Multi-State Strawberry Weather Update on Sunday Afternoon (4:25pm, 3/19/17)
I was just noticing this afternoon how the Monday minimum temperature map for NC has changed since yesterday. Compare Fig. 1 (current forecast for Monday) to yesterday’s (Fig. 2)
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. Still, the minimum temperatures for Monday are “not that bad,” compared to what we went through last week! Some growers will likely just sit this one out due to losses of blossoms and popcorns to last week’s freezes. For growers who managed to hang on to their blooms and “green fruit,” I would surely approach this frost tomorrow morning with a great deal of caution, and don’t be too surprised if the minimums are lower than what is in the forecast today. One good thing I see is that we are not dealing with incredibly low dew points, like last Thur/Fri.
Widespread “white frost” is expected in many areas tomorrow, and in just glancing at a sample of AWIS Detailed Hourly Forecasts for Greensboro, NC, it looks like a minimum air temp of 33 expected, and that dew points are in the mid-20s. For this area, AWIS is making a forecast for FROST at about 5 a.m. Growers in this area can watch closely for formation of ice crystals on solid objects like a lay flat hose, or edge of a row cover, as their visual cue as to when to start sprinkling.
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.
MD Md Outlook
Virginia Va Temp Outlook
South Carolina SC Temp Outlook
Georgia Ga Temp Outlook
Kentucky KY Temp Outlook
Questions from the field this weekend
1. Granville/Person County
I am the new horticulture agent for Granville and Person counties, and I had a call from a strawberry grower this morning, about whether or not to put his row cover on strawberry plants that lost their blooms this week due to the cold temperatures. Is there any benefit to having the covers on to encourage new blooms or is he better off leaving them off for sunlight purposes? I know if he still has blooms uncovered would be better for pollination purposes, but I did not know if he would benefit from increased temps by leaving them on.
The main concern with plants that lost blossoms last week is to try to get these plants cleaned up! A number of growers who lost a lot of blossoms last week are going ahead and “cleaning up” these plants now (removing the dead blossoms), and then probably applying captan. As far as leaving covers on to stimulate new blooms, I am not optimistic this will work. I actually ran a small study of this idea of using row covers in early March to try to add some new blooms at the Piedmont Research Station in Salisbury, and we did not see a benefit compared to the non-covered plots (variety was Camarosa). In the end, these are short day plants, and though there may be an opportunity to add blooms with row cover applications when the days are getting shorter in November (and, this is being done); I believe our days are getting too long in the month of March.