Pesticide Safety… “I should know this.”

Jennifer Weber, University of Arizona Pesticide Safety Education Program

Welcome to the second edition of the

Pesticide Safety… “I should know this” series, where we will answer pesticide-related questions that seem to stump the best of us.  

Compatibility Jar Tests. Why Can’t We All Just Get Along?

I am happy to note we have another topic for the Pesticide Safety… “I should know this” series, where we answer pesticide-related questions and provide safety information you can pass along to others.

Request: I went to your “Measuring and Mixing Pesticides” presentation during the Yuma Ag Summit. I liked the jar test activity. It showed the importance of testing out the products you want to mix together to make sure they are compatible before you load them into the tank. Will you write a short article about jar tests? I think pesticide handlers should know this.

I am glad you liked the tank mixing demo and I want to thank you for the great article suggestion. How to perform compatibility jar tests before tank mixing is a perfect topic for the Pesticide Safety… “I should know this” series.

I’ll start by providing a bit of background about tank mixing and compatibility concerns to bring readers up to speed with your request. I’ll wrap up the article with jar test instructions. 

Background. Tank mixing is when two or more pesticides are mixed together for a single application. Tank mixing is convenient and can save time, money, and fuel if applying with an ATV or tractor.

You can purchase prepared tank mixes (often referred to as premixes and prepacks) or you can mix products together yourself. However, not all pesticides are physically or chemically compatible.

Incompatibility could cause ingredients to gel, clump, separate or become less effective. Other mixtures create problems inside your spray tank, such as the formation of heat, gas, or precipitation; or result in damage to plants treated with the products.

A great source for compatibility information is the pesticide label. Some labels include details about specific combinations known to be incompatible, including problems that could occur when adding adjuvants, such as spreaders, detergents, or drift reducing agents. Other labels contain more general compatibility statements and jar test recommendations.

Not all labels include tank mixing guidance or restrictions. However, the lack of such statements doesn’t give you the green light to mix away to your heart’s content. You are responsible for performing a jar test to ensure compatibility, even when the label doesn’t list a potential problem.

A jar test is quite simple. It’s a small-scale tank mixing practice run, which allows you to see what could potentially happen if you combined the same products in your spray tank. The steps are the following:

  • Put on the personal protective equipment listed on the label to protect yourself from splashes or spills.
  • Fill a small glass or plastic jar with water or other carrier (often fertilizer) until it is 20-50% full.
  • Add products one at a time in proportionate amounts and in the proper order (a perfect topic for another article).
  • Lightly mix, swirl, or shake the contents in the jar.
  • Look for incompatibility issues, such as heat, precipitation, ingredient separation, or clumping.
  • Let the mixture sit for 10-15 minutes and check it again for any changes.
  • If nothing happens and the mixture appears consistent, it is probable the products are chemically and physically compatible.
  • Don’t forget to test the mixture out at the site for performance and plant damage issues.

I realize this article is an extremely brief response to the request for a description of compatibility jar tests.  If you would like to dive deeper into the topic of tank mixing, jar tests, compatibility concerns, and solutions, I have a great resource recommendation. The Purdue Pesticide Program produced a booklet called, “Avoid Tank Mixing Errors.” It is available as a pdf on the webpage:

Is there something you know you should know, or would like others to know?  If so, send me your requests and questions by email or phone (602) 827-8222. I’ll be happy to add them to the Pesticide Safety… “I should know this” series.

Pesticide Safety… “I should know this.”

Jennifer Weber, University of Arizona Pesticide Safety Education Program

Welcome to the very first edition of the

Pesticide Safety… “I should know this” series, where we will answer pesticide-related questions that seem to stump the best of us.  

Gloves, sleeves, boots, and pant legs – What’s a handler to do?

Question: “I should know this, but… When applying pesticides, am I supposed to tuck my sleeves into my gloves or my gloves into my sleeves? What about my boots and pant legs? Should I tuck my pant legs into my boots or wear them out over my boots?”

These are excellent and very commonly asked questions. If you search the internet for photos of pesticide handlers spraying overhead, 9 times out of 10 you will find photos of how NOT to position your gloves and sleeves. Trust me, I’ve surfed the internet many times in search of the perfect photos for pesticide safety presentations and hit a few snags.

Luckily, my coworker Christian Conner was happy to pose for these two photos to demonstrate the correct way to arrange your gloves, sleeves, pant legs and boots when applying pesticides.

