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Low-Level Maintenance Control Dr. Ben Sperry & Dr. Jason Ferrell

What's the problem?

Waterhyacinth is a rapidly growing invasive plant that has been a management challenge in Florida for over 130 years.

It impedes navigation, irrigation and recreation, while reducing water quality and sheltering mosquito species responsible for spreading human diseases. Managing waterhyacinth is critical for protecting Florida's waterways and human health.

Previous Research

A significant study done by UF researcher, Joe Joyce, was published in Aquatics magazine in their 1985 winter issue. Joyce' s study addressed:

  1. Public concern of too much chemical spraying.
  2. Public concern of herbicide affects on water quality.
  3. Public concern of muck accumulation in lake bottoms created by dying plant matter.

Joyce found that low-level maintenance control, spraying herbicide more often with less overall chemical solution used over time, can:

  1. Reduce the amount of chemical solution, or herbicide, used annually.
  2. Prevent a decrease in dissolved oxygen concentrations.
  3. Reduce plant matter accumulation in lake bottoms.

Current Study

UF/IFAS Center for Aquatic and Invasive Plants (CAIP) is excited to scientifically recognize these results by validating findings through a new study currently underway.

Dr. Sperry and Dr. Ferrell are using the same 6 treatment levels conducted by Joyce (1985) with 2 additional treatments:

  1. A mesocosm is harvested back when the waterhyacinth fills the tank to 100%
  2. A non-treated mesocosm has shade cloths, for minimal light, to help with plant matter accumulation measurements

Problem

Waterhyacinth management relies on chemical solutions; however, the public is very concerned with excessive herbicide use.

Carpets of floating waterhyacinth can be found in many lakes across the state.

Purpose

The purpose of the study is to collect quantitative data that validates Joyce's (1985) findings on low-level maintenance control of waterhyacinth.

Experiment Overview

UF/IFAS CAIP researchers are currently testing maintenance control of waterhyacinth with mesocosm experiments. Every mesocosm, or tank, acts as a model lake system (see right). They are each managed differently in order to investigate the three research goals.

The plants are managed based on the percent of area covered (PAC). The PAC is the amount of surface area the waterhyacinth covers in the tank. The original six treatment levels used by Joyce were: zero, 5%, 25%, 50%, 100%, and 100% (unsprayed). UF/IFAS CAIP researchers are also including two additional treatment levels: one tank will demonstrate mechanical harvest (shovel) and the second serves as a control for muck accumulation measurements near the end of the study (shade cloth).

An illustration of the 8 treatment levels in the experiment.

Research Goals

Current Data Collection

Public concern of herbicide affects on water quality. Measuring dissolved oxygen levels in each tank every 2 weeks. Dissolved oxygen is an important measure for non target species and fish health.

[Bi-weekly dissolved oxygen measurements help researchers determine the appropriate chemical treatment to use for second variable of the study, herbicide carrier volume]

Public concern of too much chemical spraying. Changes in herbicide carrier volume in management.

Final Data Collection

Public concern for sediment and muck accumulation. Will be measuring the resulting accumulation at the end of the trials to determine effects.

Conclusion

Currently researchers are running mesocosm trials to observe the three research goals in this study. Data collection is currently underway.

Future research will investigate alternative application techniques with other herbicides and plant species, as well as field trials of these techniques.

Low-level maintenance control brings invasive plant populations down to manageable levels through more frequent herbicide application, using HALF as much herbicide over time.

Ultimately, this research aims to help industry professionals manage aquatic plants in a more efficient way.

ABOUT THE RESEARCHERS

Dr. Benjamin P. Sperry is an Assistant Research Scientist at University of Florida Institute of Food and Agricultural Sciences (UF/IFAS CAIP). He received his bachelor’s and master’s from the UF College of Agricultural and Life Sciences in Plant Science and Agronomy – Weed Science, respectively. He then went on to earn his Ph.D. from Mississippi State University in Agronomic Weed Science in May of 2019. While his formal training is weed science in agricultural systems, Dr. Sperry has held several positions prior to graduate school related to terrestrial invasive plant management. He is an avid outdoorsman who became familiar with aquatic invasive plants and their associated problems at an early age.

Dr. Jason Ferrell has been faculty at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) since 2004. In 2017, he became the Director of the UF/IFAS Center for Aquatic and Invasive Plants (CAIP). As the Director of CAIP he leads a multidisciplinary group of faculty and staff whose mission is to develop and disseminate strategies for addressing the impact of invasive plants. He also serves as the Director of the Pesticide Information Office where he works to ensure that pesticide applicators are trained and licensed in a relevant and timely manner.