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Frost/freeze damage assessments are becoming a little clearer, although it will be weeks before any semi-authoritative estimates take shape. Emerging trends include:



How much trees will compensate remains an unknown.


Forecasts continue to show potential for frost and lows in the 20s, at least for the upper stretches of our coverage area. After a warming trend next week, more rain is expected. Diseases like jacket rot and shot hole are on everyone’s radar at the moment.


The real concern now centers on bee activity. Cold weather slowed bee movement, and rains and wind this week kept them in the hive, as well.


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Franz Niederholzer, UC Farm Advisor, Sutter/Yuba Counties

“There’s nothing definitive yet in terms of damage estimates, and I suppose it could be August before we really know the full extent of what’s happened. Where we see damage in places, it’s mainly in the Sonoras and other early varieties. In places with little protection, they look like they were beaten up pretty badly.


“Varietal differences make it harder to estimates potential in a given block. At the Nickels Soil Lab, we have a block with 25% Sonora, 25% Aldrich and 50% Nonpareil. It looks like the Sonoras are either all or partly gone. In those cases, we’ll have to figure out how to differentially fertilize the crop. Otherwise, we’ll probably be giving some of those trees too much, which could lead to other problems later.


“One alert PCA has already asked how to fertilize orchards where they lost the crop. Dr. Patrick Brown, Professor in the UC Davis Plant Sciences Department and a world authority on almond nutrition, told me this week that you’ve got to approach this based on the age of the tree and its stage of development. Your fourth- to eight-leaf trees are still growing wood, extending branches and filling space, and you need to maintain that progress through this season, despite the lack of crop.


“His research suggests that these trees will use 40 to 50 pounds of nitrogen per acre per year without a crop. Remember that when applying nitrogen, you should use an efficiency factor of 70%. To get 50 pounds of N into the tree, you'll need 71 pounds per acre per year. That’s based on 50 pounds divided by 0.7, which equals 71.  Dr. Brown also suggested multiple, small applications through the season to get the most benefit from the fertilizer.


“For older trees that have filled their space but were ‘frosted out,’ Dr. Brown recommends 30 to 45 pounds of nitrogen per acre per year needed to maintain the canopy and renew spurs. Again, use that 70% efficiency value to determine the amount of N to apply. By comparison with a normal crop load, you need 68 pounds of nitrogen for every 1,000 pounds of crop. So for a 3,000-pound/acre yield, the crop will use just over 200 pounds or close to 300 pounds of N applied, using that 70% efficiency factor.


“We had rain here yesterday (3/1), from 0.5 of an inch to 2 inches in places. Temperatures during all that were on the cool side, maybe highs at 58 in warmer spots. Most people, I think, applied fungicides ahead of that rain, plus rain is in the forecast this weekend and late next week. So, it was a good time to apply fungicides.


“Low temperatures remain in the forecast, too. In the very upper reaches of the Sacramento Valley’s almond production area, there’s a 15% chance of temperatures dropping to 22 overnight. That’s a ‘lights out’ situation in terms of potential damage. We have at least some frost potential across a wide area overnight, and temperatures in general have been running 5 to 10 degrees cooler than normal.


“A warmer weather trend would really help. As nuts get older, they are even less tolerant to frost and sub-freezing temperatures.”


Rick Foell, Field Manager, Capay Farms, Hamilton City

“We’re past petal fall on much of our almonds and are starting to clear jackets on the earlier varieties – the Sonoras and Winters. They seem to be the only varieties growing right now. The Nonpareils are kind of at a dead standstill.


“It’s been pretty cold up here – highs in the low 50s at most and we actually had a frost last night, with chances of frost in the forecast into the middle of next week. This weather seems to be never-ending, and all the guys say they’ve never seen anything like it.


“Where we can find damage, it’s in pockets. But we’re hesitant to venture any estimates – partly because we still have nights ahead of us with frost. Today (3/2) I noticed some trees dropping nuts, especially in Sonoras. Some of those trees actually looked pretty good, but we also have places with obvious frost and cold damage.


“By this time next week, we should know more, at least with early varieties, and get some idea about what kind of crop we have.


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“Cold weather varied in spots. Most ranches were at least below 32 for 5 hours, with some below 30 for 3 hours. In a few spots, it remained at 28 to 29 for a couple of hours. We’re hearing that almonds around Corning probably took the brunt of the cold weather.


“We’re in the middle of our second bloom spray. Rain out of this last storm varied, depending on the ranch or location, from 0.10 of an inch to 1.25 inches.”


Aaron Beene, PCA, Simplot, Merced

“We’ve been assessing the crop for about a week. In places along the hills on the east side, cold temperatures crept down from the mountains and hit almonds pretty hard. In some of those cases it appears to be 60% damage.


“It dropped to 20 to 21 in those areas early last week. That would be around Snelling and Oakdale. But most of our guys in the valley who ran water – either through micros or sprinklers – appear to have had minimal damage. However, we really won’t know the extent for another couple of weeks. We’ll have to wait for jackets to split and then see what does or doesn’t stay on the tree.


