NC State Extension Publications

 

All trials conducted by North Carolina State University and North Carolina Cooperative Extension should adhere to a standardized design that provides a minimum data set. Assessment of alternative products for insect, weed, or disease control, plant health, soil health, or fertility benefits should adhere to these minimum standards. Trials should include well-constructed controls and discussion of mode of efficacy.

The best way to investigate these alternative products is to ensure that there is coordination between Extension agents and specialists for all trials in order to ensure that experiments are designed correctly for field conditions, plant/crop/soil information, insects, weeds, and diseases being studied.

An alternative product is a product without a demonstrable and clear mechanism of action.

Examples of alternative products:

  • Products for which the claim of efficacy contradicts or is beyond the scope of the label
  • Biologics (those without a demonstrable and clear mechanism of action)
  • Section 25b products, which are determined by the United States Environmental Protection Agency (EPA) to be minimum-risk pesticides that pose little to no risk to human health or the environment. The EPA has exempted these products from the requirement that they be registered under the Federal Insecticide, Fungicide, and Rodenticide Act.
  • “Fertilizer type” or “soil enhancing” products

These products should be tested using an agreed upon standardized experimental design that delivers a minimum data set to produce scientifically defensible science-based research results. Sometimes companies may have their own testing protocols that deviate from the agreed upon testing standards, but it is important to use the agreed upon design.

Who should conduct product trials: Extension specialists, or agents in coordination with the appropriate specialists, to ensure that experiments are designed appropriately for field conditions, crops of interest, and disease, weed, insect, soil or plant health, or fertility issues. Specialist involvement assures that trials are completed across time and space and are defensible.

Trial Information

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Product description: Provide the commercial name (trade name), company, label information with any usage recommendations, ingredients, mode of action, and percent composition. Often the reported mode of action is based entirely on proprietary information and cannot be independently verified.

Objective or hypothesis: The research objectives and associated questions should be clearly stated before the trial is established, and data collection and analysis should support these objectives. Based on the nature of the product, there should be some expected result. The result should be considered when designing the experiment as it will guide the collection of explanatory variables.

Proper trial design starts with a specific hypothesis or research question. For example, the research question for many alternative products will be “Does this product increase crop yield?” or “Can this product be used to replace a traditional product?” The research design should therefore be structured to clearly answer this question and be of sufficient quality that confounding effects or natural variability will not result in a false positive. If data supports that a product did increase yield, then a second question is likely “Is increased yield worth the additional expense from the alternative product?” A well-designed trial will address both questions while being of sufficient quality to withstand critical peer review, which is a necessary part of the scientific method.

Site selection: Trials should be established in areas with expected disease, weed, or arthropod pressure, or soil health, plant health, or soil fertility issues. For weed, disease, and insect studies, if the problem is not present in the nontreated control plots, data from treated plots should not be analyzed. Design the experiment for the product tested. For example, if the products enhance fertilizers, make sure that the replications are blocked for soil mapping units and multiple locations are used to test across physiographic regions. To draw reliable conclusions, trials should span at least two or more years and be conducted across multiple locations.

Experimental design:

