Target crops

Crop and crop grouping. Residue studies have to be conducted with each target crop proposed for registration one variety of the target crop is acceptable. 

Site/location selection. Residue studies are conducted at two or more sites for each target crop. Trial sites should be selected from typical growing areas for the target crop and should include different environmental conditions that might affect the levels of pesticide residues. 

Trial sites should be selected in the growing areas of the target crop, from at least two different areas. Test sites must be far enough apart to avoid cross-contamination. 

Application frequency (single vs. multiple applicaji6is) Target crop(s) and cultimtf system... 

Region A or B Site must match the climatic, soil, and agricultural conditions typical of the target crop Some crops are grovm only in certain regions (e.g., rice) while others are common to many regions (e.g., maize). Thus, selection of a test region may be restrictive or relatively flexible... 

Application of the test substance to the target crop prior to harvest represents a worst-case scenario for potential exposure to workers for the crop category. 

Sprayers should be calibrated prior to each application. If, at the time of application, the wind is blowing in the direction from the treated plot to the control plot, then wait until the direction changes to prevent contamination of the control plot. Applications should occur within 1 h of mixing. Check weather forecasts to determine if wind or rain could be a problem. Airblast sprayers must be adjusted to spray through the target crop and cover the top of trees. Research sprayers often do not have the power for this job. 

Colorado potato beetle, diamond back moth, pear psylla, and Liriomyza leafminers can be achieved at extremely low application rates of MK-936 in the range of 0.005-0.03 lb per acre (5.5 - 33 g per hectare). For foliage applications a 0.15 EC (1.8% w/v) emulsifiable concentrate formulation has been developed. Field studies have shown that the formulation is non-phytotoxic to all target crops on which it has been evaluated including many varieties of sensitive ornamental plants. 

Other herbicides are selectively inactivated by the target crop whilst the weeds that they control either do not metabolise them or they do it so slowly that the weed is killed before it can inactivate the herbicide. There are a number of key plant enzymes that are used in the inactivation of herbicides. Microsomal mixed function oxidases are able to hydroxylate a wide range of herbicides such as bentazone and diclofop-methyl (Figure 2.30). It is often the case that these hydroxylated metabolites are subsequently glucosylated by sugars in the tissue and these conju-gants can be stored in the cell vacuole where they can have no phytotoxic effects. 

An important factor in the redistribution of fungicides throughout a target crop is their level of vapour phase activity. Compounds that are relatively immobile in the plant may be extensively redistributed through the vapour phase and effect commercially acceptable disease control. A good example is fenpropimorph. 

Fungicides are selective through their placement on the target crop, because they inhibit biochemical pathways that are absent or less sensitive to the applied compound in higher plants or because they are metabolically fragile in less sensitive organisms. 

Compound Main Target Crops Main Usage Against Application Methods... 

Figure 3 shows data for a spinner atomizer in a 110 mi/hr airstream. The vmd is 140 microns, the % volume in drops less than 122 microns is now 24% while the relative span has increased to 1.23. It is this tremendous increase of drops (less than 122 microns dia.) from 2.0% for the 300 microns spray to 24% for the 150 microns spray that is a potential source of trouble from airborne transport of these small drops. These are carried away from the treatment area and a potential exists for contact with humans and animals as well as unwanted deposit on non-target crops. These small drops have been found at distances of several miles from the actual applications (5). If the material being released is of low toxicity, or in a remote area, the problem is not serious. But for high toxicity materials the 24% loss which is not controlled, poses a serious problem. 

The preharvest drop of citrus fruit can be reduced or prevented with 2,4-dichlorophenoxyacetic acid, which delays development in the abscission zone of the fruit stem, thus allowing the fruit to remain on the tree longer. Because of 2,4-D s herbicidal properties, however, care must be taken in spraying to prevent the chemical from damaging other crops, as well as the target crop... 

The application process is getting the pesticide to the target crop. This process usually involves a carrier, liquid, solid, or gas, which transports the pesticide to the intended surface or target. The application may be the simple act of spraying an aerosol repellent on our skin or applying a fumigant with a high-pressure applicator. 

The highest residue level reported from residue trial studies in target crops following the critical GAP are used to estimate MRL. 

Although rice is the main use crop, the compound can also be applied in cereals and sugar cane [33]. Selectivity is achieved due to a differential metabolism in the target crops to that in the weeds [34]. With an application rate of 15-60 g-a.i. ha a wide range of important annual and perennial rice weeds are controlled. 

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