One new one, though, is Physoderma brown spot. The good news is that after this spring’s prolific rainfall, dry weather curbed disease development. Corn is vulnerable to the following infections by plant pathogens throughout the growing season under favorable environmental conditions: seed rots and seedling blights soon after planting, foliar diseases in mid-season, and stalk and ear rots toward the end of the growing season. Thus, there is an increased risk of some of these diseases in corn-following-corn fields. Corn farmers wrestled with old and new corn diseases in 2019 that likely will again be present in 2020. There, it’s called tar spot complex because a secondary fungus, Monographella maydis, is often associated with the lesions, says Dean Malvick, a University of Minnesota Extension plant pathologist. Common ear rots in Iowa include Fusarium ear rot, Gibberella ear rot, and Diplodia ear rot when normal to above normal rainfall seasons occur from silking to harvest and Aspergillus ear rot when hot, dry conditions occur over the same period. Remember, preventing corn diseases in the garden is very important, since the rapid growth of sweet corn makes it very difficult to spray adequately with chemicals. Its spores (the microscopic biological particles through which fungi are reproduced) can survive for several years in the soil and in corn debris. The pathogen is not seed transmitted, but it can survive on corn residue. Warm humid weather favors infection by the fungus, Exserohilum turcicum, which causes this disease. Fungal diseases are often caused by fungi that are common in the environment. Apart from the rusts, which are windblown from the South each growing season, the fungi that cause these diseases survive in infested corn residues left on the soil surface. Northern Corn Leaf Spot. phaseoli (beans) Aschochyta collar rot (peas) Gummy stem blight – Didymella bryoniae (cucurbits) Alternaria leaf spot – Alternaria cucumerina and A. alternata (cucurbits) Black leg – Leptosphaeria maculans (brassicas) Copyright © 2020 Iowa State University of Science and Technology. Colletotrichum graminicolacauses several anthracnose diseases of corn including stalk rot, top dieback, and foliar and seedling diseases. Root Rots. Crops are hosts to numerous plant pathogenic microorganisms. Damage caused by weather conditions, such as hail, and insect feeding also opens the corn up to fungal infections. As mentioned before, these fungi survive in crop residue on the soil surface and also in the soil, and their populations will be higher in corn-on-corn fields. If environmental conditions are favorable next year, the pathogen will more easily move from the crop residue to the next crop of corn. It’s physically impossible to assess every acre of corn for stalk breakage potential. Thus, the risk of increased disease severity is higher when corn follows corn. Dr. Robertson receiv... ISU Extension and Outreach Disease emergence is favored in areas where a corn crop is followed by more corn with no rotastion; severity and incidence of disease is likely die to continuous corn culture with minimum tillage and the use of susceptible hybrids in in the midwestern corn belt of the USA; prolonged periods of foggy or cloudy weather can cause … Corn smut is caused by a fungus called Ustilago zeae, which is commonly blown on the wind from an infected stand to an uninfected stand of corn. Southern Corn Leaf Blight is a devastating fungal disease that attacks your corn crop and spreads quickly. Frequently found in backyard gardens and small farms, corn smut is caused by the fungus Ustilago zeae and can appear in the stalks, leaves, tassels or ears. If that happens, it’s more important than ever to target diseases in fields ready for harvest first. If these fields have spindly stalks, target those areas for harvest first, he says. Corn farmers wrestled with old and new corn diseases in 2019 that likely will again be present in 2020. The fungal pathogens that cause these diseases survive on residue, so fields under minimum tillage and corn-on-corn rotations are at greatest risk. Information is provided 'as is' and solely for informational purposes, not for trading purposes or advice. Spores are spread long distance by wind and locally by rain splashing from crop debris in soil onto host plants. Stewart's Disease. The primary means of control of the most important diseases is through the use of genetic resistance. Compared to NCLB, it develops at warmer temperatures, between 68 to 90o F, and under damp conditions. This fungus also causes Northern corn leaf blight. One new one, though, is Physoderma brown spot. Corn hybrids vary in their resistance to Gib ear rot. Lesions develop and produce more spores that are spread to and infect the upper leaves. Prevent damage from insects, such as corn borers, with Monterey® Garden Insect Spray or other organic