Effects of Mosquito Control Chemicals on Aquatic Fauna

No mosquito abatement districts have ever been organized in Arkansas. Mosquito control efforts have been largely adulticiding operations by either aerial application or ground thermal fogging machines. Practically no chemical applications have been directed at the larval stage in residual water in ditches and depressions from which adult populations arise. Some larviciding with ethyl parathion has been done in ricefields. Although the treatment is very effective in mosquito reduction, voluntary treatment has not been completely successful. Because relatively little insecticide has been used as a larvicide in Arkansas, it was possible to evaluate the effect of recommended larvicides on non-target organisms in the aquatic environment. A developing mosquito control demonstration program in the rice-producing area provided the study site

Harmful Elements in Estuarine and Coastal Systems

Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities

Diel susceptibility of the boll weevil, Anthonomus grandis boheman to certain organophosphorous insecticides

Studies were conducted to determine the effect of the thermoperiod and photoperiod on the diel sensitivity of the boll weevil, Anthonomus grandis Bohemn, to organophosphorus insecticides. Other studies related to insecticide sensitivity, respiration and locomotion were also investigated. Experiments to develop a satisfactory technique for applying insecticide to boll weevils were conducted. The topical method of treating weevils with insecticide produced less variability than tests using a drench or a filter paper surface technique. The latter 2 methods were not different from each other. Boll weevils entrained in various thermoperiods at LD9:15 were treated topically with malathion at dawn and dusk. Weevils treated at dawn were more tolerant to the insecticide than those treated at dusk. In a similar experiment when weevils were caged on malathion treated cotton plants, moralities were 56 percent at dawn and 86 percent at dusk. Greater mortality was produced with equivalent dosages of insecticides in warm temperature than in cooler temperature regimens. Other experiments 4 techniques for treating boll weevils with malathion. In all treatments insects were treated hourly for 24 consecutive hours in photoperiods of LD10:14, 12:12 and 14:10. In each regimen weevils were more resistant to malathion at dawn than at dusk. In the majority of tests, the percentages of weevils killed were greater for those insects treated during the photofraction that the scotofraction. Mortalities from weevils entrained in LD10:14 were greater than for weevils in LD14: 10.

Diel susceptibility of the boll weevil, Anthonomus grandis boheman to certain organophosphorous insecticides

Studies were conducted to determine the effect of the thermoperiod and photoperiod on the diel sensitivity of the boll weevil, Anthonomus grandis Bohemn, to organophosphorus insecticides. Other studies related to insecticide sensitivity, respiration and locomotion were also investigated. Experiments to develop a satisfactory technique for applying insecticide to boll weevils were conducted. The topical method of treating weevils with insecticide produced less variability than tests using a drench or a filter paper surface technique. The latter 2 methods were not different from each other. Boll weevils entrained in various thermoperiods at LD9:15 were treated topically with malathion at dawn and dusk. Weevils treated at dawn were more tolerant to the insecticide than those treated at dusk. In a similar experiment when weevils were caged on malathion treated cotton plants, moralities were 56 percent at dawn and 86 percent at dusk. Greater mortality was produced with equivalent dosages of insecticides in warm temperature than in cooler temperature regimens. Other experiments 4 techniques for treating boll weevils with malathion. In all treatments insects were treated hourly for 24 consecutive hours in photoperiods of LD10:14, 12:12 and 14:10. In each regimen weevils were more resistant to malathion at dawn than at dusk. In the majority of tests, the percentages of weevils killed were greater for those insects treated during the photofraction that the scotofraction. Mortalities from weevils entrained in LD10:14 were greater than for weevils in LD14: 10.