Spring is finally over, summer is here, and now is the time for growers to be looking at fall herbicide plans. For container growers, this may be the last thing done before houses are covered. In field production, growers will apply earlier in the fall to maintain a barrier that will hold until next spring.
OHP offers three products that fit into a fall herbicide application:
All three products offer control that makes them a great candidate for a fall rotational program.
Growers should rotate chemical classes with herbicides, just as they do with insecticides and fungicides to prevent weed resistance development. Marengo, a pre-emergent selective liquid herbicide, offers long-term residual control of both grassy and broadleaf weeds on ornamentals grown in production nurseries including those grown in-ground and in pot-in-pot containers. "We have trialed Marengo liquid in several Ohio nurseries and found good to excellent control of most weeds targeted," says Randy Zondag, extension agent for The Ohio State University. "Recent trials in both container and field applications have shown September to June control of most common weeds with little phyto to most species." Zondag continues: "We are currently testing to see if a split application of Marengo in fall and spring will add to length of control."
Casoron is an older but very reliable herbicide. Casoron, a 4G formulation, develops a soil barrier when watered-in with .5 to 1.0-inch of water, and is active for 9-10 months after application. Applications should be made under cool weather conditions in late fall or very early spring. Soil temperature should be less than 50 degrees F. A fall application may be necessary to control certain perennials, such as fescues, horsetail, quackgrass, thistle and dandelions. Biathlon is a pre-emergent granular herbicide built on a Verge™ granule. The engineered granule provides unprecedented dust reduction resulting in improved worker safety and ease of application. "We have trialed Biathlon against several common herbicides and found that it provides more uniform coverage and equal if not better control versus competitive products," notes Zondag. No matter what product you choose timing is a big question.
Many people tend to wait too long in the fall to apply herbicides. If weed populations get out of hand, growers should cultivate and pull weeds and then apply these products to barer ground. Pre-emergent herbicides work best if watered in within several days of application. No one product will control all weeds. Select the product that will be designed to control those weeds growing in your field this year. If you have questions, contact your OHP regional sales manager.