Pesticides application techniques

However, several application techniques are available that will place more pesticide in the target area and on the target... 

One problem that has arisen with the use of herbicides in agriculture is spray or vapor drift. When fine spray droplets are released, especially if applied aerially, they may be deposited beyond the target area due to air movements to cause damage there. In the first place, this is a question of application technique. Herbicides, like other pesticides, should not be applied as sprays under windy conditions. In most... 

Before the EPA proceeds on a regulatory action, registrants whose products exceed the 10 risk level from nitroso contamination, will be given the opport mity to lower potential exposure to applicators and other users of their pesticides. Reduction of exposure and, thus, reduction of risk can be accomplished by modification of the manufacturing process (see below), improved packaging technology, modification of application technique (e.g. closed systems), or deletion of high-exposure uses. 

Because parts of the model are used in the Dutch pesticide authorization procedure to estimate worker exposure during re-entry, a study was conducted to validate some of the aspects of the proposed model. Emphasis was put on the relationship between hie applied amount of active ingredient and the resulting increase of DFR in relevant zones (crop heights), as well as determining factors (i.e., application techniques and crop density, or leaf volume index). In addition, the influence of re-entry time and crop density on transfer factors (calculated from levels of re-entry exposure and either DFR or SFR) was studied. 

Half-life estimates of approximately 28 days for thiophanate-methyl indicate a very slow decay compared to methiocarb with an estimate of half-life of about 11 days. The application of a model based on a first-order decay process resulted in fairly high R2 and significant fit. The results suggest that both pesticides are relatively stable compared to other compounds under similar environmental conditions (Brouwer et al., 1994). With respect to the objectives of the study and the proposed model, it can be stated that the results confirm the assumption of a linear relationship between application rate (for both application techniques) and the increase of dislodgeable foliar residue. This relationship holds for modeling purposes. The contribution of the crop density or total crop surface area to the process of interception cannot be quantified with the results of the present study. Because the interception factor ranges from about 0.35 to 0.9 (Willis and McDowell, 1987), the... 

Himel and Moore (8), observed mostly small drops on western spruce budworm larvae. They used a fluorescent particle tracer in the mexacarbate spray. The question following their study was whether the drops from other pesticide tank mixes would behave in a similar manner. Was the deposition of drops on larvae influenced by physical properties of the tank mix, application technique, or other factors These and other questions provided the basis for investigations. In 1971 the FS initiated studies on an opportunity basis, to pursue the question of drop deposition on coniferous foliage. 

The selection of the pesticides that we recommend is based on many aspects and includes the registration status, product efficiency, mode of action (systemic, contact), degradation in crops, in soils under given climates, toxicity, metabolites, application techniques, waiting periods, secondary effects (predators), risk of resistance (within control programs), costs, alternatives, future of product (pressure on use) and analytical possibilities (limits). 

Brattsten et al. (7) have reported on another problem associated with the widespread use of pesticides namely, the rapid appearance of Insecticide resistance. By 1980, 260 species of agricultural arthropod pests had Insecticide-resistant strains, compared to 68 for disease vectors. They noted that some Insects have developed resistance to all major classes of Insecticides and will develop resistance to future Insecticides as long as present application techniques and use patterns prevail. 

The challenges of application techniques are complemented by a consideration of pesticide formulation science. The development of a practical and stable formulation that has the precise chemical and physical properties to enable the delivery of the active ingredient to the site of action is central to this topic. Although the discussion in this book concentrates on the development of products for the application of pesticides to crops via the use of spray application equipment, it recognises that, firstly, the same considerations apply to other areas of application, and that, secondly, formulation science can and does influence the ultimate safety and efficacy of the product. 

In order to optimise pesticide application, knowledge of its performance is required. We will examine here some of the fundamental features of pesticide application techniques, so that later we can introduce a systematic approach to targeting and examine how specific applications in specific crops can be targeted. More detail on pesticide application fundamentals is found in Mathews (1992) and Mathews and Hislop (1993). 

The scope to alter both the efficiency and safety of application through control of the fate of applied material has been explored in a classification of application equipment by hazard (Parkin et al., 1994). Application techniques as well as equipment are required to be taken into account for such a classification, which covers all four possible distinct styles of application i.e. direct, liquid, solid and space. The direct style of application, which is typified by the need to bring treated items into intimate contact with pesticide, is exemplified by admixture processes, e.g. seed treatments. Direct applications take place under highly controllable conditions and often within relatively confined environments, which can potentially mitigate the exposure risks from applied material (presented either in... 

Baraldi G, S Bovolenta, F Pezzi and V Rondelli, 1993. Air-assisted tunnel sprayers for orchard and vineyard. ANPP-BCPC Second International Symposium on Pesticides Application Techniques, Strasbourg, September 1993, pp. 265-272. 

Felber, H.U. (1993) Closed transfer systems for small volume refillable containers. Proceedings, ANPP—BCPC Second International Symposium on Pesticide Application Techniques, Strasbourg, H, 479-486. 

Confining a small dosage of pesticide to a seed is an ideal selective application technique. Seedlings can be protected at a critical stage when an insecticide spray... 

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

Figure 6.1 Main aerial application techniques used for applying pesticides and fertilisers. Application volumes are typical of those used in Australia...

Although agronomists periodically observe failures of soil-applied pesticides to control target pests, these have historically been attributed to improper application technique, unusual environmental conditions, or development of pest resistance. 

A well-designed applicator exposure study can provide information on the extent of the absorbed dose people applying the pesticide are receiving. Our studies have shown that people applying pesticides do receive an absorbed dose, and differing amounts of dose are associated with different application techniques. Me have found no case where a worker has received a dose near a level that causes effects to be observed in laboratory animals. If an extremely toxic chemical is being used, the absorbed dose can be reduced by use of protective clothing and also by the use of closed systems. 

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