hyg-4002-83	ANNUAL GRASS CONTROL

Crabgrass is the most common of several annual grasses that are a problem in

turf. Others are foxtail, barnyardgrass, annual bluegrass a?d goosegrass. Herbicides that control crabgrass usually give some control of the other annual grasses.

An annual grass is one that germinates from seed, completes its life cycle, produces seed and dies in one year. There are many undesirable perennial broadleaf grasses that infest lawns, Many people mistake perennial grasses such as tall fescue, timothy, redtop, bromegrass, nimblewill and quackgrass for crabgrass. Herbicides used to control crabgrass and other annual grasses will not control perennial grasses.

A quality lawn does not need yearly treatments with herbicides for crabgrass control. Producing a dense, healthy stand of grass is the best way to control crabgrass and other weeds. The use of an adapted variety of grass, adequate fertilization, proper mowing practices, good watering practices, and insect and disease control will produce dense turf that will seldom be invaded by crabgrass. Yearly infestations of crabgrass indicate a poor lawn management program.

The active ingredient in most pre-emergent herbicides for crabgrass control is one of five chemicals regardless of the brand name. These herbicides have been tested at The Ohio State University and the Ohio Agricultural Research and Development Center for several years. They are listed in the table below.

Pre-emergent Herbicides for Crabgrass Control

Common Name	Trade Names	Control

Benefin	Balan	Good to excellent Bensulide	Betasan, Pre-San	Good to excellent DCPA	Dacthal	Excellent	Oxadiazon	Chipco Ronstar G	Good to excellent Siduron	Tupersan	Good to excellent

All of these herbicides are safe to use on Kentucky bluegrass lawns. Bensulide is the only one that will not injure bentgrass turf.

Pre-emergent herbicides should be applied before annual grasses germinate. For crabgrass and most other annual grasses, pre-emergent herbicides should be applied before April 1 in southern Ohio and April 15 in northern Ohio. If the weather is cool in April, later applications will result in good control. Five to seven moist nights with soil temperatures about 50F or higher are required for crabgrass to germinate. Pre-emergent herbicide applications for annual bluegrass control should be made in late summer or early fall (see fact sheet "Annual Bluegrass Control in the Home Lawn").

Pre-emergent herbicides control crabgrass by killing the you?g plant shortly after germination. Most herbicides for crabgrass control will kill desirable grass as

well as crabgrass and other annual grasses. Tupersan is the only safe herbicide

to use on a new turfgrass seeding. Bluegrass can be seeded the same time Tupersan

is applied.

Herbicides are available that will kill crabgrass after it germinates and begins

to grow. These are called post-emergent herbicides. Post-emergent crabgrass herbicides should be applied as soon as the crabgrass is seen i? the turf. In Ohio studies, at least two applications have been needed to control crabgrass for the summer. Make applications about a week apart until the crabgrass is killed. If additional crabgrass germinates after the application, apply another series of treatments.

The two most effective and widely used post-emergent herbicides are DSMA (disodium methylarsonate) and AMA (octyl-dodecyl ammoniummethyl - arsenate). These materials may slightly discolor Kentucky bluegrass, but no serious injury should result

if used at the recommended rate and low temperatures.

Prepared by: John R. Street

Extension Agronomist

The Ohio State University