Interactive Influence of Leaf Age, Light Intensity, and Girdling on Green Ash Foliar Chemistry and Emerald Ash Borer Development

Abstract

Biotic and abiotic environmental factors affect plant nutritional quality and defensive compounds that confer plant resistance to herbivory. Influence of leaf age, light availability, and girdling on foliar nutrition and defense of green ash (Fraxinus pennsylvanica Marsh) was examined in this study. Longevity of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), adults reared on green ash foliage subjected to these factors was assayed. Mature leaves generally were more nutritious with greater amino acids and a greater ratio of protein to non-structural carbohydrate (P:C) than young leaves, in particular when trees were grown in shade. On the other hand, mature leaves had lower amounts of trypsin and chymotrypsin inhibitors, and total phenolics compared to young leaves. Lower defense of mature leaves alone, or along with higher nutritional quality may lead to increased survival and longevity of emerald ash borer feeding on mature leaves. Sunlight reduced amino acids and P:C ratio, irrespective of leaf age and girdling, and elevated total protein of young foliage, but not protein of mature leaves. Sunlight also dramatically increased all investigated defensive compounds of young, but not mature leaves. Girdling reduced green ash foliar nutrition, especially, of young leaves grown in shade and of mature leaves grown in sun. However emerald ash borer performance did not differ when fed leaves from trees grown in sun or shade, or from girdled or control trees. One explanation is that emerald ash borer reared on lower nutritional quality food may compensate for nutrient deficiency by increasing its consumption rate. The strong interactions among leaf age, light intensity, and girdling on nutrition and defense highlight the need for caution when interpreting data without considering possible interactions.

Differential Response in Foliar Chemistry of Three Ash Species to Emerald Ash Borer Adult Feeding

“…DIR has been observed in many plant species, in particular, in trees (Kaitaniemi et al 1998). Third, the lack of induction might reflect a general pattern of the response of mature foliage to biotic and abiotic stress (Nichole-Orians 1991;McAuslane et al 1997;Chen and Poland 2009b).…”

“…Mature leaves were chosen because EAB adults are known to prefer mature over young foliage (Chen and Poland 2009b). To simulate common levels of foliage damage in nature by EAB, adults (personal observations), ten 8-to 10-d-old adult females were placed inside the sleeve and allowed to feed for 48 h. Adult females then were removed and frass gently brushed from the leaves.…”

“…Differences in feeding and infestation preference in laboratory studies appear to be associated with such phytochemical variability (Pureswaran andPoland 2009, Chen andPoland 2010). Intact black, green, and white ash release many volatiles that trigger electroantennal responses of EAB adults (Rodriguez-Saona et al 2006;de Groot et al 2008) and possess a wide variety of phenolics (Eyles et al 2007) and protease inhibitors (Chen and Poland 2009b) that may confer resistance against EAB. Phenolics generally denature plant proteins and thus reduce nutritive values of plants (Dudt and Shure 1994;Ossipov et al 2001).…”

Chemical Ecology of the Emerald Ash Borer Agrilus planipennis

“…It is possible that low levels of volatile release indicate lower host resistance, and also that A. planipennis can detect that difference. In general, little is known about the underlying mechanisms that govern the behavior of A. planipennis with respect to ash tree resistance (Eyles et al 2007;Rebek et al 2008;Chen and Poland 2009). Rodriguez-Saona et al (2006) found at least 16 compounds from Manchurian ash that were antennally active to both male and female A. planipennis.…”

Effect of Girdling at Various Positions of ‘Huang Zhi Xiang’ Tea Tree (Camellia sinensis) on the Contents of Catechins and Starch in Fresh Leaf

“…Thus, the effect of three types of girdling on the formation of catechins was different. The detailed mechanism of the catechins formation caused by [16] reported that girdling decreased total phenolics of young leaves under shady conditions, while it elevated total phenolics of mature leaves under sunny conditions in green ash (Fraxinus pennsylvanica Marsh). Therefore, perhaps girdling at different sunlight conditions could also make impact on the formation of catechins in the fresh leaf.…”