As you can see from the picture on the left, Christian is pretending to spray a citrus tree overhead. He has correctly tucked his sleeves into his gloves. If the pesticide leaked from the sprayer’s wand, the liquid would simply trickle down his glove and onto the outside of his sleeve. His skin would be protected.

On the right, he is pretending to spray a patch of weeds on the ground. He placed his sleeves out over his gloves, which is perfectly fine in this situation. His skin is protected. He is also wearing his pant legs over his boots to prevent pesticides from entering the opening along the of his boots and potentially contaminating his socks and skin.

Feel free to share this article with pesticide handlers so they can continue to work safely when applying pesticides. Is there is something you know you should know, but for some reason, you just don’t know? If so, send me your question. I’ll be happy to help you find the answer and will add it to the Pesticide Safety… “I should know this” series. You can call me (Jennifer Weber) directly (602) 827-8222 or send me an email

UArizona Hires Two Extension Specialists

The University of Arizona hires two Cooperative Extension specialists, Dr. Debankur Sanyal (Soil Health) and Dr. José Luis Diaz (Weed Science). Both started serving the state based at the Maricopa Agricultural Center (MAC). Here’re short biographies of our new CE specialists:

Dr. Debankur Sanyal

Dr. Debankur Sanyal is a soil biogeochemist by profession and going to serve as an Assistant Specialist in Soil Health in the Environmental Science Department at University of Arizona, starting January 2022. He has a Ph.D. degree in Soil Science from North Dakota State University in 2018 and worked as a postdoctoral research associate at South Dakota State University since then.

As a researcher, he actively seeking answers to the fundamental questions about carbon nutrient cycling in the agroecosystems at multiple scales as impacted by plant-soil-microbe-climate interactions, using approaches that range from laboratory incubations to greenhouse trials to extensive field trials. Through his research program, he aims to create a climate-resilient, sustainable, and healthy agro-environment for human welfare. One of his passions is to develop cost-effective, applied, stakeholder-oriented methodologies to quantify the influence of various soil management and conservation techniques on soil biogeochemical properties and crop production.

Debankur has worked extensively with diverse crop production systems using soil conservation techniques such as minimum tillage, cover crops, livestock integration, diversified crop rotation, and manure application. Along with applied and basic research, his extension and outreach activities include participating in ‘Soil Health School’ and other workshops, demonstrating tools and techniques, and providing essential training to use them. Dr. Sanyal’s goal is to actively work with the stakeholders to design and carry out applied, stakeholder-oriented research, based on their needs and interests.


Email address:

Phone: (520) 621-1646

Please see his full CV here:

Dr. José Luiz Dias

Dr. José Luiz Dias joins the Plant Science Department at the University of Arizona in January 2022 as an Assistant Professor and Extension Weed Scientist. The challenges of economic, effective, and sustainable weed management are greater than ever with the fast-growing world’s population, the burdens of climate change, loss of water resources, labor shortages, greater pesticide use restrictions and herbicide resistance. Thus, in his new role with UArizona, José hopes to conduct an effective statewide extension program, as well as a meaningful research program based on grower’s needs, for weed biology, ecology, integrated weed management and innovative technology.

Before joined UArizona, José worked for one year at the University of California Cooperative and Extension (UCCE), as a Field Crops Agronomy and Weed Management Farm Advisor in the Northern San Joaquin Valley where he developed a multi-county extension and applied research program, targeted at solving growers’ problems and optimizing crop yield and sustainability for growers and allied industry. Prior to joining UCCE, José was a postdoctoral researcher at the University of Wisconsin, Madison, where he worked on identifying management practices and environmental factors to ensure successful establishment of alfalfa interseeded into corn silage, sustainable management of waterhemp in established alfalfa for dairy systems, and weed control, clover selectivity and resulting yield of grassclover mixed swards.

José earned a Doctoral Degree in Agronomy with a focus on Weed Science from the University of Florida, a Master’s Degree in Crop Protection and Bachelor’s in Agronomy from São Paulo State University in Brazil. His doctoral research centered on developing and implementing integrated management practices to reduce giant smutgrass populations in bahiagrass pastures. For his master’s degree, he researched herbicide selectivity in pre-budded sugarcane seedlings.


Email address:

Phone: (520) 621-1977