Are Weeds Hiding Disease in Your Customers’ Cornfields?

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Midseason corn

It’s no secret that weeds compete with crops for resources like light, water and nutrients — undoubtably impacting your customers’ yields at the end of each growing season. Unfortunately, in addition to their competitive nature, weeds can limit corn yield by acting as reservoirs for disease-causing pathogens — and the insects that move these pathogens to other cornfields.1

Johnsongrass, for example, is known to harbor Maize dwarf mosaic virus and Maize chlorotic dwarf virus complex.

Maize dwarf mosaic virus (MDMV) produces yellow blotches or streaks along the plant leaves. Infected plants are predisposed to root rot and often have small ears with kernel abortion. MDMV is often transmitted to other fields by aphids, and most outbreaks of this disease in corn can be traced back to nearby johnsongrass.2

Maize chlorotic dwarf virus (MCDV) can cause varying symptoms, including plant stunting, shortening of upper internodes, leaf reddening or yellowing, leaf twisting and tearing, and chlorosis or clearing of the smallest visible leaf veins. This virus overwinters in johnsongrass rhizomes, and studies have shown that MCDV in susceptible hybrids can result in up to 91% yield loss.3

Managing johnsongrass in cornfields

“Johnsongrass is a perennial weed, so it can impact corn yield every season if left uncontrolled,” says Jason Gibson, market development specialist, Corteva Agriscience. 

Gibson recommends cultural practices such as tillage and crop rotation to reduce disease pressure in cornfields. Early applications of postemergence herbicides can help customers manage johnsongrass and mitigate the risk of MDMV and MCDV infections.

“Many customers are not getting effective johnsongrass control with glyphosate alone, so a postemergence herbicide like Realm Q can be very helpful,” Gibson says.

Realm® Q herbicide uses multiple modes of action to control standing weeds and prevent competition from later-emerging weeds, with excellent residual activity. The “Q” stands for built-in safener technology that offers the flexibility to confidently apply Realm Q under diverse weather conditions, across more hybrids and with a wide range of adjuvants.

See how Realm Q can be incorporated into postemergence applications here.

Remember: It’s important for customers to scout fields regularly to keep an eye out for weeds that may be harboring disease in their fields and to implement a program approach for the most effective weed control.



1Byron, M., D. Treadwell, and P. Dittmar. 2019. Weeds as Reservoirs of Plant Pathogens Affecting Economically Important Crops. https://edis.ifas.ufl.edu/publication/HS1335

2University of California Agriculture & Natural Resources. 2019. How to Manage Pests: UC Pest Management Guidelines. http://ipm.ucanr.edu/PMG/r113101011.html

3Zambrano, J. L., L. R. Stewart, and P. A. Paul. 2016. Maize Chlorotic Dwarf of Maize. https://ohioline.osu.edu/factsheet/plpath-cer-08

Realm® Q is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.