summer grass also known as crabgrass and digitaria

Summer grass (Digitaria sanguinalis and Digitaria Cilaris).

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Summer grass weed is also called Crabgrass and is a member of the Digitaria family. This discuss how to identify this weed and Summer Grass herbicide options to control it.

Crabgrass is a soil indicator of acid soil pH, and a major problem for thin and weak sports fields and lawns. It grows rapidly at high temperatures and high humidity. This weed spreads aggressively, and crowds out desirable grasses.

Summer Grass Identification.

Crabgrass is a summer annual grass weed, and has long, dark green narrow leaves and flattened stems. These stems radiate out from the centre of the plant. The stems branch at the node, and form roots at the node branches. Summer grass has a membranous ligule and the sheaths at the leaf base have a light purple/white colour.

Germination of Summer Grass occurs when soil temperatures reach 12°C to 15°C at 10cm depth for 14 continuous hours. The weed emerges 2 to 3 weeks earlier than Crowsfoot.

In the spring, alternate cycles of wet and dry weather encourage Summer grass to germinate. This germination and growth occurs best when there is no shade and with good soil moisture.

Crabgrass seeds can germinate from very early in the Spring to very late in the Autumn as long as adequate soil moisture exists. Plants that germinate in the Autumn have a short life and hard frosts for example in Canberra will kill them.

Summer grass seed heads appear all through the Spring, Summer and Autumn and are made up of multiple small, finger-like spikes, that radiate out from a central point and are covered in tiny black seeds.

Crabgrass spreads from seed as well as stolons and the seed remains dormant in the soil for several years.

Classification: Monocot
Height: Digitaria grows up to 30cm in height.
Leaf Length: The leaves of Summer Grass are 5-15 cm long.
Comments: The leaves of Crabgrass are covered in coarse hairs.

Habitat: Summer Grass has poor drought tolerance and grows in full sun and shade. Its natural habitat is in sandy or sandy loam soils. However, you often find it next to driveways or pathways, and once it established it is tolerant of hot, dry, compact soils.

How to Remove Summer grass weed from your lawn.

You can use both cultural control methods and Crabgrass specific herbicides to control Summer Grass in your lawn and turfgrass.

Cultural control of Summer grass:

You can remove Crabgrass by hand but it will keep reappearing if the turf cover is thin or has bare patches. That’s why it is important to properly feed your turf with the right turf fertilizer and if possible raise the right height of cut. US work shows that mowing couch at 50mm compared to 25mm you get a 10% decrease in summer grass.

Correct nutrition results in turfgrass spreading and outcompeting the Summer Grass.

Chemical Control:

The key to manage Crabgrass is stopping seed production. Even though selective post-emergent summer grass herbicides are available, your best option is to use a pre-emergent herbicide.

Pre-emergent Control.

Pre-emergent herbicides such as granular pre-emergents like Onset 10GR, Echelon, Echelon Duo and Freehand or liquids like Barricade, Pennmag, Dimension, and Battalia will control Digitaria and Summer grass. Use these at the correct rate and with the right timing to get the best results.

Apply pre-emergent herbicides before germination occurs and when soil temperatures stabilize at 13°C for several consecutive days. Interestingly Dimension Herbicide also provides post-emergent control up to the 1-tiller stage.

Depending on where you are, split applications at half the high label rate almost always improve Crabgrass control in comparison to a single application at the high use rate. Aim to make the second application 4-6 weeks after when you expect Summer Grass to germinate.

Post-Emergent Control.

For post emergent control of Summer Grass use ProForce Geronimo (MSMA) or Quinstar (Quinclorac). For the best results with Quinclorac use Voltage MSO adjuvant.

With post-emergents, if the Crabgrass has tillered you will need two applications, 2 or 3 weeks apart, and you will get better results against smaller plants that have yet to tiller.

Be aware that injury is likely to occur if you use these when temperatures are greater than 29°C.

Dithiopyr (Dimension) is another option for post-emergent Summer grass control in warm- and cool-season grasses. Turfgrass managers primarily use Dimension for pre-emergent Crabgrass control, but applications in the Spring have the potential to provide early-postemergent control. Dimension must be applied to seedling Summer grass for best results.

Applications to Summer grass that has already tillered give variable post-emergent control in the early Summer. You should irrigate within 24 hours to reduce losses through volatilization in late Spring or Summer.