insecticide. Progress 04/12/01 to 07/23/04 Outputs (N/A) Impacts (N/A) Publications. Stewart's disease of corn is common throughout the eastern United States. Nodal infection from this disease can cause stalk rot to occur. Cool (<55 °F), wet soils favor the development of seedling diseases. These diseases can increase lignin … Fungal Leaf Disease Showing Up in Corn; June 30, 2000: Despite some earlier problems with dry conditions, that's certainly not the case now, especially in the northwestern part of the state where several fungal diseases are … phaseoli (beans) Aschochyta collar rot (peas) Gummy stem blight – Didymella bryoniae (cucurbits) Alternaria leaf spot – Alternaria cucumerina and A. alternata (cucurbits) Black leg – … Weather conditions during the growing season will still significantly impact disease severity. Apart from the rusts, which are windblown from the South each growing season, the fungi that cause these diseases survive in infested corn residues left on the soil surface. These included the usual suspects, such as gray leaf spot. None; Progress 10/01/02 to 09/30/03 Outputs 1. corn and is one of the few stalk rot pathogens that frequently causes disease prior to senescence. Seed Decay and Seedling Blight. Foliar fungal diseases of primary concern in Michigan are northern corn leaf blight and gray leaf spot. Economic losses caused by fungal diseases of corn can be reduced with the use of disease resistant hybrids. Although several of the seedling pathogens can attack both corn and soybean, there are others that are specific to corn and their populations will increase under continuous corn. Anticipated disease problems that might occur in corn-on-corn fields in Iowa include the following. ), but... read more. For more information about corn head smut, as well as options for treating corn head smut in … Northern Corn Leaf Blight. The disease is also present in central America. Dari . Gray leaf spot is the number one disease in all corn production. One new one, though, is Physoderma brown spot. Symptoms of this fungal disease include numerous lesions that appear on midcanopy leaves. Symptoms of this fungal disease include numerous lesions that appear on midcanopy leaves. Disease management in corn-following-corn fields. All rights reserved. In 2012, fungal disease caused a 10 percent loss in corn yield, and 24.4 percent of grain harvested was infected with mycotoxins. Typically, common rust on corn does not appear until later in the growing season, but this year it is already in many cornfields in Illinois. 4 Virus and virus-like diseases. Corn Ear Rot Diseases. Timing is critical, as an effective fungicide should be applied soon after tassel emergence or at the first sign of disease. 2150 Beardshear Hall On infected corn, pustules are located on leaf surfaces or leaf sheaths. Fungicides can give good control, but timing is crucial. It is characterized by tan streaks or lesions on the leaves, and may cause early seedling death, mold-covered kernels or rotten cobs. Rust spores can be rubbed off of the leaves and leave a brown or orange stain on … Seed treatments will continue to be necessary to ensure a healthy stand. However, wet weather has caused some diseases to pick up. Most fungi are not dangerous, but some types can be … Check with your local seed dealer to find out more PRO TIP: Foliar diseases that are not fungal pathogens, but sometimes get confused as fungal disease… Reduce infection points by avoiding injury of roots, stalks and leaves during cultivation. List of maize diseases. Most of these pathogens are specific to corn and their populations in the residue and soil will build up under continuous corn. Common rust is caused by the rust fungus Puccinia sorghi. Foliar Fungal Diseases. For related content and insights from industry experts, sign up for Successful Farming newsletters. Other fungal diseases of vegetables include: Target spot – Alternaria solani (tomatoes) Aphanomyces root rot – Aphanomyces euteiches pv. “Once a field has white mold, it lingers for a long time. Disease Facts Eyespot, caused by the fungus Kabatiella zeae, is common and can be found across New York State.. Eyespot is favored by cool, wet weather. Fungus: Ustilago maydis. This makes stalks prone to breakage as the season progresses, says Myers. Plant diseases that are caused by fungi reduce the crops, create markings, affect the flowers and fruits, finally causing death of the plant. Infections can also occur through wounds on stalks and leaves. She provides extension education on the diagnosis and management of corn and soybean diseases. It is edible, and is known in Mexico as the delicacy huitlacoche; which is eaten, usually as a filling, in quesadillas and other tortilla-based foods, and in soups. cause seed rots and seedling blights in corn. Remove corn plant debris after harvest to reduce diseases caused by rusts and corn smut. Symptoms of this fungal disease include numerous lesions that appear on midcanopy leaves. They have several pathways to stalk infection, including the root systems. Southern Corn Leaf Blight. READ MORE: 20 Strategies That Farmers Can Use In 2020, I realized that my farm’s service truck had all the tooling my shop had (a welder, torch, fuel supply, air, chop saws, grinders, etc. Myers says a Bayer field trial check in late August indicated no or little signs of southern rust. The fungus survives the winter on residue from the prior corn crop, ... Northern corn leaf blight. You can’t fix the damage that is done.”