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(Achillea millifolium) declined from 8.6% to 0.8 %, and black medic declined from 5.4% to 0.2 %. Cover of <br />most grass species increased; western wheatgrass (Agropyron smithii) from 0.6% in 1998 to 8.0% in 2001, <br />mountain brome (Bromus marginatus) from 0.2% in 1998 to 5.4% in 2001, and Kentucky bluegrass from <br />0.6% in 1998 to 3.2% in 2001. Interestingly, the only grass species that did not show an increase was <br />smooth brome (Bromus inermis), which declined from 2.4% to 1.0% cover. <br />Noxious species decline from 1998 to 2001 is clearly illustrated by the density graph in Figure 4. <br />R <br />12 <br />s 10 <br />Mq� L 8 <br />57. t 6 <br />E 4 <br />E 2 <br />2 0 <br />z <br />Figure 4 -Sutey Reference #2 Noxious Weed <br />Density Sample Mean <br />1998 1999 2000 2001 <br />— Noxious Weeds <br />per square meter <br />From 1998 to 2001, noxious weed density declined by approximately 75 %, from 10.3 plants per square <br />meter to 2.6 plants per square meter. The apparent increase between 2000 and 2001 was not statistically <br />significant. Noxious species represented in Figure 4 include various biennial thistle species (primarily <br />plumeless thistle), one perennial thistle (Canada thistle), and houndstongue. Although no attempt was <br />made to count different thistle species separately until 2001, it is apparent from the cover data and was <br />visually evident to the samplers that both cover and density of the biennial species (particulary the initially <br />dominant plumeless thistle) had been much reduced by the control efforts. The perennial Canada thistle <br />was apparently less impacted. In 2001, Canada thistle was the visually dominant thistle species, with a <br />density sample mean of 1.8 plants per square meter, compared to sample mean of 0.2 plants per square <br />meter for plumeless thistle. Combined thistle density declined from 6.6 plants per square meter in 1998 to <br />2.0 plants per square meter in 2001; houndstongue density from 3.7 plants per square meter to 0.6 plants <br />per square meter over the same period. <br />2001 density data for Reference Area #2 is presented in Table 7. Table 8 summarizes noxious weed <br />density for each year of the study. More detailed information for each year is presented in the respective <br />DMG Annual Weed Sampling Report. <br />As mentioned previously in this report, larvae of the painted lady butterfly were abundant on thistle plants <br />in various locations in 2001. They had not been observed in the three previous years. Larvae were <br />particularly prevalent in Reference Area #2 and adjacent areas, with most Canada thistle and plumeless <br />thistle plants exhibiting the webbed nest characteristic of the species. Many plants of both species had been <br />almost completely defoliated, other plants only partially so. A certain percentage of yarrow plants had also <br />been colonized by the larvae, but thistle appeared to be the preferred host plant. hi 2000, portions of the <br />Sutey Pile including Reference Area #2 had been intensively grazed with goats in early July. The project <br />manager observed that the goats consumed the foliage of both Canada and plumeless thistle, but <br />consistently avoided the flowering stalks of the plumeless thistle. The herder lopped off these stalks with a <br />machete. The areas subject to goat grazing had also been seeded with a perennial seedmix in the summer <br />and fall of 2000, but no effects of the seeding were evident as of the 2001 sampling. <br />5 <br />