Don't Panic!

Some of you may be wondering if your fruit trees are at risk for breaking bud and growing with all this warm weather. Certainly, if it were later in the winter, this might be the case. And, reports of (ornamental) cherry bloom in the mid-Atlantic area (Washington D.C., and Newark, NJ), don't help. (Don't Panic!) We're not too worried about apples. Stone fruit chilling and grapes, however, are further along and with continued warm temperatures (with additional heat accumulation) there is potential for injury, as winter is just beginning. A review of chilling, dormancy, and rest might help explain what is going on.

First, the concept of dormancy and chilling hours/units. Deciduous trees, such as apple and peach, gradually acquire cold hardiness and dormancy beginning in the fall with cooler temperatures and decreased day length. They have adapted such that they don't wake and start growing in early or mid-winter, because obviously this would be a problem. If they broke (or swell) buds, started growing, and then the temperature dropped below freezing, they would be toast. In fact, this concept of endodormancy (aka “rest”) has been well studied and quantified.

These chilling hours (or units as they are called when somewhat modified), in their most simple form, accumulate when the temperature is between 32 and 45 degrees F (it is generally agreed). Some studies have gone further and adjusted this accumulation based on other temperature factors, such as when the temperature is above 45 but chilling units are still accumulated (but at a slower or faster rate). For apples, it is generally accepted that approximately 1,200 chilling hours between 32-45 are necessary before they might start growing again. It is, however, somewhat variety dependent, with a range of app. 800 (low chill varieties like ‘Anna’) to 1800 chilling hours/units. Peach, however, has significantly lower chilling hours/unit requirements: 500-1,200, again highly dependent on variety. All this is important too in warmer climates where sometimes not enough chilling hours/units are accumulated to properly break bud and flower (and fruit).

Buds are most hardy (resistant to minimum winter cold temperatures) when the chilling has not been close to met and temperatures have gradually declined. This allows buds to increase in hardiness. Once the chilling requirement has been met, it is the amount of heat units that accrue that move buds forward to bloom. (But only after the chilling requirement has been met!) After chilling is met, temperatures above 32 degrees F. allow for internal development in the buds.

So, where do we stand in chilling hours/units right now? A pretty neat website, http://getchill.net, calculates them for you for any location that has a Weather Underground weather station (http://www.wunderground.com/). For the UMass Cold Spring Orchard (KMABELCH4) since November 1, 2015 (through December 22), the calculation results:

• Below 45 Model: 633 chill hours
• Between 45 and 32 Model: 522 chill hours
• Utah Model: 679 chill units

Zestar! flower bud, low risk for injury
as chilling requirement has not been met (yet)

The important numbers are Between 45 and 32 Model (633 chill hours) and Utah Model (679 chill units). Both well below 1,000. Apple buds aren't going anywhere (yet). Peach buds, well, their chilling hour/unit requirements are less (as low as 450). There could be an issue with stone fruit if the warm weather persists (especially with some chilling still). Even though we might not have enough warm temperatures to actually break bud, they will be more sensitive to mid-winter cold once rest has been broken. I would not fret too much about it yet, however, as most peach varieties we grow have fairly high chilling hour/unit requirements.

Peach buds at higher risk because
chilling requirement is close to met;
in fact, these buds look swollen on 12/23/15

Second, and this is more problematic. Any time very cold temperatures -- particularly a rapid drop in temperatures -- following very warm temperatures during the dormant season, can result in plant tissue damage. This is a cold hardiness issue. Stone fruit are more sensitive to this because of their genetic disposition to just stay “greener” all winter. Keep in mind that fruit tree buds (and the cambium layer just under the bark) do not fully stop metabolizing during the winter and are still quite “alive” despite their dormant appearance. Very warm early or mid-winter temperatures followed by a rapid drop to extreme cold is definitely not good news, although certainly it is not always a disaster either. (Just plain bad news.)

