University of KY Cooperative Extension Announces “Spring Study Tour” for March 29th (10:23am, 3/20/17)

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Good morning!

I am presently still working this Monday morning on our weekly Outlook…

30 Day Ag Weather Outlook MD – VA – TN- NC – SC

but, in the meantime, I have received a grower report from Chesapeake/VA Beach region from this morning, as well as an invitation from the University of KY Cooperative Extension to join them for a “Spring Study Tour” on March 29th. 2017 SpringStudyTourFlyer (1)

Grower feedback from Chesapeake/VA Beach (8:06 am)

<Reference: In yesterday’s late afternoon advisory I had written: We’ve had a situation in the last several days of getting forecasts on the “high side” of what actually has been happening, and so I am a little more worried about tomorrow morning this Sunday afternoon than I was just a day ago.>


Yesterday you cited the problem with “getting forecasts on the ‘high side’” recently.

That was certainly the case last night. Our worst (Chesapeake) AWIS forecast called for 5 & 6 a.m. frost. Fentress and Oceana said no frost (Oceana due to healthy wind all night).

What did we have? FROST, both farms, BEFORE 10 p.m. and the wind was on vacation (in Montana, I believe). ZERO (as in none at all) wind!!!

AccuWeather was just as bad as AWIS last night, especially their “miss” on wind.

Best thing a grower can do, in my opinion, is this: If you are depending on the wind to keep you safe…DON’T!!! If, after the fact, you had some wind that “helped” you, don’t count it a minor miracle. It was a HUGE miracle!

BUT, if you’re depending on a LACK of wind to help (like for overhead sprinkling last Tuesday night), plan on a gale, because that’s probably what you’ll have.

Tom Baker

Last minute advice on “wet row covers.”

Late yesterday afternoon, after I had posted an advisory at around 4 pm, my wife and I had left the house to meet up with some friends, and then I received this text from Roy Flanagan, VA Cooperative Extension:

5:43 pm que. from VA Beach/Chesapeake – where we are now is wet covers not on crop, if growers pull now and wind falls off aren’t the wet covers worse than the risk of a slight frost tonight or should they pull covers on no matter what? Never thought about the wet covers argument much and kinda thought having them on is like keeping plants at wet bulb temp. These are cover only growers with no overhead option

My Reply (5:55) – <we are interested in hearing from any growers in this region about how things turned out? We know from Tom Baker (above), they had FROST in Chesapeake and Pungo starting at 10 pm…AWIS had made a an incorrect forecast of 5 am for Chesapeake>

Good question!  The micro-climate under a moist row cover is something to be concerned about tonight. This is a very touchy situation, and I have seen situations in NC of a frost under a row cover that was dry when the dew point temperatures are very high (like 33 F).   I examined your area’s situation, and with dew points in the morning of around 33 F, I am concerned about possibility of frost under a moist cover.  So, if the grower doesn’t have capability to run water on the covers in case frost does start forming underneath the row cover, I would advise not applying wet covers. Another factor to take into consideration are light winds of 3 to 5 mph from 4 am to 6 am in Chesapeake, and these may be enough to keep “ice crystals” from forming on plants that are uncovered…air movement is a good thing in a situation like this – like a wind machine in peaches. In contrast, the moist cover will prevent any air movement beneath the cover, and with totally calm conditions under the blanket and this very moist air, I am concerned about frost underneath the covers. If a grower has already pulled a moist cover over the crop this afternoon, and they do not have sprinkling, I recommend running drip irrigation in the morning starting at 4:30 am and running until sunrise – this should add just enough warmth to keep the air temperature around the plants above freezing ( 32 F).  Our worry is that the air under the cover might go below the freezing point, and if it does, ice crystals could easily form in this humid environment. It would be good to monitor blossom temps under the covers with digital thermometer, and if temperatures are slipping below 32, run the drip! You can also run the drip without any row cover, and get a slight benefit as well.

<In yesterday’s advisory, I had written: We did have some scattered showers and even brief snow in some areas this morning, and if your row covers are not drying out that well by this early evening, it would be wise to monitor bloom temperatures underneath the covers tonight with digital thermometer, and if you see those temperatures slipping below 32, you may want to be ready to run some sprinkling on top of the covers before those blossom temperatures drop below 30 F. And, just to be safe, take a look underneath those row covers in the early morning to make sure there is no frost occurring beneath the cover – this actually happened in some Eastern NC locations this past Sun/Mon. When this sort of thing occurs (frost under covers), it does “shake you up,” and cause a loss of confidence in row cover protection. But, the whole premise for row covers to work properly in a frost situation is that the covers are going into the evening DRY. And, whenever there is a precipitation event prior to a cold event (like tonight), we don’t want to assume that a moist and/or frozen row cover will confer the same level of protection to open blossoms as a DRY cover. Thus, the important need to closely monitor blossom temperatures if covers have been “compromised” by some form of precipitation event prior to the cold event, and to stick a flash light under the cover a few hours before sunrise to make sure you don’t see anything strange happening, like a frost under the cover. If you do see something like this happening (frost forming underneath cover), go ahead and run the drip system to add some heat back into the system, or run sprinklers on top of the cover.>

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Photo of Dr. Barclay PolingDr. Barclay PolingFormer Professor and Extension Specialist, Strawberries and Muscadines (919) 515-5373 (Office) barclay_poling@ncsu.eduHorticultural Science - NC State University
Updated on Mar 20, 2017
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