If it feels like weed pressure keeps getting worse, you aren’t imagining it. Across the Corn Belt, more growers are seeing escapes even after applying programs that have worked for years. Waterhemp, Palmer amaranth, giant ragweed, and other tough grasses and broadleaf weeds continue to adapt, slipping through a control window that used to hold strong.
It’s not just a few fields anymore. It’s a trend — and an expensive one. In 2021, U.S. corn growers spent more than $2.2 billion managing weeds.1 That number isn’t going down, and resistance is a big reason why.
The weed pressure has changed. The weather has changed. And now, the tools growers rely on need to change too.
How We Got Here
For decades, the backbone of weed control has been a reactive approach: spraying postemergence once weeds are visible. But as resistance has evolved and weather patterns have become more unpredictable, that “chase and spray” cycle has become less reliable and more costly.
Modern weed species don’t just compete with crops early; they recover faster and produce more seeds when left uncontrolled. Missing the preemergence window due to weather, labor or logistics can mean fighting escapes for the rest of the season.
We’ve learned that the most effective weed control strategy isn’t reacting after the fact. It’s being proactive — stopping weeds before they emerge with strong, residual herbicides that provide long-lasting protection and multiple modes of action.
That’s where Surtain® herbicide from BASF, now available through Titan Pro, comes in.
An Innovative Solution for Tougher Weed Pressure
Titan Pro is excited to offer growers Surtain herbicide, one of the latest corn herbicide innovations from BASF, designed to help corn growers start clean and stay clean.
Surtain herbicide is a first-of-its-kind PPO herbicide, combining two trusted active ingredients — saflufenacil (Group 14) and pyroxasulfone (Group 15) — to deliver broad-spectrum, long-lasting control against 79 grasses and broadleaf weeds.2
Unlike traditional formulations, Surtain herbicide uses encapsulated technology to control the release of each active ingredient, helping to ensure a consistent, predictable performance across a wide range of soil and weather conditions. The result? Dependable control when growers need it most.
Why Proactive Residual Control Matters Now
Early-season weed competition is more than just an aesthetic problem. Weeds that emerge alongside young corn plants can rob yield potential before the crop has a chance to establish itself.
Even small early-season weeds can steal yield before they’re visible. Research shows even 6-inch weeds can cause a 7% yield loss in corn3, and once those weeds are established, even a timely post-application can’t undo the early damage.
Residual herbicides are designed to bridge that gap, buy growers more time, and protect yield potential until post applications can be made. But as resistance expands, not all residuals are equally effective. That’s why new formulations and multiple sites of action are critical to long-term success.
Surtain Herbicide: Built for Modern Weed Control Programs
Surtain herbicide was developed to bring next-generation performance to preemergence and early postemergence programs. It provides the kind of flexibility, endurance and consistency that growers need to stay ahead of resistant weeds.
Here’s how it stands out:
Residual Endurance
Surtain herbicide delivers up to 8 weeks of residual control against 79 grasses and broadleaf weeds, including Palmer amaranth, waterhemp and giant ragweed.2 It attacks weeds when they’re most vulnerable — before they emerge — helping growers maintain clean fields through critical early growth stages.
Resistance Management
By combining Groups 14 and 15, Surtain herbicide delivers two sites of action for strong, diversified control. It’s an ideal fit for resistance management strategies, helping slow the spread of increasingly growing resistance technologies such as HPPD Inhibitors (Group 27).
Application Flexibility
Weather delays happen. And, with Surtain herbicide, they don’t have to derail your weed control plan. It can be applied preemergence through early postemergence (up to V3), giving growers a wider window to stay on schedule even when conditions are less than ideal.
Proven Performance and Trial Data
Bancroft, Iowa. Photo taken 26 DAT. Surtain herbicide applied at 14 fl oz/acre on 06/24/2024.
Tracy, Minnesota. Photo taken 35 DAT. Surtain herbicide applied at 14 fl oz/acre on 05/15/2024.
Photos submitted by customers as part of the 2024 demo program.*
*Outcomes shown are based on individual grower experience, may be the result of combining Surtain
herbicide with other products as part of a recommended program and are not guaranteed by BASF.
Use rates and programs followed are grower-reported. For a list of grower-submitted product uses
and rates, please contact your BASF representative.
Fitting Surtain Herbicide Into Your 2026 Program
Surtain herbicide fits seamlessly into two-pass weed control programs. For growers who already run a pre- and postemergence system, it adds stronger protection upfront, making post passes more efficient and reducing the number of escapes that require costly rescues later.
