Last summer, Fred Whitford from Purdue University and Pat Hipkins from Virginia Tech conducted a presentation on the various aspects of accurately measuring pesticides. In the presentation, the two identified six important steps required to achieve a safe and effective pesticide application.
1) Correctly identify the pest
2) Select an appropriate and effective pesticide
3) Calibrate equipment to uniformly apply the correct amount of spray solution
4) Correctly measure and mix the pesticides
5) Review the treatment site before and during application
6) Monitor the results for effectiveness
Of these steps, measuring pesticides is assumed to be the easiest and is often overlooked in importance. However, the errors that occur while measuring potentially impact the rate of pesticide applied, thus affecting cost and effectiveness of the treatment. The need for precise measurements becomes increasingly important as smaller rates are used and as the cost of the pesticide increases. That is, more precision is required when measuring by the dry ounce or fluid ounce than when measuring by the pound or gallon.
Liquid formulations are measured by volume, usually with the aid of a measuring cup or spoon. Measuring the precise amount of liquid formulation needed may seem easy enough; however, errors can occur during this step, often due to the measuring device used. Consider that not all measuring devices are accurate. Some devices may have a printed disclaimer "Measurements are approximate" or "Accuracy ± __%". The graduations (markings) on some measuring devices may be off by as much as 15%! Calibration is the only way to be certain that a device is accurate. Check the accuracy of a measuring device by using a graduated cylinder available at science supply stores. Graduated cylinders use metric units. For conversion, 1 cup (8 fluid ounces) is equivalent to 236.6 milliliters.
The design and overall condition of the measuring device will also influence how well measurements can be made. Avoid measuring cups with painted graduations. The paint may wear off resulting in illegible numbers. Containers with difficult-to-read numbers should be replaced. The following were some recommended characteristics to consider when purchasing measuring cups:
• The graduations on the devices should be visible, easy to read, and etched into the container. Ideally, the measuring device should have one unit of measurement, either English or metric. Having multiple units on the same device may be confusing and could lead to measurement errors.
• Taller and narrower measuring devices tend to be easier to read because they often have more space between the graduations. They also tend to have more graduations allowing for increased precision.
• The device should have a pour spout to help prevent spillage when transferring to spray tank.
Safe and effective pest control requires an attention to detail during every step of the process, including pesticide measurement.