30 Day Ag Weather Outlook VA – TN- NC – SC (From Sunday Nov 30)

— Written By

Good afternoon,

In the course of a very busy week of meetings last week (including my final meeting with the NC Strawberry Association Board as the association’s interim Executive Director), I really dropped the ball last Sunday by not posting the 30 Day Ag Weather Outlook VA – TN- NC – SC posted on Nov. 30.

Here is last week’s outlook (it still has some relevance). A little  later today (Sunday Dec 7), I hope to have a new forecast up!

In the Nov 30 discussion it was mentioned that, “There has been a dramatic heat flux rise in the polar stratosphere. Such events often lead  to  a “Sudden Stratospheric Warming”  event which disrupts the polar vortex and result in cold out breaks.”

(More information on split in polar vortex)

Friday, November 28, 2014
Polar Vortex Split Occurring; Arctic Outbreak Possible in Mid-December
By Andrew at 12:41 p.m. (http://theweathercentre.blogspot.com/)

heat flux

“The stratospheric polar vortex has experienced a split as a result of its second interruption by warm air this season, and it appears some cold weather may be on the way as a result. The chart above shows heat flux values over the 2014 calendar year, from January 1st to present day. In this graph, shifting our attention to November and December, we find that flux values have skyrocketed to near-record levels (see red line – right of chart), only now beginning to drop down a bit. According to the Climate Prediction Center (CPC), strong episodes of eddy heat flux events to the poles may result in a Sudden Stratospheric Warming (SSW) event. You may recall that SSW events occur when wind direction in the stratosphere reverses from low pressure-favoring winds to high pressure-favoring winds. This decimates the polar vortex, and usually unleashes near-record intensity cold weather on whoever is in the line of fire about 2-4 weeks after the SSW event occurs. Considering we are seeing an eddy heat flux episode of this magnitude, it’s no surprise the polar vortex is undergoing some serious damage.”

Nov. 30 Outlook Comments (not posted until Dec 7; expect new posting later today)

Temperatures look to be mostly close to normal in the east US next couple of weeks. Probably will average out a slightly above norms for  NC-VA area and south as the cold stays to the north. But as mentioned there are some signs that next really cold outbreak here in the east US may occur mid Dec. There has been a dramatic heat flux rise in the polar stratosphere. Such events often lead  to  a “Sudden Stratospheric Warming”  event which disrupts the polar vortex and result in cold out breaks. Too early to say exactly what will happen at this point, but something to watch for over the next few weeks.
image 1Figure 1. Valid for Thur. Dec 4
Forecast discussion day 3 – 5 (3 Dec – 5 Dec) Temperatures near normal with periods of rain showers throughout the period Weak cold front moves through, followed by a high pressure that moves to the north of the region.  This will keep temperatures near the seasonal average with periods of scattered showers through the period.  High temps in the mid-50s and lows in the mid-30s.  Precipitation is expected to be in the 0.15 – 0.25” range {in hindsight, the forecast for this period was about right}.

image002Fig. 2. Valid for Dec. 7 (Sunday)

Forecast discussion day 6 – 8:  (6 Dec – 8 Dec) Temperatures above normal with rain during the period. A low pressure system is expected to move up the Mississippi Valley and into Canada during the period. This will bring above normal temperatures and rain into the region in the southerly flow ahead of the accompanying cold front.  Temperatures cool off with the passage of the cold front late in the period. High temps in high 50s to low 60s and lows in the 40s. Precipitation is expected to be in the 0.35- 0.55″ range

image003Fig. 3. Valid for 12/10

Forecast discussion day 9 – 11: (9 Dec – 11 Dec) Temperatures start near average but drop to below average by mid period. Temperatures drop behind the passage of a cold front, starting off near the seasonal average with highs in the low to mid 50s and lows in the low 30s.  The temperatures drop to below average by mid period with highs in the mid 40s and lows in the upper 20s.  Periods of light scattered rain and snow showers during in the period.   Precipitation expected to be in the 0.10 0.20″ range.

image004Fig. 4. Valid for 12/13

Forecast discussion day 12 – 14:  (12 Dec – 14 Dec) Temperatures start off below but slowly moderate to near then above normal with rain by the end of the period A strong high pressure system moves to the north of the region early in the period, which keeps things dry but on the cool side of average to start the period.  As the high moves east, a deep southerly flow is expected to develop, pushing temperatures above average with a period of rain by late in the period.  High temps start off in high to mid-40s and lows in the 20s, then rise to high temps in upper 50s and low 60s and lows in the 40s by the end of the period.  Precipitation is expected to be in the 0.30 – 0.55” range.

