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Medusahead (Taeniatherum caput-medusae (L.) Nevski), an exotic annual grass has invaded rangelands across California and the Great Basin where it successfully outcompetes cheatgrass (Bromus tectorumL.) and other introduced annual grasses. Barbed goatgrass (Aegilops triuncialis L.) is also a problematic, exotic annual grass that has invaded rangelands in California. Both of these species significantly impact ecosystem services in sites they have invaded, including livestock production. These two species are similar in habitat requirements, life stages, and life form, but different in that barbed goatgrass has delayed germination, dimorphic seeds, lower silica content, and greater resistance to defoliation. We describe phenological states at which each of these species may be most susceptible to targeted grazing or mowing treatments using defoliation studies and nutritional analysis. We estimate when, and for how long, each of these species is most susceptible to grazing or mowing treatments using multi-state modeling and phenology observations from across their range in California. Preliminary results indicate that medusahead enters the phenological state most susceptible to precision grazing 158.5 days (+/- 19.6 s.e.) after germinating rain in the fall, remains in that state for 9.2 days (+/- 1.9) and then enters the optimal phenological state for mowing treatment, remaining in that state for 9.3 days (+/- 2.1), after which it fully matures and then senesces. Barbed goatgrass enters its optimal phenology for precision grazing treatment 170.6 days (+/- 42.8) after germinating rainfalls, remains in that state for 7.3 days (+/- 2.6) and then enters the optimal phenology for mowing treatment, remaining in that state for 11.7 days (+/- 3.7). We use the resulting multi-state models as “early-warning” tools to allow managers to schedule control treatments in an efficient and timely fashion.