Preventing unwanted salad surprises
By Department of Agricultural and Biological Engineering
May 2, 2018

by Matthew Niewiara

A few weeks ago, right before spring break, our senior design team, known as “Team Frog Fence” had the opportunity to travel to California.  Our task is quite unique: come up with a suggested fence design to keep frogs out of lettuce fields.  The team consists of myself, Lucia Dunderman, Noor Farahmandpour, and Brandon Spencer.  Our advisors are Dr. Paul Davidson, Dr. Michelle Green, and Dr. Jonathan Warner.  Additionally, Dr. Daniel Hughes is our team’s herpetologist, our resident expert on the Pacific Tree Frog, the species that is causing the problem.   

Designing a fence to keep frogs out of lettuce fields seems like a simple task at first. However, due to the Pacific Tree Frog’s agile climbing ability, the task is quite complex.  These frogs have been known to climb vertical (or even steeper) surfaces.  The presumed reason they end up in the lettuce fields is that it is an ideal habitat for them.  Once the frogs breed in any source of nearby water, the moist leafy greens provide a haven from the hot, sunny, and windy environment of the Salinas Valley.

One might not think that a tiny frog, about the size of a golf ball, could cause a severe problem on these huge ranches of spinach, lettuce, and other greens.  However, due to potential food safety risks, any foreign animal entering the field could cause contamination.  Moreover, most consumers aren’t too happy when they find a frog (dead or alive) inside their bag of pre-packaged greens.  Despite the free added protein, it’s not the most appetizing sight!

Our team definitely made the most of our short trip to California.  We met up with a knowledgeable group of leafy green stakeholders to discuss the problem and potential solutions.  We were able to visit various farms in the area to see first-hand where the fence might be installed.  This was an invaluable portion of the trip because we were able to get a much better sense of the scale of the problem.

Our team has just recently finished conducting materials tests in the ABE wind tunnel to test durability.  The Salinas Valley has extreme wind conditions that can easily rip apart some materials, so it’s essential that the material is durable.  We have been considering multiple aspects of the design including the size and asperity of the mesh, as well as top lip designs.  Because we currently do not have live frogs to test with, these design components will be suggested for experimentation in the future. 

Even though our team project is coming to a close, this study originated with Drs. Green and Davidson, and their grant has a total duration of two years.  Therefore further material testing, along with testing of other deterrent methods and live frog testing, will need to be conducted.  By the end of this project, our team will have played a critical role in the development of a novel method to keep frogs out of lettuce fields - and prevent unwanted salad surprises!

[Matthew Niewiara is a senior in Agricultural and Biological Engineering]