Leafy spurge control with angora goats and herbicides.

Abstract

A 4-year experiment to evaluate herbicide treatments with grazing by goats to improve long-term leafy spurge (Euphorbia esula L.) control compared to either herbicides or goats was established on the Sheyenne National Grasslands and the Gilbert C. Grafton South State Military Reservation in North Dakota. Six treatments were evaluated including an untreated control, grazing alone, herbicides applied in the spring or fall alone, grazing following spring-applied herbicides, or grazing during the season prior to fall-applied herbicides. Leafy spurge was rotationally grazed at the Sheyenne National Grasslands but was grazed season-long at Camp Grafton South. Grazing combined with fall-applied herbicide treatment reduced leafy spurge density rapidly and maintained control longer than either method used alone. Picloram (4-amino-3,5,6-trichloro- pyridinecarboxylic acid) plus 2,4-D [(2,4-dichlorophenoxy)acetic acid] applied annually in the spring reduced leafy spurge density similar to or better than the same treatment combined with grazing. Also, leafy spurge control tended to be more rapid with continuous than rotational grazing. The best treatments averaged over both locations were picloram plus 2,4-D at 0.5 plus 1.1 kg ha-1 applied in the fall alone or preceded by spring grazing. These treatments reduced the stem density by 98% from an average of 16 stems per 0.25 m2 at the start of the experiment to 0.3 stem per 0.25 m2 3 years later. Leafy spurge stem density still only averaged 1 stem per 0.25 m2 12 months after the last treatment of season-long grazing plus a fall herbicide treatment compared to 6.5 stems per 0.25 m2 when either method was used alone. Grazing and herbicide treatments alone or in combination reduced the root protein content at both locations but the effect on root carbohydrate content was minimal.