Many growers have approached our sales team lately about anthracnose leaf blight — a disease that targets corn at higher rates after wet weather conditions, much like we’ve experienced this spring. Growers are questioning what, if anything, needs to be done to prevent the disease from affecting their yields. If you suspect anthracnose leaf blight, here are some symptoms to help you pinpoint the disease and recommendations on how to manage it.
What is Anthracnose Leaf Blight?
Anthracnose leaf blight is a disease caused by the fungal pathogen Colletotrichum graminicola. The disease overwinters on corn residue, so growers may notice it more in corn-on-corn situations, especially if they detected it in their fields the previous year. The disease can also thrive in no-till or reduced-tillage fields, and occurs at higher rates during very wet weather conditions or prolonged days with rain, soil moisture and high humidity, followed by high heat. The disease is known to spread by splashing rain and wind.
Detection
Anthracnose leaf blight appears on the leaf surface as irregular or oval-shaped tannish/brown colored lesions with a darker margin (brown to purple). The lesions typically start on the bottom leaves before working their way up the plant. In severe infections, the lesions grow together to form large patches of chlorotic (yellow) or necrotic (dead) leaf material. As the disease progresses through the end of the growing season, the disease can cause top die-back. This is detected by black lesions on the outer stalk tissue behind the leaf sheaths that kill off the stalk and leaves above the ears. Depending on how far long the grain-filling process has progressed, top die-back can affect kernel development and overall yield.
Another thing to look for are lesions on the stalk that are similar in nature to those described on the leaves. If lesions are spotted on the stalk, this may be related to anthracnose stalk rot. If you suspect anthracnose stalk rot, we recommend splitting open the stalk to check on the pith. If the pith has brownish colored areas around the nodes and appears to be rotting, you may have anthracnose stalk rot.
Prevention
While anthracnose leaf blight does not typically result in long-term damage to corn, in areas that are already susceptible or impacted by other diseases, the addition of anthracnose leaf blight can be devastating to plant development and grain fill. This is especially true if the disease results in die-back or if stalk rot is detected. The best way to reduce the chances of your crops contracting anthracnose leaf blight is to use resistant hybrids. Stine has a number of different corn options for growers to help tackle this disease, some of which have excellent ratings against anthracnose, including Stine 9401-0, 9434-11 and 9814–20 brand corn.
Growers can also use tillage to bury infected stalks at the end of the season or consider harvesting early when other disease are present. There are also fungicides available specifically to help prevent anthracnose leaf blight outbreaks.
For more information on anthracnose leaf blight development in corn, contact your local extension office or Stine agronomist.