Tag: head scab

Managing Fusarium Head Blight

Dr. Alyssa Koehler, Extension Field Crops Pathologist
University of Delaware

With the mild winter, wheat and barley are moving right along. Planting behind corn is common in our region, but this maintains inoculum for Fusarium Head Blight (FHB). Fusarium species that cause FHB can infect both corn and small grains. Walking through fields with corn stubble, you may see orange growth on old debris (Figure 1). Wet spring conditions favor fungal sporulation that can lead to infected wheat heads. As the pathogen grows on debris, spores are released that can be rain dispersed or moved through air currents. As the grain is flowering, spores land on the head or anthers, colonize these tissues, and move into the grain head. Once inside the grain, water and nutrient movement is disrupted, which results in the bleached florets we associate with FHB (Figure 2). Shriveled and wilted “tombstone” kernels can reduce yield and result in grain contaminated with mycotoxins. Deoxynivalenol (DON), also referred to as vomitoxin, is a health hazard to humans and animals. Wheat heads colonized later in development may not show dramatic symptoms, but can still have elevated DON.

Figure 1 (left). Corn stubble with Fusarium sporulation that can contribute to FHB in wheat. Figure 2 (right). Wheat head showing bleached florets from Fusarium Head Blight.

As we approach heading and begin to think about in-season disease management strategies, a well-timed fungicide application can help to reduce disease severity and DON levels. It is important to remember that fungicides can help to reduce disease levels and DON (traditionally around 50% reduction on a susceptible variety), but they do not eliminate FHB or DON. To try to maximize the efficacy of fungicides, it is important to apply at the correct timing. Fungicides for FHB are most effective when applied during flowering in wheat and at head emergence in barley. The Fusarium Risk Assessment Tool (www.wheatscab.psu.edu) is a forecasting model that uses current and predicted weather forecasts to predict FHB risk. The model is currently being configured for this season and should be accessible at the link above by the end of the first week of April. Historically about 70% accurate, this tool aids in assessing FHB risk as wheat approaches flowering and fungicide application decisions are made. The pathogen that causes FHB infects through the flower and rainfall 7 to 10 days prior to flower favors spore production and increases risk of infection. Optimal wheat fungicide application is at early flowering (10.5.1) to about 5 days after. Although new products like Miravis Ace can be applied earlier, it is still best to wait for main tillers to be at 10.5.1 or a few days beyond so that secondary tillers have a greater chance of being at 10.3-10.5.1. If you spray too early, heads that have not emerged will not be protected by the fungicide application. When wheat heads begin to flower, look for yellow anthers in the middle of the wheat head. When at least 50% of main stems are flowering, you will want to initiate fungicide applications. As the flowering period continues, anthers will emerge from the top and then the bottom of the wheat heads. Anthers can stay attached after flowering but usually become a pale white (Figure 3, next page). Triazole (FRAC group 3) fungicides that are effective on FHB include Caramba (metconazole), Proline (prothioconazole), and Prosaro (prothioconazole + tebuconazole). Miravis Ace (propiconazole + pydiflumetofen) offers a triazole + SDHI, FRAC group 7. As a reminder, fungicides containing strobilurins (QoI’s, FRAC 11) should not be used past heading because these fungicides can result in elevated levels of DON. Flat fan nozzles pointed 90° down are great at covering foliage but they do not provide good coverage on heads, which is the target for FHB management. Nozzles that are angled forward 30-45° down from horizontal (30 degrees is better than 45) or dual nozzles angled both forward and backward give better contact with the head and increase fungicide efficacy. For ground sprays, fungicides should be applied in at least 10 gallons of water per acre.

Figure 3. From left to right: Feekes 10.3, Anthesis; Feekes 10.5.1 (yellow anthers beginning flowering); 4 days after anthesis (white anthers post flowering). Image: A. Koehler, Univ. of Delaware.

Thinking beyond this season, an integrated approach can improve management of FHB and help to keep DON levels low. In your field rotation plan, avoiding planting small grains into corn residue will help to reduce the amount of initial inoculum in your field. If you have soybean fields that can be harvested early enough for a timely wheat planting, this rotation helps to break up Fusarium inoculum. In addition to rotation considerations, seed selection is another important piece of FHB management in wheat. There is no complete host resistance against FHB, but you can select wheat varieties with partial resistance. The University of Maryland sets up a misted nursery to compare FHB index and DON levels across local wheat varieties to aid in variety selection decisions. Results from 2019 can be found at https://scabusa.org/pdfs/UMD_Misted-Nursery_Factsheet-2019.pdf. Remember that these trials are conducted under extreme disease pressure and you want to look at relative DON performance. Unfortunately, barley does not have any resistance to FHB. In UMD’s 2019 trial, Calypso had the lowest DON content in local barley varieties tested.

