Effect of Nosema Carpocapsae Infection on Response of Codling Moth, Cydia Pomonella, to Three Types of Stress

Codling moth, Cydia pomonella, is the most deleterious insect pest of apples throughout the world and can also be a serious pest of pears and walnuts. Codling moth is a quarantine issue when exporting these fruits to other countries where this pest has not been introduced. Codling moth populations in laboratory colonies can often be infected with the microsporidian disease, Nosema carpocapsae, which can reduce survival of the larvae and fitness of the moth. The use of infected laboratory populations for the development and testing of new treatments may lead to overestimation of the efficacy of these treatments when applied to healthy uninfected populations in the field. To test this hypothesis, we are assessing the response of larvae with different levels of infection to three stresses: heat shock, cold shock and infection with the codling moth granulovirus. Our hypothesis is that larvae infected with Nosema will show increased susceptibility to all three stressors, with the possible exception of heat shock, which may reduce Nosema viability as well.  Intensity of Nosema infection will be assessed by quantitative PCR or by Nosema spore counts if necessary.  Codling moth fitness as influenced by Nosema infection status and stressor treatments will be assessed as percent survival and adult weight.