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Solve spring weed problems in October
Extension advice
Richard Evans
Richard Evans is the Bryan County Cooperative Extension agent. - photo by File photo

I could always tell when my roommates would eat my food without asking back in my college days. I would open up my box of cereal only to find the bag opened and half empty. There would occasionally be stragglers in the bag and if I looked hard enough, probably some on the floor. By these signs I would always know someone had eaten before me.

Fall has been in your garden, leaving evidences of its passing. Some plants are brown, but others are greening up. Unfortunately many of the green plants are weeds.

These weeds are small now but expect them to be several inches high by next April. This is when I get calls on how to control the weeds. By then, it is often too late to kill these weeds. What we need is an October solution to an April problem.

In Bryan County, we have two types of weeds that grow in four seasons. Winter weeds come up in fall and grow through winter into early spring. Summer weeds germinate in spring and grow through summer into fall.

To prevent winter weeds, apply pre-emergence or preventative herbicides around mid-October and again 45 days later. These will prevent many weeds from coming up or getting large. Once these weeds get to the size they are in April, they can be close to impossible to kill.

What pre-emergence herbicide should you use? That will depend on the kind of weeds you had last year and will expect this year and the type of lawn grass you have.

Atrazine prevents broadleaf weeds better than grassy weeds. It will control annual bluegrass, henbit and other winter weeds. Atrazine can be used on all warm season turf except green Bermuda grass. It should not be used on Bermuda grass unless it is fully dormant. Atrazine can also be used after weeds emerge to kill existing weeds.

On Bermuda grass and other warm season grasses, you can use other pre-emergence herbicides instead of atrazine. These are better at controlling grasses but will prevent some small seeded broadleaf weeds. These herbicides include Halts (pendamethalin), Surflan (oryzalin), Balan (benefin) and XL (benefin and oryzalin). These are excellent at preventing crabgrass but will have to be applied in February and April to control crabgrass. Make sure you put these herbicides out before the weeds come up. These will not work after weeds emerge. Use the same time of application as for atrazine.

Since the weeds are already emerging, is there any sense in putting these chemicals out? Atrazine will kill some existing weeds, while most of the others will not. For this and other reasons, I recommend you use atrazine to prevent winter weeds. The other herbicides I mentioned will not control existing weeds but can prevent some new weeds from coming up.

All pre-emergence herbicides will also prevent ryegrass from emerging. Do not use them on turf that is less than a year old, and avoid applying them to weak turf or during lawn green up in the spring. Be cautious. Read and follow all label directions. Each herbicide may have special guidelines you must follow.

Herbicides applied in October will have almost no effect on warm season weeds that come up in the spring — like crabgrass. To prevent the summer weeds, apply pre-emergence herbicides around Feb. 15 and again 45 days later

No weed control program will kill them all. Learn to accept a few weeds. It is not as much fun as learning to live with roommates, but it can be done!

 Evans can be reached at 912-653-2231.

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