So that you might be able to sleep tonight, consider apple trees are pretty well adapted to survive and grow despite the vagaries of weather. Peaches (and other stone fruit) are less suited for surviving wild temperature fluctuations, i.e., they are not as well adapted as apples to our wildly fluctuating weather here in central New England. Now, what the long-term effect of climate change (warming) on our fruit trees is another question? (Weather is short-term, climate is long-term. See Northeast and Northern Forests RegionalClimate Hub Assessment of ClimateChange Vulnerability and Adaptation andMitigation Strategies.) Ask me again in April how today’s “weather” will affect our 2016 tree fruit crop. (Hint: we have a long way to go until apples and peaches are harvested and in the cooler in 2016. And I might just tell you the answer is 42.)

Many thanks to my colleague Win Cowgill at Rutgers University for helping me track down and understand the concept of chilling hours/units and dormancy of deciduous fruit trees, as well as supplying some of this text. You might also want to check out About Chilling Units and Hours from University of California Davis (although the emphasis is on low chill varieties suitable for normally warmer climates) and Cold Injury to Fruit Trees (a presentation I gave at the Ontario Fruit & Vegetable Growers's Conference in February, 2014.) And, if this is all too mind boggling, well there is always The Answer to the Ultimate Question of Life, the Universe, and Everything, which of course is...

"Answer to Life" by Originally uploaded by en:User:Martinultima - en:Image:Answer to Life.png. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Answer_to_Life.png#/media/File:Answer_to_Life.png

Raynox Plus® applications to prevent sunburn of Honeycrisp apples

Raynox Plus® Sunburn Protectant "protects fruit from sun damage by forming a thin, clear, natural wax layer that blocks damaging UV rays from harming fruit" according to their website. In 2015, Raynox Plus was used in a demonstration at the UMass Cold Spring Orchard in Belchertown, MA.

Applications of Raynox Plus were made on an app. 10 year old block of Honeycrisp apples, 0.85 acre in total size. Five individual rows were divided into four treatment sections, two were an UnTreated Control (UTC, no Raynox Plus) and two were Raynox Plus treated (RNX). Thus, half the block was treated with Raynox Plus (RNX), half was left as an UnTreated Control (UTC), however, treatments were randomized throughout the block and rows were sprayed such that there was no drift of the RNX treatment into the UTC treatment. The Tree Row Volume (TRV) of this block was app. 175 gallons per acre, and treatments were applied in 62.5 gallons of water per acre (app. 3X). Rayox was applied at a rates of 2 to 2.5 gallons per acre, in a total of five application timings (all in the morning):

1. Monday, July 6, 2015, 2.5 gal per acre
2. Friday, July 10, 2015, 2 gallons per acre
3. Sunday, July 19, 2015, 2 gallons per acre
4. Tuesday, July 28, 2015, 2 gallons per acre
5. Monday, August 17, 2015, 2 gallons per acre, however, only west side of trees sprayed

Environmental data (temperature and solar radiation) along with dates of Raynox application(s) are presented in Figs. 1 and 2.

Fig 1. — Daily minimum and maximum temperature, UMass Cold Spring Orchard

Fig. 2 — Daily solar radiation, UMass Cold Spring Orchard

Direct observations of both treatments (UTC and RNX) beginning after the first RNX treatment date of July 6 were consistently made and no observable sunburn/heat injury was found within both treatments until well after the last treatment and roughly coinciding with harvest in early-mid September. Note that the highest temperature of the season (app. 95 F.) was recorded on 8-September (Fig. 1), however, by then solar radiation was reduced (Fig. 2). Although some minor sunburn symptoms were observed in September just before or at harvest, it was only on  a minimal number of fruit, and there was no observable or discernible differences between treatments. It was concluded that sunburn did not present any kind of significant fruit quality problem throughout the block at harvest, regardless of Raynox treatment or not. The harvest crew did not note any significant sunburn/heat injury issues throughout the block, although clearly there were some symptoms as noted later in this blog.