. They survive in crop residue and the soil. Mycetoma. 1 Consequently, SCLB typically is a common disease of fall crops of sweet corn in Georgia and Florida. “Some diseases like southern rust appeared early, but dryness inhibited development,” says Randy Myers, Bayer Crop Science fungicide product development manager. Bacterial Leaf Streak (Figure 1) of corn (Zea mays) was first reported in Nebraska in 2016, also the first time the disease had been reported in the United States.Since then, it has been confirmed in eight more states: Colorado, Illinois, Iowa, Kansas, Minnesota, Oklahoma, South Dakota, and Texas. What can be done, though, is to assess field areas that have experienced stalk breakage in previous years, says Myers. The spores are spread in different ways—by wind, splashing water (rain or irrigation), or manure of animals that have eaten corn with the fungus. Common rust. The fungal pathogens that cause these diseases survive on residue, so fields under minimum tillage and corn-on-corn rotations are at greatest risk. Spores from both of these pathogens can either be splashed up onto foliage or deposited by the wind. Pathogen/Disease description: The fungus infects corn ears through the silks and produces swollen light green growths that later turn white and break open to revel black masses of spores when mature. Often associated with other leaf or ear diseases, premature plant death due to frost and stalk rot. Some varieties tolerate white mold better than others, but there is no true resistance, says Myers. Corn smut is caused by a fungus, Ustilago maydis. However, many other diseases may pile on top of it to cause severe losses, Malvick says. The fact that white mold can persist in soils for years also nixes crop rotation as a control measure. The most common foliar diseases of corn in Iowa include anthracnose leaf blight, gray leaf spot, northern leaf blight, common and southern rust, and eyespot. It is also the only corn stalk rot disease with a foliar phase. This is a potentially yield-limiting disease that arrived initially in the US in 2015 and made headlines during the 2018 growing season when there was widespread economic impact in the Midwestern states. Symptoms can occur as early on corn as V-3, although symptoms can surface at any stage. The disease shows up as light brown elongated spots with a darker brown border. Top dieback in corn: Is anthracnose the cause? Research has shown that disease severity is directly associated with the amount of surface residue. Tar spot, a fungal leaf disease of corn, was discovered last week for the first time in Pennsylvania in Lancaster County. Managing the disease To prevent future Gib ear rot outbreaks, tillage following a corn rotation is encouraged. Dr. Alison Robertson is an associate professor of plant pathology and microbiology. Northern corn leaf blight can be identified by the distinctive lesions that form on the leav… Northern corn leaf blight (NCLB) has been confirmed in several fields in eastern Nebraska. On the soybean side, white mold again reared its ugly head, particularly in the Upper Midwestern states of Minnesota, Wisconsin, North Dakota, and South Dakota. Additionally, leaf diseases are often accompanied by stalk rot; therefore, it also will be important to monitor stalk quality and opt for a timely harvest if leaf diseases occur. Anthracnose Leaf Blight Anthracnose Stalk Rot Bacterial Stalk Rot Charcoal Rot Common Rust Common Smut ... Plant Diseases. The spores can live up to three years, making it very hard to completely destroy. Bacterial diseases. Blue-eye damage is caused by species of Penicillium and is characterized by a blue-green discoloration in the germ area. 5 References. Symptoms are most commonly noticed when the ears produce mushroom-like tumors or galls. Risk of aflatoxin contamination increases with hot and dry growing conditions. Huitlacoche, pronounced weet-la-COH-cheh , is a fungus that grows on ears of corn. Foliar fungal diseases of primary concern in Michigan are northern corn leaf blight and gray leaf spot. Under moist conditions, the fungi produce spores that are either rainsplashed or blown by the wind onto susceptible corn leaves and infection occurs. Thus, corn-on-corn fields, in particular those with