Currently, corn planted around March 25th in Dooly County should be approaching 36 inches tall and V6-V8 growth stage (per measurements taken May 12 from our corn sentinel plot). At this stage, your corn requires almost 2 tenths of an inch of water per day.
Weed control – If you have managed weed emergence in your corn fields, the hard part is almost over. Dr. Eric Prostko suggests that weeds that emerge 45 days after planting will likely not cause competition related yield loss, although they may still affect seed quality and harvest efficiency. There are still a number of herbicides that you can use at this growth stage. Refer to the Corn Production Guide or the Corn Production Update from April 23rd.
Insect pests – Once corn plants reach the 5 – 7 leaf stage they are large enough to escape damage by most seedling pests. Most insects of importance during the whorl stage defoliate the whorl and leaves. These include grasshoppers, armyworms, corn earworm, cereal leaf beetles and others. Whorl stage corn is very tolerant to defoliation. Grasshoppers (which shouldn’t be much of a concern this year given how wet it’s been) and cereal leaf beetles can often be controlled by treating the first 50-100 feet of the field edge. Armyworm and earworm control should be initiated when 25% of the plants in a field are infested and larvae are present.
Disease control – Northern Corn Leaf Blight has been detected in Seminole County. Keep in mind, corn in Seminole County is several weeks ahead of corn in Dooly. We are monitoring the Dooly County sentinel plots, but you should also be scouting your fields. Timely fungicide applications are crucial to prevent economic loss from Northern Corn Leaf Blight.
Fungicide recommendations for managing northern corn leaf blight include:
1. Apply a fungicide to control northern corn leaf blight if this disease appears to be spreading early in reproductive growth. If Northern Corn Leaf Blight is observed on the 3rd leaf below the ear leaf, it is indication that it could be beneficial to use a fungicide to protect the crop.
2. To date, a fungicide application at the V5-V6 growth stage on corn planted in the spring had little impact on yield or disease control. However, the V5-V6 application has had some benefit for reducing disease and improving yields on late-planted corn. This is because the later-planted corn will be affected much earlier in its growth and development than is spring-planted corn.
3. A second fungicide application may be warranted 2-3 weeks after the initial application IF weather conditions still favor the spread of the disease and the corn crop is still some time away from harvest maturity.