  1. Use plots of appropriate size for the specific crop and problem being studied.
  2. At least three replicates should be used. Four replicates or more are preferable.
  3. Randomized Complete Block Design (RCBD), or another appropriate design as agreed upon by the related specialist involved, must be used. Often a RCBD strip trial works well for many farmers’ operations and field equipment. The width of these trials should allow for combine header width plus enough for a buffer between treatments. Try to block based on predominant soil mapping units.
  4. Treatments must contain a nontreated control (negative control). Knowledge of the product is important in selecting an appropriate control treatment because sometimes in addition to the nontreated control there may need to be a second control. Additional but similar products, rates, application methods, or timing should be considered in the design. It is also advisable to include an industry-standard management strategy for comparison (positive control).
    • For arthropod studies, the nontreated control (negative control) will show field arthropod pressure, and an industry standard control (positive control) will allow for comparisons of relative efficacy for the product being tested.
    • For disease studies, include a nontreated control (negative control) to show field disease pressure and an industry-standard management strategy control (positive control) to compare efficacy of the product being tested.
    • For weed issues, select the site for uniform weed populations. The nontreated control (negative control) will show field weed populations. Also include an industry-standard management strategy (positive control) to compare relative efficacy of the product being tested.
    • Soil fertility and crop and soil health testing control (negative control) will show yield differences relative to the industry product (positive control).
  5. Agents and specialists should discuss application methods to ensure they are appropriate for treatments and research objectives prior to the start of experiments.
  6. Data collection:
    • Insects: Pre- and post-treatment arthropod counts should be collected at intervals appropriate for expected product residual activity periods. Common observation intervals include 1, 3, 7, 10, and 14 days after treatment. Consult with specialists to determine appropriate post treatment data collection periods.
    • Weeds: Pre-and post-treatment weed populations should be estimated based upon specialist recommendations. Record the date and growth stage of weeds and crop. Common observation intervals include 1, 2, 4, and 8 weeks after treatment. Consult with specialists to determine appropriate post treatment data collection periods.
    • Disease: Disease ratings should be collected before and after treatments depending on disease. Other data collection strategies may be necessary; consult with specialists to determine appropriate post treatment data collection. Record the date and growth stage. Some diseases only occur on certain plant parts and may only be visible at a specific growth stage of the plant.
    • Soil or crop health or soil fertility: Collect pre-treatment soil samples, soil mapping unit, plant stands, yield, and tissue samples if appropriate. Depending on the product, other corollary data may be needed.
    • Regardless of the product, photos and videos taken over time can be valuable as the data are analyzed.
  7. If claims will be made about impacts on yield, yield data must be collected. It is critical that yield is calibrated by either using NCDA&CS scales or calibrated weight wagons. This is critical if data will be pooled across regions. If yield monitored data is used, it is especially critical that all trials are well calibrated in order to compare across locations. If claims are only made about disease, arthropod, or weed suppression, yield data may not be required.
  8. It is important to know when to abandon a trial, particularly when it is part of a multi-location or year protocol. If the measured factor, such as yield, is impacted by inclement weather — hurricane, freeze, dry planting conditions, or similar — it is best to abandon the trial as the data will be suspect.

Analysis and Interpretation: All data shared must be analyzed and reported according to standard practices accepted within the appropriate specialists’ discipline. Agents and specialists should work together on the statistical analysis and interpretation. In trials with no significant differences among treatments, subjective statements of trial outcomes are not appropriate. If two treatments are not statistically different, then the treatments are not different.

Discuss experimental data relative to the experimental hypothesis. Product performance discussions may not be made unless there are positive and negative control treatments in the trial. Data should be discussed with relevance to other factors that could influence the trial including, but not limited to, temperature, precipitation, and disease or weed pressure (or lack thereof). Discuss all data analyses and interpretations with the associated specialist. Data, analysis methods, and results must be made available to the public upon request. Agents and specialists cannot enter into non-disclosure agreements with sponsors as individuals and must consult with NC State University.

Developing Field Days

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1. Plan your treatments with an educational objective relative to your field day. Remember that part of the educational objective revolves around the hypothesis. As always, communicate with the relevant specialist to help with this planning process.

2. Have a clear understanding with the cooperating grower.

  • You may not need to do anything to the fields. If you are demonstrating pest control, some weeds, insects, or disease may need to be left unmanaged in order to demonstrate effectiveness of treatments. Seeing uncontrolled pests is not easy for many growers. Likewise, you will need a nontreated area to demonstrate management of a fertility or soil or plant health issue.
  • Clarify from the start how this situation will be handled. Also, discuss how and who will do the cleanup after the field day.
  • Clarify when and how the field will be prepared; who will provide needed chemicals; who will make the applications; cultural practices that will need to be done for the crop (or as a component of the demonstration).
  • It is advisable to utilize only registered pesticides in field day events. If there are non-registered pesticides applied to the crop, the crop cannot be harvested.
  • Place signs around the test area so farm workers know that this is a N.C. Cooperative Extension test site. Clearly state what you do not want, such as, “Do Not Remove Weeds” or “Do Not Spray.”
  • Adjuvant control: Some adjuvants may cause crop or weed injury even if no herbicides, insecticides, or fungicides are included. Document the effects of adjuvant separately from pesticides, so an adjuvant-only or pesticide-only treatment may be needed.
  • Other controls may be necessary depending on the treatments used. This could include controls for tillage, burndown, residue, cultural practices, or anything that could interact with the treatments.
  • Record all production practice inputs, rates, dates of application, and climatic data when available.

