Can Imazapic and Seeding Be Applied Simultaneously to Rehabilitate Medusahead-Invaded Rangeland? Single vs. Multiple Entry.
Davies, K.W., M.D. Madsen, A.M. Nafus, C.S. Boyd and D.D. Johnson. 2014.
Abstract
It has recently been proposed that the cost of rehabilitating medusahead (Taeniatherum caput-medusae [L.] Nevski)-invaded
rangelands may be reduced by concurrently seeding desired vegetation and applying the preemergent herbicide imazapic.
However, the efficacy of this "single-entry" approach has been inconsistent, and it has not been compared to the multiple-entry
approach where seeding is delayed 1 yr to decrease herbicide damage to nontarget seeded species. We evaluated single- and
multiple-entry approaches in medusahead-invaded rangelands in southeastern Oregon with seeding for both approaches
occurring in October 2011. Before seeding and applying herbicide, all plots were burned to improve medusahead control with
imazapic and prepare the seedbed for drill seeding-introduced perennial bunchgrasses. Both approaches effectively controlled
medusahead during the 2 yr postseeding. However, almost no seeded bunchgrasses established with the single-entry treatment
(< 0.5 individuals . m-2 ), probably as a result of nontarget herbicide mortality. Perennial grass cover and density in the single-
entry treatment did not differ from the untreated control. In contrast, the multiple-entry treatment had on average 6.5 seeded
bunchgrasses .m-2 in the second year postseeding. Perennial grass (seeded and nonseed species) cover was eight times greater in
the multiple-entry compared to the single-entry treatment by the second year postseeding. These results suggest that the
multiple-entry approach has altered the community from annual-dominated to perennial grass-dominated, but the single-entry
approach will likely be reinvaded and dominated medusahead without additional treatments because of a lack of perennial
vegetation.
Key Words
annual grass control, invasive plants, preemergent herbicide, revegetation, sagebrush, Taeniatherum caput- medusae
