Psorophora Columbiae Research Articles

Mosquito (Dipteral Culicidae) flight behaviour near conspicuous objects

AbstractField studies were conducted in Florida to investigate the behaviour of night-flying mosquitoes includingAedes sollicitans(Wlk.),Ae. taeniorhynchus(Wied.),Anopheles atroposD. & K.,An. cruciansWied.,Culex nigripalpusTheo.,Culiseta melanura(Coq.),Deinocerites cancerTheo.,Psorophora columbiae(D. & K.) and (Uranotaenia lowiiTheo.) in relation to visually conspicuous objects. Adults of all species exceptAe. sollicitanswere taken in greater numbers in a large weathered plywood suction trap covered with black panels than in one without panels. However, both traps were attractive, as a transparent plastic suction trap covered with weathered plywood panels took larger numbers of all species exceptU. lowiithan a transparent trap without panels. Buried suction traps furnished with visible risers (extensions) that made captures at 1·2 m elevations always captured proportionately larger numbers than buried traps with visible baffles that captured mosquitoes at ground level. A woodland species,C. nigripalpus, was captured in larger numbers toy traps furnisihed with visible risers and baffles than in traps furnished with transparent risers and baffles; however, collections of field species, e.g.Ae. taeniorhynchus, were smaller. The distribution of blood-fed and gravid females in collections from these traps provided some evidence that blood-seeking females are more responsive to visible objects than engorged or gravid females. These results are compatible with the hypotheses that (1) mosquitoes are attracted from a distance to visible objects, (2) in close proximity an avoidance action occurs and mosquitoes then pass over or around the visible object and (3) woodland species approach visible objects closely (<30 cm), whereas field species pass by at greater mean distances. Consequently, a larger percentage of visually attracted woodland mosquitoes than of visually attracted field species will be captured by suction traps. Depending upon trap design and specific behaviour, increasing the visibility of a suction trap can either increase or decrease trap collections

Larval Density of Psorophora columbiae 1 in Arkansas Rice Fields 2

Studies were undertaken to determine the larval density of the dark rice field mosquito, Psorophora columbiae (Dyar and Knab) in 3 habitats within rice fields. In fields having 1 border formed by a non-levee, grassy margin, 63.5% of the larvae sampled were found in the grassy margin. In this type of field significantly more ( P < 0.05) larvae were collected in the grassy area than in the levee ditches or the pan (rice growing area). In fields surrounded by conventional levees, significantly more larvae ( P < 0.05), ca. 2 fold, were found in levee ditches as were collected on the pan.

Efficacy of Permethrin as a Larvicide and Adulticide Against Ricefield Mosquitoes in Arkansas1

The synthetic pyrethroid, permethrin, provided excellent control of 3rd and 4th instars of Culex pipiens quinquefasciatus Say, psorophora columbiae (Dyar and Knab), and Aedes vexans (Meigen) in the laboratory. The effective 24 h concentration in laboratory larvicide studies against C. P. quinquefasciatus, P. columbiae , and A. vexans was 1.25−1, 2.50−2, and 2.50−2 ppm, respectively. In 6.1×6.1-m rice plot larvicide tests against P. collumbiae larvae, the rate of 11.22 g AI/ha was effective when larvae were introduced in 1 h posttreatment. At 24 and 48 h posttreatment, 168.12 g AI/ha was required to give 90% control. After 72 h, the rate required for 80% control was 280.2–560.4 g AI/ha with only the 560.4 g AI/ha rate being effective after 96 h. When permethrin was evaluated against adult Anopheles quadrimaculatus Say, P. columbiae , and C. P. quinquefasciatus exposed in a wind tunnel, 24-h LC50’s were 32.0-, 2.0-, and 9.6-fold more effective than malathion for each species, respectively. ULV applications by truck-mounted aerosol generators at the rate of 2.91 g AI/ha produced over 90% mortality in caged C. P. quinquefasciatus placed at various down wind positions.

Bioassay of three strains of Bacillus sphaericus on field-collected mosquito larvae

Bacillus sphaericus strains 1593, 1404, and SSII-1 were assayed for infectivity against field-collected larvae of Psorophora columbiae, Culex nigripalpus, and Aedes taeniorhynchus in southwest Florida. Results indicate that all three strains are highly active against the Psorophora and Culex species. A. taeniorhynchus is also susceptible but requires higher dosages to achieve lethal responses. Tests were also conducted on the rate of infection and the differences in susceptibility of different instars to B. sphaericus. These tests indicate that nearly 75% of the mortality that occurs in the course of exposure to B. sphaericus occurs within 48 hr post-incubation with the bacteria. Furthermore, our tests indicate P. columbiae larvae decrease in susceptibility to the Bacillus with increase in larval age (instar). This investigation shows B. sphaericus to be a feasible biological control agent that warrants further study.

The Importance of Cattle Hoofprints and Tire Tracks as Oviposition Sites for Psorophora columbiae in Texas Ricelands 13

Hoofprints of cattle and tire tracks made by harvesting equipment in recently harvested rice fields appear to be important sources of oviposition sites for populations of Psorophora columbiae (Dyar and Knab) breeding in Texas ricelands. On the basis of results described here, increases and decreases in the relative egg densities in hoofprints correspond quite closely with the freshness of the prints and tracks and with the presence or absence of cattle.

Efficacy of Brahman characters in reducing weight loss of steers exposed to mosquito attack.

In a 2-year study, attack by the mosquitoes, Psorophora Columbiae (Dyar and Knab), Anopheles quadrimaculatus Say, and A. crucians Weidmann reduced the average daily gain of steers 0.05 kg/head/day or higher. Injury thresholds for purebred Hereford steers were thought to be within a grid count range of 25–36 bloodfed mosquitoes per 0.09 m2 (1 ft2) and for F1 Herford × Brahman crossbred steers within a range of 36–43/0.09 m2 (1 ft2) over a 28-day period. Mosquito population densities reached the injury threshold level for purebred Hereford steers during four out of five 28-day feeding periods in 1973 and 1975. The injury threshold for the crossbred steers was reached in only two out of the five 28-day periods. In 1973, Hereford steers protected from mosquito attack sold for $2.48/head more than unprotected Hereford steers, and the protected crossbred steers sold for $0.42/head more than the unprotected crossbred steers. The corresponding increases in value during 1975 were $4.25 and $2.20/head, respectively. Highly significant correlation coefficients (P<0.01) were obtained between grid counts and landing rate counts, grid counts and CDC light traps, and grid counts and New Jersey light traps. No significant difference (P>0.05) was found in the numbers of blood fed mosquitoes resting on the walls of barns containing either Hereford or crossbred steers or between the average daily feed intake of the 2 breeds.