Crabgrass Digitaria spp'

1
Crabgrass (Digitaria spp.)

• Summer annual weed in turf and ornamentals
• 2 species
• Smooth Crabgrass (Digitaria ischaemum)
• Seedling leaves are smooth
• The ligule (collar) is small and inconspicuous
• The leaf sheath and upper leaf surface are
  smooth, with a few hairs on the lower leaf
• Large Crabgrass (Digitaria sanguinalis)
• Seedling leaves are hairy.
• True leaves hairy on the upper surface of the
  leaf
• The collar region and flower stalk are similar
• Branches are 2 to 5 in longer

2

• Smooth Crabgrass

• Large Crabgrass

3
Identification of crabgrass

• The flowering stems are similar to bermudagrass
• Bermudagrass Branches originate at the same
  point
• Crabgrass Branches are 1/8th to ¼ in. apart

4
Biology of crabgrass

• One plant can produce 150,000 seeds.
• Germination occurs when soil reach 50-55F for
  at least 3 days.
• Germination continues throughout summer and into
  fall
• Seeds remain viable in the soil for 3 years
• Fresh seed is dormant for 2.5 to 6 months
• Can produce seeds in mowed turf
• Seeds are easily dispersed by mowers
• Adapted to hot weather
• Advantage over cool season turfgrass during the
  summer
• Produces a large root system throughout the soil

5
Conditions that favor crabgrass

• Weak turf with open areas
• Turf that is mown to close to the ground
• Increased stress to turf
• Increased light penetration to soil surface
• Overwatered turf
• High available P promotes crabgrass germination

6
Cultural management in turf

• Preventing seed set for several years
• MAINTAIN HEALTHY, COMPETITIVE TURF
• Mowing
• Select proper mowing height for turf species
• Wash mower after to avoid weed seed spread
• Fertilization
• Increases turfgrass vigor if done properly
  (proper N, P)
• Selection of turfgrass species adapted to
  environ.
• Irrigation
• Turf overwatered or frequent light irrigations is
  susceptible to invasion

7
Cultural management in ornamentals

• Hoeing and handpulling
• Mulching
• Natural or synthetic products
• Depth depends on size of particles
• Coarse 3-6 in
• Fine 2-3 in
• Soil solarization
• Effective if applied when ample sunlight
• Mow crabgrass and water
• Apply UV resistant polyethylene 4-6 weeks.
• Effective at depths upto 3 in.

8
Chemical management in turf/ornamentals

• Preemergent herbicides
• MUST APPLY before crabgrass germinates
• Homeowner (Pendimethalin, bensulide, benefin,
  trifluralin, and oryzalin WSO)
• Professional (dithiopyr, oxadiazon, prodiamine)
• Postemergent herbicides
• Use when plants are 1-3 leaf stage
• Quinclorac, MSMA, dithiopyr, fenoxyprop