Simple Tips to Combat Asian Rust By Bill Casady

While the threat of Asian rust is still an unknown in our minds as we enter the 2005 growing season, the technology for spraying the needed fungicides is a known quantity. Although we could go into many details about spraying, it all comes down to just a few simple tips.

The target for a fungicide application to combat Asian rust is the whole plant. We usually consider the target to be the top of the canopy when spraying herbicides, and specifically the targets are the leaves of the weed plants. A fungicide application to combat Asian rust should cover the entire crop plant to achieve maximum efficacy.

To achieve good coverage, fungicides should be applied with a somewhat smaller droplet than used for herbicides and those droplets must reach down inside the canopy to cover not only the leaves but also the lower stem where Asian rust is most likely to thrive first. That means choosing a nozzle from a spray catalog that is rated excellent for fungicide applications and then adjusting the boom so that you get good canopy penetration.

Late stages of Asian soybean rust Photo from MU extension http://muextension.missouri.edu/explore/agguides/crops/g04442.htm

A tip or combination of nozzles that provides dual spray fore and aft better penetrates the canopy and can provide more complete coverage. This configuration is available as a single unit or with the use of a Y adapter that supports two nozzles.

Consider selecting a somewhat slower ground speed because you will want to get the boom somewhat closer to the top of the canopy for good penetration and also because you cannot do a good job with either bouncing or swinging booms.

Fungicide application techniques to combat Asian rust can certainly be as simple as a few new tips and a couple of basic adjustments, and all for as little as five to ten dollars per foot. Although air-assist sprayers deserve recognition for excellent deposition of fungicides deep into the canopy, the additional cost of an air-assisted sprayer may run 30 to 50 times the cost of a few good tips.

Bill Casady Food Science and Nutrition 573-882-4370