Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2010. / Härtill 3 uppsatser.

We conducted an experimental evaluation of treatments to limit Heterobasidion occidentale infection of white fir (Abies concolor) stumps and wounds in California mixed conifer forests. We tested the efficacy of urea, borate, and a mixture of two locally collected Phlebiopsis gigantea strains in preventing pathogen colonization of fir stumps and separately, urea and borate as infection controls on experimental stem wounds. These were paired with a laboratory test on ~100 g wood blocks with and without a one-week delay between inoculation and treatment. Urea, borates, and Phlebiopsis treatments all significantly reduced the stump surface area that was colonized by H. occidentale at 84%, 91%, and 68%, respectively, relative to the controls. However, only the borate treatments significantly lowered the number of stumps that were infected by the pathogen. The laboratory study matched the patterns that were found in the stump experiment with a reduced area of colonization for urea, borates, or P. gigantea treatments relative to the controls; delaying the treatment did not affect efficacy. The field wound experiment did not result in any Heterobasidion colonization, even in positive control treatments, rendering the experiment uninformative. Our study suggests treatments that are known to limit Heterobasidion establishment on pine or spruce stumps elsewhere in the world may also be effective on true firs in California.

Fourteen plots of 25 loblolly pines each were excavated in order to determine incidence and severity of <u>Heterobasidion annosus</u> in asymptomatic loblolly pine in Virginia. Each plot was established between 30 m and 100 m from an identified source of inoculum. A bulldozer was utilized to excavate root systems of the trees. The root systems of all trees visually estimated to have greater than 1% infection (this included 51% of the trees sampled) were measured with a tape and the root length measurements were categorized as resin soaked, stringy or healthy. Of the trees sampled, 85% were infected with <u>H. annosus</u>. Basidiocarps were found on 9% of the sampled trees. The average frequency of roots per tree infected with <u>H. annosus</u> for all measured trees (>1%) was 30% of the primary roots and 31% of the secondary roots. The average root length infected for all the measured trees (>1%) was 14% for primary roots and 15% for secondary roots. The sample trees were tested for a growth difference with the t-test for unpaired plots. The sampled trees were placed into one of two classes: those trees with >1% infection of the root systems (diseased) and those with ≤1% infection of the root system (healthy). The average annual increment for each of the last five years was tested, and all five tests were significantly different in growth at the 0.01 level. The difference in growth between healthy and diseased trees over the five year period was 19% or approximately 4% per year. Of all the disease parameters measured in the study: crown rating, percentage of infected primary roots and percentage of infected secondary roots were the most effective parameters in describing the effect of disease on annual increment growth over the last five years prior to sampling. / Master of Science

Licenciatavhandling Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 2 uppsatser.

Licenciatavhandling Uppsala : Sveriges lantbruksuniversitet, 2009.