Bermuda and crabgrass seem to dominate lawns in late summer.  These weeds do not coexist with fescue and must be killed before seeding in September. These grasses are entirely different and have differing methods of control. Unfortunately, many homeowners confuse the weeds so, identifying the grass is very important for control.
    Bermuda grass invades weak or thinned fescue lawns during the summer months when fescue becomes semi-dormant.  The weed easily becomes 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. Bermuda 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 the first hard frost. The grass remains dormant until the return of warm weather in early summer. Patches of "dead" bermuda grass give fescue a spotty and unsightly appearance during the winter months. Systemic herbicides containing glyphosate controls bermuda grass, but repeated applications may be needed to control this aggressive grass. Timing is critical since herbicides become ineffective as the soil temperature starts to drop in September.
    Crabgrass is lawn weed often confused with bermuda grass. It is a warm season annual grass which also thrives in hot weather. Crabgrass is endogenous easily adapting to both wet or dry summer conditions of the piedmont. It is the first grass in early summer to invade thin or weak fescue lawns.
Crabgrass grows in clumps, similar to fescue, but with 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. Glyphosate or herbicides such 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. Your effort will be in vain if the grass is not completely killed.

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 or phone at 704-21-8970