Corn Disease Publication Now Available

Corn producers and other professionals in the agriculture industry depend on the Iowa State University Extension publication Corn Diseases, PM 596. It is always in high demand, and after a revision, is back on the shelf to be ordered from the Extension online store

Assess Seedling Health When Doing Stand Counts

Corn planting is virtually done, and across Iowa small green spikes are becoming visible as seed germinates. Now is the time to start assessing stands. Doing stand counts involves more than just counting the number of seedlings that have emerged. Seedling health should also be assessed. ISU Extension field agronomists Virgil Schmitt and Mark Carlton have reported that seedling rots are prevalent in southeast Iowa

Anthracnose Leaf Blight, Common Rust, Gray Leaf Spot and Goss’s Wilt Found in Iowa

I have had a few emails, tweets and phone calls from folks who are starting to find disease in corn in Iowa. It is very common to find anthracnose leaf blight on the lower leaves of young corn plants, particularly in corn-on-corn fields. If you know the disease cycle of this pathogen, this should be no surprise given all the spring rain we have had. Colletotrichum graminicola survives in surface corn residue. In moist conditions in the spring, it produces spores on the residue that are splash-dispersed onto these lower leaves. Infection and colonization of the leaf tissue occurs, and we see the dark irregular-shaped lesions on the bottom four to five leaves. Once canopy closure occurs, it is rare to see anthracnose leaf blight and, because it occurs so early in the growth of the plant, it does not affect yield. Furthermore, data from both Iowa and Wisconsin found no relationship between the incidence of anthracnose leaf blight and anthracnose stalk rot

Nineteen Species of Pythium Associated with Damped-off Soybean Seedlings in Iowa

During the 2011 growing season, extension soybean pathologists from the north central states conducted a seedling disease survey to identify oomycete pathogens that cause damping-off in soybean. The survey is part of a larger project that is being funded by USDA NIFA

Earn CEUs and Improve Your Knowledge of Phytophthora and Pythium

Oomycetes are some of the most devastating plant pathogens. Some of you may have family who settled in the United States as a result of the Irish Potato Famine in which over one million people died, while another one million emigrated. The pathogen that devastated Ireland\u27s potato crop in the mid-1800s is an oomycete calledPhytophthora infestans. Some oomycetes that are likely more familiar to us here in Iowa are Phytophththora sojae and Pythium species. These pathogens are usually associated with seedling blights on corn and soybean, although P. sojae can affect soybeans throughout the growing season. Some of you may have experienced devastating losses to these pathogens in your corn or soybean field

Towards a Successful Harvest: Stalk Rots and Standability Issues

It’s hard to believe the 2010 growing season is almost over. Most of the corn across the state is nearing or at black-layer, which means it is time to scout fields for stalk rots in an effort to evaluate standability and plan a successful harvest. Stalk rots are likely to be an issue this growing season. We have seen significant blighting of the leaves in the upper canopy predominantly from Goss’s wilt, northern corn leaf blight, gray leaf spot and anthracnose top dieback. When significant leaf blight occurs in the upper canopy, the risk of stalk rots increases. Furthermore, overcast conditions, such as we had throughout most of the grain filling period, favor stalk rot development. Since stalk rots reduce standability, fields in which greater than ten percent of plants are affected by stalk rots, should be scheduled for an early harvest

Survey of Corn Disease Management Practices

Within the next week, some of you may receive a survey from the University of Wisconsin-Madison in the mail. This survey is targeted at certified crop advisors (CCAs) in Iowa, Illinois, Wisconsin and Ohio. A similar survey will be sent to corn growers in each state in a few weeks. Extension field crop specialists, Alison Robertson (ISU), Carl Bradley (UWI), Pierce Paul (OSU) and Paul Esker (UW) have received funding from the USDA- National Institute of Food and Agriculture, Risk Avoidance and Mitigation Program to conduct this survey. We hope to understand the risks corn growers face, and the tools crop advisors recommend growers use to improve yields. The information gathered from the survey will be used to develop educational materials and tools for corn growers and crop advisors to better manage corn diseases

Corn seedling health and stand establishment

With all of the corn planted and most of the soybean, now is the time to start evaluating plant stands. Corn germination and emergence were prolonged by cooler than normal temperatures that occurred during planting. Cool soil conditions (\u3c50–55 °F) also predispose seedlings to infection by a number of fungi that cause seedling disease, and can result in seedling death. Therefore, as you start to assess plant stands, it is important to dig up seedlings every now and then to check general root health. Uneven emergence and stunted seedlings may indicate seedling disease but also can be due to insect feeding and herbicide damage

Remember to scout for corn stalk rots

Stalk rot occurs to some extent in every cornfield in Iowa each year because as corn stalks mature, they naturally decay. However, stalk rot can occur prior to physiological maturity and is considered a disease problem, which reduces yields in two ways. First, affected plants die prematurely (Fig. 1) and therefore produce lightweight ears with poorly filled kernels. Second, and this is more common, plants with stalk rot easily lodge (Fig. 2), which makes harvesting difficult, and many ears are left in the field

Time to Scout for Stalk and Ear Rots

When corn reaches black layer, the crop should be scouted for stalk and ear rots. Anthracnose stalk rot is apparent in many fields across the state andDiplodia ear rot has been reported. The incidence of corn ear rot should be determined before harvest since ear rot diseases can reduce yield and quality of the corn harvest. Furthermore, some of the fungi that infect corn ears may produce mycotoxins, which are harmful, and can be fatal, to livestock