Last week was a very busy week!

IMG_1304Fig. 5. Before the official start to Thursday’s board meeting (NC Strawberry Assn.), Mr. Allan Baucom (standing up), gave board members a summary of discussions that had taken place an hour earlier in the morning with Dean Richard Linton, CALS-NCSU, about the Steering Committee’s recommendation to move forward with a mulit-state strawberry breeding program. At this same meeting, I concluded my 11 months as the NCSA’s interim Executive Director (pro bono). I look forward to continuing as chair of the Association’s Plant Health Committee in 2015. And, in that regard, I was very pleased to receive this information (below) from Dr. Schnabel (fyi – he is seated at the board table – 3rd person to the right of Allan). Guido wrote:  “Natalia (Peres) and I wrote up this Extension Publication based on our ‘smart resistance management’ presentation session in Pinehurst.

Disease and Resistance Management in Strawberry; Top Considerations for the Coming Season

Guido Schnabel (Clemson University) and Natalia Peres (University of Florida)

The new strawberry season is just around the corner and we need to make smart choices for pest and disease management. At the Strawberry Expo 2014 in Pinehurst we talked about some important things to consider this coming season to ensure maximum disease and resistance management. Here they are in a nutshell:

Implement IPM practices in nurseries. It is not a secret that diseases often come in with transplants and we must do a better job avoiding that. Luckily, we received some funding that will enable us to work with nurseries, investigate their practices, and develop solutions to current problems. This will not happen overnight but will rather be work in progress over the next years.

Avoid Key Selectors. Some fungicides are key selectors for resistance to multiple fungicides in the gray mold fungus on the east coast. Resistance to multiple fungicides has built up in a stepwise fashion over time and resistance to some fungicides is the backbone of resistance to newer chemistries. Basically, if new resistance emerges, it is most often from a population that is already resistant to established fungicides. In particular, applications of fungicides from FRAC (Fungicide Resistance Action Committee) group 1 (e.g. Topsin M) and to some degree FRAC 11 (Abound, Cabrio, Pristine, Merivon) are frequently associated with resistance to other FRAC groups that we need for disease control. Our recommendation:

  • Avoid FRAC 1 fungicides
  • Use FRAC 7/11 premixtures (Merivon, Pristine) ONLY if gray mold AND anthracnose are a threat BUT NOT for routine gray mold control.
  • Use FRAC 11 solo products (Abound, Cabrio) only for anthracnose control
  • Do not use FRAC 7/11 premixtures or FRAC 11 solo products more than twice per season.

Spray Strategically. If applications are needed prior to bloom, thiram, captan, and maybe biologicals should be used. During bloom, stick with captan as much as possible and use the ‘at risk fungicides’ (including FRAC 1, 2, 7, 9, 11, 12, and 17) only when the weather is favorable for disease development (Table 1).

table 1 Table 1. FRAC code, trade name, and primary target of fungicides frequently used for disease control in strawberry

Botrytis control success is vastly improved if you know the resistance profile of your fields. Make sure you get the gray mold fungus tested. Download instructions at http://www.clemson.edu/extension/horticulture/fruit_vegetable/peach/diseases/br_strawberry.html.

Spray less. Spraying less is the ultimate resistance management tool because we are selecting less. But that is only an option if we do not compromise disease control success. Research has shown that we are spraying way too many times and that often more than 50% of our applications are unnecessary. We are implementing an online tool, the Strawberry Advisory System (SAS), in southern states that notifies growers when an application is truly necessary. Growers will need to be near a weather station that is hooked up through the internet to a weather database. Contact us for more information if you are interested. But if you do not have access to this system, table 2 shows the weather conditions that you may use to decide whether to spray or not. You might be surprised how many sprays you can save without compromising control especially in a reasonably dry year.

Table 2. Decision Support Chart for Gray Mold Management in Strawberry

table 2

In conclusion, after more than a decade of applying multiple fungicides of multiple FRAC codes, resistance is now common in the gray mold pathogen Botrytis cinerea. But the resistance profile is different from location to location and depends on spray history, nursery source, and nearby crops hosting the pathogen. Knowing your resistance profile will enable you to prevent ineffective sprays and improve preharvest and postharvest disease control. We must make every effort to spray strategically and to limit the number of sprays and we must include nurseries in our efforts to control pests and diseases. Good luck!

Here is the whole publication in pdf:  SchnabelPeresDiseaseAndResistanceManagement

Dr. E. Barclay Poling
Professor Emeritus (Strawberry Plasticulture Researcher)
Department of Horticultural Science
Campus Box 7609, 162A Kilgore Hall
NC State University
Raleigh, NC 27695-7609