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Flooded Soybeans – How Much Damage? What to do?

Rainfall across the state resulted in in saturated soils and sometimes flooded soybeans or fields to be planted in soybean.  Although fields are drying out, more rain is expected this weekend.

It’s difficult to know the long-term effect of flooding on soybean fields. Research is limited, but we do know that the fate of flooded fields will largely depend on 1) the development stage during which the flood took place; 2) the duration of the flood; 3) the temperature during and right after the flood; and 4) the drying rate after the flood.

Basically a flooded field depletes the roots of oxygen (O2), causing photosynthesis to slow.  After several days without O2, the plant may turn yellow, grown very slowly, and possibly die.  Other indirect effects of flooding can include reduced nitrogen-fixing bacteria (but they will recover), nutrient imbalances, and increased disease pressure.

For more detailed information, see a blog post that I wrote  in 2013 at the Virginia Soybean Update site.

In short, here are a few pointers for flooded fields.  If soybean have not yet been planted:

  1.   I don’t recommend tillage to dry the soil out for continuous no-till fields.  Tillage will destroy the soil structure that you’ve built since tillage was stopped.  The field is probably draining better than it ever was; tillage will just cause water to stand longer in the future.
  2. Bradyrhizobia japonicum, the nitrogen-fixing bacteria that helps provide soybean with that nutrient, is harmed by lack of oxygen caused by the flood.  Although the bacteria will recover, it may be prudent to add inoculant to the seed in areas that were flooded.

For flooded fields that have been planted:

    1.  Minimize any addition stress by staying out of the field.  Do not try to plant or replant too soon.  More damage can be done to the soil and more yield can be lost from planting into we soils than from planting too late.
    2. If soybean have not yet emerged and crusting evident, light tillage with a rotary hoe will help emergence.
    3. Evaluate the stand. If a stand reduction occurred, determine if it’s worthwhile to replant. Remember that after mid-June, every day delay in planting will cost you about ½ of a bushel in yield. The plants that remain are still higher yielding than seed that can now be planted, even if the stand has been substantially reduced.
    4. Stress such as herbicide injury can slow the crop down further. Still, weeds need controlling. But you may want to select herbicides (usually as tank-mix partners to glyphosate) that don’t cause a significant amount of burning.
    5. Finally, some will want to apply some type of foliar fertilizer to the crop to “kick-start” it back to health.  I see little advantage of this.  Remember that the real problem is lack of O2 to the roots and CO2 buildup in the soil; only after the roots begin to receive O2 will the recovery process start.Hopefully you haven’t experienced severe flooding (> 24 hours).  But if so, be patient and evaluate the field.  Then make good decisions on how to handle it.

 

 

New Crop Disease Management Resources

Though it has been around for several years, the Crop Protection Network (CPN) has recently added several publications on disease management in corn, soybean, and small grains that are relevant to growers, crop consultants, and extension personnel in Virginia and the surrounding region. These can be accessed at the CPN website cropprotectionnetwork.org. As stated on the website:

“The Crop Protection Network (CPN) is a multi-state and international partnership of university and provincial Extension specialists, and public and private professionals that provides unbiased, research-based information. Our goal is to communicate relevant information to farmers and agricultural personnel to help with decisions related to protecting field crops.

Extension specialists throughout the country (including myself) contribute to the publications and other resources posted on the website. An example of a recent publication on optimizing fungicide use for control of Fusarium head blight can be downloaded below. The CPN library includes over 30 publications on crop management, and additional publications are in development.

CPN-3001-Optimizing Fungicide Use for FHB

Wheat Disease Update – May 24, 2018

Fusarium head blight (FHB) risk for Virginia continues to be to high throughout the state due to recent wet, warm weather (http://www.wheatscab.psu.edu/). Most of the wheat is past the flowering stage and no longer at risk, but later flowering wheat may still need a fungicide application. Triazole fungicides including Prosaro, Caramba, and Proline are recommended. Do not apply fungicides containing a strobilurin since this can increase DON. For wheat that is past flowering, a fungicide application will not reduce FHB or DON contamination of the grain. Grain harvested from fields with signs and symptoms of FHB should be kept separate from non-infested grain.

For assistance with disease identification or management recommendations, contact Dr. Hillary L. Mehl, Extension Plant Pathologist (hlmehl@vt.edu).

2018 Weed Management Field Day

Mark your calendar and plan to attend!

June 19th, 2018

8:30 to 11:30am

Highlights:

• View over 100 herbicide plots
• The latest corn and soybean herbicides
• Nozzle selection
• Herbicide resistant Palmer amaranth and common ragweed control options
• Integrated weed management tactics
• Free coffee and doughnuts!

Location:

Southern Piedmont AREC
Field entrance near:
1200 Darvills Road
Blackstone, VA 23824

Google Maps link to field entrance: https://goo.gl/maps/iKZmYnjx7wM2 

Please register by email: flessner@vt.edu

More information in the flyer: 2018 Weed Management Field Day Flyer

Wheat Disease Update – May 15, 2018

Three-day forecast for Fusarium head blight (FHB) risk on susceptible wheat varieties.

FHB risk is increasing in Virginia and will continue to increase over the next several days. Risk is highest on the Eastern Shore, but susceptible varieties such as Shirley that are flowering over the next week will be at moderate to high risk in many portions of the state. Growers should monitor the FHB risk tool (www.wheatscab.psu.edu) as their wheat crop begins to flower. Consider applying a fungicide if risk is moderate to high, especially on susceptible or moderately susceptible varieties. Wheat that has completed flowering is no longer at risk. Fungicides should be applied at early flowering or up to one week later. Do not apply a strobilurin-containing fungicide since this can increase DON contamination. Recommended fungicides include Prosaro, Caramba, and Proline.

