Field trials of three concentrations of Laginex as biological larvicide compared to Vectobac-12AS as a biocontrol agent for Culex quinquefasciatus.

Laginex AS Biological Larvicide (Lagenidium giganteum) and Vectobac-12AS (Bacillus thuringiensis var. israelensis) were compared in plastic pools containing laboratory-reared Culex quinquefasciatus larvae located in a wooded area in Panama City, FL, in August and September 1997. The pools were dipped at 2-day intervals to assess larval control. Sentinel larvae in screen-sided cups were added to all treatment and control pools at 4-day intervals and evaluated for infection at 48 h. Laginex produced larval control up to 20 days as compared to the Vectobac-12AS compound, which required retreatment by the 10th day. The most effective control was attained by the Laginex 25 treatment, which reduced larvae in the pools by 100% for 22 days. Control in the Laginex 15 and Laginex 35 treatments dropped to 90% and 74% at day 13 and day 9, respectively. The numbers of infected larvae remained above 50% as larval control was assessed, but dropped and fluctuated when water temperatures were lowered at the onset of cold weather. Organic pollution did not prove to be a significant factor in the evaluations.

BVA 2 mosquito larvicide--a new surface oil larvicide for mosquito control.

BVA 2 mosquito larvicide was evaluated in laboratory pan tests against 3rd-instar Aedes taeniorhynchus (Wied.), Culex quinquefasciatus Say, and Culex nigripalpus Theobald larvae. BVA 2 was as effective as the standard, GB-1111, at 14 liters/ha (> 99.1% vs. 99.8%). In small field plot tests BVA 2 mosquito larvicide applied at 28 liters/ha was as effective as GB-1111 (99.0% vs. 99.8%) 24 h posttreatment. Operationally, applied by helicopter at 46.8 liters/ha, BVA 2 mosquito larvicide was more effective (> 90%) in the slightly less vegetated site than in the heavily vegetated site. As a pupicide applied at 14 liters/ha in laboratory pan tests, no significant differences were noted between BVA 2 mosquito larvicide and GB-1111 against Ae. taeniorhynchus, Cx. quinquefasciatus, and Cx. nigripalpus pupae.

Effects of Mesocyclops longisetus (Copepoda:Cyclopidae) on mosquitoes that inhabit tires: influence of litter type, quality, and quantity.

A 59-week study was conducted to evaluate the impact of adult Mesocyclops longisetus populations on larval mosquito species inhabiting tires. Greater than 90% reduction of number of 1st and 2nd instars was recorded by 4 wk with 90% reduction of number of 3rd and 4th instars after 7 wk. Reduced control was noted with the onset of cooler winter water temperature. Overall. a 52% reduction in the number of 1st and 2nd instars was achieved, and a 57% reduction was noted in number of 3rd- and 4th-instar mosquito larvae. Cooler temperatures resulted in a decline of adult Mesocyclops, which resulted in reduced larval control. Significantly greater numbers of Mesocyclops adults were collected in tires with either new litter or heavy amounts of litter regardless of litter type. Lastly, litter type, either oak leaves or pine needles, did not influence mosquito reduction or abundance of Mesocyclops populations.

Evaluation of public information packets for mosquito source reduction in two Florida cities.

The efficacies of induced backyard cleanups of mosquito development sites via 3 different literature treatments were studied in low- and middle-income neighborhoods in Gainesville and Tallahassee, FL, during July and August 1993. Results indicated that 4-color-process literature significantly reduced the number of artificial containers with or without active mosquito development in both economic areas in both geographic locations compared to no literature or black-and-white literature treatments. More importantly, there were no differences between residences receiving the black-and-white literature and residences given no literature.

Failure of the "mosquito plant", Pelargonium x citrosum 'van Leenii', to repel adult Aedes albopictus and Culex quinquefasciatus in Florida.

The efficacy of the "mosquito plant", Pelargonium x citrosum 'van Leenii', as an area-wide repellent against adult host-seeking Aedes albopictus and Culex quinquefasciatus females was evaluated. No significant differences (P > 0.05) were observed in the number of mosquitoes landing on the forearms of human subjects in locations where plants were present compared with areas without plants. In laboratory cage trials, more Cx. quinquefasciatus adults rested on excised leaves of this cultivar compared side-by-side with similar size and shape white paper leaf models.

Integrated management of waste tire mosquitoes utilizing Mesocyclops longisetus (Copepoda: Cyclopidae), Bacillus thuringiensis var. israelensis, Bacillus sphaericus, and methoprene.