 

Wheat Variety Selections—An Important Factor For Managing Head Blight

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

Compared to the 2018 wheat crop, 2019 was a much better year for Fusarium head blight (FHB, also known as head scab). Growing quality wheat in Maryland starts with proper variety selection. As you look ahead to the 2020 wheat crop, select wheat varieties that have good FHB ratings. There are no varieties with complete resistance to head scab; only varying degrees of susceptibility. Nevertheless, planting a somewhat resistant variety will go a long way in managing FHB and keeping vomitoxin levels (DON) lower in your grain compared to a susceptible variety.

To aid in your selection of wheat varieties, the University of Maryland screens several wheat varieties for their resistance to Fusarium graminearim, the causal agent of FHB. The results from the 2019 trials can be found here.

Additional considerations for FHB management include:

  • Planting behind soybeans rather than corn or other small grains. The FHB pathogen survives on residue of corn, wheat, barley, oats, and other grasses; however, it does not persist on soybean residue.
  • If planting into corn residue, consider tillage if it is an option for your farm. Sizing and burying corn residue will accelerate its decomposition and reduce the FHB pathogen survival.
  • Fungicides in spring 2020. Please note that fall fungicide applications do not have any effect on managing FHB. More information will be covered concerning fungicide recommendations in the spring, or read this article from earlier this year.

 

FHB Update: 5/20/2019

48-hour risk for Fusarium Head Blight development on susceptible wheat varieties for May 20, 2019.
48-hour risk for Fusarium Head Blight development on moderately-resistant wheat varieties for May 20, 2019.

Wheat in the North-western counties (Frederick, Howard, Carroll, Harford
counties) of the state is flowering currently. The FHB risk across the state
continues to be high, so if your wheat is flowering, it’s recommended to
spray fungicides for managing FHB. The best stage for spraying fungicides is
early flowering or within 4-5 days of that. The fungicides effective for FHB
are Prosaro/ Caramba/ Miravis-Ace. All of these fungicides are pre-mixed and
do not need to be tank mixed with any other product for spraying. Read the
label carefully for recommended rates and harvest restriction times.
Strobilurin containing fungicides should not be sprayed at this stage.
Aerial application at a rate of 5 gallons per acre or ground application at
15 gallons per acre with 300-350 um droplet size is recommended. Spray
nozzles should be angled at 30°-45° down from horizontal, toward the grain
heads, using forward- and backward mounted nozzles or nozzles with a two
directional spray, such as Twinjet nozzles. Wheat in the Eastern shore is
already past the stage for both FHB infection and fungicide spray.

–Nidhi Rawat, Small grains Pathologist, University of Maryland

For more details, go to the FHB Risk assessment tool at
http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab
Initiative, go to https://www.scabusa.org

FHB Update: May 10, 2019

72-hour risk for Fusarium Head Blight development on moderately resistant wheat varieties for May 10, 2019.

Wheat in the Eastern Shore of Maryland is finishing up flowering. The risk
for FHB is high. If you haven’t sprayed and you are still within 4-6 days
of flowering, you can still do so. Wheat in the Northern parts is heading
now and will soon start flowering. The FHB risk for this part of the state
is also predicted to be high, and the farmers should be prepared to spray
fungicides on their wheat when it flowers (50% of the main tillers showing
yellow anthers). The fungicides effective for FHB are Prosaro/ Caramba/
Miravis-Ace. The best stage recommended for spraying fungicides is early
flowering or within 4-5 days of that. These fungicides do not need to be
tank mixed with another product for spraying. The fungicide products should
be applied at the full rate recommended by the manufacturers. Strobilurin
containing fungicides should not be sprayed at this stage. Aerial
application at a rate of 5 gallons per acre or ground application at 15
gallons per acre with 300-350 um droplet size is recommended. Spray nozzles
should be angled at 30°-45° down from horizontal, toward the grain heads,
using forward- and backward mounted nozzles or nozzles with a two
directional spray, such as Twinjet nozzles. There has been no other major
disease being seen anywhere across the state in wheat so far.

