Cheadle Center for Biodiversity and Ecological Restoration

The Clethodim, grass-specific herbicide, experiment was conducted on 60 Nipomo lupine (Lupinus nipomensis) seedlings (10 replicates x 6 treatments).  The goal of the research was to evaluate the potential impact of the field application of Clethodim over growing seedlings of the endangered Nipomo lupine through direct spray or aerial (helicopter) application as part of the Guadalupe Dunes Management team’s efforts to eliminate Ehrharta calycina (perennial veldt grass) from the fragile dune habitat. Work is conducted under a CDFW Permit to Study the Effects of Clethodim Herbicide on Nipomo Mesa Lupine (Lupinus nipomensis) (permit No. 2081(a)-19-017-RP). The most effective time to apply the herbicide is early in the growing season of the grass (January) which coincides with the typical time for lupine germination. Spraying may also occur later in the winter or during the spring as perennial veldt grass continues its growth which coincides with the time when lupine may be flowering or fruiting.  The experiment was designed to evaluate the effect of the herbicide on both stages of potted lupine seedlings to determine if Clethodim and associated surfactants affects the seedlings under either stage of growth.  The goal is to more efficiently manage this invasive plant across the dune ecosystem by securing permit to allow for spraying within occupied Nipomo lupine habitat by both aerial methods (helicopter) and/or by ground crews.  Past restrictions on management of veldt grass adjacent to the Nipomo lupine population centers has resulted in a dense cover of the invasive grass around the remnant lupine population.  The results of this study indicate that there is no significant effect on vigor, lifespan, or seed production of either aerial (larger droplets) or direct spray application of the recommended herbicide and surfactant mixture on either newly leafing out seedlings or flowering individuals. In addition, seeds from the 6 treatment combinations were evaluated for their viability and we recorded the highest seed viability for all treatments (100%) relative to previous seed germination trials.