Surtain herbicide can be used alone or tank-mixed* with a wide range of herbicides for expanded control of grasses and broadleaf weeds. Its chemistry provides compatibility across many existing corn programs, giving growers flexibility without forcing them to overhaul their approach.
Operational Advantages That Make a Difference
Beyond its agronomic strength, Surtain herbicide is also designed for ease of use in real-world conditions.
• Low use rate: The concentrated formulation means fewer gallons to handle, easier storage and simplified logistics during busy spring operations.
• Liquid fertilizer compatibility: Surtain herbicide mixes with most liquid fertilizer systems, allowing for efficient single-pass applications and saving valuable time and fuel.
• Ease of mixing: The solid-encapsulated formulation reduces the risk of clogging and ensures uniform mixing and spray consistency.
The Bottom Line
Weed resistance isn’t slowing down and weather isn’t going to get easier to predict. But with Surtain herbicide, growers have a tool built for today’s realities with powerful residual endurance, two proven modes of action, and flexible application timing that fits the way real operations run.
For growers ready to take a more proactive approach in 2026, Surtain herbicide checks all the boxes.
Want to see how Surtain herbicide can fit into your 2026 weed control program?
Talk to your local Titan Pro dealer to learn more about program fit, tank-mix* options and savings opportunities.
Start clean. Stay ahead.
Because chasing weeds is no longer enough.
* Before mixing components, always conduct a compatibility jar test. Always consult respective product labels for specific mixing instructions. The most restrictive label applies.
1. Extrapolated market share from third-party market data.
2. BASF sponsored research, 2016–2022, 161 trials, primarily in the Midwest, Zidua® SC herbicide and Sharpen® herbicide labels.
3. Gower et al., 2003. Effect of postemergence glyphosate application timing on weed control and grain yield in glyphosate-resistant corn: results of a two-year multistate study, Weed Technology, 17: 821-828.
Always read and follow label directions. Sharpen, Surtain and Zidua are registered trademarks of BASF. All other trademarks are the property of their respective owners and use of any such trademark does not imply any affiliation with or endorsement by its owner. © 2026 BASF Agricultural Solutions US LLC. All rights reserved.
*This content was previously published by Corteva Agriscience.
When a weed scientist says a novel weed resistance issue is not well understood, it’s a little concerning.
Most farmers understand the need to apply multiple herbicide groups and rotate them to reduce the number of herbicide-resistant weeds going to seed. This practice reduces target-site weed resistance when a weed alters its genetic code so the chemical no longer fits the protein it was designed to attack.
However, some weeds are evolving to deploy suites of enzymes that work together to metabolize (detoxify) a chemical before it can kill a weed — known as non-target or metabolic resistance.
“Ten or 15 years ago, we weren’t seeing much metabolic resistance in waterhemp, as it was all target-site resistance,” says Pat Tranel, Professor and Associate Head of the Department of Crop Sciences in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois.
“Today, I’d estimate more than half of our waterhemp in Illinois has glyphosate resistance [target-site], and 50% have atrazine resistance [metabolic/non-target]. Approximately 10% of the waterhemp population has HPPD resistance which is all metabolic,” Tranel says. He suspects there’s more metabolic resistance than we realize in preemergence Group 15 herbicides because reduced residual control by a few weeks makes it difficult to pinpoint whether it’s resistance or weather-related.
At a molecular level, scientists can easily determine target-site resistance because they know the protein and can look directly at the genetic code of waterhemp to determine the responsible mutation. But for non-target metabolic resistance, it’s still a guessing game. Researchers can sometimes identify an enzyme class that detoxifies
a chemical but know little about which genes code for those enzymes.
Tranel and his colleagues have determined that waterhemp has evolved resistance to seven different herbicide groups, and all have some metabolic resistance. “Our research focuses on what enzymes or genes are involved, what is selecting for those enzymes, and why the same mechanism can confer resistance to other herbicide groups. Until
we understand all this, we’re at a loss to make herbicide recommendations for metabolic resistance,” he says.
Tranel uses Enlist® crops to explain metabolic resistance. The same gene used to confer 2,4-D resistance in Enlist corn or soybeans can also metabolize the Group 1
‘FOP’ herbicides like quizalofop. “The reason for this is an unpredictable cross-resistance that we talk about in weeds,” he says.
