Tank-mix Options for TSA and Dogfennel Control

Dr. Brent A. Sellers and Dr. Jason Ferrell

tsa & dogfennel Tropical soda apple (TSA) continues to be a problem in Florida pastures, but other weeds are often present in significant numbers. Dogfennel is the most widely encountered weed in Florida pastures and it is commonly found growing along with TSA. Although Milestone is highly effective on TSA, it provides little or no dogfennel control. Likewise, Forefront (a mixture of 2,4-D and Milestone) is more effective than Milestone, but still fails to control large dofennel. To illustrate, UF-IFAS research has shown that Forefront applied at 2 pints/acre was excellent on TSA, but highly inconsistent (30 to 95% control) when dogfennel were 30 inches tall or greater. Increasing the rate to 2.6 pints/acre improved the consistency of control for 30 inch-tall dogfennel. However, it was soon observed that the 2.6 pt/A rate was ineffective if plants were 40 inches tall or greater. Since TSA and dogfennel of all sizes are common throughout Florida, Forefront + another herbicide will be required to maximize control of both TSA and dogfennel.

To determine what herbicides could be tank-mixed with Forefront to provide adequate control of both dogfennel and TSA, many combinations were tested. The ultimate goal was to maximize weed control without adding more than $6/acre to 2 pints/acre of Forefront; therefore, the total cost of the tank-mix would not exceed $22/A. The most promising combinations were 8 fl oz/A of Vista, 1 pint/acre of Pasturegard, 2 pints/acre of WeedMaster, or 3 pints/acre of 2,4-D amine. Each of the herbicides, when mixed with 2 pints/acre of Forefront, provided at least 88% control of 40 inch dogfennel 60 days after treatment (Figure 1). TSA control with these tank-mixtures was approximately 90% at 60 days after treatment.

In Figure 1, the addition of $4-6/acre increases dogfennel control from 60% with Forefront to at least 88% with Forefront and one of the four tank-mix partners. Therefore, as you scout your pastures for TSA, be sure to also look for other weeds as well. If you have pastures with both dogfennel and TSA, consider one of these four tank-mix options to get the most for your money.

Fig. 1