Dec. 5, 2011
Dr John McKenzieFollow
The objective of field trials is to assess if the Plant Protection Products (PPPs also collectively known as pesticides), seeds or fertilizers do provide benefits and to assess the risks. Without field trials there is the potential of no improvement in performance and perhaps introducing hazards to the environment.
This article is presented for PPPs, however the business advantage, and in some cases the regulatory assessment, also applies to seed and fertilizers.
Field trials provide the information for business decisions; and to answer some basic questions ‘…does the product work?’, '…are there significant benefits?’ and ‘…does it compare favourably against competitors?’. This type of market research is well known and often used by progressive and well managed companies who then concentrate the main effort of development and sales on products that can show significant benefit and market advantage. Without field trials there is no real information on the products competitiveness against other products in the market; it is a bigger risk to attempt to sell a product without the basic information on its benefits and competitive edge. In addition, field trial data is usually incorporated into marketing information to allow the customers to see the advantage.
Independent science service companies, collectively known as CROs (Contract Research Organisations) are trusted to give a fair and scientifically-valid assessment. Therefore the business decisions are made on strong science and independent assessment.
Field Trials in China
Recently China introduced the concept of GLP for many products that require registration. Currently, China has a small number of GLP certified laboratories and with many more to follow. These GLP certified laboratories can have 2 GLP standards: Chinese certified GLP and an external agency from an OECD country can provide a review, audit and certification. Both China and OECD countries follow the same international GLP principles, however China has not yet agreed to be included with the OECD countries in the mutual acceptance of data (MAD) agreement.
It is possible for laboratories not located in OECD countries to obtain GLP certification. If there is benefit and a requirement from companies located in OECD countries then facilities not in the OECD region can be inspected. However there is no guarantee the reports carrying the GLP certificate will be included in other countries, nor is there a guarantee the data will accepted, the report with GLP certificate in a non-OECD country doesn`t guaranteeb acceptance under MAD.
China doesn`t yet offer GLP certification of field trials. At this moment there is no system to audit or certify field trials for efficacy or for residue studies. It is likely to be introduced but as yet there is no time scale.
Field trials are an expert area where good data is generated from GLP. The discipline requires an expert to plan a study to determine if the pesticide is efficacious, to determine the maximum residue levels, and the interval between spraying and harvest. It is also true that badly managed and scientifically inept studies can lead to poor assessment and perhaps approval of non-efficacious and harmful chemicals.
Good field tests (and good value) are run in the same principles of Good Laboratory Practice, where there has to be monitoring of variables and measurement (calibration) of critical equipment. For example:
1. Crop Management
Soil and plant conditions are prepared as close to normal practice for that region. The CROs use good agricultural practice typical of the region of interest. For example agricultural practice in Europe will differ in agricultural practice in North America. In Europe, the territory is again subdivided into north, middle and south based on climatic and soil conditions. This reflects that agricultural products under test need be assessed under a general principle to keep the environment constant (or at least known) and similar conditions. However these conditions will differ based on soil and climate depending if in a north or south (or middle) weather zone. The CROs experience allows the optimum conditions to be found to allow a fair assessment of the product.
2. Measurement of Variables
a. Water quality
Pesticides are usually applied as wettable powders, emulsions or in a solution. Water is the usual agent of dilution. However water quality can vary significantly in chemistry including: pH, salt concentration and even organic matter (turbidity). Therefore it is necessary to know the quality of water by testing the key parameters or to fix it by using best quality water (optimum pH, low salts and low particulate matter).
If the only water available is of less than ideal then it is important to measure the key parameters and allow the final assessment to consider if the water quality had affected the final outcome. This becomes critical when in a region where there is no acceptable potable water and the local water is taken from surface or ground water sources.
If the water available is adequate then it is important to keep this factor constant.
The weather has one of the greatest affect; in particular precipitation. If there is high humidity and rainfall, this can affect the outcome greatly. The prevalent weather and following weather must be monitored and its effects on the results considered in the final assessment.
3. Calibration of Critical Equipment
The application of pesticides in China is dominated by backpack sprayers using single dose packs. The success of pesticides is dependent on the appropriate dose applied in the appropriate way. Field trial equipment is calibrated and the application rate is closely calculated and monitored. This requires measurement of the spray system but also measurement of the application rate. The measurement of the application rate which in practice means measuring how fast the technician can walk through the fields.
The principle types of field trials
To determine if a fungicide, insecticide, plant growth regulator (PGR) or herbicide is effective. This is required for registration and but more commonly done early by companies to make business decisions. A pesticide should not get registered if it doesn’t work, this is obvious. But the development companies need to do this early before they proceed with long and expensive registration. This is the key objective of field trials; to determine if the product actually works.
The independence and scientific assessment is critical for this early business decision. Independent CROs will give a fair and honest assessment and provide good data for good business decisions.
To determine what concentrations may remain on the edible parts of the crop. This is necessary to determine the cost (bad effects) with the benefits (good effects). These trials are done in association with laboratories to determine the actual residue levels in the edible crop.
The monitoring of variables and calibration of equipment is necessary to prepare a well-balanced assessment of the product in the field. It is even more critical since maximum residue limits (MRLs) will be set based on these studies and international trade is affected by inappropriate assessment of residue levels.
Typically these studies are run at the same time as residue studies to determine the safest period between application and harvest; to maximize the benefits from crop protection and to know the maximum residues.
This is especially important when a product is tested in new crops. It is often small changes in the morphology of the leaves that can affect the retention of a pesticide. A closed vegetable head will hold less than an open head, while differences in leaf shape can change the pesticide retention. All of this can affect the MRLs and the pre-harvest intervals. Certainly experience can assess a product, but real data for better business and acceptable for registration depends on good quality field trials.
• Used in feeding studies – to determine risk if the treated crop is fed to agricultural livestock (milk, eggs, meat and offal)
• Used in process studies – to determine actual levels that humans may eat in processed foods (bread, tofu, wine)
• Used in assessments of risk to the environment – to determine levels remaining in the soil, groundwater and perhaps also in following crops.
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