There’s some similarity around the chemicals of those herbicide molecules, allowing them to be recognized by the same metabolizing enzyme. This process is similar in weeds. “If a weed gets selected for an enzyme that can metabolize herbicide A that the farmer has used, it’s also possible that same enzyme can metabolize herbicide B,” Tranel says.
The metabolic resistance process gets further complicated over time. Weed scientists worry about weed populations that receive different herbicides over many seasons
will lead to numerous enzymes metabolizing numerous herbicide groups. In other words, the herbicides select for suites of enzymes that can collectively work together to metabolize different herbicides.
“It’s not an exaggeration that we are selecting weed populations that can metabolize herbicides that have not even been commercialized yet,” Tranel says.
Even when research narrows down the genes responsible for metabolic resistance, growers still need to worry about target-site resistance. Using multiple effective sites of action and rotating herbicides using a three-to-four-year plan is essential to manage target-site resistance.
“But just doing this alone will not prevent metabolic resistance,” stresses Tranel. “Farmers need to know they cannot beat weed resistance with herbicides. Non-chemical strategies are needed to manage weeds. The overriding goal should always be no weeds going to seed.”
Will farmers reach a point where mechanical weed seed destruction technology on combines becomes mainstream, like in Australia, where they’ve dealt with metabolic
weed resistance since the 1980s? Tranel thinks it’s certainly a possibility.
“Weed seed destruction technology has a fit, but with limitations as it works better in some crops than others,” he says. “Weeds will adapt, as I can predict waterhemp will start shattering seeds before combines roll. We preach diversity in strategies, as the more things you throw at weeds, it’s harder for them to adapt.”
*This content was previously published by Corteva Agriscience.
Late-planted crops are generally more susceptible to crop disease. The reason is due to the “disease triangle.” Diseases thrive when all three pieces of the disease triangle coexist — a favorable host, the pathogen and the right environment. Planting dates won’t affect the pathogen or the environment — but later planting can affect the growth stage and susceptibility of the plant host during the time of significant disease pressure.
“In diseases that result from pathogens overwintering in residue, delayed planting allows more time for disease pressure to build up in earlier growth stages,” says Scott Pringnitz, Market Development Specialist, Corteva Agriscience. Examples of diseases that overwinter include tar spot, white mold, gray leaf spot, eye spot, frogeye leaf spot and northern corn leaf blight.
“Similarly, diseases that result from spores that don’t overwinter, such as common rust or southern rust, generally have more time to move from southern to northern climates during susceptible growth stages,” Pringnitz says.
To help customers stay ahead of crop disease, Pringnitz emphasizes the importance of staying informed and being proactive.
“There are several third-party resources and crop protection manufacturers that track environmental conditions that favor disease development. By staying informed, you can encourage customers to be scouting their fields or make fungicide applications before disease greatly impacts yield.”
Most fungicides are very effective for a two-to-three-week period. Timely applications can maximize the value of the application and reduce the need for additional applications. “Fungicides are unable to reverse crop damage or yield impact,” Pringnitz says. “If customers wait too long to apply fungicides, they simply will not see the same return on investment that a well-timed application can provide.”
When it comes to choosing a fungicide, growers should review product information for the specific diseases controlled to make sure it matches their disease pressure. For example, Corteva’s Aproach® fungicide is labeled for all of the diseases mentioned above.
No matter when your customers were able to get into the field for planting this spring, regular scouting can help set the stage for a successful corn yield come harvest.
Getting into the field on a regular basis after planting will improve the timing on important crop protection decisions. Is there a new flush of weeds that needs to be managed? Will postemergence herbicides need to be applied sooner than anticipated? Are there any nutrient deficiencies? Are there any new insect or disease pressures? All these questions can be answered and addressed with regular scouting.
Scouting should occur multiple times throughout the growing season, but there are times when it’s more critical, says Joe Bolte, Market Development Specialist, Corteva Agriscience.
With lengthy emergence periods, waterhemp and Palmer amaranth present an annual challenge — calling for a herbicide program approach that includes multiple modes of action for effective control. Bolte says, “Depending on your geography and planting date, waterhemp or Palmer amaranth may need to be controlled in every herbicide pass — not just the postemergence application.”
On the flip side, your customers in areas with heavy rainfall may not have had a chance to get their preemergence herbicides down in time. If this is the case, they may consider reallocating those preemergence herbicide dollars to create a more powerful postemergence pass.
Bolte also says that tar spot should be on everyone’s radar. Scouting the corn plant’s canopy will help determine if a fungicide application is warranted.