Fruit surface temperature measurements were made beginning on 18-August, and although some readings were as high as 111, most were in the 100 to 105 degree range on that date (Figs. 3 and 4). Fruit surface temperatures on 8-September, when the hottest daily high temperature of 95 F. was recorded, were in the 117 to118 degree range, however, mostly temperatures were in the low teens above 100 degrees (Figs. 5 and 6.) Note the literature suggests a fruit surface temperature of 115 F. or above may be necessary to initiate sunburn.

It was observed on September 3, and after several Raynox applications, that foliage/leaves on the Raynox treated trees took on a significantly different (silvery) appearance (Fig. 7).

Fig. 7 — it appeared Raynox-treated (RNX) foliage (right) had a more “silvery’ appearance
than UnTreated Control (UTC) on left

Some examples of the minor number of fruit with sunburn/heat injury symptoms can be seen in Figs. 8 and 9, however, damage was minimal and there were no treatment differences observed. It’s felt most of this (minor amount) of injury occurred during the September heat period(s), and personal communication with Washington apple growers suggests that fruit becomes more susceptible to heat/sunburn injury with increasing fruit maturity near harvest. Although they were not applied at this time just before harvest, RNX applications may have the most benefit then.

Fig. 8 - severe sunburn observed on a very few Honeycrisp apples that would result in cull

Fig. 9 - less significant sunburn on a few Honeycrisp apples,
would not result in cull for fresh market/direct sale

Conclusions include:

• By the time of harvest, very negligible amounts of sunburn/heat injury were observed in these Honeycrisp, and there was no difference observed in the RNX vs. UTC.
• The temperature/solar radiation combination may not have been high enough all summer of 2015 to elevate apple surface temperatures to a temperature that would result in damage. The hottest temperature occurred in September, however, solar radiation was reduced; this period, which was 2-3 weeks after the last Raynox application, may have resulted in all the injury observed (which was very minimal).
• Air temperatures greater than 95 degrees, and more likely approaching 100 degrees along with high solar radiation may be required in this climate to initiate sunburn; anything less then this probably does not warrant Raynox application.
• More study could be done here in Massachusetts, because in at least one orchard in 2015, significant sunburn was observed in Honeycrisp (Fig. 10), and in past years, sunburn/heat injury has been a more significant problem in very hot summers (but not generally the summer of 2015).
• Previous studies have shown that Raynox Plus is effective at reducing the amount of fruit with sunburn injury including the varieties Honeycrisp, Macoun, and Cortland (Valent Fact Sheet). In fact, a study done my colleague in NJ (Win Cowgill) in 2015 showed good efficacy in using Raynox Plus on Honeycrisp (Fruit Notes,), although environmental conditions there may have been more conducive to sunburn development than we saw in MA and there threshold for injury may have been less.

Fig. 10 — significant (photo oxidative) sunburn injury  to Honeycrisp apple
observed on 30-July, 2015 in Amesbury, MA

IFTA Study Tour 2015 to Washington

July 15-17, 2015. International Fruit Tree Association Study Tour to Washington (USA)

Along with app. 140 other lucky IFTA members, I had the good fortune to attend the IFTA Study Tour to Washington July 15-17, 2015 which visited orchards in the Columbia Basin area of southern Washington state, USA. Take-home messages for me were several:

