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Rice herbicides gain special local need labels

A 24(c) label is a special local need label granted by a state for a certain use or rate for an already-registered product. Arkansas and other states have issued several 24(c) labels for rice herbicides this year.

The labels allow very specific uses of the products and are not full registrations. It is very important to read and follow the label when using a product under a 24(c) registration.

Command by air enters its third season of use under a special 24(c) label in Arkansas. The program thus far has been a tremendous success. Very few drift concerns have resulted from aerial applications of Command, due to the new 3ME formulation of Command and to efforts by the Arkansas State Plant Board and the Arkansas Aerial Applicators Association to standardize most airplane spray systems with modern low drift spray systems.

The 24(c) label states that Command can be applied by air from 14 days before to seven days after planting, but prior to weed emergence. It also allows tank mixtures with certain other rice herbicides up to the one-leaf to two-leaf stage of rice.

Command provides very little activity on emerged weeds. The tank-mix options are to control grass that has already emerged. The options for Command by air are strictly limited to those listed on the 24(c) label due to concerns over the tank-mix partner’s effect on the droplet spectrum of the spray solution.

Products listed on the 24(c) label include: Aim, Bolero, Clincher, Cornerstone, Duet, Durango, Facet, Glyphomax Plus, Glyfos Xtra, Grasp, Newpath, Propanil, Regiment, RiceStar, Stam, SuperWham, Touchdown IQ, crop oil concentrates, and nonionic surfactants. They have been tested and found to be safe from a drift standpoint.

Other tested products have negative effects on spray droplet size, creating drift potential for Command. Those products are not listed on the 24(c) label.

There is still a 1,200-foot buffer restriction on Command applications near towns, houses, greenhouses and nurseries. The buffer may be reduced or eliminated in the future, based on the positive results of this 24(c) label so far, but the buffer is in effect for 2005.

RiceStar HT has also received a 24(c) label for use in Arkansas rice this year. The label allows up to 24 fluid ounces per acre of RiceStar to be used on larger, tillering grass after the rice has reached the two-leaf growth stage and prior to flooding. The label increases the use rate from a maximum of 17 fluid ounces per application to 24.

Good soil moisture is still required with RiceStar HT and other graminicides, such as Clincher, for optimum activity on grass weeds. RiceStar HT must be applied at least 14 days prior to panicle initiation.

The label also allows post-flood applications of RiceStar HT for the suppression of barnyardgrass and other grass weeds. In my research, however, a lower rate of Clincher (15 ounces per acre) has provided equivalent or better control of grass when applied seven to 10 days after flood.

With either product, good coverage is essential and no more than 25 percent of the target weed should be covered by flood water. A post-flood application of Clincher or RiceStar HT made more than 10 days after flood has been much less effective.

Finally, we are in the second year of a 24(c) label for Beyond herbicide in Clearfield rice. Our Beyond 24(c) label is for 5 fluid ounces per acre of Beyond applied no later than 14 days after panicle initiation to Clearfield varieties only. Beyond is for use only following the failure of two 4-ounce-per-acre applications of Newpath herbicide to control red rice. This label is specifically designed to help prevent the out-crossing of red rice plants that survive a Newpath program with Clearfield rice varieties.

Last year Beyond performed well on larger red rice, and in most cases was used as a spot spray to treat areas where Newpath applications missed red rice or streaks, corners and skips in the field.

Many Clearfield users are looking for ways to get around the crop rotational issues with Newpath herbicide. Beyond herbicide does not have the crop rotational restrictions that Newpath does, however, any use of Beyond outside of that described in the 24(c) label is considered an “off-label” application and a violation of state and federal law.

One factor in whether or not the EPA and state plant boards grant 24(c) special local need labels and Section 18 labels is in their ability to confirm the proper use of the herbicides under those labels. Please always read and follow all pesticide labels and directions for use.

Bob Scott is the University of Arkansas Extension weed specialist. e-mail: [email protected]

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