Weed control is an important aspect of establishing any lawn, especially cool season fescue lawns. This article is the second in a series of fall lawn care and establishment.     Bermuda and crabgrass now dominate many lawns and must be killed before seeding in September. The growth habit of these grasses is entirely different and therefore has different methods of control. Correctly identifying the grass is essential if these weeds are to be eliminated.
    Bermuda grass is the most serious and difficult of the two grasses to control.  Bermuda grass invades weak or thinned fescue lawns during the early summer months when fescue becomes semi-dormant, becoming established via seed, stolons (above ground stems) or rhizomes (underground stems). Roots form at the nodes or joints allowing the grass to become well established over a short period of time. This grass propagates itself from these specialized stems and seed are often introduced in lawns by contaminated topsoil.
    Bermuda grass turns brown and becomes dormant after a hard frost in the fall. The grass remains dormant until the return of warm weather in early summer. Patches of "dead" Bermuda grass give fescue lawns a spotty and unsightly appearance during the winter months.                     Applying systemic herbicides containing glyphosate (Roundup) is the only feasible method of controlling bermuda grass. Now is the time to kill this grass and repeated applications are often needed to control this aggressive grass. Glyphosate is not effective on plants that are not actively growing. Bermuda grass does not grow well as the soil temperature drops in mid-September.      Crabgrass lawn weed often confused with bermuda grass. It is a warm season annual grass which also thrives in hot weather. This grass is endogenous to our area easily adapting to both wet and dry summer conditions. Smooth crabgrass and hairy crabgrass are two types that now dominate weak lawns growing rapidly now.
     Crabgrass grows in clumps, similar to fescue, but may have a faint blue color to the leaf blade. A single crabgrass plant produces thousands of minute seed remaining in the soil for years.
    Crabgrass is best controlled with preemergence herbicides in early spring or with post emergence herbicides during the early summer. It is too late to control crabgrass with preemergence herbicides. Post emergence herbicides kill young seedling crabgrass, but do poorly on well established plants. Post emergence herbicides such as MSMA may burn established fescue in hot, dry weather. Crabgrass dies out completely with the first killing frost. Dead plants can be raked and fescue can be seeded to fill the void. Herbicides containing glyphosate (Roundup) or herbicides containing diquat easily kills crabgrass clumps before planting.
    Bermuda grass is a perennial returning each season from underground stems. Conversely, crabgrass is an annual germinating from seed. Bermuda grass must be completely destroyed this month before reseeding fescue in September. Make certain that the Bermuda grass is dead before reseeding.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu