The Problem
One of the world’s most recognized weeds, crabgrass (Digitaria spp.) is a light-green to bluish-green-colored summer annual that invades just about every turfgrass situation. Several Digitaria species occur including: tropical crabgrass (D. bicornis); smooth crabgrass (D. ischaemum); India crabgrass (D. longiflora); southern crabgrass (D. ciliaris); large crabgrass (D. sanguinalis); and blanket crabgrass (D. serotina). Generally, crabgrasses are tufted, or prostrate to spreading summer annuals with branched stems that root at the lower nodes and can grow up to 3 feet tall if left unmowed. Leaf blades are often longer than 2 inches (5 cm.), usually hairy on both surfaces with tall, visible toothed, membranous ligule at the base of pointed leaves. The leaf vernation is rolled and often the leaf sheaths have dense hairs. The main form of reproduction is from seed, with some spreading from stolons. Crabgrass can tolerate poor growing conditions, but is found in nearly every soil type and crop. An important distinction of blanket and India crabgrass is their ability to form extensive mats due to their creeping stolons.
What To Look For
Crabgrass grows in light-green to bluish-colored clumps which germinate in early spring, often corresponding with other flowering plants such as forsythia, redbuds and pears. One plant is capable of producing 150,000 seeds yearly, and seeds can remain viable for at least three years in soil. Crabgrass has a high light requirement for optimum germination, thus, healthy, thick turf often discourages its invasion. Crabgrass generally germinates in early spring when soil temperatures at 4-inch depth are 53-55°F for three consecutive days, and grows until a killing frost occurs. In areas without frost, it can act as a short-term perennial. Seedheads form a digitate shape where the branches arise from a common point, resembling the upward extending fingers of a hand. Herbicide resistance has been reported with the dinitroaniline herbicides and fenoxaprop-ethyl, but only in isolated instances. Rotating between herbicides with different modes of action is the best means of preventing, or at least delaying, resistance occurrence.
The Solution
Preemergence Solutions
Crabgrass control begins with an application of a preemergence herbicide applied in late-winter/early spring prior to 4" soil temperatures reaching 50°F. A key Envu solution for preemergence control in warm-season turf is Specticle® FLO. Control has been excellent with Specticle, but should be used only on well-established turf that isn’t affected by nematode damage, spring dead spot disease, insufficient establishment, winter-kill, shaded turf, etc.
Postemergence Solutions
For postemergence control, Tribute® Total can be used in bermudagrass and zoysiagrass. Typically, best results occur on smaller plants. Other postemergence herbicides in bermudagrass and zoysiagrass golf turf include Acclaim® Accelerate. On cool-season turf, Acclaim Extra, Acclaim Accelerate, Terradex™ Crabgrass & Broadleaf, or Acuvis™. are highly effective options. In sites with traditionally heavy populations, both preemergence and postemergence products are typically required for sufficient control.
Additional resources
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Solution sheet - Crabgrass |
