Asian soybean rust has been the topic of almost every meeting I have attended this winter. A lot of information has been made available; sort through it all before making any decisions. Almost everyone has your best interest at heart, but you must do your homework and stay on top of this issue.
Rust probably will be one of the biggest production issues most of us have ever dealt with, but it will remain so only for two to three years. Almost everyone is guilty of using Brazil as an example. While Brazilians have been an excellent source of information, I believe their experience will differ greatly from ours.
I am not downplaying the magnitude of rust, just letting you know it will be a couple of years until we get a better handle on it on our turf.
For starters, our winter is often ignored. This may not be much of an advantage, but it helps in China.
Second, if rust has to re-enter the United States (some years) and weather conditions vary from year to year, the impact of the disease will be different.
Third, 2005 will be our inaugural year. It has taken rust 102 years to reach the continental United States. In every country it has entered, yield losses have been minimal the first year. I do not envision us being different from any other country.
Soybean rust is difficult to identify. Under ideal conditions it can move fast. I believe growers in the Mid-South are doing a better job of in-field management, but rust can be confused with other diseases.
We keep hearing that you must spray prior to reaching 3 percent infection level. That is three plants per 100 plants with one pustule per plant (whole plant determination). That is virtually impossible. No one will take the time or make the effort to look that closely. Even if you did, by the time you identified that level, under ideal conditions yield losses will have occurred.
To aid you, all Mid-South states are planting sentinel plots. Sentinel plantings are an indicator crop; they will serve as an early warning system. In Mississippi, 23 fields were planted earlier than the bulk of the Mid-South crop.
The accompanying map shows the location of the sentinel plantings. The fields transect the state from the Mississippi-Alabama line above Lucedale to south of Natchez. Fields are also planted every 50 to 75 miles north of Natchez up the Mississippi River to north of Cleveland.
In addition, several fields are scattered in the central and eastern side of the state, and we will monitor the 27 fields in our SMART program.
Sentinel maps for other Mid-South states are available on the Internet at www.soyrust.org.
As of mid-April we had planted 18 fields. We are planting a late Group 3, a mid-Group 4, a mid-Group 5 and a late Group 5.
In mid-April, we started a second planting. By varying the maturity groups and having multiple planting dates, the sentinel fields will remain in the reproductive period for a long time. From bloom on, rust appears to have a greater impact on the crop. Our hope is that by using the indicator plots we can find rust early (if it is present) and give you a two- to three-week heads-up regarding control strategies.
Individual state control guidelines may vary slightly, but you may not get to use your first fungicide choice due to supply. If history repeats itself, rust should have a minimal impact on yield this first year. If that proves true, sufficient time will be available to fill the pipeline with needed products before next year.
All products are not created equal as far as rust is concerned. We have ranked the various materials based on efficacy, but this year we will be relying mainly on other countries' experiences. In addition to efficacy, cost and availability are factors to consider.
Several co-packs on the horizon will be priced in the neighborhood of single products. The supply problem I mentioned earlier is not your dealers' fault. Late labeling of products, the uncertainty of needs in the United States and other countries' needs will greatly affect supplies this first year.
A new Mid-South Web site is now online. The address is www.soyrust.org. Take a moment to look at it and give us any feedback since this is a work in progress.
Alan Blaine is the Mississippi Extension soybean specialist. e-mail: [email protected]