Search

Swiss needle cast, a foliar disease caused by the Ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr., continues to afflict Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in north coastal Oregon. Permanent plots were installed in 1998 to assess growth impacts and monitor disease severity. Gross periodic annual increment was measured for three 2-year growth periods and one 4-year growth period and ranged from 0.37 to 31.74 [m.sup.3] [ha.sup.-1] [year.sup.-1]. Foliage retention, defined as the average number of annual needle age classes held by a tree, was also estimated as an index of disease severity. Assuming negligible losses in stands with maximum needle retention (approximately 3.9 years), growth losses in net periodic annual increment reached slightly over 50% in stands with the lowest needle retention (approximately 1 year). Mixed-effects regression models supported a consistent relationship between foliage retention and both gross and net periodic annual increment among the four growth periods. Periodic annual mortality ranged from 0 to 19.12 [m.sup.3] [ha.sup.-1] [an.sup.-1] but was not significantly influenced by Swiss needle cast as measured by average foliage retention. Minimum and maximum foliage retention has fluctuated annually from 1998 to 2008 on the permanent plots, but growth losses at a given level of foliage retention appear to have remained stable. Estimated growth losses are similar to those reported for comparable levels of defoliation by other agents. La rouille suisse, une maladie des feuilles causee par l'Ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr., continue d'infecter le douglas vert (Pseudotsuga menziesii (Mirb.) Franco) dans la region cotiere du nord de l'Oregon. Des placettes permanentes ont ete installees en 1998 pour evaluer les impacts sur la croissance et suivre l'evolution de la severite de la maladie. L'accroissement annuel periodique brut a ete mesure pour trois periodes de deux ans et une periode de quatre ans; il variait de 0,37 a 31,74 m3 * ha-1 * an-1. La conservation du feuillage, definie comme le nombre moyen de classes d'age annuelles des aiguilles conservees par un arbre, a aussi ete estimee en tant qu'indice de severite de la maladie. En assumant des pertes negligeables dans les peuplements ou la conservation des aiguilles durait le plus longtemps (approximativement 3,9 ans), les pertes de croissance en accroissement annuel periodique net atteignaient un peu plus de 50 % dans les peuple-ments ou la conservation des aiguilles durait le moins longtemps (approximativement 1 an). Selon les modeles de regression a effets mixtes, il y avait une relation constante entre la conservation du feuillage et les accroissements annuels periodiques net et brut pendant les quatre periodes de croissance. La mortalite annuelle periodique variait de 0 a 19,12 [m.sup.3] [ha.sup.-1] [an.sup.-1] mais n'etait pas significativement influencee par la rouille suisse telle que mesuree par la duree moyenne de conservation du feuillage. La duree minimale et maximale de conservation du feuillage a fluctue annuellement de 1998 a 2008 dans les placettes permanentes mais les pertes de croissance correspondant a un niveau donne de conservation du feuillage semblent etre demeurees stables. Les pertes de croissance estimees sont semblables a celles qui ont ete rapportees pour des niveaux comparables de defoliation causee par d'autres agents. [Traduit par la Redaction], Introduction Swiss needle cast (SNC) is a foliar disease of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) caused by the Ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr. (Hansen et al. 2000). This pathogen [...]

Abstract: Swiss needle cast (SNC) causes premature loss of foliage and subsequent growth decline in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Although the mechanisms leading to this growth decline include loss [...]

Swiss needle cast (SNC) is a foliar disease of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) caused by the ascomycete Phaeocryptopus gaeumannii (Rohde) Petrak. The number of annual needle cohorts retained by a tree indicates SNC severity and associated growth losses. In previous studies growth losses have been predicted on the basis of plot-level foliage retention, and plot-level growth multipliers have been uniformly applied to all trees within a stand to simulate tree growth. In this analysis, the effects of within-stand variation in foliage retention on individual-tree growth impact and implied stand dynamics were analyzed. Models describing diameter increment of Douglas-fir were developed based on three different foliage retention ratings: (1) plot-level foliage retention; (2) tree-level foliage retention; and (3) a combination of plot-level foliage retention and the deviation of tree-level from plot-level foliage retention. Foliage retention at both the plot-level and tree-level was positively correlated with diameter increment, and a significant amount of additional variation in diameter growth was explained by the deviation of individual-tree foliage retention from the plot-level average. The SNC “effect” was assessed by comparing growth of trees with varying degrees of Swiss needle cast to growth of those that retained maximal amounts of foliage. Across all plots in the sampled population, the most severely affected dominant or co-dominant trees exhibited 30% diameter growth loss relative to trees of similar crown position with minimal SNC symptoms. Within a plot, diameter growth averaged about 12% higher on trees with the highest foliage retention relative to trees with the lowest foliage retention, implying that SNC intensifies stand differentiation. Rather than responding to SNC with proportionally uniform growth losses within a plot, these results suggest that individual trees tolerate or resist the disease differentially. Foliage retention should therefore be used as a criterion for selecting trees for removal during thinning operations in Douglas-fir stands with moderate to severe SNC. [ABSTRACT FROM AUTHOR]

Highlights: [•] Patterns in the distribution of disease may aid the management of sudden oak death. [•] SOD sites did not occur closer to roads than expected by chance. [•] Road use has not contributed to long distance dispersal of P. ramorum in Oregon. [•] Sites did occur more commonly along stream ways, especially in inland watersheds. [•] Dispersal of inoculum may be occurring in turbulent air or stream waters. [Copyright &y& Elsevier]

Presents an obituary for forest pathologist Larry Weir who died on April 3, 2000 at the age of 76.