Canarygrass Identification and Growth Habits

Canarygrass has become increasingly widespread in wheat and barley grown in the desert southwest.  Ten species of canarygrass have been identified in the western states, although only two or three of these are serious weed pests.  Littleseed Canarygrass (Phalaris minor) is the species that is most widespread and troublesome in southern California and Arizona. Carolina Canarygrass (Phalaris Caroliniana) is similar to Littleseed and can only be differentiated by a close examination of the flowers. It is littleseed canarygrass that is the principal weed pest in grain grown in this region.  Reed Canarygrass (Phalaris arundinacea) is widespread at higher elevations especially in wet areas such as irrigation ditches and canals.  Short-spiked Canarygrass (Phalaris brachystachys) is found in central California especially in rice fields as is Gnawed Canarygrass (Phalaris paradoxa).  Three species, P. angusta, P. lemmoni and P. californica, have some forage value but are also weeds. Harding Grass (Phalaris tuberosa) is a bunch type perennial canarygrass. It was introduced by the California Agricultural experiment Station for forage but has become locally naturalized in some areas.  With the exception of this species, all others are winter annuals.

Littleseed canarygrass typically begins to germinate in October and continues to germinate until spring.  It emerges from both shallow depths (top ½ inches) with the crop seed and much deeper depths (1-5 inches) where the soil cracks.  It is common for canarygrass to be at variable growth stages, from 1 leaf to tillering, at the same time within a grain crop.  These growth habits make control difficult.  The season long germination reduces the efficacy of herbicides in which weed growth stage is important and the deep emergence through soil cracks reduces the efficacy of soil active herbicides (Treflan or Prowl).

Canarygrass is a vigorous and prolific weed that can significantly reduce wheat and barley yields.  Yield reductions of 30 to 40% are common where infestations are 20 to 40 per square foot while reductions of 50 to 70% have been measured where infestations are 100 per square foot.

Canarygrass has become increasingly widespread in wheat and barley grown in the desert southwest over the past 15 years.  Prior to this time, wildoat was the principal grass weed in these crops.  The increasing problems with canarygrass and decreasing problems with wildoat are a result of the tools available to control these weeds.

Control

There have never been many herbicides available for the control of canarygrass. Pre-emergent herbicides such as Trifluralin (Treflan) or Prowl do not have good crop safety because of the shallow depth wheat and barley are planted in in the desert southwest or consistent weed control because of deep emergence through soil cracks.  Carbyne (Barban) was widely used as a post-emergence treatment for canarygrass control until about 10 years ago when it was no longer manufactured.  This herbicide was relatively inexpensive and effective but occasionally caused serious injury if the crop was stressed by cold, drought or other means.  Hoelon (Dicofop) has been used for grass weed control in wheat and barley in the southwestern deserts since the early 1980's.  This herbicide is very effective on wildoat and some other grasses but inconsistent in controlling littleseed canarygrass. Control commonly ranges from 60 to 90%.  This is probably because of the multiple growth stages canarygrass can be at, at one time, in the same field.  Hoelon has been the only herbicide available for canarygrass control for more than 10 years.  This has caused canarygrass to become increasingly abundant and widespread year after year.

Achieve (tralkoxydim) was registered in Arizona in 1999 and widely used for the control of this weed. Both of these herbicides work by inhibiting lipid biosynthesis, which are required for cell growth. Hoelon has exhibited good crop safety but has been inconsistent (60-90 percent) in controlling littleseed canarygrass. Achieve has produced generally higher levels of control of this weed (70-95 percent), also with good crop safety. Puma (fenoxa prop) was registered in California in 1999 but not in Arizona. Puma also works by inhibiting lipid biosynthesis and has produced very good (75 to 95 percent) levels of canarygrass control in our tests. It was registered in California too late in the season in 1999 to be widely used.

The three herbicides registered for canarygrass control in the low desert of Arizona and California, Hoelon, Achieve and Puma use the same mode of action and produce marginal to very good levels of weed control with good crop safety. Hoelon is frequently unsatisfactory for growers, while Achieve, in one year of use, has been more consistent with good grower satisfaction. Puma has yet to be tested commercially.

 The search has continued for a more consistent and highly effective herbicide for canarygrass control. Two newer herbicides, both using a different mode of action then the three that are registered, were tested this year. MKH6561 is being developed by Bayer and works by inhibiting protein synthesis. Specifically it is a sulfonylurea herbicide that inhibits acetolactate synthase (ALS). It has been tested in the low desert for the last 4 or 5 years. F130060 is being developed by Aventis and is also an ALS inhibitor. This is the first year it has been in our tests.

Method

This test was conducted at the University of Arizona Yuma Valley Agriculture Center between February 18, 2000 and March 6, 2000. The soil type is a silty clay loam and the crop was flood irrigated with Colorado river water. Plot size was 14 x 25 feet set in a randomized complete block with four replications. The variety of wheat was Kofa Durum planted at 120 lbs./A.

Treatments consisted of a standard rate of Puma, Hoelon, Achieve and MKH6561 and two rates of F130060 sprayed at two timings and an untreated check for a total of thirteen treatments. The first timing was applied on February 18 when the canarygrass was at the 1 to 3 leaf stage and the wheat was beginning to tiller. The second application was made on March 6 when the canarygrass was from 1 leaf to tillering and the wheat was elongating and 12 to 14 inches in height. A uniform and heavy infestation of littleseed canarygrass (20-50/ft.²) was present. Visual evaluation of percent weed control was made on April 20, 44 and 65 days after treatment. Visual evaluation of stunting and leaf discoloration were made at this same time.                                      

Results

Results of visual evaluations of weed control made 44 and 65 days after treatment appear in Table 1. These results indicate that Puma, Hoelon and Achieve produced variable levels of control of 60 to 95 percent from both the early and late applications. Leaf discoloration occurred from the Puma and Hoelon applications but was temporary. In general there was good crop safety from these three herbicides. MKH6561 and F130060 produced more consistent and higher levels (80 to 95 percent) of control. Higher levels of control were achieved from the late applications. Crop safety was marginal with both of these herbicides and ranged from 20 to 50 percent stunting. Injury was higher from the late applications. Yields were not taken in this test and the effect of this stunting on yields was difficult to access visually.