Do Cool Temperatures Impact the Parasitism Rate of Psyttalia humilis?

Overview

Objectives/Goals Parasitoid wasps are natural predators that are a great alternative to pesticides. Scientists are currently releasing a parasitoid wasp, Psyttalia humilis, to combat the olive fruit fly which has become a huge threat to California#s olive industry. Scientists are still unsure if P. humilis will survive during the cool winter months. Therefore, my project is to determine if cool winter temperatures affect the ability of P. humilis to parasitize the olive fruit fly larvae inside of the olive fruit. Methods/Materials U. C. Riverside#s Entomology Department provided me with 160 olives infested with fruit fly larvae and 40 mated female P. humilis. I prepared 20 identical containers and divided them into four treatments: Infested olives without P. humilis held at room temperatures; infested olives with P. humilis held at room temperatures; infested olives without P. humilis held at cool outside temperatures; infested olives with P. humilis held at cool outside temperatures. Each treatment was replicated 5 times. The high and low temperature was recorded daily. After seven days, all of the cool temperature containers were placed inside and all of the parasitoids were removed. The containers were checked daily and the number of emerging larvae, fruit flies, and parasitoid wasps were counted and recorded. Results The results show that cool temperatures did impact P. humilis# ability to parasitize the fruit fly larvae, but overall P. humilis was able to reproduce in cool temperatures at numbers similar to the parasitoids held in warmer temperatures. Conclusions/Discussion Although more adult fruit flies did develop from the cool temperature larvae exposed to P. humilis, P. humilis was still able to stop a large number of the larvae from developing into adult fruit flies. In addition, the cool temperatures slowed the development of P. humilis by ten days. Although the cool temperature treatment suggested that P. humilis# mobility is affected when parasitizing olive fly larvae, the most important fact is that the cool temperature treatment also produced adult P. humilis parasitoids. This means there is promise in using Psyttalia humilis as a biological control, and there is the possibility of establishing permanent populations in Southern California.

Awards (1)

• First Place

Competition history

• CSEF 2012 Zoology · Entry J2217

Resources

• CSEF project summary ↗

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