Wheat Growth Stages and Fungicide Decisions

• View the most recent stripe and leaf rust report maps on the CropWatch Wheat Disease page.

Early season fungal diseases were low prior to May 1 in Nebraska. However, there are now numerous reports of stripe rust in southern Nebraska, highlighted last week in CropWatch.

If stripe rust incidence and severity are low in your field, the variety is moderately susceptible or better (moderately resistant) to stripe rust, and you are less than one week away from early flowering, we suggest delaying fungicide application until early flowering to control the emerging stripe rust pressure and suppression of Fusarium head blight (FHB). Additionally, most fungicide products have a 14-day minimum re-application interval. The fungicides labeled for FHB provide control of stripe and leaf rust with two to three weeks of residual activity during the early grain fill period.

About FHB

• Learn more about FHB: Market Journal interview with Stephen Wegulo

Fusarium head blight (Figure 1), also called head scab, is a fungal disease that infects wheat during flowering. However, given the warm spring, flowering started this week in southeast Nebraska wheat fields. Over the past 15 years, widespread FHB epidemics occurred in Nebraska in 2007, 2008, 2015 and 2019.

Southeast Nebraska is particularly prone to FHB issues due to the humidity and higher rainfall compared to the rest of the state; however, western Nebraska dealt with challenges in 2023. The frequent rainfall events in late April and early May in southeast Nebraska may have set the stage for a potential 2024 outbreak.

In addition to yield loss as high as 50%, FHB reduces grain quality and the received price at the elevator due to Fusarium-damaged kernels (FDK, Figure 2) and presence of mycotoxins, mainly deoxynivalenol (DON, vomitoxin).

Risk of FHB

• View the fusarium risk map.

The pathogens causing FHB are always present in the field, as they survive on cereal residues — especially corn and wheat. In May, excessive and frequent rainfall two weeks prior to flowering and during flowering creates a potential high FHB risk. Other factors will increase risk of FHB including planting a susceptible variety, planting after corn or wheat, no-till, and recent irrigation.

Fungicide Use for FHB

• The North Central Regional Committee on Management of Small Grain Diseases (NCERA 184) has compiled a table of fungicides used to control wheat diseases, including the efficacy of each fungicide in controlling specific diseases.

Fungicides can significantly suppress FHB up to 70%, but not completely control it. There are six fungicides recommended and labeled to suppress FHB: Caramba, Miravis Ace, Proline, Prosaro, Prosaro Pro, and Sphaerex (Table 1).

Large ground sprayers (>90-foot boom width) are very effective due to high volume application capability (>10 gallons per acre), reduced tire damage to spray area ratio, and using recommended front and back angled nozzles.

Aerial application is often chosen since ground sprayers are tied up with corn and soybean herbicide spraying or because wet weather limits field traffic. The effectiveness of aerial applications to suppress FHB is greatly improved if the volume is increased to five gallons per acre (Table 1). Minimum volume for aerial application of several products is two gallons per acre, but it is recommended to increase to four or five gallons per acre. Some aircraft/equipment does limit maximum application to four gallons per acre.

Table 1. Information on fungicide products labeled and recommended for suppression of Fusarium head blight. You are required to read/consult the pesticide label — this table is not a replacement. Also, changes are possible since this table was created on May 14, 2024.

Product	Product Rate (oz/acre)	Volume minimum in gallons per acre (Ground/Aerial)	Applications allowed per year	Minimum interval between applications (Days)	Maximum application rate per year (oz/acre)	Pre-Harvest Interval (Days or growth stage)
Caramba	13.5 – 17.0	10/5	2	6	34.0	30
Miravis Ace	13.7	10/2	1 (forage/hay) 2 (grain)	14	13.7 (forage/hay) 27.4 (grain)	Up to Feekes 10.5.4
Proline	5.0 – 5.7	10/5	2	14	9.37	30
Prosaro	6.5 – 8.2	10/5	-	-	8.2	30
Prosaro Pro	10.3 – 13.6	10/5	2	14	13.6	30
Sphaerex	7.3	10/2	2	14	14.6	30

Timing of Fungicide Application for FHB

• Learn more about wheat growth stages: A Visual Guide to Winter Wheat Development and Growth Staging

For greatest efficacy, target fungicide application during the beginning of flowering (Feekes 10.5.1) (Figure 3) when yellow anthers first become visible (starts at spikelets just above the middle of the head) on about 15% of the main heads in the field. Within a field, the beginning of the flowering stage does vary based on topography, residue, tillering and other factors. Fungicide application can still be made up to six days after beginning of flowering (Feekes 10.5.1) with very good suppression (Bolanos-Carriel, 2020) including during flowering completed to top of head (Feekes 10.5.2) and into flowering completed to base of head (Feekes 10.5.3).

Applications after flowering is complete (Feekes 10.5.4) are less effective and can become off-label applications due to a 30-day pre-harvest interval of grain or a growth stage restriction at the watery-ripe stage (Feekes 10.5.4), so please check the product specific preharvest interval (i.e. forage, hay, straw and grain) on each product label. It is preferred that it does not rain at least four hours following fungicide application.

Note that Miravis Ace and Prosaro Pro are labeled for suppression of FBH prior to flowering during heading, but they are less effective when applied before early flowering (Singh et. al., 2021).

Literature Cited

Bolanos-Carriel et al., 2020. Effects of fungicide chemical class, fungicide application timing, and environment on Fusarium head blight in winter wheat. Eur J Plant Pathol https://doi.org/10.1007/s10658-020-02109-3

Singh et al., 2021. Evaluation of Application Timing of Miravis Ace for Control of Fusarium Head Blight in Wheat. Plant Health Progress 22:94-100 https://doi.org/10.1094/PHP-01-21-0007-RS