Weed and Feed Damage

Ronald Strahan, Koske, Thomas J.

Light yellowing on St. Augustine from herbicide.

Herbicide damage.

Shrub damage from lawn herbicide.

Weeding and feeding are two different operations. Sometimes they can be done in combination -- but not always and not for best results. We often follow a herbicide application with proper fertilization to allow the turf to outgrow any herbicide damage. Many times you should weed when you should not feed and vice versa. Many herbicides are often best applied as sprays and not as granulars for best coverage and effectiveness. On top of that, there are the issues of cultivar sensitivity, even application, over application, under application and overlapping of materials. The hot season always enhances these effects. Consequent problems often raise their ugly heads for homeowners using weed-and-feeds.

Essentially, two types of weed-and-feed herbicides are most often available to home consumers. Read the label completely for materials present and usage restrictions.

1) Weed and feeds with atrazine impregnated on a fertilizer granule are safe for St. Augustine grass, centipede grass and zoysia but not Bermuda grass. Example: Scott's Bonus S

2) Weed and feeds with 2,4-D, dicamba & mecoprop (or with Trimec) are safe for Bermuda grass and zoysia. Some manufacturers will have centipede grass on the label but almost never St. Augustine grass because of the potential for injury. Example: Ferti-lome's Weed and Feed with Trimec

If you have a St. Augustine grass yard that is not growing well and shows some yellowing foliage after a weed-and-feed application, check what kind of weed and feed you used. Also, look for 2,4-D-type symptoms on nearby shrubs.

Damages are not always lethal to the lawn, but they can be. Reversing this situation is not always possible or especially feasible for homeowners. It can definitely be very messy. The yellowing may be embarrassing but usually goes away in a few weeks. Iron chelate foliar sprays may help relieve symptoms sooner.

5/15/2007 6:28:03 PM
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