• Water, although perceived by us here in the East to be a problem out there in the west, is not really a problem for most apple growers in Washington. A massive federal reclamation project which dams the Columbia River (although salmon be-damned!) and provides a series of canals and reservoirs means there is plenty of water in the Columbia Basin. Much overhead irrigation of corn, wheat, and other field crops was seen. Trickle, overhead, and cooling water was used in orchards. I believe there was some water restriction on orchards farthest removed from the water source, but that did not seem to be a big deal. That remains to be seen with time I suppose. It should be noted there is virtually no snowpack in the U.S. mountains out there, and the spigot originates in the Canadian Rocky Mountains, so there was some talk about Canada perhaps trying to gain some advantage for supplying all this water to the U.S. I suspect California would like to tap into some of that water too?
• Honeycrisp, like water, is perceived by us East coast apple growers to be a problem in Washington too. "Poor quality, poor flavor, shouldn't be growing them out there!" Maybe, but what I saw looked pretty darn good -- fruits on the trees looked good, trees looked healthy, and growers are serious about producing quality Honeycrisp and lots of them. Sure, I saw some sunburn, but foliage was dark green and healthy and the fruits were clean and very Honeycrisp-like. You would not have known it wasn't a tree in the east or mid-west (or Nova Scotia even). And I repeat, the growers we visited were very serious about producing top-quality Honeycrisp fruit. I was impressed and won't likely 'diss,' and in fact probably defend, their ability to grow good Honeycrisp out there. Did I mention overhead cooling is a necessity with this fruit though.
• Apple yields, all the talk was 100, 22 bushel bins per acre being the new standard (or at least the achievable goal). 2,200 bushels per acre! Wasn't it all that long ago that 1,200 to 1,500 bushels per acre was considered pretty magical? (Still pretty magical here on the East coast.) To get this yield, angled V-canopies were prevalent. (Maximum light interception = maximum yield.) A side-effect of using V-canopy support systems, however, was the need to re-assess support system construction methods because 2,000 bushels per acre = 40 tons of fruit per acre to hold up. It was noted some support systems were failing under this fruit load, hence the need to analyze and re-construct our notions about what an adequate support system should look like. Note that we did see some vertical canopies, super-spindle and tall-spindle, although they did not call it tall-spindle out there, what did they call it, I can't remember? These vertical canopies do lend themselves to mechanization better, however, than the angled canopies. Despite the allure of high yields, after looking at lots of angled canopy systems (lots, trust me!), I don't feel the need to bring that system back east. Unless I want to grow 2,000 bushels per acre, hmmm....
• Labor, some discussion, most notable, when cherry harvest starts, there is little labor left to do apple orchard work like hand thinning. Hand thinning was ongoing while we were visiting, some orchards had not been hand thinned. This is late. Offshore H2A labor seems to be an increasing option to supplement the more traditional local and seasonal Hispanic labor.
• The apple crop will be big again out there this year, perhaps not as big as last year's record-breaker, but still big. There did not seem to be too much concern about this, especially if growing managed varieties and/or Honeycrisp. The legacy varieties are in trouble, although Washington State University Extension's Karen Lewis thinks we still need a "value" apple at 99 cents per pound that is more affordable than the club varieties at $4 per pound which are out of the reach of a lot of people. So, stay tuned to see if over-production truly becomes a problem or will we as an industry figure that out?

OK, those are my major observations. What follows are a picture or two (or more) from each tour stop and a brief description. (If you want to see all my best pictures, they are here on Flickr.) If any questions, or comment, please feel free to post. And of course, thanks to IFTA and all the local hosts and tour coordinators and sponsors for their hard work and hospitality. Everyone seems to be busier than ever, so it is a real accomplishment of great value by IFTA to be able to continue to offer these education and networking tours to beautiful scenery and friendly, knowledgeable growers and industry people!

Day 1, Wednesday, July 15

Click here for Day 1 map of where we were; may not include all stops, GPS/Verizon may not have been all there!

Stop 1 - Stemilt Ag Services, Saddle Mountain West, Othello, WA. Dale Goldy and Robin Graham were our hosts. Fuji, Gala, Honeycrisp, Cripps Pink were featured, planted 4 X 12, tall-spindle. Noted use of Surround to prevent sunburn and on transitional organic (2015) plantings. Nice looking tall-spindle Honeycrisp with 60 bins per acre (3rd crop) and 40 bins per acre (1st crop) orchards.

Stop 1 IFTA Washington tour, Stemilt Ag Services

Nice looking organic (I believe, I am sure there were some) Honeycrisp

Stop 2 - Yakima Valley Orchards, Basin City, WA. Dave and Travis Allen our hosts. First, a modest angled system planted in 2013, Buckeye Gala, first crop year, 30 to 40 bins per acre expected. And, as explained by Dave Allan, an experimental pedestrian Buckeye Gala orchard. One acre block planted in 2010 produced 100 bins per acre. Allan says ability to manage from ground (labor efficiency) might trump high yield efficiency, but verdict is still out.

