Nidhi Rawat, Small Grains Pathologist University of Maryland
Welcome to the wheat and barley heading and flowering season, Maryland! This is the first FHB risk forecast for this season from me, and I will continue to provide you with regular commentaries over the next 6-7 weeks. Wheat is some weeks away from flowering, but barley is starting/ will soon start to head, especially in the Eastern shore of the state. Unfortunately, for barley, there are no FHB-resistant varieties available so far. So, if you have planted barley, keep monitoring closely for the FHB risk over the next couple of weeks. With the rainy spell of the last week, and some more rain forecasted this week, currently, the Epidemiological models are showing elevated FHB risk over the next 6 days. So, if your barley is starting heading you might consider applying fungicides on it. If you are still some weeks away from your barley heading, keep monitoring for the risk. Remember, the best stage for applying FHB fungicides on barley is when the heads are completely out of the boots. The FHB fungicides are triazole-containing products (Miravis-Ace, Prosaro, Prosaro-Pro, Sphaerex). Do not apply strobilurin-containing fungicides after heading. Wheat is not at a stage susceptible to FHB right now.
Some barley growers from across the state reported stunting, yellowing, and death of barley plants in their fields. The most probable cause of this issue in my opinion is freeze injury. Sudden dips in temperature after the plants caught up after winter may have led to the issue. I have discussed this issue with the other regional pathologists from the US, and they also report similar issues in North Carolina, Pennsylvania, and New York. They also think it to be a result of cold injury.
Alyssa Koehler, Extension Field Crop Pathologist | akoehler@udel.edu University of Delaware
Wheat anthesis (flowering) is underway and will be continuing for the next 1-2 weeks across the region. Up until the rains this past weekend, we have been at low FHB risk. We are currently tracking as medium-high risk for very susceptible varieties and low-medium risk for varieties with some level of resistance (Figure 1). If you are planning for wheat fungicide application, scout frequently, looking for yellow anthers in the center of the wheat head (Figure 2) to signal that flowering has begun (Feekes 10.5.1). Depending on the weather, we can usually expect flowers to start showing up on wheat heads 3-5 days after full head emergence, with cool weather this can stretch this process out to 7-10 days. Anthers can remain attached after flowering, but become a pale white. For best mycotoxin (DON) control, it is better to be at flowering or a few days beyond than to spray too early when heads are not out yet (especially those secondary tillers). Fungicide products should be applied at the manufacturers recommended rate with nozzles angled 30-45° from horizontal (30 degrees is better than 45). Nozzles angled both forward and backward or twinjet nozzles that spray in two directions give better contact with the head and increase fungicide efficacy. For ground sprays, fungicides should be applied in at least 10-15 gallons of water per acre; aerial applications are recommended at 5 gallons per acre.
Figure 1. FHB Risk Model for very susceptible (top) and susceptible varieties (bottom) May 3, 2023 (wheatscab.psu.edu).Figure 2. Wheat at flowering (Feekes 10.5.1) with yellow anthers visible 3-4 days after heads emerge.
Once wheat has flowered, symptoms of FHB are usually visible in 18-24 days, but cool weather can slow symptom development. Heads with FHB will have bleached florets or bleached sections of the head and may have pink growth on spikelets. Glume blotch may also be present, but typically has more of a grey appearance. You can follow these steps to assess the severity of FHB present in your field.
For every 10 acres of field, randomly select one spot to survey.
Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to look at on the plant or detach and place into a bag. (Looking down may bias the heads you select).
Once you have randomly collected the heads, rate the percent of each head with symptoms of FHB (bleaching or pink growth on spikelets). You can use the scale below to help calibrate your eye (next page).
After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected. (Ex. You rate 10 heads with severity values: 0%, 10%, 30%, 0%, 0%, 20%, 10%, 0%, 0%, 0%. These add up to 70. 70/10 heads = 7% overall FHB severity). Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight. It is possible to have delayed or lower levels of symptoms and still have DON.
Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvested as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested.
Seyedali Hosseinrad, Nidhi Rawat, Nicole Fiorellino, and Vijay K. Tiwari Department of Plant Science and Landscape Architecture, University of Maryland, College Park
Fusarium Head Blight of wheat and barley
Fusarium head blight (FHB) is a severe fungal disease that affects small grains, wheat and barley. It is particularly problematic in regions with wet and warm springs, such as the Mid-Atlantic region. FHB is caused by several species of Fusarium, F. graminearum being the most common in the USA.
