With so many Bt trait offerings on the market today, it can be challenging to determine which package best fits your farm. Each package contains different combinations of traits with different levels of effectiveness against specific pests. Understanding best management practices is critical to ensuring control options for years to come.

A corn rootworm (CRW) beetle infestation can decimate corn yield. They have a keen ability to adapt to control strategies, which makes vigilant scouting and management a priority. Regions with heavy continuous corn acres can harbor high CRW populations. However, rotation-resistant beetles and extended diapause beetles contribute to increased populations, even with a rotation in place. With careful monitoring, a timely insecticide application can manage CRW pressure and mitigate damage the following year.

Traditionally a problem disease in the western Corn Belt, Goss’s wilt is now prevalent across the Corn Belt and spreading into Canada. Once corn plants are infected, yield potential can be reduced by up to 50 percent. There are no effective chemical control measures for Goss’s wilt. The best way to limit spread of the disease is by selecting hybrids with strong Goss’s wilt tolerance.

This bulletin provides information about Goss’s wilt and tolerance ratings for Mycogen® brand corn hybrid families. The ratings are the result of 2011-14 field trials conducted in Illinois, Iowa, Minnesota, Nebraska, South Dakota and Wyoming.


DISEASE INFORMATION
Goss’s wilt is caused by the bacterium Clavibacter michiganensis subsp. nebraskensis. It overwinters in infected corn residue, primarily found on or near the soil surface. Inoculum in the infected residue primarily spreads by wind and splashing rain. To a minor degree, Goss’s wilt also can survive in seed.

To infect a corn plant, the bacterium needs an entry point or wound, which is generally caused by heavy rain storms, hail, wind, blowing sand or mechanical damage. Humid, wet weather is another risk factor because moist or wet leaves are conducive to the spread of disease.


IDENTIFYING GOSS’S WILT
Scouting is important because infection can occur at any point during the growing season. Infested seedlings show systemic wilting, stunting and a variety of leaf symptoms.

More-mature plants demonstrate the foliar leaf blight version of the disease. The first signs of infection are dark green to black, oblong spots that are water-soaked with a greasy look that appear parallel to leaf veins. Streaks of freckles within the lesions are a distinctive feature of Goss’s wilt. Droplets of bacterial exudate ooze from the freckles, leaving a crystalline substance that glistens in direct sunlight. The spots coalesce as they enlarge, forming long lesions with wavy edges. As the lesions age, they turn tan and can blight much of the leaf. Systematically infected plants have discolored (orange) vascular tissue and likely slimy stalk rot.

Key Symptoms:
• Freckles in lesions
• Crystalline deposits
• Droplets of exudate

Commonly confused with:
• Drought damage
• Heat stress or sun scalding
• Other leaf blights


CONTROLLING GOSS'S WILT
Because Goss’s wilt is a bacterial disease, it cannot be treated with fungicides. The best method of control is planting hybrids with strong Goss’s wilt tolerance. Tables 1 through 4 demonstrate the wide range of tolerance in hybrids.

Growers can limit the spread of Goss’s wilt to uninfected fields by selecting tolerant hybrids, harvesting infected fields last and thoroughly cleaning harvest equipment. Destroying infected crop residue will lower the amount of bacteria present. This is most effective when done immediately after harvest. In most situations, rotating to a nonhost crop, such as soybeans, dry beans, sugarbeets or alfalfa, is a more viable option. Last, manage irrigation to reduce humidity in the field during the growing season.

Talk to your Mycogen Seeds sales representative or customer agronomist to learn more about managing Goss’s wilt on your corn acres.

Between the V3 and V5 growth stages, corn transitions from deriving energy directly from the seed to acquiring energy from sunlight through photosynthesis. Visual appearances during these stages offer clues to overall plant health.

Stand establishment depends not only on the success or failure of germination but also on early season stresses. If you notice early stand problems, carefully examine damaged seedlings to discover clues to the likely causes.

Northern corn rootworm (NCRW) is one of the most damaging corn pests in North America. Because the NCRW typically has a one-year life cycle, rotating corn with another crop has been a successful management strategy. Unfortunately, some populations of NCRW have successfully adapted to a corn soybean rotation and now have a two-year life cycle. This is called extended diapause because the eggs remain dormant in the soil for almost two years before hatching.

Nitrogen (N) can be lost from the soil between application and crop uptake. By managing applications, you can maximize yield by making sure N is available when corn plants need it most.

Like a house with a poorly prepared foundation, corn plants with rootless corn syndrome (or floppy corn syndrome) between the V3 and V8 growth stage can topple at any moment, leading to stunted growth and even plant death. What causes this phenomenon and how can plants survive?

Flooding affects fields differently based on a variety of factors. Manage flooded corn to minimize damage and ensure optimum plant health and yields.

Palmer amaranth is a resilient weed with increasing herbicide resistance and territorial expansion that could harm your crops. Through identification and precaution, you can maintain your plant health and yield potentials.

Corn rootworm is one of the most damaging pests in the Corn Belt. Don't let corn rootworm rob your yields. Scout for the pest by digging for larvae. Jeff Housman, Mycogen Seeds customer agronomist, walks through how to do root digs to find corn rootworm to evaluate the damage in your fields.

Corn aphids are becoming a common pest for corn growers, as populations can develop in massive numbers. Aphids are problematic during tasseling and can colonize corn later in the summer, with populations building to striking levels, threatening yield potential.

A high rate of black cutworm (BCW) moth catches, green fields and late planting dates are the perfect recipe for significant damage from black cutworm. Damage can range from very little to almost 100 percent stand loss. To give late-planted corn the best yield potential, make controlling this pest a high priority.

In areas of the Corn Belt, frost and variable soil temperatures can place corn under significant stress after planting.

Slug damage in corn and soybeans has increased with the adoption of no-till and minimum-till practices. Because rescue treatment options are limited, growers should take steps to prevent slug damage.

Increased use of reduced tillage and no-till production practices has increased gray leaf spot occurrence. Caused by a fungus, the disease leads to leaf tissue loss, resulting in a decrease in plant sugars and decreased grain production. Potential yield losses range from 5 percent to 40 percent.

Crop harvest removes valuable nutrients from the soil. Understanding the amount of nutrients removed is crucial to understanding how to fertilize for the highest yield potential next season. With high input costs, it can be tempting to skimp on nutrients to save cost. Over time, however, this approach can reduce yield potential and profitability.

Southern rust is a common threat to corn crops across the southern United States. The disease damages crops in the Corn Belt only about once every five years, but when it does yields may be cut by more than 40 percent.

Glyphosate-tolerant corn and soybean systems have become commonplace. But more than a decade after the introduction of glyphosate-tolerant crops, weed control has again become a major problem in nearly every crop-producing state. Many weeds have become more difficult to control and herbicide application rates have spiked. Learn to effectively balance your management approach.

Corn nematodes are plant parasites that exist in every field to some degree. Yield loss varies by nematode species and their populations. Collecting and submitting samples for plant parasitic nematode analysis is the only way to evaluate your exposure.

When low temperatures or frost injure young corn plants, you may wonder if these plants will recover. Carefully weigh your options and don’t make any quick replanting decisions. The key to assessing corn seedling viability is to find and observe the growing point.