“I had my guys start applying fungicides 7 to 10 days ago and recommended they time applications around full bloom, so most of them were covered when it started raining this week. Petal fall had started, but all this rain and wind moved that along more than anything else.


“This has been an extended bloom, more so than anything I can remember. It’s been stretched out by the cold weather. I was seeing trees blooming on February 10 and were still blooming until the last couple of days (from 3/2). So, that’s essentially a 3-week bloom.


“On one hand, that gives bees more opportunity to pollinate. But with the cold weather, bees didn’t really have a full day to pollinate, maybe just a couple of hours when they could work.


“Right now, we’re looking for jacket rot because of all this moisture. The petals have dropped and next week it’s supposed to warm into the mid to high 60s, with another chance of rain toward the end of next week. Compared to temperatures with this last round of storms, this next system could be 15 degrees warmer.


“If any growers haven’t put protection in place, we’ll have them spraying for jacket rot. There hasn’t been high disease pressure, per se, but we’ve had enough moisture now to disperse it, and things could develop once temperatures do increase.


“I’ve been holding off on fertilizer applications and I’m glad now I did because this big rain would have leached quite a bit of it through the root zone. Trees aren’t leafing out as fast as they normally do. Usually, that’s a sign that we might have a decent crop up in the trees. So, we’re crossing our fingers and waiting to see what kind of hand we’ve been dealt.”


Dan Prentice, Prentice Ag Consulting, Bakersfield

“We had quite a bit of frost in the last 10 days or so and are seeing some damage. We don’t know the extent of it yet, and it varies from area to area, as you might expect.


“Damage is definitely more pronounced in the earlier varieties and seems a little more prevalent in the younger trees, although we really don’t know why that’s the case. At least so far, I haven’t found anything too bad, but we will have to wait and see how this goes.


“A little rain fell earlier in the week and then again last night. Totals haven’t been anything big, but more is expected Saturday (3/3) and maybe another round toward the end of next week. But the main concern has been the temperatures, especially the effect on pollination, since bees won’t fly as much when it’s cold like this.


“Fungicide applications have still been fairly limited. In cases where guys made nutrient sprays, we included a fungicide. Otherwise, fungicide applications have been kind of scattered. With temperatures this cool, brown rot isn’t a major concern, but some guys were getting a little nervous, so we treated. Other clients wanted to hold off.”


David A. Doll, Pomology Farm Advisor, Merced County

“Frost and freeze damage varies. On the west side, almonds look okay and I’m not hearing many complaints from that side of the county. Damage might range from zero to 10%.


“Somewhat more damage occurred in the north and north-central parts of the county. In areas along the Highway 99 corridor it may range from 10% to 20% in some orchards. The foothill areas were hit harder, with damage in places at 30% to 40%. But with any of this, it’s still too early to make definitive statements.


“Also, we still don’t know how much trees might compensate. Trees will maybe set 20% of the blooms, anyway. If you lose 20% of the total number of flowers, a tree might compensate by setting 24% of what’s remaining. Also, it might fill out nuts a bit more or set more of the nuts from the end of bloom than it normally does.


“All that said, the main issue is bee activity and pollination. How much have they been able to work? After the frost, we moved into a really cold spell, with very few bee hours. Now, we’ve had 3 days of rain and wind that further limited bee activity.


“This probably has been the worst bloom in the 10 years I’ve been here. The 2011 bloom was pretty bad but conditions were warmer. As far as fertilizer goes, let’s see how much crop we have after nuts drop before making decisions. If trees went into the year with ample nitrogen, we don’t need to apply fertilizer until late March anyway.


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“Be on the lookout for further frost. As nuts get older, they become even more sensitive to cold damage, and even a low of 32 could do harm. And if the forecast calls for 32, that doesn’t mean that colder temperatures can’t sneak into orchards.


“Anyone with crop insurance should contact the company. At one time, insurers or adjusters might call you when a big weather event unfolded. But it’s now the farmer’s responsibility to make the first contact if a claim might be necessary.


“Along with that, get a sense of how much damage you might have sustained in the worst places. Realistically, there’s no point in running water to protect a crop that’s no longer there.”


Nathan Stewart, PCA, AgVantage Consulting, Inc., Visalia

“Damage is really spotty. I’m hearing about some worst-case situations in other parts of the valley, although we have not seen anything that extreme in our area. That said, we do have damage – especially on younger trees.


“In places, damage is running as high as 25% to 30% on those trees. I do think that the tree, itself, will survive. These are third- and fourth-leaf trees.


“Overall, the actual damage probably isn’t as big an issue as the limitations on pollination due to all these swings in the weather.


“We went with a fungicide at full bloom just to be cautious. It’s been 10 to 14 days since my last fungicide. With this rain, we’re coming back and I’m starting to rotate chemistries. Some areas are into petal fall and I don’t want to give an opening to jacket rot and things like that. We’re also going with something that includes shot hole coverage now that leaves are expanding.


“These haven’t been big rains but they have been consistent and won’t completely shut down for several days, if the current forecast holds.”



California Almonds, Walnuts: Water And Nutrient Field Day, Corning, March 27   2-25


California Almonds, Walnuts: Nickels Spring Field Day – Focus On Nutrients, Water Management   2-24



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