This study evaluated the compatibility and efficacy of using a predatory copepod, Mesocyclops longisetus in concert with 3 "biorational" compounds for mosquito control in waste tires. The toxicity of Bacillus thuringiensis var. israelensis (B.t.i), Bacillus sphaericus, and methoprene to Mesocyclops longisetus was assessed in the laboratory using concentrations 10 times the maximum labeled or suggested rate and based on a water depth of 7.6 cm. Microbials were tested using mature copepods exposed for durations of 24, 48, and 72 h. Methoprene bioassays consisted of individually exposing newly hatched copepods (i.e., nauplius larvae) and monitoring their development to maturity. The toxicity tests indicated B.t.i., B. sphaericus, and methoprene were not deleterious to copepods at concentrations exceeding those expected in the field. Copepods exposed to methoprene matured normally, and when mated, 50% developed egg sacs. A 5-month field test, integrating the copepod and B.t.i., B. sphaericus, and methoprene provided better mosquito reduction together than either copepods or control agents alone. When copepods were combined with B.t.i. or methoprene, overall reduction of 3rd- and 4th-instar larvae during the 5-month interval was equal to or greater than 90%. Bacillus thuringiensis var. israelensis alone temporarily produced a high degree of larval reduction (up to 100%), however reapplications were necessary to maintain that level of control. Of all the treatments, B. sphaericus alone produced the lowest degree of mosquito suppression due to lack of toxicity to Aedes albopictus, the predominant species during the study. It is recommended that mosquito control managers consider integrating M. longisetus and B.t.i. or methoprene against mosquitoes in waste tires.

Susceptibility of first instar Toxorhynchites splendens to malathion, naled and resmethrin.

Acute toxicity tests were conducted to measure the response of first instar Toxorhynchites splendens to commonly used mosquito adulticides: malathion, naled and resmethrin. The concentrations of pesticide causing 50% mortality (LC50) after 24 h was 2.87, 69.1 and 623 ppb for resmethrin, malathion and naled, respectively. Naled was determined to be the least toxic of the 3 compounds tested for integrated use with Tx. splendens. The latter assessments were based on comparisons between laboratory-derived dose-response curves and maximum concentrations reached in standing water calculated using standard application rates.

Distribution of Culex tarsalis larvae in a freshwater marsh in Orange County, California.

The distribution and abundance of mosquito larvae in a freshwater marsh were determined during a low water period in the late summer. Culex tarsalis larval abundance was significantly associated with the percent cover by Typha spp. root masses and Typha spp. stem density in 1-m2 quadrants. Larval mosquito abundance was not significantly related to bulrush (Scirpus californicus) stem density, position in the marsh (transect compass direction), position in the inundated vegetation on each transect or several physicochemical factors. As water levels decline seasonally, mosquito developmental sites in San Joaquin Marsh change from mats of decaying vegetation to cattail root masses.

Impact of new insect growth regulators and their formulations on mosquito larval development in impoundment and floodwater habitats.

Four insect growth regulators were evaluated in the laboratory and field. In the laboratory, AC-291898 showed excellent activity, inducing 90% mortality in Culex quinquefasciatus and Aedes aegypti at 0.5-0.7 ppb. The EC formulation of XRD-473 was slightly more active than the technical material with an LC90 of 0.84 ppb and 0.92 ppb against Ae. aegypti and Cx. quinquefasciatus, respectively. In the field, AC-291898 at the rates of 0.005 and 0.01 lb AI/acre caused 85 and 100% inhibition of adult emergence of Cx. tarsalis 2 days after treatment. Activity, however, declined at the low rate, while the high rate remained active for more than 7 days. In the same species, XRD-473 induced complete inhibition of adult emergence 2 days after treatment at the rates of 0.01, 0.025 and 0.05 lb AI/acre. At the low rate (0.01 lb AI/acre), activity declined markedly, while the 2 higher rates remained active for one week. In Cx. peus larvae, AC-291898 at the rates of 0.005, 0.01 and 0.025 lb AI/acre produced complete inhibition of adult emergence 2 days after treatment, but activity declined at the 2 lower rates 7 days after treatment, while the high rate (0.025 lb AI/acre) remained active for more than one week. Methoprene (4%) pellets were effective against Cx. tarsalis for 7 days at the rates of 0.25 lb AI/acre whereas 0.5 lb AI/acre was required to obtain similar results against Cx. peus larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Dispersal of Culex quinquefasciatus from a dairy in southern California.

The dispersal of Culex quinquefasciatus was studied near Norco, California in a periurban situation of southern California. Concurrent studies indicated that host-seeking females were most active up to one hour after sunset. A mark-release-recapture technique was used to document a mean distance traveled of 0.91 km in 12 hr (the first flight period) and a cumulative distance of 1.27 km after 36 hr (following the second flight period). Nearly 0.32% of 47,750 marked females were recaptured. A majority of the population moved with the prevailing wind. Unmarked females were captured at all trapping locations in the study.

Vertical distribution and species coexistence of tree hole mosquitoes in Louisiana.

Vertical distribution and species coexistence of mosquitoes inhabiting a deciduous forest in southern Louisiana were determined using 470 ml black jars for larval collections at ground level and 1, 3, 5, 7 and 9 m on selected trees. Specific preferences for discrete microhabitats by Aedes triseriatus, Ae. hendersoni, Ae. vexans and Ae. albopictus were not evident. Niche overlap indices, however, showed little overlap of these species and seemed to indicate that the mosquitoes partitioned the ovipositional/larval sites. Competition between the most abundant species, Ae. triseriatus and Ae. albopictus, was not apparent. The tree hole mosquito community structure appeared to be mediated by the predator, Toxorhynchites rutilus septentrionalis.