Laboratory Evaluation of the Relative Effectiveness of Plant and Animal Source Oils for Control of Notonectidae in Fish Ponds

Abstract

Predation on small finfish fry and juvenile crustaceans by air-breathing insects such as Notonectidae can be a significant problem. Effective and widely used control methods employ petroleum products to create a thin surface film that prevents insect respiration, but these products pose an environmental concern. This study was conducted to evaluate potentially safer plant- and animal-based oils as effective methods of insect control. Based on their physical properties when added to water, menhaden fish oil (MO) and corn oil (CO) were selected as the most promising candidates. These oils were then compared with two previously recommended petroleum product mixes (a 2:1 motor oil : diesel fuel mix [PC-I] and a 1:20 motor oil : diesel fuel mix [PC-II]). The two oils and two oil mixes were evaluated at two application rates (1.48 mL/m2 and 4.45 mL/m2) with three replicates of each treatment. These were tested in 8-L glass aquaria filled with 6 L of reservoir water with a water-surface area of 0.107 m2. Thirty minutes prior to treatment, each aquarium was stocked with five adult Notonectidae. After 2 h, all oil treatments at the high application rate had total mortality. At the low application rate, the PC-II and MO treatments produced complete insect mortality while the PC-I and CO treatments resulted in 87% mortality in 2 h. These trials indicate that menhaden fish oil is a potential alternative to petroleum products for the control of predaceous, air-breathing insects at similar application rates. At higher application rates, corn oil may also be an effective control agent.