Phytophthora ramorum. [Distribution map].

A new distribution map is provided for Phytophthora ramorum Werres, de Cock & Man in't Veld. Oomycota: Pythiales. Hosts include California black oak (Quercus kelloggii), California live oak (Quercus agrifolia), Rhododendron, shreve oak (Quercus parvula var. shrevei), tanoak (Lithocarpus densiflorus) and Viburnum. Information is given on the geographical distribution in Europe (Belgium, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Poland, Slovenia, Spain, Sweden, Switzerland, UK) and North America (Canada (British Columbia), USA (California, Florida, Georgia, Louisiana, Oregon, South Carolina, Tennessee, Virginia, Washington)).

Ecology of Armillaria spp. in Mixed-Hardwood Forests of California

Incidence of Armillaria root disease and the population structure of associated Armillaria spp. was studied in California mixed-hardwood forests. Four 3,000-m2 plots, consisting of Quercus kelloggii, Q. agrifolia, Lithocarpus densiflorus, Arbutus menziesii, Umbellularia californica, and Pseudotsuga menziesii, were intensively sampled. Root collars were examined for mycelial fans, decayed wood, and rhizomorphs. From 404 trees (333 living, 71 dead), Armillaria mellea and A. gallica were recovered and identified from 148 isolates. The most abundant tree species in each plot was the tree species most frequently infected by A. mellea or A. gallica. The majority of A. mellea isolates were recovered from mycelial fans on living trees. Recent mortality due to A. mellea was found only in one plot. A. gallica was mainly identified from epiphytic rhizomorphs. Only one to three somatic incompatibility groups (SIGs) for each species were found in each plot. Estimated sizes of SIGs varied from the extent of a single root system to the entire width of the plot. Based on our results, both A. mellea and A. gallica are common in mixedhardwood forests, yet A. mellea appears to be a more aggressive pathogen. A. gallica is capable of attacking live hosts, but occurs on living roots more frequently as epiphytic rhizomorphs.

Visual Counts of Acorns of California Black Oak (Quercus kelloggii) as an Indicator of Mast Production

In 1995, acorn production of California black oak(Quercus kelloggii) was measured on 20 mature trees located in two stands in Placer County, California. Acorn production of each tree was measured using three 0.8 m² cone traps and a single 30 sec visual count. Visual counts were compared with trap data to develop statistical relationships between the two methods because visual counts have some advantages over traps, and we desired an efficient measure of the amount of acorns available as food for wildlife. Visual counts were positively correlated (P < 0.020) with several trap measures including wet acorn weight, weight of sound acorns, dry acorn weight, and total number of sound acorns. Linear regression of square-root transformed data found that visual counts could be used to predict total weight of sound acorns and total weight of dry acorns (P < 0.003). These results indicate that visual counts are adequate surrogates for more detailed measures of acorn production. West. J. Appl. For. 13(1):27-31.