Is Sulfur Cinquefoil a Candidate for Control with Sheep and Goats?

Is Sulfur Cinquefoil a Candidate for Control with Sheep and Goats?

Summary

Sulfur cinquefoil (Potentilla recta) is long-lived perennial weed that is a prolific seed producer and is adapted to nearly every soil type and vegetation complex in the western U.S. This invader reproduces solely by seed, and a single plant can produce as many as 6,000 seeds annually. The purpose of this 2-year study was to determine the optimal timing and intensity of defoliation to decrease plant yield and seed production of sulfur cinquefoil plants on foothill rangeland in southwestern Montana. Each year, 150 individual sulfur cinquefoil plants within a 250-m2 enclosure were tagged for identification and assigned to one of 15 treatments with 10 plants per treatment. Treatments were all possible combinations of 3 timings: pre-flower (early June), flower (late June), and seed set (mid-July) and 2 stubble heights, 7.5 cm and 15 cm. Results indicate that clipping reduced (P < 0.05) yield and bud production of sulfur cinquefoil compared to control plants for all treatments except pre-flower clipped to 15 cm. Clipping to either 7.5 cm or 15 cm at all times or combinations of timings reduced the total number of mature seeds produced per plant by 99% compared to controls. Defoliation of sulfur cinquefoil can reduce its yield and seed production.
The effect of sheep and goat ingestion on the germination and viability of sulfur cinquefoil (Potentilla recta L.) seeds was also investigated. Each animal was fed 5,000 sulfur cinquefoil seeds in a single meal and total fecal output was collected for 10 days following seed ingestion. Fecal subsamples were taken to determine recovery and viability of recovered seed will be assessed through staining with tetrazolium chloride Preliminary results indicate that most seeds are recovered by Day 2 following dosing.

Objectives/Performance Targets

Objective 1: Year 2 of the 2-year clipping study (Objective 1) was completed on foothill rangeland in southwestern Montana. Sulfur cinquefoil plants were clipped to one of 2 stubble heights (7.5 cm or 15 cm) during 3 different phenological stage (pre-flower, flower, or seedset), at 3 different clipping frequencies (1x, 2x, or 3x). Unclipped plants served as controls. Sulfur cinquefoil seeds were collected from each of the 150 plants in the experiment, counted and tested for viability in the laboratory. Results indicate that clipping reduced (P < 0.05) yield and bud production of sulfur cinquefoil compared to control plants for all treatments except pre-flower clipped to 15 cm. Clipping to either 7.5 cm or 15 cm at all times or combinations of timings reduced the total number of seeds produced per plant by 99% compared to controls. The results from Objective 1 have been accepted for presentation at the annual meeting of the Society for Range Management and the Montana Weed Control Association Annual Meeting. A manuscript to be submitted to Rangeland Ecology and Management is in the preparation phase.
Objective 2: The effect of sheep and goat ingestion on the germination and viability of sulfur cinquefoil (Potentilla recta L.) seeds was investigated. Sulfur cinquefoil seeds were collected at two different maturity stages: “green seed stage” following the flower stage, but prior to seed maturation and dissemination, and “mature seed stage” where seeds were fully mature and disbursing from the plant. Previous research demonstrated that clipping during the green seed stage virtually eliminated viable seed production from sulfur cinquefoil plants. Eight sheep and 8 goats were divided into 2 treatments: 4 animals of each species received “green seeds” while the remaining 4 animals of each species received “mature seeds”. Each animal was fed 5,000 sulfur cinquefoil seeds of the appropriate stage in a single meal and total fecal output was collected for 10 days following seed ingestion. Fecal subsamples were taken to determine number of seeds excreted per gram of feces and germination and viability of seed recovered from feces. Viability of recovered seed will be assessed through staining with tetrazolium chloride Preliminary results indicate that most seeds are recovered by Day 2 following dosing. When complete, this information will establish recommended holding periods to minimize the risk of viable seed dispersal by sheep and goats used in a weed management program for sulfur cinquefoil.
Objective 3: Sulfur cinquefoil forage samples were collected for subsequent tannin analysis.

Accomplishments/Milestones

Field and laboratory work have been completed for Objective 1. Field work has been completed for objective 2 and laboratory work continues. Final data analysis continues. Results from Objective 1 were presented as a poster at the annual meeting of the Society for Range Management, to the Joe Skeen Institute for Rangeland Restoration and to sheep producers.

Impacts and Contributions/Outcomes

Results from the clipping trial in Objective 1 demonstrate that defoliation is an effective method to decrease seed production of sulfur cinquefoil. This information has added grazing or mowing as potential control measures for this noxious weed. Follow-up grazing and mowing projects are being planned by the project team with input from producer cooperators.