Question: Is it more effective to treat lawns to prevent crabgrass now, or should we wait for it to grow up before killing it with herbicides? Last fall, I put down some herbicides. Is that enough? Do you think that verbena survived the harsh winter? Part of my lawn is newly sown.
A: The hawthorn plant that you planted on your lawn last year has now died. However, before they die, most may produce thousands of seeds, which will now germinate on your lawn in the next few weeks. The way to prevent early rice blast is to solve the problem, not to try to kill the weeds after they have established on your lawn.
Although autumn is a good time to treat broadleaf weeds with herbicides, there is not much benefit in using verbena preventatives in the fall, because verbena is annual in summer and germinates in early spring instead of in fall. When the freezing temperatures of winter come, plants die. Before verbena seeds start to germinate and grow, a verbena preventive (“pre-emergent herbicide”) must be used.
In newly sown lawns, you must choose and use herbicides more carefully to prevent killing or damaging the new lawn grass you are planting. Mid-March to mid-April is the best time to apply the first round of pre-emergence herbicides to control horsetail grass. These chemicals are applied before weed seeds germinate. They can prevent horsetail seeds from germinating or kill horsetail seedlings when they begin to germinate. Make sure that the product you buy can be safely used on new lawns that contain active ingredients such as siduron (Tupersan). This can even be used during planting or after planting in spring. It can control horsetail grass and foxtail grass.
On mature lawns, you can choose more pre-germination control methods for horseshoe grass, foxtail grass and goose feathers, including befen+trifluralin (Team), benzsulfone (Betasan, PreSan, Lescosan), and Austrian Sand pine (Ronstar), pendimethalin (Weedgrass Control, Pre-M, Halts, Pendulum), dithiopyr (Dimension), Prodiamine (Barricade) and bensulide + oxadiazon (foie gras/crab grass control). In northern Kentucky, these chemicals need to be used before April 15. Follow up after six weeks and use it repeatedly to extend the control range throughout the summer. If gooseweed is the main target weed, please do the second application around May 15.
When sown lawns, on new lawns or on the ground that will be sown in the next few weeks, broadleaf weed control is generally not a real option, as most herbicides will kill dandelions, clover, and plantain Grass, violets, ivy, etc. Containing 2,4-D or similar products, they can also kill or destroy newly sprouted lawn grass. Check the product label for details, but many broadleaf herbicides can only be applied to a new lawn after they have been mowed about four times. If the herbicide is applied to the weeds before weeding, you must wait several weeks after applying the herbicide before finally sowing the grass seeds. Check the product label for restrictions.
On mature lawns without over-seeding, you can use a combination product containing 2,4-D to kill broadleaf weeds such as plantain, wild garlic, and dandelion.
For more information on lawn and landscape care, as well as updates to the upcoming extended course, and to win free vegetable seeds for your spring garden, please visit www.facebook.com/BooneHortNews or www.twitter.com/BooneHortNews.
• Growing tomatoes and peppers at home: Thursday, March 26, 6:30-8 pm, Boone County Extension Office. It is free, but please call 859-586-6101 to register, or register online at boone.ca.uky.edu.
• Locally grown fruits: April 7, Boone County Extension Office, 9-11 am. It is free, but please call 859-586-6101 to register, or register online at boone.ca.uky.edu.