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Dr. Jordan Marshall
Department of Biology
Indiana University – Purdue University Fort Wayne
Emerald ash borer (EAB) has caused significant mortality of North American ash (Fraxinus spp.) since its introduction from Asia during the 1990s. While a large proportion of ash does succumb to EAB infestation, some trees are able to survive the attack. These surviving individuals still are infested by EAB and show signs of the infestation; however, some mechanism exists allowing them to tolerate attack and continue to grow vigorously. Following emergence, EAB adults spend time in ash canopies feeding on foliage during a maturation period. A choice feeding study was established comparing the preference of female:female, male:male, and female:male feeding pairs on foliage from green ash trees, that are growing on the IPFW campus, categorized as tolerant and susceptible to EAB attack. The EAB adults were reared in the lab from green ash logs from Allen County, IN and Shiawassee County, MI that were placed in barrels with attached containers, exposed to the light, so that the adult beetles could be collected. Tolerant and susceptible trees did not differ in diameter and both groups of trees were currently experiencing attack from EAB with evidence from bark splits, EAB exit holes, and woodpecker activity. The trees also had the same amount of beetle activity due to the similarity in crown light exposure. However, susceptible trees had significantly more crown dieback than tolerant trees and also had a significantly higher numeric vigor rating (one is healthy and five is half dead). Foliage was collected from wild-grown green ash and replaced in each feeding cage every 1-3 days. Leaf area was measured before exposure to EAB adults in cages and after removal. Beetles that died during the experiment were frozen, dried, and weighed at the end. In comparison, the females and males in the female:male pairs weighted more than the females in the female:female pairs and the males in the male:male pairs this result was due to the formation of sex gametes making the females and males in the female:male pairs heavier than the beetles that were paired with the same sex. The mean body mass of the females together weighed more than the male beetles, which was expected since female beetles usually weigh more than the male beetles. The different feeding pair treatments (F:F, M:M, M:F) did not differ in the ratio of the mean area of susceptible:tolerant leaf consumed; suggesting that a preferential difference did not occur between sexes or mating pairs. However, pooled adult pairs fed significantly more on susceptible leaves than tolerant leaves. Previous research has demonstrated a feeding preference between host species by EAB adults. The identification and subsequent selection of one host species over another is likely related to the possibility of a host chemical or structural component that can drive EAB to select the tree to feed and oviposition on.
Biology | Life Sciences
Hunnicutt, Rachel, "Feeding Peference of Emerald Ash Borer Adults on Tolerant and Susceptible Ash Foliage" (2013). 2013 IPFW Student Research and Creative Endeavor Symposium. 20.