SCN Escapes Flooding Unscathed

Soybean Cyst Nematode ( Sam Markell )

After this spring’s deluge of rain, farmers might be wondering if there was any benefit in terms of reducing pest populations. For soybean cyst nematode (SCN), the unfortunate answer is no.

SCN does require oxygen, but not as much as farmers might think and therefore survived the spring’s less-than-ideal conditions.

“They absorb oxygen through their body wall or cuticle, which is made almost exclusively of proteins (and no chitin),” said Greg Tylka, Iowa State University nematologist and leader of the SCN Coalition in a recent press release. “Waterlogged soils may have greatly reduced levels of oxygen. But many plant-parasitic nematodes, including SCN, can survive long periods of time with little oxygen.”

According to research from the University of Arkansas, SCN juveniles can survive in water up to 630 days and possibly longer. In flooded soil they survived seven to 19 months depending on soil type. SCN eggs can survive through dormancy for years even without soybeans.

“Typically, the eggs are more tolerant of environmental stresses than hatched juveniles,” Tylka said. “So, it’s likely that SCN eggs in infested fields are not adversely affected by waterlogged soils either.”

Excessive water could spread the pest farther.

When soil moves it can spread SCN to new places. This year’s downpours lead to soil erosion in many areas, potentially spreading SCN’s infestation to new areas.

“Consequently, soil samples should be collected this fall to test for SCN in field where soybeans will be grown in 2020,” Tylka advised.