Symptoms and signs: The disease primarily attacks the wheat and barley heads, or spikes, at flowering. Early symptoms of FHB include the appearance of small, water-soaked lesions on the glumes and awns of the heads. As the infection progresses, these lesions become larger, and the spikelets (sections of the heads) become brown and dry progressively (Figure 1a, b). In particularly conducive weather conditions, the spikelets may take on a pink or reddish color due to a mass production of fungal spores called sporodochia on the glumes. The disease causes the kernels to shrink or abort, leading to reduced yield, poor-quality grain, and in severe cases, crop failure (Fig. 1 c). In addition, the fungus also produces mycotoxins, such as Deoxynivalenol (DON), which is toxic for human and animal consumption. The epidemiology of FHB is complex and multifaceted and can be influenced by various factors, including weather conditions, crop management practices, and genetic susceptibility.
Figure 1. FHB symptoms on wheat and barley. A.) Wheat heads showing brown and bleached spikelets indicated by yellow arrows. B.) A malting barley spike showing bleached spikelets. C.) Fusarium damaged kernels.
Factors affecting FHB
Weather conditions play a major role in determining the severity of FHB in field conditions. The disease thrives in warm, wet environments and is severe in areas with high humidity and frequent rainfall. Wet weather conditions during the flowering stage of wheat development provide an ideal environment for the fungus to infect and proliferate on the developing grain heads. In particular, warm and humid weather between heading and anthesis (flowering) is highly conducive to FHB infection. Warm temperatures between 70 and 80°F are favorable for fungal growth and production of mycotoxins.
Crop management practices can also contribute to the development and spread of FHB in winter wheat. Practices such as reduced tillage and corn-wheat rotation can increase the risk of FHB infection. Reduced or no-tillage can leave plant debris on the soil surface, providing a potential source of inoculum for the fungus. At the same time, corn acts as a secondary host of the pathogen, allowing the fungal inoculum to build up in the soil over time.
Management of FHB
Effective management of FHB in winter wheat typically involves using an integrated disease management approach that incorporates a combination of cultural, chemical, and biological control measures.
Use of FHB-resistant varieties: One of the most important cultural practices for reducing FHB infections in wheat is the selection of resistant cultivars. Several wheat varieties have been developed with genetic resistance to FHB. In fact, the UMD small grain pathology program, in collaboration with the small grain breeding program, tests upward of 60 regional commercial varieties in their misted nursery in replicated trials every year to provide growers with a robust assessment of the levels of the genetic resistance of these varieties to FHB (https://psla.umd.edu/extension/md-crops). It is highly advisable for regional farmers to refer to these ratings for making their planting decisions to reduce the severity of infections in their crops.
Due to the importance of FHB in the Mid-Atlantic region, developing FHB-resistant varieties is one of the primary goals of the MD small grain breeding program, in addition to their yield and quality. Resistance to FHB is a complex genetic trait and is influenced by a range of genetic factors. So, any breeding program targeting to incorporate a high level of genetic resistance in their varieties has to pyramid several genes toward that goal. However, a high level of genetic resistance in barley is difficult to achieve on account of the lack of resistance genes available in it.
Chemical control: The use of fungicides is a key component of FHB management in wheat and barley. Fungicides can effectively reduce the severity of infections and minimize the production of mycotoxins. Fungicides with Group 3 and 7 FRAC code ingredients have been successful in controlling FHB. FRAC group 11 fungicides should not be applied for FHB, as there are reports of them increasing DON content in the grains. Several effective chemistries with a mix of active ingredients against FHB have recently been released by manufacturers, such as Prosaro-Pro and Prosaro by Bayer, Miravis-Ace by Syngenta, and Sphaerex by BASF. All these fungicides have been tested by the UMD Small grain pathology program and are found to be equally effective when sprayed at anthesis.
In addition to the chemistry of the fungicide, the timing of spraying is very critical in managing FHB. Spraying fungicides at anthesis (when yellow anthers pop out of the wheat heads) in wheat and heading in barley is important. As weather plays a major effect in determining the severity of FHB infection, the risk of FHB can be predicted with a significant correlation with conducive weather conditions. In conjunction with the US Wheat and Barley Scab Initiative, the MD small grain program releases FHB risk commentaries for growers registered with the FHB risk prediction website (https://www.wheatscab.psu.edu/). The growers are advised to register on this website to receive the alerts on their cell phones as text messages with advice on spraying decisions for FHB.
Biological control: Some biological control agents, such as bacterial and fungal species antagonistic to FHB, are available with the claims of reducing disease severity and mycotoxin production. However, the efficacy of these biological control agents is not high yet. Researchers at UMD are testing some new promising biological products currently under development, especially for the organic growers of the region.
