While the Northeast has come to a halt under the blanket of snow delivered from Winter Storm Stella, tree fruit growers kept an eye on the thermometers, hoping temperatures didn’t dip too low for bud damage. Thanks to a warm February, where temperatures were in the 50s and 60s for several days in a row only to have temperatures dip into the 20s in early March.
Following Winter Storm Stella, AccuWeather said an icy blast would follow with highs at below freezing throughout the Great Lakes and Northeast, with gusts of 35 to 45 miles per hour expected.
Researchers from around the Northeast and Midwest have responded with best practices and observations from the roller coaster that the weather has been in 2017.
Poliana Francescatto, PostDoc Research Associate in the Department of Horticulture at Cornell University in Geneva, NY:
“The warm weather experienced a couple of weeks ago speeded up bud development for sure. I have calculated the degree days (base 40°F) for our area and we have reached between 1,700 to 2,000 degree days (we consider 2500 DD as sufficient for apple “bud break”). Most of the accumulation happened in around 15 days, between mid-February to the beginning of March. Then, in the beginning of March, temperatures dropped severely. We went from 68.5°F to down 21°F in less than 20 hours. The drastic fluctuations in temperatures have been my main concern.
I noticed the cold damage on our ‘Redhaven’ peach block last week when I just did some transverse cut using a regular razor blade. The damage was intense. But thinking that we need only 5% of flowers to get a good crop we seem to be ‘ok.’ Thinning was done!
I have opened few ‘Regina’ and ‘Rainier.’ ‘Rainier’ looks very bad. Hard to find a good flower within a bud in the middle of 3-4. ‘Regina’ as I expected from the experience we had last year is on a good shape. Very few with damage.
We also saw damage to our apples again this year. Depending on the block (lower vs upper areas) some king flowers are dead. I am not really worried about apples yet. If I look back to what happened last year where we thought we wouldn’t have a crop, apples are my last concern.”
Mark Longstroth, Michigan State University Extension Fruit Educator in Paw Paw, MI:
“This morning, our lows were from 8 to 15. That is cold enough to cause SOME damage in Southwest Michigan. Mainly to early stone fruit and the earliest apples in the extreme south. The really cold temps were not in fruit sites and the big lake protected us there by keeping temps higher and delaying growth during that warm spell in February.
At this time, I do not expect damage to grapes or blueberries.
Down in Southwest Michigan, we say the spring comes three times, meaning we get growth spurts and cold snaps severe times and we seem to have gotten through the first on with scattered damage.
The cool weather we have had in Michigan has stopped development at the swollen bud stage. No green is visible in any of the major fruit crops. Apples are at silver tip and stone fruit at swollen bud. Apricots and Japanese plums are at bud burst.
The temperatures have dropped into the teens but I do not believe we have had any damage yet. Not worried about this storm but about the cold dry air behind it.
We would expect some damage with temperatures into the mid-teens, but would need to go to the single digits to cause severe damage.
I don’t think pruning does much after growth has begun in the spring. The cool temps these last two weeks have been a godsend. The only frost mitigation techniques that would work at those low temperatures would be orchard heaters or frost fans during a radiation freeze (clear sky, no wind, low dew point).”
Win Cowgill, Professor Emeritus with Rutgers University in Baptistown, NY:
“Last week, I began to urge growers to stop pruning peaches and even apples in front of extremely low temperatures. We had forecasts for single digits that have moved upward to low teens for the most part. Peaches have swollen with the 70°F temperatures the week before.
Pruning before cold de-hardens the buds and wood and makes them more susceptible to cold injury. We are in a major blizzard from Monday night through Wednesday in New Jersey and up through New England with extreme winds and low temperatures. No pruning should be done until temperatures moderate and risk of low night temperatures is passed, at least 7 days out.
Also, apply no dormant oil yet. Some growers were ready after the last 70°F temperatures. Never apply oil with 32°F anywhere in sight. I would be safe and have 5 to 7 days forecast above 33°F following an oil application. This may be as long as two weeks out.”
Jon Clements, University of Massachusetts Extension Educator in Belchertown, MA:
“We have dropped into the single digits several nights over the last 10 days with buds ranging from dormant to silver-tip/bud swell. Plenty to worry about, but I suspect we pulled through (so far) with minimal damage. Time will tell.
The longer range forecast looks pretty seasonal if not cooler than normal through the rest of this month, which would be good. I agree with Win [Cowgill] about not pruning, although I will admit I did some apple pruning yesterday, kind of need to get caught up for when spring does arrive.”
Jim Schupp, Professor of Pomology at Penn State University in Biglerville, PA:
“Apples in Adams County Pennsylvania are at green tip, peaches are swollen bud-calyx green, and apricots in early bloom. With the return of winter at the start of March, there has been almost no change in buds for two weeks. We had 14°F last week, with some additional temperatures in the mid-teens forecast for later this week. I suspect apricots are toast, but I still hold out some optimism for the apples and peaches that are our major crops.
Last April, we experienced four freezes in April, during bloom in peach and tight cluster-pink in apple. Three of these freezes were cold enough for a ‘90% kill.’ We picked a half crop of peaches and a full crop of apples. I question if the critical temperatures are always a hard and fast line.
There are still a lot of pages to turn before we can read the 2017 crop. With breaking dormancy in February, then descending back into winter will do to the crop remains to be seen. We plan to let this next wave of cold pass before we check bud damage.
As far as what to do/ not do, I don’t know if anyone around here has ever been through a crop year that started in February! Pruning dormant trees in mid-winter ahead of cold weather can activate the cambium tissues, making such trees more susceptible to mid-winter injury. I don’t know of any evidence that buds on trees that have already de-acclimated and started to grow can be made less hardy by pruning. We have continued pruning activities.
Perhaps the best advice is to encourage growers to focus on activities that support their faith and well-being.”
Nikki Rothwell District IPM Educator for Michigan State University in Traverse City, MI:
“In Northwest Michigan, we have had a bit of the roller coaster with the weather; but overall, we have been colder than other parts of the state and temperatures have fluctuated less. We cut apple and cherry buds last week after a very cold weekend, and we have not seen any damage. So far, I think we are in good shape, but as it has been typical in the past few years, these up and down temperatures are worrisome.”