Author Archives: Hillary Mehl

The Peanut-Cotton Infonet has moved

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InfoNetMap

The Virginia Tech Tidewater AREC (TAREC) maintains the Peanut-Cotton Infonet which provides growers in the region with daily weather data (e.g. temperature, rainfall), peanut leaf spot and Sclerotinia advisories, peanut heat units, cotton degree days, and a frost advisory. Four weather stations located in Suffolk, Capron, Skippers, and Waverly are maintained by the TAREC Plant Pathology program. These weather stations transmit data to a computer at the Tidewater AREC, and the data is used to run fungicide advisory models. Data are available on the Virginia Peanut-Cotton Infonet website (http://webipm.ento.vt.edu/cgi-bin/infonet1.cgi).

The data and information available here include:

Maximum, minimum, and average air temperatures
Average soil temperature at a 4 inch depth
Daily and accumulated (from May 1) peanut heat units
Daily and accumulated (from May 1) cotton degree-days
Daily and total seasonal (from May 1) rainfall
Last effective spray date for peanut leaf spot
Sclerotinia blight risk
Frost advisory (from September 25th to completion of harvest)

Virginia Peanut-Cotton Infonet Update

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The Virginia Tech Tidewater AREC (TAREC) maintains the Peanut-Cotton Infonet website (webipm.ento.vt.edu/infonet/) which provides growers in southeast Virginia with daily weather data (e.g. air and soil temperatures, rainfall, relative humidity), peanut leaf spot and Sclerotinia advisories, peanut heat units, cotton degree days, and a frost advisory. Four weather stations located in Suffolk, Capron, Skippers, and Waverly are maintained by the TAREC Plant Pathology program. Thanks to funding from the Virginia Peanut and Cotton Boards, we have been able to upgrade our equipment which should improve the overall reliability and consistency of data transfer from our weather stations. The new equipment has been installed and we are receiving data, but we are temporarily unable to post the data to the Infonet website. This technical issue should be resolved by next week, but in the meantime daily weather data will be sent out as an email to extension agents and posted to the Virginia Ag Pest Advisory Blog. We apologize for the inconvenience, and we are working hard to get the Peanut-Cotton Infonet website up and running for the season. If you have any questions or concerns feel free to call the TAREC Plant Pathology lab at (757) 657-6450 ext. 428 or email Dr. Hillary Mehl (hlmehl@vt.edu).

Please find below the current weather data for Suffolk, Capron, and Skippers. The Waverly data will be available shortly.

SE VA Weather Data 5-1-15

 

Be prepared for scab in small grains

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Wheat in the southeastern portions of Virginia will start flowering soon if it has not already. Wheat is susceptible to scab (Fusarium head blight) from early flowering until approximately 10 days after first flower. An online scab risk assessment tool (www.wheatscab.psu.edu) provides information on relative risk of wheat infection by the scab fungus which also has the potential to contaminate grain with DON (vomitoxin). The risk model is based primarily on relative humidity during the 15 days prior to flowering since high moisture favors inoculum production by the scab fungus on crop residues. However, the model also takes into consideration variety resistance to scab. No wheat varieties have complete resistance (immunity) to scab, but commercially available varieties vary in their susceptibility. Current variety rankings for scab resistance can be found here:

Wheat variety rankings for scab resistance

If you do not know the relative susceptibility/resistance of your variety, it is probably best to err on the side of caution and assume that your wheat crop is susceptible or at least moderately susceptible to scab. Currently, the predicted scab risk for wheat that is flowering in Virginia is low for all but the most susceptible varieties. Dry weather is predicted after the current storm passes through, so scab risk will likely remain low to moderate over the next week. However, it is prudent to be prepared to apply a fungicide for scab management as the wheat crop approaches the flowering growth stage. Keep in mind the best management tactic for minimizing yield and quality losses to scab and DON is to plant resistant varieties and to make a properly timed fungicide application when wheat is in the susceptible growth stage (flowering) and weather conditions favor dispersal of the scab fungus.

If a fungicide is applied for scab, strobilurins should NOT be used as they may increase DON (vomitoxin) contamination of the grain if applied after flag leaf. Foliar diseases are starting to increase in some fields in Virginia, but if the wheat is at or near flowering, a strobilurin or premix fungicide containing a strobilurin is not recommended. Fungicides recommended for scab also provide very good to excellent control of common foliar diseases of wheat (see last week’s post), so a scab fungicide application may provide the added benefit of controlling leaf spots and rusts. The triazole fungicides Prosaro, Proline, and Caramba are the most effective fungicides for scab and should be applied at early to mid-flowering and up to one week later. For maximum efficacy, fungicides for scab and DON control should be applied with nozzles angled at a 30 degree angle from the horizontal using both front and back facing nozzles. This will ensure that the product is applied to the grain head rather than the leaves or the ground.

Growers, agents, and consultants can subscribe to the U.S. Wheat & Barley Scab Initiative’s (USWBSI) FHB Alert system at http://www.scabusa.org/fhb_alerts. Region-specific scab alerts that provide growers with updates during critical times are sent as emails and/or text messages.

Wheat disease update

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As the wheat crop approaches flag leaf emergence and heading growth stages, it is time to start thinking about disease management. When conditions are conducive to disease development (e.g. high humidity, warm temperatures) foliar fungicide applications may be necessary to protect wheat yield and quality.