Crop Rotation and Tillage: Other important cultural practices include crop rotation and tillage. Planting non-host crops such as soybeans in rotation with wheat can help reduce the amount of FHB inoculum in the soil, as corn is a secondary host of the pathogen and can increase inoculum build-up in the soil for the wheat crop. Reduced tillage practices that manage crop residue on the soil surface with minimal disturbance to the soil are helpful in reducing the amount of infected crop residue on the soil surface while minimizing soil erosion and loss.
Post-harvest management: Post-harvest management practices, such as grain cleaning and drying, can help to screen the Fusarium damaged kernels that are expected to have high levels of mycotoxin contamination in the harvested grain. Cleaning equipment such as air screen cleaners or gravity tables can remove lightweight and damaged kernels. Drying grain to a moisture content of 14% or lower as soon as possible after harvest can also help minimize mycotoxin contamination. The fungus may continue mycotoxin production at high moisture conditions in storage. Proper storage conditions, such as cool and dry storage facilities, can also help to prevent mycotoxin contamination during storage.
Fusarium head blight (FHB) is a significant fungal disease affecting wheat and barley crops in the Mid-Atlantic region, causing yield and quality losses. Small grain pathology and breeding programs are working on multipronged approaches to reduce FHB impact, such as using fungicides, developing resistant cultivars, and adopting cultural practices such as crop rotation and tillage management. Also, research and innovation are crucial to ensure the region’s long-term sustainability of wheat production.
For more information:
Gillum, M., & Van Sanford, D. (2023). Understanding the Effect of Fusarium Head Blight Resistance on Agronomic Characteristics of Soft Red Winter Wheat.
Singh, L., Wight, J.P., Crank, J., Thorne, L., Erwin, J.E., Dong, Y., Rawat, N. (2021). Evaluation of application timing of Miravis-Ace for control of Fusarium head blight and DON content in wheat. Plant Health Progress. 22: 94-100.
Singh, L., Wight, J.P., Crank, J., Thorne, L., Dong, Y., Rawat, N. (2020). Efficacy assessment of a new fungicide, Miravis Ace, for control of
Nidhi Rawat, Small Grains Pathologist University of Maryland
Flowering is finishing up across all of Maryland now, except for a few late planted fields in the northern part of MD that may still be flowering. FHB risk across the state continues to be high. So, if your wheat is currently flowering or has flowered within last 4-5 days, you can still spray FHB fungicides. I have started scouting the wheat variety trials for FHB symptoms on the Eastern shore and am already observing moderate FHB incidences in untreated plots there. The weather conditions have been conducive for FHB this season so far. If you have planted resistant varieties, the situation is expected to be better. Natural infections of leaf rust and stripe rust are also being seen sporadically. I do not expect any major losses due to these two now though. So, it’s okay not to spray any fungicide specifically for these diseases.
Nidhi Rawat, Small grains Pathologist University of Maryland
Date 5/18/2022
With the recent showers and warming weather, FHB risk in the state is increasing. Wheat in the Eastern Shore of Maryland has finished or is just finishing flowering. If your wheat has just flowered last week, and you have not sprayed FHB fungicides you can still do so, as fungicide application 4-6 days after flowering is also known to provide some control. Wheat in the Northern parts is either flowering/ will soon start flowering. The FHB risk for this part of the state (Frederick, Carroll and Harford counties) is predicted to be moderate to high, especially if the wheat variety planted is susceptible. If the planted variety is resistant, the risk is not predicted to be particularly high. The recommended stage for application of fungicides on wheat is at flowering (50% of the main tillers showing yellow anthers) or within 4-5 days of that. The fungicides effective for FHB are Prosaro-pro/ Caramba/ Miravis-Ace. 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.
Alyssa Koehler, Extension Field Crop Pathologist | akoehler@udel.edu University of Delaware
Symptoms of Fusarium Head Blight.
Wheat anthesis will be occurring over the next few weeks. So far this season we have been at low FHB risk, but we will keep a close eye on the rain events predicted over the next two weeks. Some areas are getting a bit dry, so the rain is needed, but we hope for sun after rather than multiple grey days that keep canopy moisture high. If you are planning for wheat fungicide application, scout frequently looking for yellow anthers in the center of the wheat head to signal that flowering has begun (Feekes 10.5.1). Once around 50% of heads are flowering, fungicides (Caramba, Sphaerex, Miravis Ace, Prosaro, Prosaro-Pro) are most effective when applied within a 4-5 day window. Anthers can remain attached after flowering, but become a pale white (Figure 1). Once wheat has flowered, symptoms of FHB are visible in 18-24 days, but cool weather can slow symptom development. Heads with FHB will have bleached florets or bleached sections of the head (Figure 2) and may have pink growth on spikelets. Glume blotch may also be present, but typically has more of a grey appearance. You can follow these steps to assess the level of FHB present in your field.
