Crop selectivity test

The crop selectivity and safety of IVE-7 and IVE-ll were further exanuned by post-emergence spray treatment at 450 g ai/ha. Maize, rice, wheat, cotton, rape, and soybean were selected as tested crops. 2,4-D was used as a control (Table 5.27). 

Agricultural Products. Pesticides are frequendy appHed as emulsiftable concentrates. The active insecticide or herbicide is dissolved in a hydrocarbon solvent which also contains an emulsifier. Hydrocarbon solvent selection is critical for this appHcation. It can seriously impact the efficacy of the formulation. The solvent should have adequate solvency for the pesticide, promote good dispersion when diluted with water, and have a dash point high enough to minimise dammabiUty ha2ards. When used in herbicide formulas, low solvent phytotoxicity is important to avoid crop damage. Hydrocarbon solvents used in post-harvest appHcation require special testing to ensure that polycycHc aromatics are absent. 

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. 

To select and define the target analytes for the residue analysis of crops in a field trial, applicants should consider metabolites/degradation products of the test materials by conducting plant and animal metabolism studies and by assessing toxicity of the metabolites/degradation products. 

Selectivity and sensitivity of available instruments are tested in all laboratories in the initial step of validation. The crops used for fortification experiments and the concentration levels are identical in all laboratories. Recoveries are determined with all available detection techniques, but after discussion of the results each laboratory selects individually one valid result for each analyte-matrix-level combination. Only this result is used for the calculation of the final mean recovery and standard deviation. Typical criteria for the acceptance of methods are given in Table 11. 

For studies involving test substance application to soil, there may be a requirement for more soil information than for studies where applications are made to foliage of established crops. The study protocol should describe any specific requirements relative to soil type selection and how to confirm the soil characteristics for the study. Most studies simply require that the soil be identified by its name (e.g., Keystone silt loam) and composition (e.g., percent sand, silt, and clay). This information can typically be acquired from farm records, a soil survey of the local area, or a typical soil analysis by a local soil analysis laboratory. In some instances, a GLP compliant soil analysis must be completed. The study protocol must clearly define what is needed and how it is to be obtained. Unless specified in the protocol, non-GLP sources are adequate to identify the soil and its characteristics. The source of the soil information should be identified in the field trial record. 

Pesticides used on crops grown on the test site in previous seasons may also have an impact on the outcome of a field residue trial. Carryover of prior pesticide applications could contaminate samples in a new trial, complicate the growth of the crop in a trial, or cause interference with procedures in the analytical laboratory. For this reason, an accurate history of what has transpired at the potential test site must be obtained before the trial is actually installed. The protocol should identify any chemicals of concern. If questions arise when the history is obtained, they should be reviewed with the Study Director prior to proceeding with the test site. In most annual crop trials, this will not be a significant issue owing to crop rotations in the normal production practices, because the use of short residual pesticides and different chemical classes is often required for each respective crop in the rotation. However, in many perennial crops (tree, vines, alfalfa, etc.) and monoculture row crops (cotton, sugarcane, etc.), the crop pesticide history will play a significant role in trial site selection. 

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... 

For the purposes of these field studies, a test system is defined as a specific tract of land managed in part through use of pesticides. Test systems are normally limited to one crop or land use type and may include row crops, grains, fruits or golf courses. The tract of land, of course, has associated biota that are present naturally or as part of the management practices. These biota are also part of the test system and are normally described as test species or species of interest. Selection of test systems is critical to evaluate wildlife exposure scenarios in a sufficient number of sites within appropriate geographic regions. 

However, it has recently been shown that when the substituents in the benzene ring of the phenoxy acid are changed, then alternation in activity is exhibited in the wheat-cylinder test, whereas in the pea curvature and leaf epinasty tests, only the first member of the series was active. This means that the / -oxidizing system present in pea and tomato tissue is incapable of degrading the side chain of these particular substituted phenoxy acids. This approach1 opens up the possibility of selectively controlling weeds in a wide range of crops. 

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