Sugarcane Brown Rust Information
By Jeff Hoy, Department of Plant Pathology and Crop Physiology, LSU AgCenter
Brown rust is evident in more advanced plant cane in the southern areas, so it turns out fungicide applications will be advisable in some areas this season. You guys are the front line for providing information to your growers concerning whether to spray, what, and when. Blaine alerted me, and I looked at fields yesterday along the Teche and Bayou Lafourche. Was not sure of the variety always, but rust has been observed in HoCP 96-540, L 01-283, and HoCP 09-804.
Fungicide options most available are Priaxor and Quilt Xcel. The application rate ranges are 5-7.5 oz/acre for Priaxor and 16-20 oz/acre for Quilt Xcel. These are broadcast rates. If the crop has not covered the middles, a banded application will be effective and less expensive.
Headline at 9 oz/acre broadcast is effective, but BASF has steered users to Priaxor, and this product is effective. A new fungicide combination has been labeled by Syngenta for brown rust control in sugarcane: Aprovia Ace. The recommended rate is 13.7 oz/acre broadcast. It has a fungicide with a different chemistry, solatenol, along with propiconazole. I have no experience with it, as we have not had enough rust to have an efficacy trial for several years. It has worked well in Florida. It will be helpful in rotation to prevent resistance developing to the strobilurins that have carried the load for us. Aprovia Ace may have limited availability at the dealers this season.
Rust will hit plant cane fields of susceptible varieties on light soil with high fertility and more protected locations. These are the fields that will need to be monitored closely and possibly treated. There will not be that much plant cane acreage of HoCP 96-540 and L 01-283, but much of it will be on light soil. HoCP 09-804 is in the expansion phase. The bottom line is: managing rust with fungicides will provide a positive economic return, particularly with a broadcast application.
As far as when to apply, rust will take off when the crop does. A fungicide spray will protect emerging leaves. The fungicide will provide approximately 3 weeks of protection. If new leaves do not emerge during that time period, then a spray will have little value. Consistent night temperatures in the mid-60s are needed, and the application of nitrogen is then what gets everything going.
It is likely that fields developing strong rust in April will need two applications, if growers can manage it. Growers need to protect the yield potential in what will probably be some of their highest yielding fields. We always get more tillers than can make millable stalks. Our goal is to prevent rust from holding back spring shoot growth that contributes to eventual yield. We have an indeterminate growth grass crop, so every bit of shoot growth during the season contributes to yield.
If you have questions, please let me know (cell 225-485-4227), and I would like to know your observations so we can do the best job possible effectively managing the disease.