Figure 1. 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.
For every 10 acres of field, randomly select one spot to survey.
Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to look at on the plant or detach and place into a bag. (You don’t want to be looking down and biasing the heads you select).
Once you have randomly collected the heads, rate the percent of each head with symptoms of FHB (bleaching or pink growth on spikelets).
After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected. (Ex. You rate 10 heads with severity values: 0, 10, 30, 0, 0, 20, 10, 0, 0, 0. These add up to 70. 70/10 heads = 7% FHB severity). Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight. It is possible to have delayed or lower levels of symptoms and still have DON.
Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvested as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested.
Alyssa Koehler, Extension Field Crops Pathologist University of Delaware
Most barley has made it past flowering, with wheat fields approaching anthesis. Over the past few weeks we have remained at low risk for Fusarium head blight (FHB) http://wheatscab.psu.edu/. There have been some rain events this week, and we will keep an eye on the model over the next 1-2 weeks. The recommended stage for fungicide application is when 50% of main tillers are flowering (yellow anthers visible) until 4-5 days after. Once wheat has flowered, symptoms of FHB are visible in 18-24 days, but cool weather can slow symptom development. Heads with FHB will have bleached florets or bleached sections of the head (Figure 1) and may have pink growth on spikelets. Glume blotch may also be present, but typically has more of a grey appearance. You can follow these steps to assess the level of FHB present in your field.
Figure 1. Symptoms of Fusarium head blight on wheat. Image: A. Koehler, Univ. of Delaware.
For every 10 acres of field, randomly select one spot to survey.
Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to look at on the plant or detach and place into a bag. (You don’t want to be looking down and biasing the heads you select).
Once you have randomly collected the heads, rate the percent of each head with symptoms of FHB (bleaching or pink growth on spikelets).
After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected.
(Ex. You rate 10 heads with severity values: 0, 10, 30, 0, 0, 20, 10, 0, 0, 0. These add up to 70. 70/10 heads = 7% FHB severity).
Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight. It is possible to have delayed or lower levels of symptoms and still have DON.
Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvested as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested.
Nidhi Rawat, Small Grains Pathologist University of Maryland, College Park
Fusarium head blight risk to susceptible wheat as of June 1, 2020. Visit www.wheatscab.psu.edu
Flowering is all finished across all counties of Maryland now, except for a few late planted fields in the northern part of MD that may still be flowering. Currently the risk of FHB is high in these areas and so FHB fungicides (Prosaro, Miravis Ace, Caramba) should be applied here. For most parts, wheat is now in the grain filling stage and should be ready for harvesting in the next couple of weeks. We experienced some showers this season, but the temperatures remained low, so symptom development in terms of bleached spikelets will be limited. It is advisable to get the DON content of the harvested grain analyzed before taking it to the market.
This is the last FHB risk commentary of the season, but feel free to contact me (email: nidhirwt@umd.edu) if you have any questions related to wheat diseases any time of the year!
Nidhi Rawat, Small Grains Pathologist University of Maryland, College Park
Fusarium head blight risk to susceptible wheat varieties as of May 19, 2020. Image from: wheatscab.psu.edu.
Wheat in the Eastern shore and the Southern part of Western shore of Maryland has finished flowering, except for a few late planted fields. Up in the North-western counties of the state (Frederick, Howard, Carroll, Harford) wheat is flowering currently. Past week’s low temperatures slowed the progress of wheat. Heads emerged but waited for a week or so to flower in several places. The FHB risk for Maryland does not show to be high currently. However, the unusual pattern of weather has caused several other foliar diseases to appear across the state. Fungal diseases such as Stagonospora nodorum blotch, Stagonospora tritici blotch, Tan spot, Powdery mildew and even some viral diseases such as Wheat streak mosaic virus and Soil-borne mosaic virus have been observed in wheat fields this year. It is important to remember that Strobulurin containing fungicides should not be applied at this stage. Fungicides will not be effective against any viral diseases. However, the FHB fungicides (Prosaro/ Caramba/ Miravis Ace) will be able to control the other fungal foliar diseases. 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. 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.
