In rice, herbicide-resistant barnyardgrass (Echinochloa crus-galli [L.] Beauv.) is the most common noxious weed, as it inhibits rice growth and reduces grain yield. Barnyardgrass infestations in rice can result in yield losses ranging from 30 percent to complete crop loss.
Identifying barnyardgrass
To prevent yield loss, proper identification of barnyardgrass soon after emergence is critical. However, one should always try to control the weed prior to emergence.
Barnyardgrass is a summer annual grass weed that can reach heights over three feet tall with a large inflorescence capable of producing more than 39,000 seeds per plant.
It is easily visible in rice fields at maturity. To identify barnyardgrass earlier in the season, examine the collar region of the leaf. Barnyardgrass has a flat stem with no ligule, auricle or pubescence hair on the plant. The first true leaf is often smooth and wide with a rounded leaf tip. It will likely be observed growing in clumps with a fibrous root system.
When barnyardgrass reaches maturity, it produces a large, dense inflorescence with typically erect, branched panicles.
Why is barnyardgrass hard to control?
Barnyardgrass has a highly efficient C4 photosynthetic pathway, which makes it biologically dissimilar from C3 grass crops such as rice. This gives barnyardgrass a competitive advantage over these crops, and allows it to proliferate in the high light and high temperature environment of the Mid-South.
This weed seed also has the ability to spread through contaminated seed sources, irrigation water and the movement of equipment through infested fields. In recent years, barnyardgrass has developed resistance to several active ingredients, including glyphosate, propanil and ALS chemistries. Therefore, control of this troublesome grass weed has become more difficult to achieve in many rice fields.
In order to prevent yield loss, its important for growers and consultants to properly identify and control barnyardgrass early in the season. On acres where barnyardgrass has been identified in prior seasons, growers are encouraged to use pre-emergent residual herbicides and not rely solely on a post-emergence herbicide strategy.
Control measures
With some barnyardgrass populations showing resistance to multiple modes of action, it can be beneficial for growers and consultants to submit samples to their local university for herbicide resistance screening.
Work with your local UPL representative to determine an ideal herbicide strategy for your acres. One solution from UPL that growers can incorporate into their herbicide strategy is RICEONE® CS herbicide, which contains a mix of pendimethalin and clomazone active ingredients, and UP-STAGE™ 3CS herbicide, the number one pre-emergent solution for control of annual grasses in dry-seeded rice. As a delayed pre-emergent or early post-emergent application, RICEONE offers long residual control of grass and broadleaf weeds.
Learn more about the UPL Rice Portfolio from your local UPL representative or your local retailer.