There are several free resources available to help customers with in-field corn scouting. “Many universities will put together scouting guides or calendars for common pests. Use these to determine when weeds, disease and insects are most likely to emerge in your geography,” Bolte says.
You also can contact your local Corteva Agriscience representative and download our Corn & Soybean Disease ID Guide and Corn Weed Scouting Checklist for more detailed information.
Corn & Soybean Disease ID Guide
Corn Weed Scouting Checklist
Disease management is necessary to protect yield potential in any crop. In corn, integrated disease management tactics include corn product selection, crop rotation, residue management, and fungicide applications. Fungal leaf blights, stalk rots, and ear rots are the major categories of diseases affecting corn. 1 Crop scouting is the backbone for all pest management programs. Corn should be monitored for evidence of diseases during each field visit. Understanding the potential timeline when specific diseases may show up in fields can help target scouting and management strategies. The following calendar can be used as a guideline for scouting corn diseases. The specific time for scouting can be affected by planting date and growing degree day accumulation (Table 1).
The first line of defense against corn diseases is tolerant corn products, especially in corn-on-corn rotations. Products are evaluated for tolerance to diseases that are common in each geography. Corn products are rated for resistance relative to known susceptible and resistant products using a 1 (best) to 9 (worst) rating system (Figures 1 and 2). Your seed representative can help with selecting a product with appropriate levels of resistance or tolerance to specific diseases.
In corn-on-corn rotations, opt for products with high yield potential, good resistance to leaf and stalk diseases, as well as good insect protection, and good emergence and seedling vigor traits. Diseases such as seedling blights, gray leaf spot (GLS), northern corn leaf blight (NCLB), many common stalk and ear rots, and in some areas Goss’s Wilt are all potentially more severe in corn-on-corn production situations.
Many common corn diseases survive on infected corn residue. Crop rotation, tillage and residue management help to naturally reduce the level of many pathogens from crop residue and the soil by decreases inoculum levels which helps reduce the risk of some disease development. Surface residues also impact the soil environment (cooler soil temperatures, higher soil moisture), which can foster disease development. While crop rotation and residue management can help reduce the potential for some corn diseases, corn diseases such as Goss’s Wilt, NCLB, tar spot and southern rust can be blown into corn fields from adjacent fields or even from long distances, depending on the disease.
Seed treatment fungicides are a critical component of an integrated disease management strategy in corn. When corn is between germination and seedling establishment, protection against fungi that cause seed decay, seedling blight, and damping-off may be needed. Seed treatment fungicides help provide protection from these issues, particularly in high residue, cold, wet and/or compacted soils, or that are excessively dry. These environmental conditions can slow germination and emergence, leaving seeds and seedlings more susceptible to attack. The fungicides available in Acceleron® BASIC Seed Applied Solutions protect against the top three seedling diseases including Fusarium, Pythium, and Rhizoctonia solani. Acceleron® ELITE Seed Applied Solutions also protects against these soil-borne diseases and also helps to reduce the infections caused by Colletotrichum graminicola. Acceleron® Seed Applied Solutions products also contain insecticides that protect against early season insect damage. These may contribute to seedling disease management by protecting against root feeding insects, which can create wounds for fungal infection.
Foliar fungicides are an important management option for fungal diseases. Plant health aspects such as photosynthetic capability, stress tolerance, standability, and grain quality can all be impacted when fungal diseases become established. A properly timed foliar fungicide application may greatly improve overall plant health and help protect yield potential. Disease development in corn around the tasseling stage of growth (VT) can result in yield loss, particularly if favorable weather conditions support continued infection of leaves around and above the ear.
Foliar diseases of corn are a concern when they develop early and progress up the plant before grain fill is complete. Some diseases to watch for include northern corn leaf blight (NCLB), gray leaf spot (GLS), Southern Rust, eyespot, tar spot, and Anthracnose leaf blight. There are several Bayer fungicides labeled for use in corn that can help manage several of the foliar fungal diseases (Figure 3). Fungicides are not effective on bacterial diseases such as Goss’s wilt.
Fungicides typically work better at preventing rather than curing disease. Specifically, GLS lesions may take up to two weeks to become visible after infection. For that reason, scouting when weather conditions favor disease development is important. Begin scouting fields for foliar disease symptoms just before tasseling and continue through the grain filling stages of growth.
