Microencapsulation of rodenticides
Advances in the process of microencapsulation over the past two decades are described, as are the proposed reasons why it may be desirable to microencapsulate rodenticides. However, recent attempts have resulted in problems such as poor bait acceptance, poor palatability, excessively rapid toxic action, or reduction in toxicity. One researcher, after trials with 4 rodenticides and multiple materials used as coatings, reported that most lab trials resulted in increased consumption of the active ingredient, but they rarely resulted in improved kill of the rodents beyond the biological variation normally found in groups of laboratory animals. Taste and/or odor-masking are the research objectives most often pursued in rodenticide microencapsulation, followed by a goal of delaying the release of the toxicant in the gastrointestinal tract. However, we lack of biological knowledge of the feeding mechanics and digestive physiology of various pest rodents; for example, the site(s) of absorption of toxicants or toxic metabolites is not known for some rodenticides and rodents, thus inhibiting our ability to tailor the onset of symptoms or toxicosis. Potential disadvantages of microencapsulation are listed, which could lead to increased risks to nontarget species. Recent studies involving microencapsulation of several rodenticides are summarized.