crop residues left on the surface, will be more prone to seedling diseases due to higher inoculum pressure and cooler, wetter soils. Look! The principal research activities in the lab focus on northern leaf blight of corn, caused by Setosphaeria turcica , and gray leaf spot of corn… Fungal diseases. Anthracnose stalk rot Colletotrichum graminicola. Fungal Wheat Diseases – short descriptions and images Leaf Blotch (Septoria tritici) Conditions for disease development include temperatures between 59 to 77 °F and periods of rainy or humid weather that last for more than 1 day. What major problem or issue is being resolved and how are you resolving it? It is also the only corn stalk rot disease with a foliar phase. © 2020 Meredith Corporation. It is also known as cuitlacoche, corn smut, and Mexican truffle. Usually, corn ear rot diseases are fostered by cool, wet conditions during silking and early development when the ears are susceptible to infection. 6) . When soil temperatures are below 55 °F, germination and emergence are greatly retarded. Corn stunt (achapparramiento, maize stunt, Mesa Central or Rio Grande maize stunt) Spiroplasma kunkelii. More information on how to grow corn is available in the fact sheet HGIC 1308, Sweet Corn. Remember, when disease symptoms are noticed it is usually to late to spray a fungicide. Nematodes, Parasitic. Futures: at least 10 minute delayed. The fungal pathogens in corn that cause ear rot diseases can survive in the crop residue. Tar spot, a fungal leaf disease of corn, was discovered last week for the first time in Pennsylvania — in Lancaster County — reports Extension plant pathologist Alyssa Collins. Like most other diseases caused by pathogens in plant residue, lesions may … Originally written February 1, 2006 | Last updated February 23, 2014. These included the usual suspects, such as gray leaf spot. Corn Leaf Diseases. In Latin America, severe tar spot has been shown to reduce corn yields by more than 40 bushels per acre by increasing stalk rot and lodging. Several days later, it scattered all over the field. Typical symptoms include a dark green fungal growth on and between … Foliar disease impacts corn plants at a different rate every season, but understanding which pathogens we can suppress with tillage this fall and which ones overwinter in your area will greatly help you prepare for 2020. It is a bacterial disease, caused by the bacterium Erwinia stewartii (E. F. Gray leaf spot disease severity is directly associated with the amount of surface residue. These included the usual suspects, such as gray leaf spot. Fungus -Trichoderma viride. Common stalk rots in Iowa include anthracnose stalk rot, Fusarium stalk rot, Gibberella stalk rot, Diplodia stalk rot, and charcoal rot. The download package contains the video in mp4 format and nine language versions (English, Chinese, French, German, Hungarian, Polish, Portuguese, Russian, and Spanish). Economic losses caused by fungal diseases of corn can be reduced with the use of disease resistant hybrids. Southern corn leaf blight ... corn diseases, it is recommended that suspicious samples be sent to the Arkansas Plant Health Clinic in Fayetteville for proper identification. Like other smut diseases, common smut of corn derives its name from the sooty masses of teliospores found on infected host plants (Figure 2). Although high levels of resistance to some of the important diseases may be found hybrids are rarely highly resistant to all diseases. Thus, accurate identification and an awareness of potential disease losses are essential ... Foliar Fungal Diseases. Many bacterial, fungal and viral diseases attack vegetable crops in Maryland home gardens. Page last reviewed: May 6, 2019. More common when rainfall is above average the month preceding harvest. State & National Extension Partners. Tags: Corn diseases ISU Extension and Outreach 2150 Beardshear Hall Ames, IA 50011-2031 (800) 262-3804. MAIZE DISEASES I. Fungal diseases; Anthracnose leaf blight. The fungal disease causes lesions that lead to yellowing leaf tissue and reduced photosynthetic activity, causing shortened yield potential through smaller ears with fewer kernels. So the first line of defense has to be fungicides,” he says. Pythium Stalk Rot. Most of these are not serious and in very few cases is spraying a fungicide recommended. Within the lesion, there are often noticeable black conidia formed by sporu-lation of the fungus giving the lesion an ashy gray to dark olive appearance. Southern Rust. While the genetic basis of resistance to multiple fungal pathogens has been studied in maize, less is known about the relationship between fungal and bacterial resistance. Fungi live outdoors in soil and on plants and trees as well as on many indoor surfaces and on human skin. Physoderma Brown Spot. Infected corn stalks fall over (called lodging) and losses result from unharvested ears