Spartina Alterniflora

Spartina, a smooth cordgrass which is found in the intertidal mudflats of estuaries and wetlands along the coast of the United States forms large, deep rooted colonies which are posing great threat to the Willapa Bay and other open mud flat estuaries of the Pacific coast. The invasive Spartina alterniflora is thought to have come into the Willapa Bay estuary in as packing material in shipments of eastern oysters around 1894 (styce, 1988). Others such as Cohen and Carlton (1995) feel that Spartina did not make it to the Willapa Bay until 1907, as a solid ship ballast, and was not reported until 1911. Either way Spartina has been in the Willapa bay for about 100 years. In this amount of time it has established large colonies and begun displacing native plants an animals converting the open mudflats of the region into dense communities of Spartina, replacing an aquatic ecosystem with terrestrial ones (Wecker, 1998). Currently over 6% of the Willapa bay mudflats have been densely colonized by Spartina grass, the large-scale conversion of mudflats into Spartina colonize threatens to alter the ecological processes of the Willapa and has the potential to effect the local economy. The dense Spartina colonies will destroy the nurseries of the chum salmon and the english sole, also the populations of dungeness crab, and the commercial oyster beds will be effected since Spartina decreases the available area for oyster growth and decreases the available nutrients in the oyster bed. It is obvious that some control must be implemented before the Spartina infestation gets too far out of control. Several control methods have been explored, but to date the rate of spread is greater than the rate of control.

The following control methods have been explored:

Prevention, by destroying small Spartina colonies and cutting off seed heads before they reach maturity Spartinas spread can be greatly reduced.

Biological Controls: Proven effective in other instances of biological invasion by foreign species one of the most viable ways to keep Spartina populations under control, although it does not eradicate the weed, and can take up between five and ten years to become established biological controls can provide an economical long term control for Spartina. It is thought that a plant hopper (Prokelisia marginata) will be able to severely damage Willapa bay infestations of Spartina since they since these plants have been growing in the absence of a natural predator for approximately 100 years.

Manual control is one of the most accessible and current methods of control, methods such as hand pulling, digging, and covering have been proven effective yet time consuming and expensive in controlling Spartina colonies.

Mechanical removal is less time consuming than manual methods but is more expensive and most effective in areas where there are large dense populations of Spartina which are easily accessible and contain few other species of plants since mechanical controls are non selective. Possible mechanical controls are mowing repeatedly to stress the plant and weaken it, as well as controlling the spread by limiting the production of seeds, additionally mowing followed up by an application of herbicide, and clipping the seed heads of Spartina have proven to be effective methods of control.

As one can see the threat of bioinvasion is of utmost concern to the Willapa bay and the surrounding area. This threat is not isolated to the Willapa bay alone bioinvasion has become a great problem in many of the world's pristine ecosystems and has led the extinction of several species. For this reason it is important that we understand the dynamics and learn new and effective control methods from our experiences in ecosystems such as the Willapa Bay in Washington State.