Field trials with methoprene, temephos, and Bacillus thuringiensis serovar israelensis for the control of larval Culiseta melanura.

In 1992, Altosid (methoprene) pellets, Abate (temephos) 5 CG, and Bactimos (Bacillus thuringiensis serovar israelensis) granules were applied aerially to small field plots within a Culiseta breeding swamp. Aspects measured included the deposition and diffusion of larvicides into larval crypts and effects on larval Culiseta melanura and nontarget aquatic organisms. Formulations were deposited at approximately 50% of application rates. The presence of methoprene in 8 crypt water samples indicated that this larvicide was able to diffuse into Cs. melanura larval crypts. Methoprene was selected for evaluation in a large-scale field trial. In the spring of 1993, methoprene pellets applied to 25% of the study area were an effective larvicide against Cs. melanura. The inhibitory effect on pupae exceeded 81% over a 5-wk posttreatment period.

Use of a modified chemical transfer pump for sampling Culiseta melanura larvae.

The cryptic nature of Culiseta melanura larval habitats has limited the use of the conventional one-pint dipper for enumerating the larval density of this species. A modified chemical transfer pump was used in a survey of a known breeding swamp. Field trials assessed the practicality and potential biases towards instars in open vs. closed crypts. From 148 samples taken at 37 sites, 631 Cs. melanura larvae were collected. Closed crypts accounted for 21% of the positive samples. The pump had utility in the field but a relative scarcity of 4th-instar larvae in the samples may indicate a source of bias toward younger instars.