–Nidhi Rawat, Small grains Pathologist, University of Maryland

For more details, go to the FHB Risk assessment tool at
http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab
Initiative, go to https://www.scabusa.org

FHB Update: May 3, 2019

Current risk for Fusarium Head Blight development on susceptible wheat varieties (eg Shirley) for May 3, 2019.

Wheat in the Eastern Shore of Maryland is beginning to flower or will do so
in a couple of days. With yesterday’s rains, and more showers coming our
way, the risk of Fusarium Head has increased significantly in this part of
the state. Growers with wheat flowering (50% of the main tillers showing
yellow anthers) are advised to spray head scab fungicides (Prosaro/ Caramba/
Miravis-Ace) at early flowering or within 4-5 days of this stage. These
fungicides do not need to be tank mixed with another product for spraying.
The fungicide products should be applied at the full rate recommended by the
manufacturers. Strobilurin containing fungicides should not be sprayed at
this stage. Aerial application at a rate of 5 gallons per acre or ground
application at 15 gallons per acre with 300-350 um droplet size is
recommended. Spray nozzles should be angled at 30°-45° down from
horizontal, toward the grain heads, using forward- and backward mounted
nozzles or nozzles with a two directional spray, such as Twinjet nozzles. Up
in the North wheat is booting, and still roughly around 2 weeks away from
flowering.

–Nidhi Rawat, Small grains Pathologist, University of Maryland

For more details, go to the FHB Risk assessment tool at
http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab
Initiative, go to https://www.scabusa.org

Checklist For Head Scab Fungicide Applications

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

wheat infected with head scab
Wheat infected with Fusarium head blight. Image: A. Kness, University of Maryland.

Wheat in the southern parts of Maryland will soon be flowering and the rest of the Maryland wheat crop will follow suit over the next few weeks. As wheat approaches flowering, here are a final list of reminders/tips to make the most of your fungicide applications that are targeted to manage Fusarium head blight (scab):

  • Use an effective fungicide. These include: metconazole (Caramba®), prothioconazole + tebuconazole (Prosaro®), prothioconazole (Proline®), and adepidyn (Miravis Ace®).
  • Apply an effective fungicide at the correct time. The most effective application window is from flowering (anthesis; Feeks 10.5.1) + 6 days after. Late applications (5-7 days after anthesis) are better than early heading/head emergence applications at reducing DON content in the grain.
  • Apply fungicides using the correct equipment. Ground applications should be made with 80-degree flat fan nozzles angled down from horizontal. For ground applications made at speeds over 6 mph, use a single nozzle angled forward (towards the grain heads), 30 degrees down from horizontal. For ground applications less than 6 mph, better coverage is achieved with dual forward and rearward facing nozzles, angled 30-45 degrees down from horizontal.
  • Sprayer should be operated to achieve droplet sizes of 300-350 microns.
  • Use 10-20 gallons of water per acre and keep the spray boom 8-10 inches above the crop.
  • For aerial applications: Use 4-5 gallons of water per acre. Fine to medium sized droplets (300-350 microns). Small aircraft should operate 8-10 feet above the crop; large aircraft 10-12 feet. Nozzles should be mounted to cover 65% of the aircraft’s wingspan and mounted as low as possible.

New Section 3 MD Label: Miravis Ace for Scab in Barley and Wheat

wheat infected with head scab
Wheat infected with Fusarium head blight. Image: A. Kness, University of Maryland.

A new Section 3 MD label for Fusarium head blight (head scab) control on barley and wheat was just awarded for the Syngenta fungicide Miravis Ace, (see the label here: MIravis Ace Syngenta Label-ue1r8d).

See this article for more information on Fusarium head blight management, and stay on top of scab this year by subscribing to scabalerts and using the Fusarium Head Blight risk assessment map.

Managing Fusarium Head Blight

Alyssa Koehler, Extension Plant Pathologist
University of Delaware

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

When it comes to controlling Fusarium Head Blight (FHB) and keeping deoxynivalenol (DON) levels low, it is important to have an integrated approach. Considering the disease cycle of FHB (Figure 1), the FHB pathogen (Fusarium graminearum and other Fusarium sp.) is able to grow on crop residues from corn and small grains. In your field rotation plan, try to avoid planting wheat or barley into corn residue; this will help to reduce the amount of initial inoculum in your field. As the pathogen grows on debris, it eventually releases spores that can be rain dispersed or moved through air currents. While the grain is flowering, spores land on the head or anthers, colonize these tissues, and move into the grain head. Once inside the grain, water and nutrient movement is disrupted which results in the bleached florets we associate with FHB (Figure 2). Shriveled and wilted “tombstone” kernels can reduce yield and result in grain contaminated with mycotoxins. DON, also referred to as vomitoxin, is a health hazard to humans and animals. Wheat heads colonized later in development may not show dramatic symptoms, but can have elevated DON.

