Longevity of Leafy Spurge Seeds in the Soil Following Various Control Programs

Abstract

Although picloram provided adequate control of leafy spurge (Euphorbia esula L.) for a minimum of 3 years, from 3,500 to 11,000 viable seeds remained in the soil, providing a source for rapid reestablishment of the infestation. Continuous sheep grazing for 8 years prevented annual seed set and reduced the size of the soil seed bank from > 3,500 to 15 seeds/m2, greatly reducing the chance of reestablishment from seed. Combining the data from the various treatments indicated that the average annual loss from the soil seed bank is 13% of the original population. This means that even though an initial application of picloram kills most of the vegetative portion of the plant, a repeat treatment is necessary to greatly reduce the number of seeds in the soil seed bank to prevent reestablishment by seed.