Rimsulfuron, marketed as Matrix SG by Corteva, is registered on tomatoes in California is widely used both PRE and POST for nightshade and other broadleaf weed control. Based on research conducted in Italy that showed promising broomrape control with rimsulfuron applied in the irrigation water through surface drip lines (Conversa et al.), we did pilot studies in 2021 and 2022 in California.
With initially promising results, the California Tomato Research Institute submitted a 24c label (“Special Local Need”) request to California Department of Pesticide Regulation. The request was to add a chemigation application technique specifically for management of broomrape. The 24c label was approved in September 2022 and is available.
A breakdown of the 24c describing the approved chemigation application process is below.
From Corteva Matrix Label (https://ucanr.edu/blogs/UCDWeedScience/blogfiles/97715.pdf):
- For use on processing tomato for management of broomrape (Phelipanche ramosa, aka Orobanche ramosa) and Egyptian broomrape (Phelipache aegyptiaca). For management of broomrape, apply Matrix SG through buried- or surface-drip irrigation tubing to transplanted tomato. Apply at an application rate of 1.33 oz/A for up to 3 applications per season at approximately 30, 50 and 70 days after transplanting.
- Refer to product label for Matrix SG for Use Precautions, Mixing and Application directions.
- Surface or buried drip irrigation applications simulate banded applications.
- The amount of water and injection time may vary depending on soil type and irrigation system used. Introduce Matrix SG into the irrigation system at approximately the midpoint of the irrigation set to limit movement of the herbicide beyond the tomato root zone, where broomrape germination and attachment occurs, which may improve broomrape control. Factors such as soil type, irrigation system, injection timing and length, drip tape placement, etc. may affect weed control when Matrix SG is used through the drip irrigation system.
- After Matrix SG has been evenly applied across the field, flush the irrigation system prior to ending the irrigation.
- Do not apply more than a total of 4.0 oz/A Matrix SG (0.0625 lb ai/A rimsulfuron) on tomato during the same year.
- Do not make more than 3 applications of Matrix SG per year.
- Preharvest Interval: Do not apply within 45 days of harvest.
- This label must be in the possession of the user at the time of application. Follow all recommendations and restrictions on the Matrix SG Section 3 labeling.
It is important to note that when using rimsulfuron as a chemigated material following the label, you are using the yearly maximum rate of 4 oz/acre. For growers that do not use rimsulfuron as a PRE or POST product, this will not change current weed control programs. However, if growers currently utilize rimsulfuron as a PRE or POST product in their current programs, it will need to be excluded to avoid going over the annual 4 oz/acre maximum. This may affect general weed control, as rimsulfuron is often used to target nightshade species. Research into alternatives to rimsulfuron for general weed control in processing tomatoes will begin in 2023.
As with any pesticide, it is important to read and follow the most current label instructions for application.
We would like to thank the California Tomato Research Institute for funding ongoing broomrape management research and coordinating the 24c request, Corteva Agrisciences for providing product for the research and internal data from the US and Europe to CDPR, and our cooperators who hosted herbicide research trials that support the entire processing tomato industry.
Matt Fatino is a UC Davis Ph.D. student with Brad Hanson's Lab.
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