Angled orchard systems were commonplace in the Columbia Basin; here, Buckeye Gala planted in 2013

Dave Allen touts the virtues of an experimental pedestrian orchard. "It may be our future" he says....

Stop 3 - Hi-Point Orchard, Basin City, WA. Rick Orozco our host. Angled-V, BC2 Fuji planted in 1992 on M.7A rootstock, but grafted to Aztec Fuji in 2009 and 2011. BC2 peaked at 98 bins per acre, Aztec Fuji (pictured below) in 2014 produced 50 bins per acre. And, nice looking 6 X 18 ft. perpendicular-V peach on this excellent stone fruit site.

Angled orchard top-worked to Aztec Fuji produced 50 bins/acre in 2014

Hi-Point Orchard was a real nice peach site; here, either 'Sierra Rich' or 'August Brite' wait to be harvested

Stop 4 - Cameron Nursery, Eltopia, WA. Todd Cameron our host at this family owned (Allison and Eric Cameron) fruit tree nursery that specializes in finished 1- and 2-year old (knip-boom) nursery trees, bench grafts, and sleeping eyes. Todd Cameron is truly outstanding in his field in producing uniformed, modestly branched finished apple trees. Cameron and other nurseries are trying to ramp up production of Geneva rootstocks, of which they currently have 20 acres out of a total of 40 acres of layerbed. Geneva rootstocks are in-demand because of selection of dwarfing and semi-dwarfing characteristics, and fire blight and re-plant disease resistance. Click here for handout.

Todd Cameron 'outstanding' in a field of apple nursery trees already pre-sold for 2016

Geneva 11 rootstock layer bed

Day 2, Thursday, July 16

Click here for Day 2 map of where we were; may not include all stops, GPS/Verizon may not have been all there!

Stop 1 - Doornink Fruit Ranch, near Yakima, WA. Jim and Phil Doornink our hosts. Gala block planted in 2014 on G.935, 3 X 12 ft. spacing, training with up to two leaders for 2,420 leaders per acre. Phil demonstrates snapping of vigorous branches and "letting them hang" to reduce vigor. And, 2009 planting of Gala on M.9-337, 1.5 X 14 ft. spacing. Produced 79 bins per acre in 2014 according to Jim. Nice angled-V wall of fruit, meticulously managed with pruning to desired bud count.

Gala/G.935 planted 3 X 12 ft. and grown to 2 leaders in an angled system

Phil Doornink demonstrates bending and snapping of vigorous shoots and leaving them hang (promotes ethylene stress) to reduce vigor

Gorgeous mature Gala (planted 2009) angled system at Doornink Fruit Ranch --
but, have we seen enough angled systems yet?

Stop 2 - Chiawana Orchard, Yakima, WA. Host Bruce Allen. Honeycrisp the theme of this stop. Bruce is regarded as one of the best Honeycrisp growers in the region, and he stressed the need to grow quality Honeycrisp with good flavor or else "we'll screw up the market." This 1,200 ft. elevation orchard has a lot of good looking Honeycrisp with overhead cooling and reflective fabric to improve red color. Well, maybe they need a little more hand-thinning? But thinning starts at bloom with fish oil and lime sulfur. This is when I decided they can grow OK Honeycrisp!

IFTA members in a block of Honeycrisp, grown to - you guessed it! - an angled System at Chiawana Orchard

Nice Honeycrisp at Chiawana Orchard - do these need some hand thinning?

Extenday® reflective fabric in a Honeycrisp block at Chiawana Orchard

Stop 3 - Matson Fruit Company, Selah, WA. Several stops here with host and manager Jason Matson, below pictured in a last-to-be-picked Sweetheart cherry orchard. (We enjoyed eating the cherries, but the angled support and pruning/training system came under considerable scrutiny.) Also visited mature Honeycrisp blocks, including top-worked in 2010 V-system with 4 leaders per stump, and vertical trellis planted in 2008 with single leader per tree. And a young angled trellis of Honeycrisp planted in 2014 which was cut-back in the last year to two leaders per tree. Much discussion ensued here, with Stephano Musacchi and Karen Lewis from MSU.

