Vegetation Management and Maintenance Plan - Watsonville ...

applications will be needed to control new flushes of weeds. Recent work has also examined
essential oils as potential herbicides. It was found that clove oil or cinnamon oil at concentrations
of 1 to 5% controlled most small weeds. The use of organic sprays could be evaluated for use
within the VMMM project area as part of a pilot project.
3.1.7 Flaming/ Selective Burning
Within the VMMM project area, flaming/selective burning is a suitable treatment for many
invasive weeds during the seedlings stage or growth of new shoots. This management option
should prove effective with French broom, Harding grass, and some annual weeds. Flaming or
selective burning should be done under strict guidelines related to safety, moisture and the life
history stage of target species. Larger scale prescribed burning is an option unlikely to be
acceptable, due to the limited number of isolated large patches of invasive weeds and the
extensive effort required to coordinate a prescribed burn.
3.1.8 Selective Grazing/Browsing
Within the VMMM project area, selective grazing/browsing is a suitable treatment for Harding
and canary grass. Potentially effective grazing animal species may be limited, due to several
factors. Sheep are adversely affected by Harding grass and goats are browsers, rather than
grazers. However, due to the fencing/containment needs for grazing animals, the aquatic nature in
which the Harding/canary grass is found, animal-safety concerns, and existing recreational uses,
grazing as an invasive weed control treatment may be limited. One potentially suitable area is the
relatively confined area along Middle Struve Slough, immediately downstream of Main Street.
Although goats are browsers, they may prove helpful in reducing the amount of poison hemlock,
wild radish, fennel, and Harding grass. They remove biomass, thereby lowering green waste
removal costs. Additionally, they increase the ability of personnel to access areas and roots of
some invasive plants. Revegetation will be required in all cases where goats are utilized. Because
goats do not kill many invasive plant species, re-infestations by aggressive, surviving invasive
plants may limit the success of revegetation, unless secondary control methods are utilized in
conjunction with the use of goats. The effectiveness of goats is predicated on a number of
additional factors, as presented below:
• Goats should not be utilized on slopes, soils, or in habitats where erosion is likely to
occur, unless an acceptable, effective erosion control plan is created and provided for,
prior to the arrival of the herd.
• Goats often require regular active management and almost always require rapid response
capabilities, by the goat providers. Specific conditions as to management and response
requirements should be placed into contracts to assure compliance. Proximity to more
desirable food and delays in proper management or response may result in destruction of
desirable vegetation, both inside and outside the fenced area, including the girdling of
riparian trees. Increases in erosion or sedimentation may also occur.
• Goats are much more likely to eat certain plant species. Some plants will be eaten only
when nothing else is available, reducing the effectiveness and increasing the cost of
utilizing goats.
• Goats do not kill many invasive plants. The survival of many plants results in the need
for repeated visits, over a number of years. Additionally, other methods will be needed in
conjunction with the use of goats to achieve success.
• Safety and health concerns must be addressed for the goats and people who may come in
contact with them.
Vegetation Management and Maintenance Manual
Draft 20 July 27, 2007