Involvement of Phytophthora species in white oak (Quercus alba) decline in southern Ohio

Abstract

This study was initiated to investigate the possible role of Phytophthora species in white oak decline (Quercus alba) in southern Ohio at Scioto Trail State Forest. Surveys demonstrated the presence of four species of Phytophthora including one novel species. By far, the most common species was P. cinnamomi; P. citricola and P. cambivora were isolated infrequently. In few instances, P. cinnamomi was isolated from fine roots and necroses on larger roots. No special pattern of incidence was found, but P. cinnamomi was more commonly isolated from greater Integrated Moisture Index values suggesting moist lower bottomlands favour this Phytophthora species. When tree crown condition was examined relative to the presence of Phytophthora, no significant association was found. However, roots of declining P. cinnamomi-infested trees had 2.5 times less fine roots than non-infested and healthy trees, which was significantly different. The population densities of P. cinnamomi from declining trees were significantly greater than from healthy trees, suggesting increased pathogen activity that has the potential to cause dieback and decline and possibly the cause of a reduced fine root amount found on declining trees.

Phytophthora Species Emerging as Pathogens of Forest Trees

“…Surveys in temperate forests in other parts of the world support these findings, although they usually cover larger, more diverse forested areas and investigate only forest soils or streams [15][16][17][18][19][20][21][22][23][24][25][26]. Similar numbers of species and many of the same taxa are reported from soils, streams, or trees in the eastern USA and from Europe.…”

More than Drought: Precipitation Variance, Excessive Wetness, Pathogens and the Future of the Western Edge of the Eastern Deciduous Forest

“…The event has not be described as a decline, defined by a slow gradual mortality, but rather a distinct abrupt mortality event that targets dominant long-lived species. Similar mortality events of this species have been observed and studied in Ohio by Balci et al (2010), who showed Pc associated with the same host tree species as in Missouri Ozarks (Q. alba).…”

“…Increasing climate variance, including excessive soil moisture either followed or preceded by drought contributes to the deleterious effect and the further advancement of this group of pathogens (DesprezLoustau et al, 2006). Balci et al (2010) directly implicated P. cinnamomi in white oak decline in Ohio and the presence of the root pathogen was associated with soils of higher moisture content. Experimentally, Corcobado et al (2014) simulated extreme weather events in seedlings and showed that drought may predispose seedlings to sensitivity to Phytopthora root infection.…”

Emergent insects, pathogens and drought shape changing patterns in oak decline in North America and Europe

“…Phytophthora cinnamomi, P. quercina (an oak-specific species), and several other Phytophthora spp. have been detected in recent decades in Europe (Jung et al, 1999(Jung et al, , 2002Gallego et al, 1999;Vettraino et al, 2002;Balci and Halmschlager, 2003) and in North America (Table 1; Balci et al, 2007Balci et al, , 2010Nagle et al, 2010). Although their role is not yet completely understood, it may be exacerbated by changing climate conditions (reviewed by Brasier, 1996;Jönsson, 2006).…”