Wheat diseases observed in Virginia so far in 2015 have included viruses (which cannot be managed with fungicides), powdery mildew, and leaf blotch. Disease severity thus far has been relatively low in most areas but an increase in disease can be expected with warm, humid weather. Leaf blotch, for example, has been observed on the lower leaves where it is unlikely to impact yield, but once the flag leaf emerges, this leaf surface, which feeds the developing grain, should be protected from disease if symptoms are observed on the lower leaves and conditions are conducive to disease development. Once heading and flowering occur, the developing grain need to be protected from infection by the Fusarium head blight (scab) fungus if scab risk is high. Factors contributing to scab development and proper timing of fungicides for scab management will be discussed in a later post.

Slide1

Each year plant pathologists from throughout the U.S. update the following wheat fungicide efficacy table based on the most current data. Efficacy ratings for each fungicide listed in the table were determined by field testing the materials over multiple years and locations. Efficacy is based on proper application timing to achieve optimum effectiveness of the fungicide as determined by labeled instructions and overall level of disease in the field at the time of application. Judicious use of an appropriate fungicide for the target disease can protect both yield and quality of the wheat crop.

NCERA-184-Wheat-fungicide-table-2015

Peanut Disease Update – August 14, 2014

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Sclerotinia blight risk has been, and continues to be, high this summer and timely fungicide applications based on advisories (Peanut-Cotton Infonet, http://webipm.ento.vt.edu/cgi-bin/infonet1.cgi) and scouting are needed to avoid devastating outbreaks of this disease. Unfortunately, it has been reported that Omega, the most effective fungicide for Sclerotinia blight control, is in short supply, and growers are looking for alternatives. At this point we are recommending Fontelis at a rate of 1.5 pints per acre. According to Barbara Shew, Extension Plant Pathologist at North Carolina State University, 1.5 pints per acre of Fontelis provide Sclerotinia control similar to one pint of Omega. Note that lower rates of Fontelis typically used for leaf spot control are not adequate for control of Sclerotinia. A follow-up Fontelis application should be made 2 to 3 weeks after the first application or according to the Sclerotinia blight advisory, but keep in mind that only two applications of this fungicide class (SDHI, group 7) should be made per year to minimize the risk of fungicide resistance. In fields with high Sclerotinia pressure, avoid using chlorothalonil (Bravo and generics) in August or early September for leaf spot control since this can increase the severity of Sclerotinia blight outbreaks. Alternatively, use strobilurin fungicides such as Abound or Headline or a triazole such as Provost for leaf spot control. However, the final leaf spot application of the season should be chlorothalonil for the purpose of fungicide resistance management. Sclerotinia blight peanut

Southern Rust in Corn – Update

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Southern rust on cornSouthern rust continues to be reported on corn in Virginia. Southern rust was first confirmed August 3 on corn samples from Chesapeake and Suffolk. Since then, reports of southern rust have been made from Sussex and Albermarle counties, and it is likely that the pathogen is throughout much of the state. Yield of corn at or near the dent stage is unlikely to be impacted by the disease, but late planted corn in fields with good yield potential (120 bu/ac +) may need to be protected with a foliar fungicide. Strobilurins are good preventative fungicides whereas triazoles are recommended once sporulation is observed in a field due to their curative activity. A combination fungicide is a good option as long as a strobilurin fungicide has not been applied previously. Wet, warm weather favors disease development. Once sporulation occurs, symptoms of rust are relatively obvious. Lesions start out as raised, blister-like pustules then break open to reveal orange spores. Samples of corn plants with symptoms of southern rust can be submitted to the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu).

Southern Rust on Corn – Update August 5, 2014

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Southern rust on corn

Southern rust was confirmed August 3 on corn samples from Chesapeake and Suffolk. Yield of corn at or near the dent stage is unlikely to be impacted by the disease, but less mature corn in the region may need to be protected with a fungicide application. Strobilurins are good preventative fungicides whereas triazoles are recommended once sporulation is observed in a field due to their curative activity. A combination fungicide is a good option as long as a strobilurin fungicide has not been applied previously. Wet, warm weather favors disease development. Once sporulation occurs, symptoms of rust are relatively obvious. Lesions start out as raised, blister-like pustules then break open to reveal orange spores. Samples of corn plants with symptoms of southern rust can be submitted to the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu).

Southern Rust on Corn in North Carolina – Update

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Southern rust was confirmed on a sample from Camden County, NC on July 21. At this time, southern rust has NOT been reported in Virginia. Yield of corn at or near the dent stage is unlikely to be impacted by the disease, but less mature corn may need to be protected with a fungicide application. Contact your local extension office for recommendations if you suspect southern rust is in your area. Samples of corn plants with symptoms of southern rust should be submitted to your local extension office or the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu). Typically the disease has little impact on Virginia corn since it arrives too late in the season to affect yield, but if southern rust is confirmed in Virginia prior to corn reaching the dent stage (R5), fungicide applications may be warranted. Updates will be provided as more information is obtained.

Southern Rust on Corn in North Carolina

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Southern rust, a potentially devastating disease of corn, has been reported from several counties in North Carolina. At this time, southern rust has NOT been reported in Virginia. Samples of corn plants suspected to be infected with southern rust should be submitted to your local extension office or the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu). Signs of the disease are pustules filled with powdery masses of orange spores (see attached photo). Typically the disease has little impact on Virginia corn since it arrives too late in the season to affect yield, but if southern rust is confirmed in Virginia prior to corn reaching the dent stage (R5), fungicide applications may be warranted. Updates will be provided as more information is obtained. Additional information: southern-rust-on-corn-jpg