The Aerial Application of Pesticides

The Aerial Flagger. The aerial flagger, who had the highest HDE of all workers monitored, is not now commonly used in the aerial applications of pesticides to crops. Still, a flagger is sometimes used in special situations, and was therefore monitored. The flagger was the only worker that had a discernibly different exposure for different application rates. For example, the total HDE for XLR was 606 mg/h for a rate of 2 lb Al/acre and 408 mg/h for a rate of 1 lb Al/acre. 

Fortunately, in comparison to the number of missions flown by agricultural aircraft, the incidence of significant drift incidents is low. It is the responsibility of all applicators to ensure that the aerial application of pesticides is optimised to avoid any off-target movement of pesticide which could have the potential to cause adverse economic impact or damage to the environment. 

Figure 6.1 gives a general overview of the main techniques adopted for the aerial application of pesticides and fertilisers. 

Woods, N. and Dorr, G. (1996) DGPS for the aerial application of pesticides Agricultural Engineering Australia 25(2), 31-33. 

One of the special rotary atomizers worth mentioning is the windmill type atomizer. In this atomizer, radial cuts are made at the periphery of a disk and the tips of segments are twisted, so that the disk is actually converted into a windmill that can rotate rapidly when exposed to an air flow at aircraft flight speed. The windmill type atomizer has been demonstrated 1171 to be an ideal rotary atomizer for generating a narrow spectrum of droplet sizes in the range most suitable for aerial applications of pesticides at relatively high liquid flow rates. 

The introduction in the early 1970 s of the soil-incorporated, water-soluble systemic insecticide/nematicide aldicarb was regarded as a major advance in the technology of pest control. It eliminated the once prevalent hazard of inadvertent exposure of applicators or inhabitants of nearby dwellings, wildlife, and useful insects to toxic chemicals during spraying or aerial application of pesticides. 

A rather unusual case of pesticide exposure repoted to the New Zealand Poisons Information Centre concerned a helicopter pilot who was involved in the aerial application of a carbamate insecticide onto crops. Foolishly, he mixed the dry powder formulation under the still rotating blades of his helicopter, which caused the powder to disperse into... 

Table II. Aerial Application of Pesticides and Defoliants in the United States in...

Among the main sources of the pollution of ecological systems, conventional use of pesticides in agriculture, forestry and water systems, and public health care and hygiene, should be considered. This concerns particularly aerial large-scale spraying of fields and forests, and the frequent application of pesticides to waters to control the carriers of diseases or aquatic plants in irrigation systems. 

Inhalation Route - Estimation of Vapour Exposure. In a study of drift exposure following aerial application of an organo-phosphorus pesticide, Crabbe t al (16) found that the vapour concentration in areas remote from the spray line increased gradually up to 10 hours after the spraying. Increasing temperature was undoubtedly the major explanation for this. Other factors such as volatility of the pesticide, windspeed and sorption properties of the target would also influence the actual vapour concentration on the target. 

To illustrate this distribution, Figure 1 shows the result of an actual aerial application of a typical pesticide spray to a broadleafed tree species (3). The "application level" (A) simply assumes that all the spray leaving the aircraft becomes uniformly distributed over the target area (1.12 kg/ha), and the curve shows the parathion levels analytically detected on a statistical sampling of leaves. A major part of the applied pesticide (B) fails to reach the canopy, as corroborated by Barry (2) with conifers, and is assumed to represent airborne drift, volatilization, and, to a lesser extent, penetration to the ground. Once on the... 

In general, workers involved in the manufacture of 2,4,5-TCP and subsequent products were exposed to far greater levels of 2,3,7,8-TCDD than those involved in the handling and application of chlorinated pesticides containing CDDs. Current serum lipid levels of 2,3,7,8-TCDD in a small number of U.S. Air Force veterans who were directly involved in the aerial spraying of herbicides (Agent Orange contaminated with 2,3,7,8-TCDD) in Vietnam as part of Operation Ranch Hand,... 

Despite their ease in handling, formulation, and application, dnsts are the least effective and, ultimately, the least economical of the pesticide formnla-tions. The reason is that dusts have a very poor rate of deposit on foliage, nnless it is wet from dew or rain. In agricultnre, for instance, an aerial application of a standard dust formulation of pesticide will result in 10 percent to 40 percent of the material reaching the crop. The remainder drifts npward and downwind. 

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