Nuisance caddisflies associated with an irrigation system in Arizona, USA

The Central Arizona Project (CAP) delivers water from the Colorado River to much of Arizona.  Recently large numbers of nuisance (homeowner complaints) caddisflies (Smicridea fasciatella) have been associated with the CAP in urban areas of Arizona.  Understanding life history characteristics is critical to caddisfly control and for predicting their outbreaks; therefore larval stages and associations with the rest of the canal benthic community were studied using newly developed techniques.  Adult abundance data was collected with canal-side sticky traps.

 Larval Smicridea densities averaged 4,700 individuals per square meter on artificial substrates.  Adult emergence peaked in the spring and then again in September of each year.  Smicridea were the most abundant macroinvertebrate on samplers, with Cricotopus midges of secondary abundance.  Of interest was documentation of canal invasion by quagga mussels (Dreissena bugensis) in August 2007. 

 Control measures for larval caddisflies had limited impacts.  Copper concentrations of 100 mg/L had no effect on survival in 24-hr toxicity tests, while chaining or squeeging canal sides did not affect larval abundance.  A recently developed brush treatment may have more impact, and mimicking this activity resulted in ca. 50% decreases in abundance.  It is hoped this treatment may abate caddisflies in populous parts of the city