- Author: Whitney Brim-DeForest
- Author: Roberta Firoved
The labeled weeds that RebelEX®controls are sprangletop, watergrass (both early and late), barnyardgrass, ricefield bulrush, Monochoria, redstem, ducksalad, California arrowhead, and water plantain. It does not have a water-holding period. The application timing begins from when the rice has one leaf or more, up to 60 days before harvest. Efficacy, as with most products, is better when the weeds are smaller. For flooded fields, it is important to have maximum contact, so it is recommended to lower the water in the field until at least 70% of the weed biomass is exposed, before application.
The product is “rainfast” (meaning it isn't affected by water) within 2 hours, so reflooding quickly is recommended. The label recommends restarting the flood at 3 hours after application, and to have the field completely reflooded within 24 to 48 hours at a maximum. Long drainage periods can encourage additional germination of certain weed species, including smallflower umbrella sedge, watergrass, barnyardgrass, and sprangletop.
Since RebelEX® also contains penoxsulam, it cannot be applied in the same season as Granite GR® or Granite SC®. Doing so will cause significant phytotoxicity to the rice, and will likely impact yields. Clincher® can be applied in the same season, but depending on the rate of RebelEX® applied, the Clincher® application rates will vary, so please refer to the label for rates and timings if planning to also apply both herbicides in the same season. For management of resistance, however, it is not recommended to apply Clincher® and RebelEx® in the same season, as both contain the same active ingredient, cyhalofop. Repeated applications of the same active ingredient (cyhalofop) will select for resistance in sprangletop, barnyardgrass, and watergrass (both late and early).
Remember to always follow all label instructions when applying any pesticide, as the label is the law. Make sure to pay particular attention to the Use Precautions and Restrictions. Consult your local Agricultural Commissioner's Office regarding buffer zones and aerial restrictions, before making any applications.
This year we are conducting a study at the Rice Experiment Station to look at lodging differences between M-206 and M-105. There has been anecdotal evidence that M105 is more susceptible to lodging than M-206. We want to quantify this and see if we can manage N to reduce lodging if need be. Anyways, with this experiment, we have both of these varieties side-by-side in experimental plots. We used Cerano as part of the herbicide program. You can clearly see from the picture that M-206 is more susceptible to Cerano bleaching than M-105. Ray talked with Kent McKenzie about this and he also said he had seen similar findings. Anyway, we thought this might be interesting information for you.
- Author: Luis Espino
While checking traps recently, I noticed a lot of activity in the water in several recently flooded fields. A quick glance into the water might make you believe that tadpole shrimp is present in large numbers, or even perhaps that a treatment did not work. Make sure you look closely and don't confuse clam shrimp with small tadpole shrimp.
Clam shrimp are small crustaceans that look like a miniature clam; they are about a tenth of an inch and swim in the water slowly. Clam shrimp don't have the "tail" that tadpole shrimp have at the end of their shell. Most freshwater clam shrimp feed on algae and organic detritus. I am not sure what the ones in rice fields feed on, but they do not injure the rice. In the past, I have noticed that these clam shrimp come back after a tadpole shrimp treatment very quickly.
Clam shrimp close up
Large congregation of clam shrimp around decomposing rice roots
Tadpole shrimp are more problematic during seed germination. Once the seedlings have a well anchored root and the spike is green, tadpole shimp are less likely to injure them.
Following my blog post about a week ago about using urea or aqua-ammonia (aqua), a number of people have been asking to see the data. The study was conducted in 2017 at the Rice Experiment Station. Aqua and liquid urea were applied at three rates (50, 100 and 150 lb N/ac). Both N fertilizers were injected into the soil at 3 to 4 inches depth. Treatments were replicated three times. Across the N treatments, yields were similar between the aqua and liquid urea treatments. Yields were low, but overall state-wide yields in 2017 were low as well. In other studies (data not shown), we used dry urea banded into dry soil before flooding to the same depth as aqua we saw almost identical yields across seven on-farm studies. Based on these data, liquid or dry urea that is injected or buried into a dry soil before flooding, performs the same as aqua.
This morning I was out with several members of our research team on the northwest side of the valley planting a variety trial. The grower we were working with had just finished planting all of his rice acreage (1200 ac) yesterday (April 30). Pretty amazing how fast the rice is getting in this year. I know the west side is often earlier than the rest of the valley; however, growers around the valley are moving much faster this year. By the end of next week, we will likely have all of our variety trials (we have seven this year) planted. We have accomplished this so early before.
This is a good start to the season! Generally, when we plant early, yields tend to be higher. This is clear from the figure below. This figure shows state-wide yield averages from 1994 to 2019 relative to the date when 50% of the rice acreage had been planted (based on USDA data). One reason for higher yields is that dry springs (which allow for early planting dates), also give growers time to prepare their seedbed exactly how they want to without skipping passes. From the UCCE Rice Yield Contest, we have seen that good and uniform stand establishment is a key for high yields. Realizing, that the yield potential may be higher this year, the N fertilizer requirement may be a bit higher. It will be important to access the crop midseason (around PI) to see if the crop may need more N fertilizer to realize its potential. This can be done with either a Leaf Color Chart or the Green Seeker.
The UCCE Rice Yield Contest (http://rice.ucanr.edu/Rice_Yield_Contest/) will be running again this year and we look forward to your participation and learning more about how to achieve high yields. The 2020 forms will be available soon. You will need to enter the contest by the Annual Rice Field Day in late August.