Low-rate pesticides require precise measurement

Some chemicals are really active at low rates, and applicators should be using measuring devises calibrated to the specific product and specific batch.
Carol Ryan Dumas

Capital Press

Published on February 5, 2018 10:20AM

Carol Ryan Dumas/Capital Press        Ronda Hirnyck, University of Idaho pesticide coordinator, listens to a question during her presentation on the importance of precise pesticide measurements in a grower session at Agri-Action in Twin Falls on Feb. 1.

Carol Ryan Dumas/Capital Press Ronda Hirnyck, University of Idaho pesticide coordinator, listens to a question during her presentation on the importance of precise pesticide measurements in a grower session at Agri-Action in Twin Falls on Feb. 1.


TWIN FALLS, Idaho — Effective pesticide application has some basic rules, such as making sure the product is right for the issue addressed, calibrating equipment for the proper rate of application and reviewing the treatment site before and after application.

But producers and applicators should also not overlook precision when measuring pesticides, Ronda Hirnyck, University of Idaho pesticide coordinator, said during a workshop at this year’s Agri-Action.

“It’s not rocket science,” but it’s good to be reminded, she said.

Applicators using coarse measurement units, such as 2.5 gallon jugs or 100 pound bags, don’t have to be too worried about being fussy. However, applications for horticulture and many agricultural fertilizers are focused on ounces.

Those chemicals are really active at low rates, and too much of them can do damage, cost the applicator money or lead to carryover, she said.

“You don’t want it to cost you too much money or bite yourself in the backside. It’s common sense if you’re going to be working with these low rates that measuring is going to be really critical,” she said.

Proper measuring devices are critical when applications call for quantities such as 2.8 ounces, she said.

“Close enough for government work is not that good” when it comes to low rates, she said.

Measuring devices are calibrated differently for liquid and dry products. Volumetric measuring devices for liquids aren’t meant to be used for products measured by weight, she said.

She cautioned applicators against using freebie measuring cups or containers because, as they state on the container, the measurements are only approximate. Some devices for dry measuring are up to 20 percent plus or minus true measurements.

For liquids “we recommend measuring cups that are calibrated to be accurate for volume … and they’re worth the money,” she said.

Some product jugs have tip-and-pour components that pre-measure amounts in half-ounce increments. Graduated cylinders, with measurements for very small amounts, are also available.

“Make sure the device you’re using is accurate. Some of these devices might be a little off, but usually they tell you,” she said.

When it comes to measuring dry product, it’s a whole different ball game. Dry ounces are measured by weight, and it can be confusing, she said.

An 8-ounce cup of liquid is not the same as 8 ounces of a dry weight. For example using volumetric measurement to measure the recommended dry weight of salt would double the rate, she said.

Dry pesticides are formulated differently; some are bulky and heavy and others are light and fluffy.

For that reason, applicators need to use the measuring device that comes with the dry product. Those devices are produced by the company that makes the product and are specific to brand formulations and the particular batch of product.

Manufacturers use resources they can find close by and purchase more cheaply. So different batches might be formulated with different kinds of clay, for example. The company has calibrated the measuring device to match the bulk and weight of individual products and individual batches, she said.



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