RESUMO
The lesion nematode, Pratylenchus thornei, was clearly demonstrated as a parasite of wheat. It reduced plant stands and stunted plants in the field under the environmental conditions found in Sonora, Mexico. Other soil organisms also may have contributed to the problem. The nematode is widely distributed throughout the wheat-growing region, and may be a problem each growing season. Nematicides controlled the nematode and increased yields, but they were not economical. No resistance was found in existing commercial wheat cultivars. A pest management approach using variety selection, nitrogen fertilizer, planting in cool soil (15 C) and a crop rotation avoiding wheat after wheat was the most practical solution to this problem on a commercial scale.