No abstract

In a study to evaluate the deposit distribution from aerial sprays on cotton in the Sudan Gezira, a combination of subjective visual assessment and quantitative chemical analysis was used. Spray deposits on leaf discs, made visible in ultraviolet light by the addition of a fluorescent pigment, were subjectively grouped into classes according to a series of standards. The mean chemical deposit on the discs in each class was measured by the gas‐liquid chromatographic determination of the profenofos content. The 810 leaves needed to define the deposit distribution with good confidence could be examined economically within the required period by this combination of quick subjective assessment and subsequent quantitative chemical calibration. Results showed that the vertical profile of the deposit distribution within the canopy followed the classical exponential decay curve. The rate of decrease depended mainly on the foliage density. The foliage effectively dampened the wind turbulence so much that the penetration of visible droplets within the lower two‐thirds of the canopy was predominantly by gravity. Suggestions for the use of the deposit distribution probability to predict the likely biological effectiveness in the field are discussed.

Recent trends in integrated chemical and biological pest control call for further refinement of the effectiveness of existing chemical pesticides by more efficient spray application. One aspect of improving spray efficiency is by the use of the correct range of droplet sizes. In this way the volume of spray, and the amount of active ingredient used, particularly in ultra-low volume techniques, can be further optimised, and when combined with correct application time, gives maximum biological efficiency with minimum disturbance of the environment. This necessitates a study of the size spectrum of droplets deposited on rigorously defined biological targets which in turn calls for an investigation of suitable tracer methodology. Additional details of the previously published fluorescent particle method are discussed, and its reappraisal shows that it is a unique method capable of estimating droplet sizes on all biological surfaces, especially insect larvae. The reversibly soluble fluorescent pigment method based on the relative balance between soluble and insoluble state of the pigment proves highly successful in imprinting fluorescent droplets on broad leaves, particularly on cotton.

Fluorescent analogs of insecticides, synergists, and a series of enzyme inhibitors have been synthesized. Synthesis of designed fluorescent molecules to meet specific requirements is important in the application of fluorescence spectroscopy to research involving the mechanism and mode of action of insecticides and synergists in vitro and in vivo. The 5-dimethylaminonaphthalene-l -sulfonyl (dansyl) moiety imparts favorable fluorescence characteristics to fluorescent probe molecules. Fluorescent probes which successfully mimic the activity of insecticides extend other research methods. The ultimate potentials from the use of fluorescence spectroscopy in enzyme research are dependent on synthesis of fluorescent molecules to meet specific requirements. Most insecticides are nonfluorescent or have unsuitable spectral properties. Many present applications of fluorescence in insecticide research involve conversion of insecticides to fluorescent products as an aid in analysis. Others use fluorogenic substrates in kinetic studies.This research involved synthesis of fluorescent analogs of insecticides and synergists and active-site-directed enzyme

No abstract