With the flooded or merely water-logged fields of the Corn Belt finally drying out and farmers salvaging what remains of their crops or replanting them, the struggle is far from over, says Troy Bettner, senior marketing manager, Makhteshim Agan of North America. The disease pressure this year is likely to be intense in many areas. Even if seed was protected, the pathogen-laden environment seedlings have emerged into is likely to be very hostile as the season progresses.



This much early-season moisture, along with the high humidity and heat of summer, will set up ideal conditions for some of the worst diseases those crops will need to withstand. Farmers will have to scout early and often, and many will need fungicides to keep crops from succumbing to disease.



Growers will want to harvest as much grain as possible to take advantage of these favorable market prices if they are to recover from a very difficult year. Yet, it is just this kind of year when the stewardship of those fungicides takes on added urgency. With so many pathogens on crop residues and debris, in weeds, and riding the winds, the risk of resistance is magnified.



What diseases to expect? Plant pathologists have suggested looking back to 1993, the last time so much of the Midwest was under this type of flooding conditions. In corn, rusts and crazy top, which is caused by a class of downy mildew fungus, were common. This time, dry conditions across much of the South may make Southern Corn Rust less a concern.



In soybeans, there was extensive brown stem rot in 1993, along with brown spot, and SDS. Delayed planting may make soybean white mold less a concern, though it has been prevalent in every even-year for the past decade.



Other diseases likely to be a problem this year include frogeye leafspot in soybeans and bacterial stalk rot and common smut fungus in corn. Anthracnose leaf blight already has been seen in corn in some areas. The virulence of any of these may be stronger than we have seen in recent years.



Scouting is paramount. Similarly important are the rotation of fungicides with different modes of action and the use of full rates of those products. These are three major elements of an Integrated Pest Management plan combining both disease control and resistance management.

In recent and more typical growing seasons, some producers have experimented with the use of fungicides primarily to ensure healthier plant growth and increase yield. Some have found the practice pays off, especially in bullish commodity markets. Other producers have not seen sufficient yield increase to offset the cost of product, fuel, equipment wear and tear, and time involved in the applications.



Generally, Cooperative Extension agronomists are sticking by their IPM programs. These specify that any pesticide should be used only to manage a specific pest problem, as indicated by scouting and generally accepted thresholds of pest prevalence. Full rates should be used and label instructions followed. Shaving rates and/or applying purely preventive treatments can breed resistance and shorten the effective life of much needed active ingredients. This is especially true of fungicides because pathogens can flourish if they escape or have mutated in the presence of either under- or over-used fungicides.



This is a year when producers may be under severe time and weather-related pressures, and when diseases may pop up suddenly and virulently. Field conditions and market rewards may make pre-emptive use of fungicides just about irresistible. Nonetheless, growers must be good stewards of fungicide products. Take the time for proper, systematic scouting to identify specific diseases and to determine whether they have reached threshold levels. This will pay off regardless of whether the fungicide application is justified and saves the crop, or whether it is not justified and saves the expense.



In any scenario, rotating chemicals and utilizing multiple chemistries is another responsible step. There are a number of products available that are designed to treat just about every disease problem that could possibly find its way into a field. But not all of these fungicides work in the same way, and some are more prone to create resistance issues within their target. This is a problem that growers need to consider.



Resistance can develop quickly. Recent studies have indicated that some fungi are demonstrating strong signs of resistance toward strobilurin fungicides. Strobilurins were introduced in 1997 and were widely adopted in many parts of the world. Since then, certain strains of fungi have adapted to their mode-of-action. Septoria is one such disease, causing brown blotches and various kinds of common leaf blight on corn, wheat and other crops throughout Europe. Independent studies from France and the United Kingdom have shown that up to 80 percent of Septoria samples from 2004 demonstrated strong strobilurin resistance, a striking increase from 39 percent in 2003. While this is a problem currently facing European growers, similar pathogens on this side of the Atlantic may be prone to develop resistance in a similar manner.



One way to manage potential strobilurin resistance is to use a fungicide with an alternate mode of action, such as a triazole, as the base treatment of a fungicide application program. It's the best resistance management strategy so far. Another aspect of triazoles that will be especially significant this year is that they have preventive as well as curative activity, to stop the spread of disease to uninfected plants.



Triazoles are used for largely the same purposes as strobilurins, but have consistently demonstrated low to moderate potential for resistance development. Over the past 20 years, triazole resistance has developed in a number of crops including apples, peanuts, sugar beets, pecans, grapes and turf. Even in those situations, research has shown that triazoles can still be used effectively in a management program in combination or rotation with other fungicide classes.



MANA offers premier triazole chemistry in Bumper fungicide, a product proven to be an effective tool against a broad spectrum of fungi. Bumper, with the same active as Tilt and Orbit, is part of a chemical family that provides growers with more flexibility than the most common strobilurins. In some crops, Bumper also combats a broader spectrum of diseases. Economical as well as efficacious, Bumper costs less than $10 per acre.



It is impossible to forecast what challenges and conditions this season will bring, but adhering to a recommended IPM program is the best way to manage both disease and potential resistance issues while protecting very valuable, much needed crops.