Steve Rideout, Extension Plant Pathologist at the Eastern Shore AREC, confirmed stripe rust on research plots of Shirley on Monday. FHB risk continues to be high on the Eastern Shore, so growers in this part of the state with varieties that are susceptible to stripe rust should consider an application of Prosaro, Caramba, or Proline since these will control both FHB and rust.

Stripe rust on wheat.

For assistance with disease identification or management recommendations, contact Dr. Hillary L. Mehl, Extension Plant Pathologist (hlmehl@vt.edu).

 

Wheat Disease Update – April 30, 2018

As wheat starts flowering in the region, it is time to consider whether or not to make a fungicide application for Fusarium head blight (FHB). Currently, risk is low in most parts of Virginia. There are a few exceptions, including portions of the Eastern Shore, where risk is moderate to high.

The most effective fungicides for control of FHB and DON are Caramba (metconazole), Prosaro (prothioconazole + tebuconazole), and Proline (prothioconazole). Less expensive triazoles such as Tilt (propiconazole) and Folicur (tebuconazole) will provide some control, but if FHB risk is high these fungicides are unlikely to prevent unacceptable levels of DON contamination. Keep in mind that fungicides containing a strobilurin should not be applied after the flag leaf stage since they can increase DON contamination.

Current FHB risk in Virginia and the surrounding region. Green, yellow, and red indicate low, moderate, and high risk, respectively. FHB risk can be monitored using the Fusarium Risk Assessment Tool (http://www.wheatscab.psu.edu/).

To maximize their effectiveness, fungicides for FHB and DON control should be applied at early flowering or up to one week later. Fungicides that control FHB and DON will also control foliar diseases including powdery mildew, leaf rust, stripe rust, and leaf blotch. Stripe rust has been found in NC and was recently reported from a single field in Warsaw, VA so be sure to scout susceptible varieties for this disease. For specific wheat disease management recommendations or assistance with disease identification, contact Dr. Hillary L. Mehl (hlmehl@vt.edu).

 

Peanut-Cotton Infonet Update

The Peanut-Cotton Infonet is up and running for the 2018 growing season. As in previous years, the website will provide:

  • 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)

The web address has changed slightly and the website can be found here.

Soil temperatures in southeastern Virginia have been cool over the past couple of weeks (average less than 60 °F), and cool, wet conditions in some fields will favor seedling diseases in early planted crops. A warming trend over the next week will hopefully result in more favorable planting conditions towards the beginning of May.

For questions or concerns regarding the Peanut-Cotton Infonet throughout the growing season, contact Dr. Hillary Mehl (hlmehl@vt.edu).

Wheat Disease Update – April 19, 2018

Currently the wheat crop in Virginia is near flag leaf emergence, and flowering will start within a couple of weeks. As flowering begins, be sure to monitor the FHB risk in your area using the Fusarium Head Blight Prediction Center website. Currently, most of Virginia has low risk for FHB infection. The exception is the Eastern Shore where risk is moderate to high in many areas, especially on susceptible varieties such as Shirley. Powdery mildew outbreaks have been observed in some fields this season, and incidence of common rust has been sporadic. Stripe rust has been found in North Carolina, but it has not been reported from Virginia. The 2018 Wheat Fungicide Efficacy Table can be downloaded below. Once wheat approaches the heading stage, keep in mind that strobilurin fungicides should no longer be applied. For specific wheat disease management recommendations or assistance with disease identification, contact Dr. Hillary L. Mehl (hlmehl@vt.edu).

2018 NCERA 184 Wheat Fungicide Table

Wheat Disease Update – April 12, 2018

Currently the wheat crop is in the jointing stages, and we are several weeks away from flowering. Currently the Fusarium head blight (FHB) risk is low for most areas of the state except for the Eastern Shore. These conditions may change as the wheat crop approaches flowering, so be sure to continue monitoring the FHB risk tool (http://www.wheatscab.psu.edu/). Moderate to severe outbreaks of powdery mildew have been reported from several fields in the past week. Be sure to scout wheat fields at this time and apply fungicide when disease is first detected. The updated Wheat Fungicide Efficacy Table can be downloaded below. For specific wheat disease management recommendations or assistance with disease identification, contact Dr. Hillary L. Mehl (hlmehl@vt.edu).

 

NCERA 184 Wheat fungicide table 2017_Final

Invitation to NRCS/VCE Cover Crop Training–April 12, 2018

You are invited to attend the 2018 Natural Resources Conservation Service/Virginia Cooperative Extension Cover Crop Training on Thursday, April 12, 2018 (9:00 am to 3:30 pm) at the Virginia Tech Tidewater Agricultural Research and Extension Center (6321 Holland Rd., Suffolk, VA). The event is free and open to the public. Lunch will be provided–please RSVP to Gail White (guwhite@vt.edu) by April 5 so that she can get a head count for lunch. Here is the agenda: Final Agenda_April 12 2018

If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact the Tidewater Agricultural Research and Extension Center at 757-657-6450 during business hours of 8 a.m. and 4:30 p.m. to discuss accommodations 5 days prior to the event.  *TDD number is (800) 828-1120.