3. Calibrate the sprayer or spreader.

To demonstrate efficacy of any product, you must be confident in the dose applied. If the grower is doing the application, make sure the equipment has been recently calibrated and check the calibration before treatment.

4. Field layout.

  • It is often helpful to have a nontreated area between each treatment. This is often referred to as a “running check” or buffer. It can provide a strong visual element for field day demonstrations.
  • The minimum treated area will depend on the crop, equipment, and space available. For weed control trials, a minimum width of the treated area should be about 3 feet (at least a two-nozzle boom). Wider is better. The length of the treated area should be enough to ensure you have adequate weed populations — 10 to 20 feet is common.

5. Data collection. Review data collection plans with a specialist.

  • The amount of data to record may vary depending on if you wish to present results at conferences, publish the results, or compare results with other studies.
  • Be sure you have correctly identified the weeds, disease, insects, soil fertility, or other main variable of your study.
  • Specific information for weed control demonstrations.
    • Consult with specialists to determine which assessment is most appropriate for target weeds.
    • Record data by species, if possible. This is very important to provide useful information. Only those species present in all replicates should be evaluated.
    • Consult with the specialist to determine whether other species can be grouped into broad categories such as “summer annual grasses” or “other summer annual broadleaf weeds.” Make a list of species in these categories and estimate the abundance of each weed present.
    • Percent weed control can be visually estimated. Compared to the nontreated areas, “what is the estimated reduction in above-ground biomass?” Another common evaluation method is to visually estimate the “percent ground cover” of weeds.
    • Weed counts are also useful. If populations are high or plot areas are large, you may do counts within a smaller representative area — such as the center square meter.
  • Specific information for disease control demonstrations.
    • Consult with specialists to determine which assessment is most appropriate for target pathogens.
    • Record for target pathogen incidence and severity. If non-target organisms are present, data can be collected, but making statements about control of non-target pests post hoc is not always appropriate.
    • Percent control must be calculated relative to a nontreated control.
  • Specific information for insect control demonstrations.
    • Counting damage in the absence of insects is generally not advised. Consult with specialists for appropriate data collection methods.
    • Record for target pest. If non-target species are present, data can be collected but making statements about control of non-target pests post hoc is not always appropriate.
    • Arthropod assessment can be made of individual pests (for example, caterpillar numbers) or “infested plants” (such as plants with at least one caterpillar or plants with greater than 50 aphids). Consult with specialists to determine which assessment is most appropriate for target pests.
    • Percent control must be calculated relative to a nontreated control.
  • Specific information for soil fertility or soil or crop health.
    • Consult with the specialist to determine which assessment is most appropriate for the target study.
    • Measure the variable on which the product is based. For instance, if the product enhances nutrient use, above ground biomass (grain and stover) should be analyzed for that nutrient.

10. Data summary.

  • Review the data summary in association with the specialist before the field day. Based on your summary, you can select the most representative areas to display for the field day.

11. Signage for the field day

  • Signs should have lettering large enough to be read clearly from 10 feet away.
  • Include treatment and dose applied.
  • If rain is likely, signs can be laminated. If rain is not likely, you often don’t need to go to the expense of lamination.

12. During the field day

  • Be sure to provide the right message to the audience. Inform them of the limitations of the results, like specificities of the site or the weather, necessity of year repetition, or any other factor that can result in different behavior of the product in another field condition.

13. After the field day

  • Clean up the site. Remove signs, flags, and plot stakes.
  • Ensure weeds, insects, or diseases are managed to prevent their spread.
  • Where necessary, ensure crops are not harvested. This may require plowing-under this section of a field.
  • Send results of the study to the cooperating grower.
  • Consider how else you might use the data from the field day demonstration in your educational programs. Your results can be useful contributions to newsletter articles or presentations at grower groups, but please review these with appropriate specialists to ensure that the results you obtained are consistent with other test results.

Authors

Department Extension Leader (Nutrient Mgt and Water Quality)
Crop & Soil Sciences
Extension Soil Fertility Specialist and Assistant Professor
Crop & Soil Sciences
Professor and Extension Specialist
Crop & Soil Sciences
Professor and Extension Specialist (Berry, Tobacco and Specialty Crops)
Entomology & Plant Pathology
Assistant Professor & Extension Specialist
Entomology & Plant Pathology
Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science
Associate Professor Vegetable and Small Fruit Weed Science
Horticultural Science

Publication date: Nov. 21, 2019
AG-868

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