Mosquitos, Black Flies and many species of aquatic and riparian insects can reach tremendous numbers in population. Many molt into winged adults and some become pests in and around shorelines and nearby buildings. Chemical control of these insect pests at their source is environmentally sensitive and may not permissible because of risks to their aquatic habitats.
Mosquitoes, Black Flies, Horse-Flys and Ticks are serious biting pests and obligate vectors of many vertebrate pathogens. Their immature larval and pupal life stages are a common feature in most tropical and many temperate water bodies and often form a significant proportion of the biomass. Control strategies rely primarily on the use of larvicides and environmental modification to reduce recruitment and adulticides during periods of disease transmission. Larvicides are usually chemical but can involve biological toxins, agents or organisms.
The four main types of insecticides used today are pyrethroids (PYs), organophosphates (OPs), carbamates (CBs), and biological insecticides (BIs).
PYs, especially synthetic ones, are the most toxic group of insecticides to fish and aquatic invertebrates. They should be used with extreme caution near waterways. Despite the fact that PYs are highly toxic to aquatic animals, they seldom cause fish kills because: (1) they are strongly absorbed to bottom muds, (2) they are short lived and usually last only days, (3) they rapidly decompose in 1 to 10 days when exposed to sunlight, and (4) they usually are applied at lower rates compared to the other insecticides.
OP and CB insecticides are extremely hazardous to fish and wildlife. Fish kills involving these insecticides have been documented. OP insecticides can bioconcentrate in fish, frogs, tadpoles, and toads to levels that pose hazards to their predators. OP and CB insecticides are water soluble and metabolized quickly. They generally have short persistence (half-lives of days to months), and their residues do not pose long-term problems for aquatic animals. The CB insecticide carbofuran is extremely toxic to wildlife and fish.
BI insecticides are less hazardous to fish and other aquatic animals, because many target specific insects (narrow spectrum). BIs include microbials and insect growth regulators. For example, the microbial, Bacillus thuringiensis (BT), is a bacterium that causes disease in some insects, but does not harm other animals or plants. Insect growth regulators affect the normal growth and development of some insects. For example, Diflubenzuron (Dimilin) inhibits the formation of an insect's hard exoskeleton (outer shell). Some insect growth regulators can harm beneficial aquatic invertebrates and thus reduce the food supply for young fish.
Be certain to comply with all Federal, State and local ordinances along with product labeling when applying aquatic insecticides.
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