Marking adult mosquitoes using an aerially applied fluorescent pigment.

A water soluble, fluorescent pigment was aerially applied to caged Culex quinquefasciatus adults in a south Louisiana marshland pasture. Mosquitoes held in cages on 1 m stakes were greater than 90% marked. This number was significantly greater (P less than 0.01) than the number of marked mosquitoes held in cages that were placed in dense vegetation (greater than or equal to 0.5 m high) near the ground surface (70% marked). In a second aerial test with caged Aedes sollicitans in an open, grassy area of the marshland pasture, the pigment marked 100% of the adult mosquitoes held in cages 1 m above the ground and 98% of the caged mosquitoes on the ground surface. Greater than 96% of the adults collected from an emerging population of Ae. sollicitans within the test area were marked as well as 100% of wild caught deer fly adults, Chrysops flavidus complex, in the test area.

Strategies for the emergency control of arboviral epidemics in New Orleans.

A study was initiated to evaluate the effectiveness of aerial ULV spraying for the control of Aedes aegypti and Culex quinquefasciatus as an emergency antiepidemic measure against dengue fever and St. Louis encephalitis, respectively. Malathion was aerially applied at 219 ml/ha over 344 ha area of the Ninth Ward in New Orleans. Laboratory susceptibility tests and field-cage exposures indicated that the target populations were susceptible to malathion and that acceptable coverage of the study area occurred. Two consecutive aerial applications decreased the relative abundance and ovipositional activity of adult mosquitoes. However, suppression was transient and, in the event of an epidemic, multiple treatments may be required to decrease vector abundance below the threshold levels required for the spread of virus to the human populations.

Mortality and survival patterns for the immature stages of Psorophora columbiae.

To determine the patterns of Psorophora columbiae survival and mortality, methods were employed that involved the simultaneous use of laboratory-reared cohorts, predator-exclusion cages, and field estimates of larval dynamics. Laboratory studies indicated that the maximum daily survival averaged from 0.92 for day-old larvae to 1.0 for the older age classes with no significant differences (P greater than 0.05) in survival among days. Data from predator-exclusion cages indicated that mortality inflicted by factors other than predation was significantly (P less than 0.05) more intense in the younger age classes and the relatively few individuals that survived to the older age classes had a high expectation of successful emergence. A quantitative estimate of the mortality inflicted on Ps. columbiae larvae by all indigenous natural enemies indicated that mortality rates were higher in the older age classes. This supports the view that the predator complex is a major source of irreplaceable mortality for immature mosquitoes inhabiting Louisiana rice fields.