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Recent Articles on Diseaes Affecting corn:
Monitor Fields for Stalk Quality Problems
Published on: Sept 25, 2015
Maximizing the Value of Foliar Fungicides in corn
Published on: July 7, 2015
Diseases are already showing up in Iowa corn
Within the past week several foliar diseases have been reported in Iowa cornfields.
Published on: Jun 29, 2015
Early Season Fungicide Applications to Corn
I have received a couple of questions about the value of including an early fungicide application this season.
Published on: Jun 16, 2015
Black cutworm moths migrate northward on southerly spring winds, typically beginning in mid-March and peaking in April through mid-May. Larvae can cut corn plants above or below ground, reducing plant stands up through the V5 growth stage. An insecticide rescue treatment is recommended when greater than 3% of the corn plants are cut. Herculex® I hybrids from NuTech will provide moderate control of Black Cutworms. Also, all NuTech corn seed is pre-treated with Smartcote™ Corn seed treatment which will provide additional protection.
European Corn Borer
Yield losses from first generation corn borer can amount to as much as 5% while losses from second generation generally ranges from 2-3%. Severe losses occur under drought or stressful conditions. Corn borer moths are attracted to the tallest, darkest green corn to lay their eggs, thus late planted corn is especially vulnerable to second generation corn borer. Moth flights and ensuing pressure is somewhat unpredictable since successful egg laying, hatch, and early larvae survival is highly dependent upon weather conditions. Fortunately, today's growers can easily control this annual pest by planting NuTech corn hybrids containing the Agrisure® CB/LL or Herculex® I technologies.
Western Bean Cutworm
Eggs are laid on upper leaf surfaces. After hatching, if corn has not tasseled, larvae move to the whorl to feed on pollen in the developing tassel. If corn has tasseled, larvae feed on silk in the ear. If silk feeding persists during pollen shed, pollination may be poor. Once the ear has formed, it becomes the major feeding site for Western bean cutworms. One cutworm per ear can cause up to four bushels per acre yield loss. Severe infestation can result in the reduction of grain yield by as much as 30-40%. Herculex® I hybrids will provide good control of Western bean cutworms. Under heavy infestations, an insecticide application should be considered when more than 8% of the plants have egg masses or small larvae and 95% of the corn is tasseled.
The number one pest of corn is becoming harder and harder to control due to extended diapause in the Northern corn rootworm and the soybean variant in the Western corn rootworm. Crop rotation alone no longer provides adequate protection. Since pruned roots are less capable of supplying water and nutrients to the growing plant, yield losses are greatly accentuated under drought stress. Injury also increases susceptibility to root and stalk rot fungi and high adult densities may clip silks. In areas that have not experienced extended diapause or soybean variant, crop rotation is still the most cost-effective control. NuTech hybrids with either the Herculex rootworm or Agrisure rootworm technology provide excellent control of corn rootworm. In very high pressure fields, the use of transgenic rootworm resistant hybrids and in-furrow granular insecticides provide the most protection available.
White Grubs & Wireworms
White grubs and wireworms may cause early-season stand reduction in corn by feeding on the roots and sometimes seeds of young corn plants. As with most soil insects, it is difficult to predict when and where these troublesome pests will be found in most corn acres with one exception. An increased incidence may be anticipated in cornfields following pasture or Conservation Reserve Programs (CRP). All NuTech hybrids are pre-treated with Smartcote™ Corn seed treatment which provides good control of both pests, but a soil insecticide application is recommended if extremely high pressure is expected such as long-term pasture or CRP acres.
Corn Flea Beetle
Economic damage is caused by over-wintering beetles carrying bacterial wilt of corn (Stewart's disease). Damage is greatest after a mild winter followed by a cold spring. In which high numbers of beetles survive the winter and attack the slowly-growing corn over a prolonged period. Good weed control will help to eliminate over-wintering sites, but planting seed treated with low rate seed-applied insecticide is the most cost effective control. All NuTech corn hybrids are pre-treated with Smartcote™ Corn seed treatment which has shown effective early season control of flea beetle.
The Corn earworm, also known as the tomato fruitworm or cotton bollworm, feeds on a number of crops including corn, tomato, cotton, green beans, clover, lettuce, peppers, and sorghum. The most severe infestations generally occur in the southern United States. Losses due to corn earworm in field corn range from 2-15% depending upon infestation levers. This occasional pest does not overwinter successfully in most areas of the cornbelt. Similar to Black cutworm, adult moths migrate northward each spring on weather fronts and high level winds. Moths lay eggs on the emerged silks of a mature corn plant and the larvae feed on developing kernels under the protective husk for entire larvae stage. Feeding on kernels at the tip of the ear can also pre-dispose the ear to ear rots. Control of this occasional pest is challenging as insecticide spray residue needs to be present during eggs hatch so that the larvae will come in contact with the insecticide wehn migrating to the ear shoot. Corn hybrids containing the Herculex® 1 technology will provide some protection from Corn earworm, but not adequate under moderate to heavy pressure.
Leaf Blights & Gray Leaf Spot
Leaf blight pathogens are favored by warm, humid weather and frequent rainfall. Eyespot is more common in the northern half of the NuTech market area. Gray leaf spot is more common in the central and southern half, and Northern leaf blight is more common in the eastern states of Indiana, Michigan & Ohio. Control is based upon several factors, including selection of resistant hybrids, crop rotation, selected use of tillage where appropriate and foliar fungicides. Because pathogens can overwinter on corn debris, burial of infected material may be helpful but cannot substitute for other control measures. Please refer to the NuTech performance rating guide as needed for selection of more tolerant hybrids.
Seedling Blights & Root Rots
Cool or wet conditions that reduce or delay corn germination or seedling development may lead to early-season seed rots, seedling blights and/or root rots. Poor stand establishment, non-uniform emergence and missing plants are symptoms of seed or seedling infection. Several different fungi can cause these diseases. The most common are Phthium, Fusarium, Gibberella, Trichoderma and Penicillium, but other fungi such as Diplodia and Rhizoctonia could be involved. All Nutech hybrids are pre-treated with Smartcote™ Corn seed treatment and the fungicides found in Smartcote™ Corn will help improve plant stand and vigor by helping to protect young seedlings from these early season diseases.
Stalk rot is caused by an interaction between soil or residue-borne fungi and environmental stresses acting on the plant. Any conditions that reduce photosynthesis and the production of sugars can predispose the plant to fungal infection and severe stalk rot. Such stresses include leaf disease, hail damage, crowding of plants, drought, soil saturation, lack of sunlight, extended cool weather, low potassium levels, high weed pressure or insect damage. There are differences in hybrid tolerance, but prediction of hybrid interaction is difficult to test for and predict since stalk rots are secondary infections. The best prevention for stalk rots is to keep plants healthy and free of most stress.
Goss’s Wilt mainly a western cornbelt disease until the widespread planting of susceptible germplasm enabled the disease to spread across the central cornbelt as far east as Indiana. The disease is caused by a bacterial pathogen that overwinters in corn residue and several grasses. Plant wounding from wind and other causes provide openings for the bacteria. In severe cases, yield losses can be severe approaching 50%. Typical symptoms incude long, water soaked lesions that have wavy margins. Lesions kill large portions of the plant photosynthetic capacity reducing reducing a plant’s ability to produce carbohydrates and predisposing the plant to secondary pathogens such as stalk rots. There are no rescue treatments available, but the disease can be controlled by managing overwintering sites and planting resistant hybrids. Fortunately for all NuTech customers, NuTech provides tolerance ratings for all of our hybrids to help protect you from this devastating disease.