A new herbicide is available this year for use in California rice: RebelEX®, manufactured by Corteva. It is a premix of two other well-known herbicides: Clincher® and Granite SC®, both from Corteva. The active ingredients in RebelEX® are cyhalofop (same as Clincher®) and penoxsulam (same as Granite SC®). Since it contains cyhalofop, it is important to check with your respective counties on the buffer zones and aerial application restrictions for Clincher®, as the same permit conditions will apply.

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.

Label and SDS: https://www.corteva.us/products-and-solutions/crop-protection/rebelex-ca.html  

 

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. 

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.

I have heard that there may be a shortage of aqua-ammonia (aqua) fertilizer for the start of this year's rice season. This begs the question as to what are the options. In previous studies, we have compared aqua to urea fertilizer. In one study, we compared aqua to liquid urea; and in another study we compared aqua to granular urea. The liquid urea was applied exactly as one would apply aqua (injected 3 to 4 inches below the soil surface). The granular urea was applied to the soil surface, but then lightly incorporated. How much you incorporate depends on the state of the seedbed. If you have a cloddy seedbed, a lot of the urea will fall into the cracks between the clods and relatively little is needed (maybe a light harrow in front of a roller). If you have a fine seedbed it may require a light disking. Importantly (and good news), is that urea dissolves relatively quickly and the flood water also helps move the dissolved urea further down the soil profile (this is not the case with ammonium sulfate). In both studies, we found that urea performed similar to aqua (in terms of yield and N uptake efficiency). However to get these results, you must make sure that the urea is applied to a dry soil before flooding and it be managed so that it gets incorporated below the soil surface before planting (or banded as you do with aqua). I have found that when urea is used, that the crop never seems as uniform as when aqua is used as the main N source; however this has not affected rice yields. It may affect your ability to assess the crop mid-season for an N deficiency.

If you flood the field before applying your nitrogen fertilizer, then have to apply all of your fertilizer N into a flooded rice field. In this case, your N use efficiency will be less and the cost of application will be higher. If you are in this position, apply N in four split applications. Apply 20, 30, 30 and 20% of the N rate at around 2, 4, 6 and 8 weeks after planting, respectively. The first N application should be ammonium sulfate or a starter blend of fertilizer (one that contains N, P and K). We do not recommend urea for the first N application. The other three applications could be urea. Efficiency will be lower in this system, so you may need to increase your overall N rate.