Numerous pesticide compounds in addition to the ones presented in this guide have been suggested or investigated for zebra mussel control and are discussed in a variety of research and product information literature. However, most are currently not in common use, either because they are less effective on zebra mussels, harmful to native bivalves as well as zebra mussel and therefore limited to use in contained systems (Claudi and Mackie 1994), or have not yet been registered for zebra mussel control. Although USEPA regulations may allow use of pesticide compounds in sites where they are registered (see next section), efficacy data should be consulted before any of these are used. Some pretreatment chemicals have been studied, such as the use of carbon dioxide before chlorination to narcotize the bivalves and cause them to Agape (Elzinga and Butzlaff 1994).
Some of the proposed compounds are given in the following tabulation, along with their primary use.
A number of compounds derived from natural sources such as plant toxins have been tested for use in controlling zebra mussels (Taylor and Zheng 1995, 1997). In addition, antibiotic materials excreted by other aquatic organisms to keep them free of biofouling are relatively common, and these are being investigated for their ability to prevent settling when applied as extracts or as a component in coatings. However, none of these has become commercially available yet. Compounds that are toxic to mussels are also potentially toxic to other life forms, and they must be tested and handled as carefully as other molluscicides.
One such natural compound, Endod, is a plant toxin product that includes chemicals called Lemmatoxins derived from the fruit of the African soap berry tree Phytolacca dodecandra. Two U.S. patents for its use as molluscicides have been awarded. Lemmatoxins have been shown to be lethal to zebra mussels at concentrations higher than 15 mg L-1, while lower concentrations inhibited attachment and aggregation of adult mussels (Lemma et al. 1991; Lee, Lemma, and Bennett 1993). Toxicological studies have been done on nontarget mammals (Hietanen 1997).