Factors affecting realized fecundity and offspring fitness of Arkansas Sirex

Arkansas Sirex adults do not feed and therefore all adult activity must be accomplished on energy reserves acquired during larval stages. Drilling into hosts and ovipositing is an energy consuming process. Host tree factors that increase the amount of energy expended during oviposition could limit numbers of eggs a female oviposits. Drilling through thicker bark requires more time and energy and may lead to exhaustion of a female’s energy reserves and subsequent death before she oviposits all of her eggs. Yet ovipositing through thick bark may afford developing larvae greater protection from parasitoids and the elements. If an ovipositing female detects and avoids blue-stain fungi then that behavior may lower her realized fecundity by increasing the number of drilling probes that do not contain eggs. However, the detection and avoidance of blue-stain fungi may increase larval survival and development. Factors of hosts such as bark thickness and presence of blue-stain fungi may limit a female’s realized fecundity, but where a female oviposits can have a profound effect on her offspring’s survival and fitness. We conducted studies in the lab to determine how bark thickness and presence of blue-stain fungi affect the realized fecundity of Arkansas Sirex. These bolts were then placed in the field to determine how offspring fitness is affected by the various treatments.