Nidhi Rawat, Small Grains Pathologist University of Maryland, College Park
Wheat in Maryland has either already flowered or is finishing-up flowering. The FHB prediction maps for today and up to the next 6 days predict high FHB risk. If your wheat is still in the window for FHB fungicide application (from flowering up to the following 4-7 days) you should consider the application of FHB fungicides: Miravis-Ace, Prosaro, Prosaro-Pro, or Sphaerex. These fungicides are also effective against other fungal foliar diseases such as stripe rust, powdery mildew, and tan-spot etc. Strobilurin-containing fungicides are not recommended for application at this stage.
Nidhi Rawat, Small Grains Pathologist University of Maryland, College Park
Wheat is mostly ending flowering across Maryland now, except for some late-planted fields. The FHB prediction map shows enhanced FHB risk. If your wheat flowered within the past 4-7 days, you are still in the window for FHB fungicide application. This season, we are also observing several foliar diseases such as stripe rust, powdery mildew, BYDV, and tan-spot in our variety trial plots. Some farmers are also reporting these issues from their fields. If you are considering the application of fungicides at this stage, use FHB fungicides: Miravis-Ace, Prosaro, Prosaro-Pro, or Sphaerex. These will control other fungal diseases, in addition to FHB, but not BYDV. For BYDV none of the fungicides can provide control, as it is a viral disease, and genetic resistance is the only real solution for it. Strobilurin-containing fungicides are not recommended for application at this stage.
Andrew Kness, Senior Agriculture Agent | akness@umd.edu University of Maryland Extension, Harford County
This article may come a little too late for some of you depending where you are in the state; but nevertheless, here is a review/reminder. As we get into May, wheat will begin flowering and we will have to consider fungicide applications to wheat to manage Fusarium head blight (FHB), also known as head scab. FHB is the most economically important disease of wheat, causing not only yield reductions, but more seriously, grain quality issues due to the production of the mycotoxin deoxynivalenol (DON), also called vomitoxin.
The pathogen that causes FHB, Fusarium graminearum, persists in wheat, small grain, and corn residue. It infects the wheat plant through the open flower, which is why flowering is such an important management timing for quality wheat production. Fusarium graminearum requires moist conditions and moderate temperatures (59-86 °F) to initiate infection. If these conditions are met during flowering, the pathogen will infect susceptible wheat varieties and cause disease.
Management of FHB requires a layered approach of IPM practices, with the major management practices being the selection of a good wheat variety and subsequent good planting and fertility practices, plus the use of a fungicide at flowering should the environmental conditions be conducive for FHB development. The wheatscab.psu.edu map can be helpful in predicting FHB risk to wheat around flowering. Historically, this model has been over 70% effective at predicting FHB outbreaks and should be consulted when making fungicide decisions. If you decide to apply a fungicide to manage FHB, there are three important factors to consider: 1.) Timing, 2.) Application method, and 3.) Active ingredient.
As mentioned earlier, the pathogen can only infect wheat through the open flower, so you need to time your fungicide application as close to flowering, or Feekes Growth Stage 10.5.1, as possible (Figure 1). This growth stage is defined by the appearance of yellow anthers in the center of the wheat spike on at least 50% of the plants. Once this stage is reached, the application window is about 5-7 days. Some fungicide products are labelled for application as early as Feekes 10.3 (half head emergence); however, this timing is not as optimal as 10.5.1—so wait if you can.
Figure 1. Wheat at Feekes 10.5.1, indicating proper fungicide timing for FHB management. Photo: A. Kness, Univ. of Maryland.
The second factor is application method. Most of our fungicides on wheat go on with a ground sprayer. For ground applications it is important to achieve good coverage of the wheat heads, not the foliage. To do this, spray volumes should be at least 15-20 gallons/acre and you should use bi-directional spray nozzles angled forward and backwards. This combination of spray volume and angled nozzles results in thorough coverage of the wheat heads. Aerial applications should be done at 5 gallons/acre for maximum coverage.
The final consideration is fungicide active ingredient. Triazole and HDMI fungicides work best on FHB. Products include: Prosaro Pro, Prosaro, Miravis Ace, Saphaerex, Proline, and Caramba; Folicur has less efficacy than the others and Tilt is no longer effective on FHB. An added benefit is that these products will also do a good job of keeping other fungal diseases at bay during grain fill. Do not apply any group 11 (Qoi/strobilurin) fungicides such as Aproach, Headline, or Quadris after heading as these products can actually increase DON levels in the grain.
Nidhi Rawat, Small Grains Pathologist University of Maryland, College Park
Wheat on the Eastern shore of Maryland is heading and should start flowering within a week or so. Wheat in the north-western part (Frederick, Carroll, Hartford counties) is also close to heading or has started heading. The FHB fungal pathogen infects the wheat plants at the flowering stage (when the yellow anthers emerge from the heads), which is the stage at which the application of fungicides is conducted in wheat. The FHB map currently does not show high risk, especially for a genetically resistant variety. However, keeping an eye on the forecasts and weather patterns over the next few days as your wheat flowers is recommended. If you are planning to apply fungicides for FHB, remember that triazole-containing fungicides (Miravis-Ace, Prosaro, Prosaro-Pro, and Sphaerex) should be used for controlling FHB. They can control other fungal pathogens like powdery mildew as well, in addition to scab. Strobilurin-containing fungicides should not be used at this stage.
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.
Results from the University of Maryland Small Grain Variety Trials are in the tables below. To download a pdf copy of the report, click here.
University of Maryland also rates the relative susceptibility of select varieties of wheat and barley to Fusarium head blight. The results from this trial can be found here.
For questions regarding the small grain trials, contact Dr. Vijay Tiwari (vktiwari@umd.edu) or Dr. Nidhi Rawat (nidhirwt@umd.edu).
If you’d like to learn more about how to interpret variety trial data, view our fact sheet by clicking here.
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.
