Barley Grass Control in Crop

Factsheet

Date 14 January 2015

Barley grass control in crop

Key points

Barley grass does not produce hard seed, and has little long-term dormancy.
Barley grass seeds germinate rapidly in response to autumn rain
Over 99 per cent of seeds germinate in the first year after seed-set, the majority at the break of the season.
Delayed sowing followed by a knockdown is a very good control method.
Correctly timed pasture spray-topping will achieve good control for the following season.

Barley grass is a major weed because the seed is readily dispersed and post-emergent herbicide control is limited. It can also act as an alternate host for a number of cereal diseases and can develop resistance to herbicides. There have been reports of barley grass being resistant to paraquat and diquat and to several Group A ‘fop’ herbicides. Some populations have cross resistance to the Group A ‘dim’ herbicides.

Barley grass has the potential to be most problematic in ley pasture–crop systems, especially when the pasture phase is more than 3 years. Without intervention, barley grass tends to build up as fertility increases and can be seen in animal camp areas. Barley grass has been shown to establish on a bare surface more rapidly than annual ryegrass. While stock will enthusiastically graze the weed in its vegetative phase, under low grazing pressure they will avoid it almost completely once it flowers. Therefore, in good spring conditions barley grass can produce large amounts of seed.

Barley grass (Hordeum spp.) can be confused with other grasses such as brome grass and wild oats but:

Seed remnants are often still attached to the roots after germination, frequently with the characteristic multiple awns clearly visible.
Leaf colour tends to be a lighter green than other species such as great brome (Bromusdiandrus), which tends to be a darker green with a dull purplish tinge.

Germination and persistence

Barley grass seeds germinate more rapidly in response to autumn rain than other grasses (such as annual ryegrass) and can establish before the soil surface dries out. Slightly saline conditions favour establishment mainly because barley grass has a greater tolerance to higher osmotic potentials at germination than most other pasture species. It has low levels of hard seed and over 99 per cent of seeds germinate in the first year after seed-set (very little long-term dormancy). A very high proportion of barley grass will germinate on the autumn break and it is unusual for further significant germinations during the year.

Control

As the majority of barley grass seeds germinate in the first year after seed set, any activity to stop seed set, such as pasture spray-topping, will provide good control.
Most of the seed germinates directly after the autumn break, so delayed sowing followed by a knockdown should also provide good control.
In cereals, an IBS (incorporated by sowing) metribuzin and trifluralin tank-mix is registered for barley and tolerant wheat varieties. Sulfosulfuron (Monza®) is registered for wheat and triticale as both a pre- emergent and a post-emergent.
Monza® and OnDuty® can be used as effective barley grass control in Clearfield wheat.
Use a break crop such as lupins or canola so triazines and Group A herbicides can be used.

Contact

Alex Douglas, DAFWA Katanning, (08)98213246, 0455067755

Important disclaimer
The Chief Executive Officer of the Department of Agriculture and Food and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.