Growers and PCAs asked about the potential injury that can be caused by a mix of RoNeet (Cycloate) with Dual Magnum (S-Metholachlor) to spinach. We did a small evaluation including the treatments suggested by our friends to collect data. A 1.33pt rate for Dual M and 4.0 pt of RoNeet was sprayed for this trial. The lower Dual M recommended rate by the SLN for AZ in 2017 of 0.33 - 0.67 pt per acre was not included in the trial¹. Here’s the treatment list:

1. RoNeet 2.0pt + Dual M 1.33pt
2. RoNeet 4.0pt
3. Dual M 1.33pt
4. UTC

Plots consisted of two rows 30ft long replicated four times with 10 seed lines, and the test was established in a randomized complete block design with four replications. All treatments were applied preemergence. A CO₂ backpack with a 4 flat fan nozzle boom spaced at 20” was used delivering 20 gallons/acre. 
Planting was done on Nov 17, 2022, then the next day the treatments were applied and incorporated immediately with sprinkler irrigation. Crop injury was evaluated on December 13, 21 and 27. The combination of RoNeet plus S-Metolachlor at the rates above mentioned presented the highest phytotoxicity symptoms in the form of chlorosis, stunting, and reduced stand. Also, Dual Magnum alone at the rate of 1.33 pt/a presented injury in lower proportion compared to the combination with RoNeet. In this evaluation the 4pt/a rate of RoNeet did not present injury to the spinach as you can see comparing with the untreated plots below. Weed control data was not collected due to inconsistent and low populations. Only phytotoxicity was evaluated.

The most representative images of the plots are below:

Figure 1. Preemergence herbicide injury evaluation on spinach

1. https://searchagriculture.az.gov/esd/slns/AZ120006.pdf