Rapid grain filling occurs from R2 (blister) to late R5 (full dent). It is especially important to protect the ear leaf, and those leaves above, as corn plants enter reproductive stages of growth. Examine the ear leaf and leaves above and below the ear at several locations throughout a field. If disease is present on a majority of the leaves, a fungicide application may be necessary (Figure 4).
Harvest restrictions vary by fungicide that is being considered for use. Depending on the product applied, fungicide harvest restrictions for field corn harvested for grain vary from 7 to 45 days or the R3 (milk) growth stage. Restrictions may also vary for other types of corn (sweet, seed or popcorn, etc.), and corn for other uses such as forage or fodder. 2 Always read and follow the product label instructions.
Early scouting and correctly identifying an infection are key for determining the status, progression, and best management practices for foliar diseases.
All plant diseases require three components for an infection to occur: the pathogen must be present, the environment must be suitable for the pathogen, and a susceptible host plant must be available. Many sources can lead to a pathogen becoming present in a field. Depending on the disease, some pathogens may survive the winter on previously infected crop residue (e.g., northern corn leaf blight, tar spot) and some may be moved into northern growing areas on winds from southern locations (e.g., southern corn rust). For a suitable environment, many foliar diseases need warm, humid, and wet conditions to propagate. Fungal diseases (e.g., grey leaf spot) can infect and penetrate plant tissue without a wound. However, bacterial diseases (e.g., Goss’s wilt) can only infect and penetrate plant tissue via a wound to the plant. Finally, in terms of susceptibility, many Bayer seed products have been bred to have genetic resistances to many common plant diseases. Your seed provider can provide information on a corn hybrid’s susceptibility levels to many of the common foliar diseases.
When to Scout
Depending on the disease, field history, and the susceptibility of the corn product, scouting should start at the whorl or tasseling stage (Table 1). If a susceptible corn product is planted in an area with a history of foliar disease, that area should be scouted prior to tasseling to determine the presence and severity of the disease.
Impact on Yield and Standability
Corn foliar diseases are a concern when they develop early and progress up the plant before grain fill is complete. Disease development in corn around the tasseling stage can result in yield loss, particularly if favorable environmental conditions support the continued infection and the top 8 to 9 leaves above the ear become infected, as the photosynthetic capacity of these leaves provides at least 75% of the carbohydrates needed to complete ear fill.10 Studies conducted at Iowa State University demonstrated that when grey leaf spot and common rust were controlled using a fungicide, the incidence of stalk lodging was reduced.(11)
Anthracnose leaf blight. This disease is very common in fields that are in a continuous corn cropping system. Anthracnose leaf blight spores are spread primarily by splashing water from the crop residue onto the corn leaf. The disease develops soon after planting and continues to develop until canopy closure. Plants develop oval- or spindle-shaped lesions that are brown with very dark-brown or purple margins (Figure 1). Lesions can coalesce to create larger areas of dead tissue, and leaves may die. Spores formed on the dead tissue will look spiny under magnification, much like a sea urchin.
Northern corn leaf blight (NCLB). Typical symptoms of NCLB are large (1 to 6 inches long), cigar-shaped lesions (Figure 2). Lesions are initially grey green with a water-soaked appearance and turn tan to brown as infected tissues die. A distinct margin between the infected and healthy tissue is often apparent. Distinct dark areas of fungal sporulation develop within necrotic lesions when weather is humid. Mature NCLB symptoms can look similar to the leaf blight phase of Goss’s wilt or to drought/heat stress.
Grey leaf spot. This disease causes grey to tan, rectangular lesions on leaf, sheath, or husk tissue (Figure 3). The spots are opaque and long (up to 2 inches). Lower leaves are affected first, usually after silking. Lesions may have a grey, downy appearance on the underside of leaves where the fungus sporulates. Grey leaf spot has become more prevalent with increased use of reduced tillage and continuous corn.
Physoderma brown spot. The symptoms of this disease include very small (approximately ¼ inch in diameter), round- to oval-shaped lesions that are yellowish brown in color, occur in high numbers, and appear in broad bands across the leaves (Figure 4). In addition, dark purple to black spots occur on the midrib. The midrib lesions help distinguish this disease from other diseases such as eyespot and southern rust. The infection requires a combination of light, free water, and warm temperatures during the whorl stages, which results in the commonly seen alternating bands of infected and non-infected tissues on the plant. Symptoms may also appear on the stalk, leaf sheath, and husk.
