Inhibition of Growth of Protozoa Population by Neem Oil and Insecticidal Soap Spray

Pesticides, organic and synthetic, are often used in agriculture. Runoff can enter water sources and negatively disturb animal populations. The research detailed here examined which organic home remedy pesticide, neem oil or insecticidal soap spray, also referred to as pepper spray, would be less detrimental to the environment through the destruction of the population of protozoa in a water sample. Pesticides examined for environmental damage are usually synthetic, rather than organic, since organics are often assumed safer, which is not always true. Protozoa are a necessary part of an aquatic environment as they consume bacteria, reducing pathogens and helping reduce the spread of disease. Neem oil works by disturbing an organism’s hormones when consumed, causing them to not eat or reproduce, whereas pepper spray works by dehydrating the organism on contact. From this, it was hypothesized that the neem oil would be more detrimental to the population of protozoa in a water sample than the pepper spray.

The experiment was conducted by obtaining samples of river water and mud, separated into beakers. Samples of water were taken from each beaker, analyzed under a microscope, and the protozoa population was recorded. The treatments of control, neem, or pepper were randomly allocated to six beakers each. After 24 hours, the populations were examined with the same procedure as prior to pesticide application. The percent difference in population for each treatment was computed, and the data was analyzed through a two-sample t-test, revealing that when compared to control, neem and pepper both proved to significantly decrease the protozoa population. With outliers, the neem and pepper treatments were not significantly different. However, with outliers removed, the neem yielded a significantly lower population, accepting the hypothesis that the neem oil would be more detrimental to the population of protozoa than the pepper spray.

Research Conducted By:

Madison Kirby
Lakeview High School

Emily Koury
Cousino High School