By Janet Raloff
Many people don’t like the biting taste of mustard. Neither, it turns out, do sting nematodes—small, parasitic roundworms that siphon food from plant roots. That finding could prove good news for maintaining golf courses, sports fields, and other picture-perfect lawns.
Some weeds and other plants naturally resist sting nematodes (Belonolaimus longicaudatus Rau). Suspecting that these plants produce defensive chemicals, Campbell J. Cox and his colleagues at Clemson (S.C.) University applied extracts from several of these plants and a few other candidates to the roundworms in test tubes and greenhouse soils. The group included spotted spurge, tall lettuce, goldenrod, lantana, poinsettia, and a mustard.
Mustard-seed and poinsettia-shoot extracts proved most effective, Cox’s team reports in the July-August Agronomy Journal. In their greenhouse experiments, the poinsettia preparation killed virtually all the sting nematodes in grass, but only if it remained in the root zone for 4 days. Irrigating the grass during that period dramatically diminished the extract’s effects.
On the other hand, the mustard killed most of the roundworms within 2 days after an application, even when the researchers watered the grass during that time. Indeed, such irrigation might be essential in applying the mustard extract, Cox notes, since the extract caused leaf damage when it dried on the blades of grass.