Eyespot. This disease causes small (about 1/16 of an inch), circular, translucent lesions surrounded by yellow to purple margins that give them a halo effect (Figure 5). Lesions occur on leaves (most commonly as plants approach maturity), sheaths, and husks. The disease is favored by cool, moist weather.
Common rust. Infections begin as light-green to yellow spots on leaves and develop into circular or elongated, small (2-10 mm long), reddish-brown, raised pustules.6 Pustules rupture the leaf epidermis and contain small, cinnamon-brown, powdery spores that can become darker brown to black later in the season (Figure 6). Pustules are often found in bands or patches, indicating that infection occurred while the leaf was in the whorl. Pustules can form on the upper and lower leaf surfaces. Severely infected plants may have issues with water balance and show symptoms of moisture stress during hot, dry weather, even when soil moisture is adequate.
Southern rust. Early symptoms of southern corn rust are small, circular- to oval-shaped lesions, which are often accompanied by a light-green to yellow halo. Unlike common rust, the lesions are almost exclusively located on the upper leaf surface. Within the lesions are light-orange to cinnamon-red pustules, which are unique to this disease and key to identification (Figure 7). Southern rust pustules tend to be smaller, have a more circular shape, and are more densely packed than common rust pustules. Also, unlike common rust, the lesions can develop on tissues other than the leaves, including the stalk, husk, and leaf sheath.
Tar spot. A preliminary identification of tar spot can be done in the field, but a laboratory diagnosis is required to definitively distinguish this disease from other pathogens. Leaves with tar spot have small, raised, black, circular spots, which are called stromata (Figure 8). Stromata can be present on the healthy or dead tissue of leaf sheaths, stalks, and husks, and can be surrounded by a narrow, tan halo. The stromata are raised, bumpy, and vary in shape from small, pinhead structures to more elongated structures. Tar spot stromata can be easily confused with structures associated with other fungal diseases, such as the black pustules produced by the corn rust pathogen as it ages. Tar spot can also be easily confused with the black saprophytic organisms that grow on dead leaf tissue. However, saprophytes can be rubbed off, whereas stromata cannot.
Goss’s wilt. The leaf blight symptoms of Goss’s wilt usually appear as long, grey-green to black, water-soaked streaks extending along leaf veins. Small, dark, water-soaked flecks referred to as “freckles” often occur inside larger lesions and at the edges of lesions where symptoms are advancing. Leaf freckles are luminous when lighted from behind, such as when the sun is used as backlighting. Bacterial cells may ooze from infected leaves and dry on leaf surfaces, forming a shellac-like sheen. As lesions mature, large areas of tan to brown, dead leaf tissues become visible (Figure 9).
Bacterial leaf streak. Disease symptoms have been observed in corn as early as the V7 growth stage, in which lesions first appear on the lower leaves (Figure 10). Incidences of bacterial leaf streak are more common under continuous corn production, overhead irrigation, or rainfall during hot weather. Symptoms in the upper canopy are more common when the disease occurs after tasseling. It can be confused with grey leaf spot and common rust, so a laboratory test is often needed to confirm if an infection really is bacterial leaf streak.
(12)While fungicides can help reduce the incidence of fungal diseases, they will have no effect on the bacterial diseases that infect corn. Triazole and strobilurin fungicides are labeled for corn to help manage foliar fungal diseases. Triazole fungicides interfere with fungal membrane structure and function, and must be applied preventatively or in the early stages of infection. Following application, the active ingredients in triazole fungicides move locally into the leaves on which they were applied, but they are not necessarily transported to other leaves. Strobilurin fungicides inhibit fungal respiration and should be applied preventively or as early as possible in the disease cycle. They are absorbed into the leaf and have some upward movement in the xylem. Most triazoles and strobilurins have some residual activity based on the rate of application, coverage, and environmental conditions. Consult individual product labels for harvest interval and other restrictions for use.
In most cases, fungicides should be applied at or after tasseling. For example, a fungicide has been shown to be most effective for northern corn leaf blight and grey leaf spot when applied between two weeks prior to tasseling and two weeks after tasseling.13 Follow all individual product label instructions for proper application timing, application volume, application equipment, and environmental and harvest interval precautions.
There are many factors to consider when determining if a fungicide application is warranted. Prior to making an application, evaluate each field for the susceptibility of the corn products to the diseases, the current yield potential of each field, disease severity, and corn stage of development. Then check the weather forecast to evaluate if upcoming conditions will continue to promote disease development. Finally, consider the cost of treatment and corn price to determine if an application is likely to provide an economical return in each field.