Sweetheart cherries, Jason Matson

Matson grafted Honeycrisp with 4 leaders, 82 bins/acre in 2014

2008 replant Honeycrisp, 62 bins per acre in 2014

2014 Honeycrisp V-system with 2 leaders

WSU's Musacchi and Lewis in discussion with Matson

Day 3 - Friday, July 17

Click here for Day 3 map of where we were; may not include all stops, GPS/Verizon may not have been all there!

Stop 1 - McDougall and Sons, Whispering Rocks Orchard, Mattawa, WA. Hosts Brent Milne and Dr. Stefano Musacchi. WSU mechanical thinning trial the highlight with the objective to reduce labor cost while maintaining (increasing?) productivity. Cripps Pink/M.9-337 planted in 2013, 3 X 12 ft. trained to a vertical spindle. (I think that is what they call tall-spindle.) Produced 37 bins per acre in 3rd-leaf (2014).

Dr. Stefano Musacchi mechanical thinning trial

Fruit bud initiation effect of early summer hedging

4th-leaf Cripps Pink grown to vertical spindle, 37 bins/A in 3rd-leaf

Stop 2 - Valley Fruit Company, Royal 1 Orchard. Scott Jacky and Bill McCombs were our hosts, where WSU's Karen Lewis lead a discussion on support system strengths and weaknesses. Here, Karen Lewis with Bill McCombs have this discussion in a newly constructed, impressive (and expensive!) support system. It replaces the weaker, T-post system pictured. (I am not sure what they were thinking when they built that one?)

WSU Karen Lewis and Bill McCombs discuss the need for improved support systems to carry 100 bins per acre of apples

Inadequate T-post support system at Valley Fruit Company, now looking to beef-up their support systems

Stop 3 - Winchester Orchard, Quincy, WA. Enjoying lunch and pie -- purported to be the best in Washington, it was good -- and an equipment show featured Automated Ag Systems Bandit XPress and Bin Bandit platforms, as well as platforms, sprayers, and hedgers from other vendors. Thanks to Karen Lewis for arranging this. Then we visited with Tim Welsh of Columbia Fruit Packers and IFTA President who showed us tall-spindle plantings of Brookfield Gala and Kanzi®, their new managed variety Nicoter cv. 63 acres are transitioning to organic and a comparison of single vs. two leader trees was made: 66 bins/A for the single leader, 59 bins/A for the 2-leader in year 3 of yield. Tim made the point he expects the 2-leader trees to overcome the single-leader trees this year or next, but the verdict is still out whether he would do it again.

Karen Lewis hosts equipment show featuring Automated Ag Systems

Columbia Fruit Packers and IFTA President Tim Welsh

Single leader Nicoter cv. (Kanzi® brand)

Double leader apple trees at Winchester Orchard

Still hand thinning (damn cherry harvest!) apple trees with platform

Stop 4 - McDougall and Sons, Prospector Orchard, Quincy, WA. Hosted by Scott McDougall and Dr. Lee Kalcsits from WSU. Kalcsits discussed their photoselective netting research to prevent sunburn and improve fruit quality in this young Honeycrisp orchard. (Note that the crop was removed to improve growth in this 3rd-leaf except under the netting experiment.) The netting filters light by up to 20%, but that does not seem to effect photosynthesis and productivity, while the shading reduced temperature, sunburn and improves fruit condition significantly. McDougall showed us a 2 X 12 ft. steep V system planted to Cameron Select® Honeycrisp on G.11, G.41, G.935, Bud.9, and M.9 rootstocks with under-tree micro irrigation and overhead cooling.

Sunburn developing on Honeycrisp apple

WSU photo-selective netting for apple experiment

Cameron Select® Honeycrisp rootstock comparions

An IFTA tradition, President Tim Welsh thanks Scott McDougall for allowing us to visit their orchard and sharing their experience