Researchers at Montana State University have found microscopic root-lesion nematodes at economically damaging levels in 14 percent of the fields sampled in the state. The nematodes were discovered more often in no-till fields than in fully tilled fields, and in fields that had been previously cropped to winter wheat rather than spring wheat.

Damage from root lesion nematodes in wheat results in stunting, premature yellowing of older leaves, reduced tillering and low kernel weight. It is difficult to distinguish the nematode damage from that caused by nutrient deficiencies and drought.

The nematodes are microscopic “worms” that are practically transparent. Root lesion nematodes thrive where other nematodes don’t. By invading plant roots and spending most of their life cycle inside the root, they remain active when the absence of free soil moisture would limit most nematodes.

No Easy Solutions.

There are no chemical control methods approved for use against the nematodes in small grain, and no wheat varieties have been bred to resist them because nematodes were not previously known to cause economic damage. However, tests conducted in Oregon last summer show two of Montana’s spring wheat varieties, Choteau and McNeal, have some tolerance to nematode infestations.

In addition, winter wheat breeder Phil Bruchner is working on developing nematode resistance. “We have made initial crosses for moving resistance to root-lesion nematodes into varieties,” he says.

The nematodes were discovered after Dave Wichman, superintendent of the Montana Agricultural Experiment Station’s Central Agricultural Research Center at Moccasin, noticed a poor yield and a…