and poor ear … Because senescing flower petals are the medium for infection, treat when the first flowers develop and before canopy closure, he says. Southern rust. This means that in corn-on-corn fields, inoculum pressure will be considerably greater, especially in those fields where foliar diseases were a problem the previous season. Numerous fungal species in several genera (Fusarium spp., Rhizoctonia spp., Pythium spp., Diplodia spp., Penicillium spp., Trichoderma spp.) Corn farmers wrestled with old and new corn diseases in 2019 that likely will again be present in 2020. The disease is most readily identified by large cigar-shaped lesions on the leaf with reddish or purple margins (Fig. Sm.) ... Mats of white fungal growth of Diplodia maydis may be evident on affected tissues. Many of these diseases are caused by pathogens that survive in crop residue or in the soil. Other fungal diseases of vegetables include: Target spot – Alternaria solani (tomatoes) Aphanomyces root rot – Aphanomyces euteiches pv. Glomerella graminicola [teleomorph] Glomerella tucumanensis a disease), rapid development, spreading … Small, elongated (0.25 to 0.75-inch long), parallel-sided lesions that are tan with brownish borders are typical, although symptoms vary considerably on different corn products, often requiring microscopic examination of the fungal structures to confirm diagnoses. 1 Bacterial diseases. Corn Ear Rot Diseases. If disease is a problem on more than 10 percent of the ears, timely harvest, quick dry down to 15 percent moisture or less, and cooling the temperature of the grain will be crucial to maintain quality. It is a plant disease that causes smut –multicellular fungi with many spores – to grow on maize and is a delicacy in Mexico. They are caused by various species of fungi, including Diplodia zeae, Fusarium species, and Colletotrichum graminicola. Tar spot, a relatively new corn disease, started out slowly in 2019, but picked up steam in some areas in 2019. Nematodes. Corn germinates and emerges quickly at soil temperatures above 68 °F. Head smut of corn is caused by the fungus Sphacelotheca reiliana (syn. Ear galls can grow to 4- to 5-inches in diameter and release thousands o… Corn is vulnerable to the following infections by plant pathogens throughout the growing season under favorable environmental conditions: seed rots and seedling blights soon after planting, foliar diseases in mid-season, and stalk and ear rots toward the end of the growing season. Caused by the fungus Sporothrix, which lives throughout the world in soil and on plants. The most common foliar diseases of corn in Iowa include anthracnose leaf blight, gray leaf spot, northern leaf blight, common and southern rust, and eyespot. Majority of the plant diseases, about 8,000, are caused by fungi. The following corn ear rot info delves into these concerns. Although the effects of tillage on stalk rots are complex, the presence of corn residue in the field increases the risk of some of the stalk rots; additionally, the likelihood of an extended harvest because of increased corn acreage increases the risk of stalk rot developing. The fungus affects every part of the corn and causes the kernels to swell up into mushroom-like growths called galls. Scouting for foliar diseases will be critical in corn-on-corn fields to ensure that fungicide applications are applied in a timely manner, and the ear leaf and leaves above the ear are protected from infection and extensive blight development during grain fill. fungal disease of corn: corn smut (about a disease) affecting many people at once; widespread, very common: epidemical (about a disease) affecting many people at once; widespread, very common, fast-spreading disease, outbreak, plague, something which spreads quickly (i.e. Foliar disease management. A similar disease, northern corn leaf blight, results in grayish green or tan lesions on the leaves and reduced yields. This year, it could be found everywhere around the Midwest, but it did not progress as rapidly due to dry conditions.”. Many of these diseases are caused by … Any stressful conditions that reduce photosynthesis and the production of carbohydrates during grain fill predispose corn plants to stalk rots. Sporisorium holci-sorghi) and occurs in some fields in Nebraska. Maize has several major disease issues; thus, breeding multiple disease resistant (MDR) varieties is critical. Like many foliar Corn smut and wheat rust are crop diseases caused by _____ fungi. This article reports on distribution, incidence, and prevalence of various fungal diseases and points out gaps in knowledge where s … Infected stalks often have shiny, Gray leaf spot. Diplodia also produces fruiting bodies which may be seen as small black specks embedded in the white fungal mat. 3 Nematodes, Parasitic. Contents. Bacterial leaf streak ( Figures 1-4) is common in many parts of Nebraska … Since 1970, anthracnose stalk rot has emerged as one of the two most important stalk rot diseases of corn in the country. There are three main types of ear rot in corn… “Last year, gray leaf spot around the Midwest was the worst I have ever seen. Blue-eye mold occurs in stored corn with high moisture content. However, it is uncertain what conditions favor it in the United States. “There is not good resistance in Midwestern corn genetics. To see all exchange delays and terms of use, please see https://www.barchart.com/solutions/terms. Consider! Corn Diseases: Symptoms, Scouting, and Management . Page. Fungal Corn Diseases. “Playing catch-up with the disease is hard. Growers need to be aware of this disease and monitor it closely,” says Myers. with intermediate levels of disease resistance, fungicides should be considered if symptoms are present on the third leaf below the ear or higher on at least 50% of the plants, at least 35% of the soil surface is covered with corn residue, the pre-vious crop was corn, and weather is favorable for foliar fungal diseases. You can assume you will have it for the next 10 years,” says Myers. of Corn Diseases Tamra Jackson-Ziems Department of Plant Pathology ... •sometimes confused with fungal disease, gray leaf spot Bacterial Leaf Streak (BLS) of Corn U.S. Distribution •Confirmed First in NE, 2016 Nebraska (75 counties), Kansas, Colorado, Iowa, Illinois, Oklahoma, The most obvious symptoms are tumor-like galls that vary in size from less than 1 cm to more than 30 cm (0.4-12 inch) in diameter. Fungal diseases require greater attention today than ever before, given the expanding population of immunosuppressed patients who are at higher risk for these diseases. Virus and virus-like diseases. Experience and regular monitoring will alert gardeners as to the seriousness of the problem. If 2020 mimics 2019, farmers will face tough choices in a rain-soaked, snow-packed harvest. Five Major Fungal Diseases of Corn DIGITAL DOWNLOAD. Fungal disease of corn can cause a multitude of problems including yield loss of the corn, mycotoxin contamination and a decrease in plant quality for animal feed. The most common diseases of field corn in New York include: Anthracnose Leaf Blight; Anthracnose Stalk Rot; Common Rust; Common Smut; Eyespot; Gray Leaf Spot; Northern Corn Leaf Blight; Northern Corn Leaf Spot; Stewart's Bacterial Leaf Blight; Recommendations for management of these diseases in New York through foliar fungicides is available. Southern Corn Leaf Blight is another fungal disease. Fungal infections come in different forms, like ringworm athlete’s foot, toenail fungus, yeast infections, and jock itch. Therefore, as the season progresses, and provided environmental conditions are conducive to disease development (moderate temperatures and high moisture), the disease moves up the plant from the lower canopy to the upper canopy. Yield loss due to the disease is variable and directly dependent upon disease incidence because infected Figure 7. Fungal and Bacterial Diseases - Vegetables Fungal leaf spots, which include brown, yellow, or black spots, are common on many vegetable plants. However, do not forget the disease triangle (below). Before applying fungicides to corn: Stop! Dark streaks may appear inside galls as fungal strands develop into spores. Damage caused by weather conditions, such as hail, and insect feeding also opens the corn up to fungal infections. Weather conditions, including cloudy days, moderate temperatures (64-81°F), high humidity and frequent rainfall will favor further infection and spread of this and other fungal pathogens that survive in infected corn residue from recent years. Corn Diseases. 2 Fungal diseases. 20 Strategies That Farmers Can Use In 2020, USDA announces changes to hemp crop insurance, Analyzing yield barriers, unleashing soil activity, Vise attachment for hitch completes a shop on wheels. This fungus is an aggressive pathogen of corn and is one of the few stalk rot pathogens that frequently causes disease prior to senescence. Some corn varieties have a purple colored plumule All these fungi are common microbial inhabitants of corn fields. The discoloration results when Penicillium fungi invade the germ area through the tip of the kernel. Therefore, checking stalk quality in the field will be increasingly important in corn- following-corn fields so that a timely harvest can be scheduled if necessary. Below are twelve tips that can help you prevent disease … Bacterial Leaf Streak. SOUTHERN CORN LEAF BLIGHT (SCLB) This disease is caused by the fungus Bipolaris maydis. The disease is driven by moisture and in some instances irrigated fields have been especially hard hit, compared to non-irrigated fields. (800) 262-3804, Iowa State University So far, continuous corn with minimum tillage and high rates of nitrogen (N) fertilizer appear to be factors, says Malvick.