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Corn+Soybean Digest

Ask The Experts

What can I do now to better prepare for the inevitable soybean rust infestation?

(SAX) Preparation will be a key part of limiting potential yield losses from soybean rust. Farmers can better prepare themselves in the following ways:

First, don't hesitate when you need to spray. Given the explosive nature of soybean rust, delays in spraying can result in significant yield losses. Typically farmers are most hesitant to spray for a pest the first time they need to treat for that pest. Make up your mind before someone finds rust in your area.

Second, have the right equipment available. If having fields custom applied, know who will spray the fields for you and that they will do it correctly. By right equipment I mean a sprayer that can apply high gallonage (15-20 gal./acre) at high pressure with appropriate spray tips.

Third, monitor the movement of soybean rust in the U.S. Be prepared to spray before soybean rust is found in your region.

Fourth, know the products that you might use and their availability. The first time we need to treat for soybean rust will most likely be the year that appropriate products may be in shortest supply.

(HARMS) Step one is to spend some time this winter learning what rust looks like and understanding spray options. There are two basic groups of chemicals you can use. One has some curative ability and the other is strictly preventative. If you have a rust infection of 10% it's a little late to spray a preventative material.

Soybean rust causes so much damage so fast that the key is constant vigilance. Monitor your beans at least once a week until the reproductive R1 stage. After R1, keep a closer watch on your beans. If rust is reported within 500 miles upwind, check them at least two times per week and be ready to take action.

Rust can infect beans as early as the cotyledon stage, but the worst damage is usually after reproduction starts. Check the undersides of the leaves on the lower parts of the plants, since that's usually where it will start.

The first symptoms will look somewhat like septoria brown spot or bacterial pustule. It may also be confused with bacterial blight or downy mildew.

The key to fighting rust is to monitor your beans often and thoroughly. If you suspect rust, immediately bring in an expert. There are no magic bullets but the key is quick action. You cannot wait to see what your neighbor does. Have a plan ready and take action quickly.

Will soybean aphids be a problem in '05?

(SAX) Predicting soybean aphid populations from year-to-year is difficult. We are still in the learning phase of multi-year population dynamics.

Some researchers have suggested that we may experience two-year cycles in aphid populations — a high population year followed by low population year.

One factor that may impact multi-year aphid populations is the improvement in aphid management by producers. Will next years population be decreased by proper management of current aphid populations? Will the use of seed treatments suppress aphid populations such that yearly infestations are not as significant? Or is overwintering and early season climate the major factor affecting next year's population? So many questions, so few answers!

In my experience, the single most significant factor affecting infestation level differences is distance from overwintering sites.

I have client fields adjacent to overwintering areas that have been treated each of the last three years. Other fields more distant have only been treated one year. As I have tracked population dynamics, it's evident that speed of dispersal from overwintering areas and population doubling time are closely related to extent of infestation each of the last three years.

I recommend my clients plan to treat 50-75% of their acres this year. If the infestation does not materialize, then cash flow will be improved. If the infestation does materialize, most or all of the treatment expense will be accounted for in the yearly cash flow.

As last year proved, treatment should always be based on thorough field scouting. We'll need to scout fields in 2005 to know for sure whether or not soybean aphids will be a problem in 2005. As a businessman, I'll manage my business expecting the added workload of soybean aphid monitoring from early July through late August of 2005.

(HARMS) We've monitored soybean aphids since they entered this country about five years ago in Lake County, IL. They can cause significant yield loss if ignored, but can be controlled with little loss if monitored.

Unlike other aphids, they don't like hot, dry weather. There's no way to predict if we will have a problem, but it's best to plan for one and monitor your beans closely between the first of July and the end of August.

It's important to look for predators as well as aphids. If there are sufficient predators and small numbers of aphids, then the predators can control them best. But if the aphid population starts off with few predators, then the aphid population can explode rapidly.

Also look for winged aphids. This means that they're probably moving to a new field.

Are there any seed treatment options for soybean aphid control?

(SAX) Currently, Gaucho seed treatment is labeled for soybeans and also provides some level of control for soybean aphids. CruiserMaxx Pak has also been approved.

Both of these products will provide soybean aphid population suppression well into July. Under low population scenarios, I have seen these population reductions last into late July and early August. In years when the soybean aphid population is marginal, this might be enough reduction in population to avoid the need for treatment of aphids.

Current research suggests that in high-infestation years, these products will not provide season-long aphid control. Our best protection appears to be coming from a resistance gene which is expected to be available to producers in a few years.

(HARMS) There are two materials that will probably be registered by spring, but I have not been convinced that either of them will provide sufficient control in a heavy infestation.

The best approach is still to monitor and treat when necessary. We do have hope for a resistant gene that shows promise in reducing the affect of aphid feeding.

Have a question? Simply e-mail it to [email protected] and we'll address it in a future issue.

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