Warmer Weather Is Here…now What? (10:30am, Tuesday, 4.9.13)

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central crops photo 1

Figure 1. Strawberries are in heavy bloom across North Carolina this week, and with temperatures moving into the 80s today and tomorrow, it will be vital for strawberry growers to keep their beds at an optimum mositure level.  If some of your plants are smaller and may have virus infection, it will be all the more important to make sure the plants are getting “good moisture” and checking soil mositure is going to be critical this week. This photo was taken this morning at Clayton, and shows Camarosa in full bloom. We are preparing for the possibility of having to do some evaporative cooling on Wed (see Fig

How warm will it get in my area?

It’s nice to be finally able to turn off the house heater this week, but I thought we might have a little break before moving into our air conditioning season (and, possibly evaporative cooling season for strawberry blossoms).

Here is the latest AWIS Maximum Temperature map for today (Tue):NC Table Tue April 9 – Max temps

tue max download 4.9

Fig. 2. Maximum temperatures across NC today – the light gray areas will be in the 82-84 range. The one really warm spot is nc_cnty1

Fig. 3. County map. You can see the warmer pinkish purple areas (84-86) are in northern Pender, southern Duplin and southeastern Sampson.

wed max temp 4.9 download

Fig. 4. Temperatures will be even warmer on Wed., and we are preparing to do some evaportative cooling at the Central Crops Research Station in Clayton tomorrow. Please note the pink area in Surry, Yadkin and northern Iredell could be in the 86 to 88 range (air temperature at weather shelter height of 6.5 ft). So, what is interesting to consider is what the bloom temperature might be when the air temperature hits 88 F. If you look at our Skybit below (Clayton) there will actually be a significant differential tomorrow between canopy temperature and air temperature outside canopy (weather shelter height).

clayton canopy temps

Fig. 5. In this SkyBit for Clayton you can see it might be 92 F in our canopy tomorrow at research station, so we are “trying” to get ready to do some evaporative cooling because we have a ton of open blossoms (see Fig. 1). We are now getting the sprinkler lines set up to do this.

If you look at tomorrow’s AccuWeather Pro for Clayton, they are saying it will be 85 F at 4 pm (and sunny). This is in very close agreement with Skybit (air temp of 84 outside canopy). Thus, there could be quite a large difference between the canopy temperature tomorrow (92) and 84 or 85 at weather shelter. If the bloom temperature gets above 92-93, that could be damaging.

clayton wed afternoon

The good news is that:

1) most of you have sprinkler irrigation still in the field

2) overhead irrigation for evaporative cooling of blossoms can protect fresh blossoms from heat stress when it is sunny, calm and temperatures are above 87/88°F. If temperatures were to reach upper 80s/lower 90s, then I would have some concern about bloom “heat stress,” and overhead sprinkling for about 20-25 min in the mid-afternoon can significantly lower canopy temperatures. If clouds come in, or there is a nice steady breeze, our experience has been that the evaporative cooling is probably not needed. The only reliable way to tell if your blossoms are approaching some daner possibly in some trouble is with a digital thermometer with thermocouple inserted in the blossom (see below). IMG_0101Figure 4, This is the Omega digital thermometer that we use at Clayton, and when it reads a blossom temperature of 90, or slightly higher, it may be justified to run an irrigation cycle of 20-25 minutes in mid-afternoon. It is extemely difficult to relate air temperatures to blossom temperatures, and that is why it is good to invest in one of these instruments.

How do you use one these instruments, and where can you purchase one? Well, we did a nice video on the use of digital thermometers for both strawberry blossom cold and heat protection a few years ago:


Also, if you were to purchase the instument shown in the photo, these are the specifications: (the prices are current as of 12/20/12)

Manufacturer: Omega Engineering Inc., 1-800-826-6342

Model and components required:

1. Handheld digital thermometer Model HH 21A (a quality unit that can handle Type T thermocouple wire), about $185.

2. Miniature connectors, SMPW-T-M, $1.95 each (Get 5 or 10 of these, depending on how many blossoms you wish to sample.)

3. Type T teflon-coated thermocouple wire (Allow about 10 feet for each blossom sampled. Ten blossoms require 100 feet of wire.)

~ TT-T-20-100 – $80 for 100 feet of 24-gauge wire. (the 20 gauge is too stiff)

When I contact Omega, I ask for a Technical Representative.

I have had good results in talking with

Dennis Frisby
Applications Engineering
Omega Engineering
1-800-872-9436 x 2344
fax 203-968-7331


Hi Barclay,
When looking at this morning’s advisory I noted your comment about the 20-gauge wire being too stiff, but the number you gave was for 20-gauge.
The correct no. for 100 ft. of 24-gauge is PR-T-24-100 (this is for the 24-gauge polyvinyl “rip cord” (PR) wire that we just ordered/received to replace the stiff 20-gauge wire that Gail Milteer got through the grant).
The cost for 100 ft. of this wire is just $27.00. 1000 ft. is $155.00.
CODE EXPLANATION: P is for polyvinyl coating; R is for ripcord, T is for type “T” thermocouple wire (copper & constantan), 24 for gauge, 100 for length.
Tom & Anne Baker and Amanda McCann
Brookdale Farm
2060 Vaughan Road


Please note: mention of the Omega Digital thermometer in this advisory does not imply a recommendation or endorsement of the NCCES.  There are several other manufacturers of digital thermometers you should contact. I recently located this one below, but have not had time to try it out. dwyer

Good Afternoon Dr. Poling.

Last year in one of your advisories you mentioned someone using infrared thermometers to check bloom temperatures (I think?). I’m wondering if you have any more information on that and if its a viable option or whether a digital thermometer is still the way to go. I’d be happy for your thoughts when you get a chance?

Lowell Yoder

REPLY – I had poor success with these. But, other people like them! They are much cheaper, but if you buy these in bulk (as VA growers have been able to do under a grant), then you can get some awesome values on top of the line digital thermometers.

Dr. E. Barclay Poling
Professor Emeritus/Extension Strawberry Specialist
Department of Horticultural Science
Campus Box 7609, 162A Kilgore Hall
NC State University
Raleigh, NC 27695-7609
919-418-9687 (Cell)
919-515-2505 (Fax)

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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 Apr 30, 2013
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