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Do You Believe In Fairy Tales?

Terry Niblack
Terry Niblack
Professor of Soybean Cyst Nematode Management
Department of Crop Sciences
(217) 244-5940; tniblack@illinois.edu

“Once upon a time, a contented farmer named Illinois Bois grew corn and soybeans in his fields. One day, he was out walking his beans, and he saw large patches of stunted, yellow bean plants. His heart sank, because he had heard that an evil worm called SCN was attacking beans throughout the kingdom, and that stunted, yellow patches were a sure sign that SCN was in his field. He knew his crop would be poor. Worse, it was no consolation to know that he could buy magic beans to plant in the affected field, because he’d heard they weren’t as productive as the beans he was used to growing . . .”

Figure 1 figure 1
Figure 2 figure 2
Figure 3 figure 3

The story could go on, with unscrupulous wizards and magic potions to kill the evil SCN, but everyone has heard the same tale in several variations. They all come out the same in the end: Nobody is happy ever after. But it doesn’t have to end that way—it only does because we haven’t questioned the myths at the beginning of the story. How many of these do you believe?

Myth 1: The evil worm SCN causes patches of stunted, yellow plants.

Myth 2: Stunted, yellow plants are a sure sign of SCN.

Myth 3: Magic beans aren’t as productive as regular beans.

The truth about Myth 1 is that SCN reduces yields without causing stunted, yellow plants. Look at Figures 1 and 2, constructed from data collected from field studies in Illinois, Iowa, and Missouri. What they show is the truth about Myth 1: perfectly healthy-looking plants lost a lot of yield if they were infected with SCN.

The truth about Myth 2: Stunted, yellow plants are a sure sign that something is wrong, but not that SCN is necessarily the cause. The only way to determine whether SCN is a problem in a field is to sample the soil and have a soil test run by a reputable lab.

The truth about Myth 3: “Magic” beans for us are SCN-resistant varieties. Many of these varieties yield as well as susceptible varieties in fields with high levels of SCN. But are all resistant varieties the same? No, and they don’t all have the same resistance. Look at Figure 3, from the 2002 Soybean Variety Testing program, showing the levels of resistance in 183 different varieties to “Race 3” SCN. In this graph, higher bars mean less resistance, and you can see that many of our top-selling resistant varieties are twice as susceptible as others. For the 2002 screening data, visit the Website. There will be information on 438 varieties in the fall of 2003.

Keep the truth in mind and don’t believe the myths about SCN. That way, “happily ever after” is possible.

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