Control jubata grass hotspots in the Point Reyes Wilderness: Review of project funded FY2016–2018

Hamingson, Ellen

doi:10.36967/2302636

Jubata grass--one of Point Reyes National Seashore’s highest-priority invasive species--threatens important habitat in designated wilderness. Natural Resource funding ($210,000) was obtained to eradicate small infestations and bring 3,025 acres to maintenance level. Work was conducted 2016-2019 in the central wilderness, source of the highest jubata grass concentration. We treated 278 patches (7.8 gross and 3.0 net infested acres), 13% (37 patches) twice, across 3,300 landscape acres. About 17% were initially treated chemically; 83% were manually removed. Due to increased costs, jubata grass spread, and unexpected challenges, treatments were not implemented over the full project area. Patches treated manually and chemically with and without retreatment were monitored in summer 2019. We assessed effects on jubata grass cover and presence of regrowth; variation among treatments; and factors that might explain variability. Treatment resulted in highly significant reductions in patch-level jubata grass cover. Over half the monitored patches had over 50% jubata grass cover pre-treatment; by summer 2019, about half had no jubata grass, and none had 50% or higher jubata grass cover. Results did not differ significantly among treatments. With marginal significance, results indicated post-treatment cover and regrowth could be related to patch size, plant distribution, or soil type. Smaller, more isolated, or patches on sandier soils were more likely to be eradicated. Though the largest patches were not eradicated, cover was substantially reduced if retreatment was applied. Lessons learned may help guide future management, ideally with new approaches as they develop, given significant constraints on herbicide use.

Control jubata grass hotspots in the Point Reyes Wilderness: Review of project funded FY2016–2018

Series