Treesearch

The mycoparasite Nematogonum ferrugineum (Gonatorrhodiella highlei) was associated commonly with Nectria galligena cankers on Betula lenta in New Hampshire and Connecticut, and was isolated from N. galligena cankers on Juglans nigra from Virginia. In inoculation trials, parasitized isolates of N. coccinea var. faginata and N. galligena spread more slowly than non-parasitized isolates in bark and cambial tissues; parasitized N. coccinea var. faginata produced fewer perithecia.

Beech trees in an experimental plot in the Odenwald (southwest Germany), with different intensities of attack by Cryptococcus fagisuga Lind. since at least 1970, were observed from 1972 until 1982 in order to ascertain the role of scale insects in beech bark disease and to facilitate decisions for the management of infested stands. At the beginning of the research 13% of the dominant trees were infested by C. fagisuga. Until 1979 the attack decreased continuously, only in the dry years 1975 and 1976 did the number of trees with moderate attack increase. Since 1980 new infestations on...

Since 1976 on two observation plots in northern Bavaria 600 trees have been regularly observed. Preliminary results of disease development on 96 trees, formerly moderately or heavily infested by Cryptococcus fagisuga, are reported.

Within a sample of European beech, partial resistance to attack by the beech scale, Cryptococcus fagisuga, was associated with a smooth bark which had a regular, vertical pattern in its surface 'growth lines'. Such bark contained relatively little lignified outer parenchyma, and the main stone cell layer was strongly developed. The 'dimpling' symptom of infested stems was brought about by locally reduced and abnormal xylem development.

The specificity of the Cryptococcus fagisuga and N. coccinea association is studied by artificial inoculation of 4 species of Nectria: N. coccinea, N. ditissima. N. galligena and N. cinnabarina on bark infested with beech scale. N. coccinea appears to be the most efficient species for producing necrosis at the cambial level. The composition of the bark, in relation to induced pectinase activity gives a good explanation of the specificity recorded here.

The pectinase activity of Nectria coccinea was studied in vitro and in vivo in relation to the pectinases of Cryptococcus fagisuga and the nature of the bark. Any pectinases necessary for degradation of pectic material were secreted by the fungus in vitro. Some pectinases produced by the insect are of great significance in the predisposition of the bark to alteration by the fungus. The assistance given by the scale insect and the pectinase pool of N. coccinea which is well adapted to the trunk bark, is a possible explanation of the specificity of the association C. fagisuga/N. coccinea.

Observations of the mycoflora of beech bark infested with Cryptococcus fagisuga suggested that Nectria coccinea can colonise sites on and in the outer tissues, and that invasion of imer bark could later develop. Although these sites harboured fungi antagonistic to N. coccinea, experiments suggested that it is well adapted under some circumstances to escape serious competition.

Investigations were made of necrophylactic peridems which were found to delimit natural and experimentally induced cankers in American beech. Anatomical evidence is presented which supports the hypothesis that the necrophylactic periderm is generated from recent derivatives of the vascular cambium as well as from living cells of the bark tissues present at the time of wounding or infection.

The role of Armillaria mellea in the mortality of beech trees affected by beech bark disease was determined by excavating root systems of beech trees infested by beech scale, Cryptococcus fagisuga, or also infected by the bark fungus, Nectria coccinea var. faginata. Only trees infected by Nectria showed any effect on the root system. They had fewer 4th order nonwoody branch roots and less starch than trees only infested by scale. A. mellea colonized roots only on Nectria-infected trees and was consistently found on roots associated circumferentially with areas of stem bark necrosis caused...

Cryptoeoccus fagisuga has infested over 70,000 acres (28,000 ha) of forest in West Virginia. Beech bark disease is causing heavy mortality in two areas of the Monongahela National Forest and additional scattered mortality. In the areas most affected, per-acre losses total 1,369 board feet of sawtimber and 2.67 cords, with a potential loss of 5,697 board feet and 9.29 cords. Nectria galligena appears to be the only species of Nectria involved in the disease complex.