summer grass also known as crabgrass and digitaria

Summer Grass (Digitaria sanguinalis).

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Summer Grass is a member of the Digitaria family. This discusses how to identify this weed and options to control it.

Digitaria sp are a soil indicator of acid soil pH, and are a major problem for thin and weak sports fields and lawns.

They grow rapidly at high temperatures and high humidity.
This weed grass spreads aggressively, and crowds out desirable grasses.

Summer Grass Identification.

Digitaria sp are a summer annual weed grass, and has long, dark green narrow leaves and flattened stems. These stems radiate out from the centre of the plant.

The stems of Summer Grass branch at the node, and form roots at the node branches. It 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 present.

Summer Grass seeds 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.

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

Digitaria sp spread from seed as well as stolons, and the seeds remain dormant in the soil for several years.

Summary.

Classification: Monocot.

Photosynthetic Pathway: Summer Grass is a C4 weed.

Height: Digitaria grows up to 30 cm in height.

Leaf Length: The leaves of Summer Grass are 5 to 15 cm long.

Comments: Coarse hairs cover the leaves.

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 establishes it is tolerant of hot, dry, and compact soils.

How to Remove Summer Grass.

You can use both cultural control methods and Summer Grass herbicides to control Digitara sp in your lawn and turf grass.

Cultural Control of Summer Grass.

You can remove Summer Grass by hand but it will come back if the turf cover is thin or there are bare patches.
It’s important to properly feed your turf with the right turf fertilizer, and if possible raise the right height of cut.
US work shows that if you mow couch at 50 mm vs 25 mm, you get a 10% decrease in Summer Grass.
Correct nutrition encourages turf grass to spread and outcompete Summer Grass.

Chemical Control of Summer Grass.

The key to manage Digitaria sp is to stop seed production. Even though selective post-emergent Summer Grass herbicides are available, your best option is to use a pre-emergent herbicide.

Initial Pre-emergent Application.

Make an Initial application before any Digitaria sp germinates. Pre-emergents prevent germinating seedlings from developing, so . apply these before any Summer Grass germinates.

Split Pre-emergent Application.

Make split applications 6-8 weeks after the initial application. A second application extends the residual control of Digitaria sp, and also increases Crowsfoot control. This approach is especially effective on sandy soils with low organic matter.

Post or Pre-emergent + Post emergent Tank Mixes.

Apply post-emergents or a standard pre-emergent herbicide with post-emergents to control germinated Digitaria sp. You get the best results on germinated Digitaria sp with post emergents, when you apply them to small 1 to 3 leaf Summer Grass.

Summer Grass Germination.

Digitaria sp germinate in the Spring when soil temperatures reach 13°C or there is an air temperature of 18°C for four or more days. Once the soil temperature reaches 13°C, Digitaria sp germinate over the next 2 to 3 months.

Pre-emergent Control of Summer Grass.

Pre-emergent herbicides include granular pre-emergents like:

Liquid options include:

Barricade.
Pennmag.
Dimension.
Envu Specticle and
Battalia 435.

All of the above will prevent Digitaria seed from establishing. Use these at the correct rate and with the right timing to get the best results. Do not apply any of these pre-emergent herbicides if you plan to seed within several weeks after application, as these herbicides will kill turf grass seedlings.

Apply pre-emergents before germination occurs and when soil temperatures stabilise at 13°C for several consecutive days. Dimension Herbicide also gives 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 Digitaria sp control in comparison to a single application at the high use rate.

Aim to make the second application 4 to 6 weeks after Summer Grass germinates.

Post-Emergent Control of Summer Grass.

For post emergent control of Summer Grass options include:

ProForce Geronimo (MSMA).
Quinstar (Quinclorac). For the best results use Voltage MSO adjuvant. Control is inconsistent when you apply this at the 2- to 4-tiller growth stage, and larger plants need sequential applications to get good control.
Pylex is registered in the US. It is important to add a methylated seed oil (MSO) in the tank with Pylex. Pylex bleaches Summer Grass leaves for 7 to 14 days after application before the plants die.

With post-emergents, if the Summer Grass has tillers you need two applications, 2 or 3 weeks apart. You get the best results on small plants that have yet to tiller, and if you get uniform coverage. Thus, apply these only when plants are visible in the stand.

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

Dithiopyr (Dimension) is another option for post-emergent Summer grass control in warm and cool season turf. Turf grass managers mainly use Dimension for pre-emergent control, but applications in the Spring do provide early post emergent control. You must apply Dimension to seedling Summer Grass for best results.

Applications to Summer grass that already has tillers, gives variable post-emergent control in the early Summer. Aim to irrigate within 24 hours to reduce losses through volatilisation in late the Spring or Summer.

Non Selective Control of Summer Grass.

Glufosinate-ammonium provides control for 4 to 6 weeks, but it regrows and recovers due to the limited movement of glufosinate.
Glyphosate. You can use Glyphosate but if you use Glyphosate, and water quality is an issue then use ProForce Manta Ray.

The following are non-selective but also have a long term residual and stop re-growth of Summer Grass.

- Renegade. Renegade stops germination for up to 12 months, and reduces the need for multiple herbicide applications.
- Numchuk Quad. This gives effective post and pre emergent Summer Grass control for up to 12 months.
- Cortex Duo. Cortex Duo gives a rapid knockdown of Summer Grass, and residual control for up to 3 months. It is also safe to use around trees.