The project was funded by the California Rice Research Board, and is led by Whitney Brim-DeForest (UCCE Sutter-Yuba) and Marie Jasieniuk (UC Davis).
We are reaching out to ask for locations of rice fields from growers and PCA's, so our team can go out and collect seed. We are looking for all types of watergrass: "mimic", early watergrass, late watergrass, barnyardgrass (Figure 1), and the new species that we started seeing a couple of years ago (Figure 2). We hope to start collecting in the next week or two, through the end of September.
For more information, and if you are interested in having us come out and sample your field(s), please contact Whitney Brim-DeForest (firstname.lastname@example.org), or call 530-822-7515.
I have been to several farm calls in the past few weeks with this weed (pictured below). I have seen 7 fields between last year and this year that appear to have bad infestations of this new watergrass species (Echinochloa spp.). We are unsure of the exact identification yet, but we know it is in the watergrass family.
The weed is maturing around mid- to late-July. It is small-seeded, and the awns are long and purple. All of the plants I have seen so far have seed heads that are completely awned, which makes it different than barnyardgrass (which has seed heads that are variably-awned).
How to ID:
o Every seed head has awns (unlike barnyardgrass)
o Should already be headed (by mid- to late-July)
o Awns are purplish in color (see photos)
o Seeds are small (smaller than late watergrass)
Please call Whitney Brim-Deforest (541-292-1553) or Luis Espino (530-635-6234), if you suspect that you have this weed in your field. We would like to collect seed samples to see what can be done to control it.
Photo 1. Seed head of unknown watergrass species (Echinochloa spp.) Notice visible purple awns.
Photo 2. Seed heads of unknown watergrass species (Echinochloa spp.) Notice visible purple awns, which can be seed before seeds are fully mature.
Photo 3. Full plant sample of unknown watergrass species (Echinochloa spp.). This plant headed in late July.
As many of you are aware, many of our grass species in California rice are resistant to multiple herbicides. Late watergrass aka "mimic" (Echinochloa phyllopogon), early watergrass (E. oryzoides) and barnyardgrass (E. crus-galli) are among some of our most competitive weed species, causing large yield reductions when uncontrolled.
One of the last remaining chemicals that our grass species are not yet resistant to is pendimethalin. Commercial formulations for pendimethalin registered for California rice are Prowl H2O and Harbinger. Prowl H2O is a delayed pre-emergent herbicide applied onto dry, drill-seeded fields. Harbinger is also a delayed pre-emergent herbicide, but the Harbinger system can be used in fields that are seeded by air. Both are viable uses of the chemical, and which one you choose will depend on your available equipment. For more information on how to apply, refer to the product labels.
Although I have used Prowl H2O in field trials and have a pretty good idea of its efficacy, I was curious to see how Harbinger looked in the field, since I have not yet had the opportunity to use it in a trial. I recently visited Rice Researchers, Inc., a rice breeding facility in Glenn County, where they are using a Harbinger-based program, for the second season. The photo (below) shows the rice at about 30 days after seeding. No weed species were present in the field. This is after one delayed pre-emergent Harbinger application.
It is too late to utilize pendimethalin this season, but for help incorporating pendimethalin into your herbicide plan for 2018, talk to your PCA, or give one of the UCCE Rice Advisors a call. Especially for growers that have herbicide resistant grasses, it can be a valuable tool in reducing grass populations.