Figure 1. Fusarium Head Blight Disease Cycle. For more information on the FHB disease cycle visit https://www.apsnet.org/edcenter/disandpath/fungalasco/pdlessons/Pages/Fusarium.aspx Image: apsnet.org.

In addition to rotation considerations, seed selection is another important piece of FHB management in wheat. There is no complete host resistance against FHB, but you can select wheat varieties with partial resistance. The University of Maryland sets up a misted nursery to compare FHB index and DON levels across local wheat varieties to aid in variety selection decisions https://scabusa.org/pdfs/UMD-UDE_Misted-Nursery_Factsheet-2018.pdf. Unfortunately, barley does not have any resistance to FHB. At this point in the season, rotation order and variety are established, but you can consider these factors as you plan for next season.

Figure 2. Wheat head with Fusarium head blight. Image: Andrew Kness, University of Maryland.

As we think about 2019 in-season disease management strategies, a well-timed fungicide application can help to reduce disease severity and DON levels. It is important to remember that fungicides can help to reduce disease levels and DON (traditionally around 50% reduction on a susceptible variety) but they do not eliminate FHB or DON. To try to maximize the efficacy of fungicides, it is important to apply at the correct timing. Fungicides for FHB are most effective when applied during flowering in wheat and at head emergence in barley. As wheat approaches heading, the Fusarium Risk Assessment Tool (www.wheatscab.psu.edu) is a forecasting model that uses current and predicted weather forecasts to predict FHB risk. This tool is historically about 70% accurate, and can help you assess your risk for developing FHB as your wheat approaches flowering. The pathogen that causes FHB infects through the flower, and rainfall 7 to 10 days prior to flowering increases spore production and risk of infection. Optimal wheat fungicide application is at early flowering (10.5.1) to about 5 days after. For initial signs of wheat heads beginning to flower, look for yellow anthers in the middle of the wheat head. When at least 50% of main stems are flowering, you will want to initiate fungicide applications. As the flowering period continues, anthers will emerge from the top and then the bottom of the wheat heads (Figure 3). Anthers can stay attached after flowering but usually become a pale white.

Method of fungicide application is also important. Flat fan nozzles pointed 90° down are great at covering foliage; however do not do a good job of covering the heads, which is where the product needs to be located. Use nozzles that are angled forward 30-45° down from horizontal (30 degrees is better than 45) or dual nozzles angled both forward and backward. Research has shown that a single forward-angled nozzle or nozzles angled forward and backward allow for significantly more product to contact the head and increase fungicide efficacy. Optimal spray volume is 10 gallons per acre.

Triazole (FRAC group 3) fungicides that are effective on FHB include Caramba (metconazole), Proline (prothioconazole), and Prosaro (prothioconazole + tebuconazole). This year, a new mixed mode of action product is on the market, Miravis Ace. This product contains propiconazole (DMI, FRAC 3) and pydiflumetofen (SDHI, Group 7). On the label, application can begin at Feekes 10.3 through 10.5.2. Although this product can be applied at the earlier timing, preliminary data has shown that optimal FHB control and lower DON levels are achieved at the 10.5.1 timing or a few days beyond this timing. If you spray too early, heads that have not emerged will not be protected by the fungicide application. Rainfall during flowering can increase levels of FHB and delay the ability to get into fields to apply fungicides. The expanded application window of Miravis Ace may offer options if periods of extended rainfall are in the forecast. However, if the weather allows, 10.5.1. to about 5 days after appears to provide the best control to reduced DON. We will be collecting local data on optimal application timing in Georgetown this spring. As a reminder, fungicides containing strobilurins (QoI’s, FRAC 11) should not be used past heading because these fungicides can result in elevated levels of DON.

Figure 3. From left to right Feekes 10.5, Feekes 10.5.1 (beginning flowering), Feekes 10.5.2 (flowering growth stage), Feekes 10.5.3 (full flower). Image: C. Knott, Univ. of Kentucky https://mccracken.ca.uky.edu/files/identifying_wheat_growth_stages_agr224.pdf.