp and in cooler upland orchards and more advanced buds at green tip on early cultivars and in warmer areas. Recent cold temperatures, especially on April 5, when we saw 10°F in South Burlington, are cause for concern, but don’t write off the crop yet. Critical temperatures for bud damage to apples at silver tip are 15°F for 10% kill and 2°F for 90% kill as a rule of thumb, although many factors can adjust those numbers. If buds were more advanced to the green tip stage, then the 10% and 90% kill temperatures are 18 and 10°F, respectively. I have only looked at a handful of buds at the UVM orchards, and saw a few with browning in the flower primordia. I prefer to take a wait and see approach because I just don’t trust evaluations yet, I don’t feel the damage was too extensive, and we still need to manage our trees for disease in the early spring regardless of whether there is a crop or not.

Apple scab management is right around the corner, and when the warm temperatures arrive by the weekend we can expect rapid bud stage development and plenty of green tissue exposed that will need protection. Many orchards has issues with late-season apple scab in 2015 and inoculum may be on the high side, so it would make sense to keep things covered during early scab infections this year. Luckily, the cool/cold weather has kept ascospore maturity low, with NEWA estimating 2% maturity in South Burlington and a predicted 3% of spores mature by the weekend. However, warmer sites like Putney are predicting maturity of 5% by this weekend, and if inoculum is high, 2-5% can cause substantial infection. Rains are expected for next Tuesday, and while I wouldn’t put too much faith in an eight-day forecast, I would plan on protecting trees as soon as possible after green tip emerges. This likely means spraying Friday and through the weekend. Remember to avoid using phytotoxic materials (coppers, captan, oil) before or after a freeze. Copper would be preferred for its efficacy against fire blight at this stage as it’s probably the best and maybe only window to apply it before 1/2” green bud stage comes and chances for phytoxicity and fruit russeting increase. This may also be a good window for applying oil so long as you wait at least 24 and preferably 48 hours after a freeze event to avoid damaging developing tissues. As always, materials and rates are best found in the 2015 New England Tree Fruit Management Guide, please let me know if you need a copy.

Weather looks great for planting trees, so get them in the ground this week before you get pulled away with spraying later.

Early apple season considerations

By Terence Bradshaw

As has been the case in the past several even-numbered years, growers are increasingly concerned about early bud break and potential for cold weather to damage developing apple buds. At the UVM Hort Farm, ‘McIntosh’ buds were just entering silver tip yesterday March 31. Growers are reporting silver tip across most of the major growing regions of the state, and a tiny bit of green tip has been mentioned. That may push out a bit today with warm temperatures, so some orchards may be in green tip by April 2.

This is a good time to look over and be familiar with the critical temperatures for bud damage in tree fruit. Michigan State University has published a guide at http://agbioresearch.msu.edu/uploads/396/36740/TreeFruitCriticalTemperatures.pdf

Based on this chart, orchards in silver tip can withstand 15°F with 10% fruit bud kill, and 2°F with 90% bud death. An orchard in green tip would have critical temperatures, respectively, of 18 and 10°F for 10% and 90% kill. It’s a pretty good bet that any bud development will slow through tomorrow, Saturday April 2 and halt after that through next week until warmer weather comes. So where you are at tomorrow is where your critical temperatures will be through the next expected cold spell. Orchard with no bud development (pre-silver tip) should be fine through this event.

Depending on where you are or what models you are looking at, low temperatures are expected to be in the teens on Monday and Tuesday mornings next week, and low spots will may be colder. There isn’t anything to do now but sit tight and see what comes. Get your pruning done and prepare your sprayers because the growing season will be here any time. I wouldn’t worry too much about early season scab right now unless significant green tip occurs, and even at that, it’s going to be tough to run sprayers around freezing weather (and definitively do not spray oil within 48 hours before or after a freeze event).

When the time comes, copper should be applied any time after green tip but before the half inch green ‘mouse ears’ stage. Copper’s primary benefit is in reducing overwintering populations of fire blight bacteria. Fire blight has become a regular disease to manage in Vermont, and a multi-pronged approach will be needed to keep it at bay. Copper applied at green tip will also give about seven days’ protection against apple scab. Applications should be made to all trees in the orchard, not just susceptible varieties. The specific copper material is less critical than the amount of metallic copper that is applied in the spray, and copper sulfate, copper hydroxide, copper oxychloride sulfate products all will be effective when used at label rates. I’ve attached a presentation by Kari Peter and Brian Lehman of the Plant Pathology Dept at Penn State that should provide good information on use of copper in early season apple sprays to manage fire blight inoculum and potentially that first scab infection period.

Now that the ground is clear and firming up, it also would be a good idea to perform spring orchard sanitation to reduce overwintering scab inoculum. Leaf shredding with a flail mower is an effective practice that also may be used to reduce small pruning wood to mulch, but the mower must be kept low in order to lift and grind leaves that harbor overwintering inoculum. Alternatively, there is still time to apply urea (40 lbs/100 gal water/acre) to leaf litter which aids in decomposition and breakdown of inoculum. Leaves should be wetted thoroughly and the majority of material directed into the tree row. This application would add 18 lb actual nitrogen per acre which should be accounted for in your fertilizer applications later in the season.