Crop dusting

Biocides should not be present in water used for aquaculture. Sources of herbicides and pesticides are mnoff from agricultural land, contamination of the water table, and spray drift from crop-dusting activity. Excessive levels of phosphoms and nitrogen may occur where mnoff from fertilized land enters an aquaculture faciUty either from surface mnoff or groundwater contamination. Trace metal levels should be low as indicated in Tables 4 and 5. 

The difficulty with analyses by occupation and industry is that they do not identify specific agents as risk factors. For example, farmers may be exposed to pesticides, but they also have potential for exposures to other agents, including fuels, solvents, welding fumes, wood dust, silica, crop dust, animal danders, zoonoses and endotoxins. In addition, although some farmers use pesticides, many others do not (Blair and Zahm, 1993). An elevated risk in a job can only be suggestive of particular exposure risks. 

In many countries, however, the use of agricultural aircraft has significantly diminished over the last 20 years. With some, the very mention of agricultural aircraft or crop dusting (an incorrect term) spawns a reaction and fear of widespread pesticide drift. In Europe, the use of agricultural aircraft has declined rapidly over the last 20 years. The number of aircraft in the UK has been reduced from more than 100 aircraft in the mid-1970s to about a dozen today. So what are the facts, and how can application using airborne platforms be optimised ... 

Similarly, in Gongalez v. Virginia Chemical Co., a chemical manufacturer was held liable when the pilot of a crop dusting airplane was overcome from... 

Helicopters have also impacted such diverse fields as fishing, crop dusting, intercity and short-range transportation, electricity, and broadcastjournalism. 

As recent experience has shown, however, it is dangerous to underestimate the resourcefulness of a determined adversary. While the wide and effective dispersal of CW agents generally requires some sort of sophisticated delivery system, and while some of the public s understandable alarm is exaggerated, a crude apparatus, even a crop-dusting plane or simple canister in the hands of a fanatical subway rider, could cause a devastating amount of injury. 

While aerial crop dusting was once a typical method of insect and plant disease control, enviromnental concerns and advances in synthetic pesticide development have relegated this method of application to the history books. Dusts are now employed for restricted area treatments such as carpets, pets, and crop seeds in storage. 

Sulfur and its compounds are among the oldest and most widely used pesticides. Elemental sulfur is especially effective as a dust for the control of mites attacking citms, cotton, and field crops and as a protectant against chiggers, Trombicula spp., attacking humans. Sulfur also is a valuable fungicidal diluent for other dust insecticides and is used in wettable form as a spray mixture. Time sulfur has been a standard dormant spray for the control of the San Jose Quadraspidiotuspemiciosus and for other scales and various plant diseases. Time sulfur is a water-soluble mixture of calcium pentasulfide,... 

The term agriculture refers to the operations involved in growing crops or raising animals. Dusts, smoke, gases, and odors are aU emissions form various agricultural operations. 

The preparation of soils for crops, planting, and tilling raises dust as a fugitive emission. Such operations are shll exempt from air pollution regulations in most parts of the world. The application of fertilizers, pesticides, and herbicides is also exempt from air pollution regulations, but other regulations may cover the drift of these materials or runoff into surface waters. This is particularly true of the materials are hazardous or toxic. 

The wide publicity given DDT and the many new pesticides that have been developed during the past few years has made the public aware of the widespread use of spray chemicals. Many misstatements about the poisonous properties of these new products have caused abnormal concern and fear over the possible presence of excessive amounts of spray residues on food crops. This concern is a natural one, because the public does not realize the very small amount of the insecticidal residue that may remain on a single service of food, which usually does not exceed 0.25 pound in weight. Nor does the public realize that only a relatively small percentage of the food we eat has ever been treated with a spray or dust of a specific pesticide. 

Field test work with the chemical has consisted of many tests and a large number of commercial applications in both spray and dust forms. Insecticidal action has been satisfactory in all cases where materials have been properly applied. No toxic residue has been found on any treated plants or food crops, which include most varieties of crops. 

A sample of hops which had been treated with tetraethyl pyrophosphate showed a negative chemical analysis. The plant material was also extracted and the extract added to the drinking water of test animals and sensitive insects. The animals and insects that drank this treated water for several days showed no reaction. With the sensitive insects it would have been possible to detect even a few parts per million. In addition, there have been extensive commercial field applications of the chemical in dust and spray form to crops such as apples, pears, grapes, celery, broccoli, Brussels sprouts, and others up to within a few days of harvest there has been no detectable poison residue on any of the crops. The lack of poison residue with use of tetraethyl pyrophosphate is due to the fact that it hydrolyzes within a few hours of application, breaking down into transient nonresidual and nonpoisonous chemicals. Thus it is possible to use tetraethyl pyrophosphate well up to harvest time of food products without danger of residual poison on crops. The fact that the chemical is used in extremely small amounts is a definite advantage in respect to freedom from poison residue. 

The alfalfa used was second crop in 1947 and first crop in 1948. It was cut when the majority of the plots dusted with DDT were judged to be in the tenth-bloom stage. The alfalfa within each plot was allowed to sun-cure, and was then baled and hauled to-the college barns for storage. 

Popendorf et al. (1975) suggested a relationship between respiratory exposure and organic foliar dust released from the foliage due to crop disturbance therefore, it was hypothesized that crop density may be associated with both dermal and respiratory exposure. However, in the present study, no such relationship could be observed. This may be due to the large variation in the method used to determine crop volumes. Improvement of the crop-volume/leaf-surface-area method may contribute to the clarification of whether crop density can be considered a determinant of re-entry exposure. 

Allelopathy found hopeful utilization in plant protection against parasite weeds. The main world parasitic species are the witchweeds (Striga spp.), broomrapes (Orobanche spp.), and eventually dodder (Cuscuta spp.). Witchweeds and broom-rapes attack many economically important crops especially throughout the semi-arid regions. Early detection of parasitic weed infestation and protection is difficult because of the growth habit of a root parasite and huge production of dust-like seeds viable up to 20 years (Kebreab and Murdoch 1999). 

With aridity increasing, various plant species of forage crops become gradually less numerous to finally disappear. In Dry Steppe ecosystems xerophylic half-shrubs and salt-tolerant plants replace the grasses. However, the ash content is higher in these species. This is attributed not only to a higher concentration of major ash elements in the plant tissue, but also to the exposure to finely dispersed dust adhered to the plants exterior (Table 9). 

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