Date of Graduation
Master of Science in Plant Science (Agriculture)
College of Agriculture
insect immunity, Lepidoptera, Galleria mellonella, bioinsecticides, essential oils, azadirachtin, hemocytes, phagocytosis, encapsulation
Worldwide resistance to current insecticides continues to grow at an alarming rate, with the danger of pesticide overuse reducing acceptable doses. Alternative strategies for insect pest management are therefore imperative. By compromising the insect immune system with plant-derived substances and studying the detailed processes involved in hemocyte-mediated responses, one can develop improved methods for insect control. Hemocyte numbers change in response to stress. This allows essential defense mechanisms such as phagocytosis and encapsulation to take place. In this thesis, plant-derived substances were used to challenge larval-stage Galleria mellonella (Family: Lepidoptera) due to their nontoxic nature and high value in pest management. Insects were subjected to chemicals of botanical origin including essential oils and various neem formulations. Azadirachtin, the presumed insecticidal compound of neem, was also tested in addition to a mycoinsecticide containing Beauveria bassiana fungi. Differential hemocyte counts were conducted, phagocytosis was assessed using Sumi ink, and nylon implants were inserted to measure encapsulation. Final results indicate a correlation between hemocyte release and insect cellular defenses. Interestingly, neem oil significantly disrupted pupation while simultaneously inhibiting plasmatocyte production. Azadirachtin similarly halted larval growth, but did not elicit a hemocytic response.
© Katherine Haszcz
Haszcz, Katherine, "Impairing The Insect Immune System With Plant-Derived Substances" (2016). MSU Graduate Theses. 2383.