49 Extension Note June 2000 Evaluation of the Effectiveness of Chondrostereum purpureum for the Control of Mechanically Brushed Trembling Aspen (Populus tremuloides Michx.) Suckers in a -year-old Conifer Plantation: Third-year Results (MOF EP .) Ministry contact: Introduction will attack only woody species that have T. Conlin, G.J. Harper, P.G. Comeau been selectively wounded, the effect of B.C. Ministry of Forests Research Branch Several vegetation control options are this mycoherbicide is restricted to the Forest Dynamics Section currently available to British Columbia target vegetation. P.O. Box 9519 Stn Prov Govt Victoria, BC V8W 9C2 foresters. Some of the more common This extension note reports on the options, such as herbicide application mortality and growth response of or manual brushing operations, may be trembling aspen (Populus tremuloides limited in their effectiveness for a num- Michx.) suckers years after applica- ber of reasons. For example, public tion of the fungus Chondrostereum opposition may curtail the operational purpureum ([Pers.: ex Fr.] Pouzar). The application of herbicides, while site data presented here were collected from conditions may preclude the use of one of two British Columbia installa- manual brushing of competing vegeta- tions that are part of a larger national tion (Boateng and Comeau ). Other research program testing the efficacy of less common methods may be restricted C. purpureum. This extension note does in their use to specific ecosystems. The not discuss the field trial that tested Research Branch of the B.C. Ministry the effectiveness of C. purpureum in of Forests, in partnership with the controlling the growth of Sitka alder Canadian Forest Service, the Biology (Alnus sinuata [Regel] Rydb). For fur- Department of the University of ther information on C. purpureum and Victoria, and Mycologic Inc., are cur- its control of Sitka alder see Harper rently involved in testing the use of a et al. (). fungus, Condrostereum purpureum, as a method of controlling vegetation that Methods competes with planted conifer seedlings. The purpose of this research was to During the spring of , a site evaluate promising methods for man- containing a plantation of -year-old aging vegetation in conifer plantations. lodgepole pine (Pinus contorta Dougl.) Condrostereum purpureum is an and Western larch (Larix occidentalis ideal candidate for vegetation control Nutt.) seedlings was selected northwest (Harper et al. ). It occurs naturally of Grand Forks to test the effectiveness in British Columbia forests. Because it of C. purpureum for the control of Ministry of Forests Research Program trembling aspen. Nine treatment formu- Results stems per hectare (Figure ). This was lations were tested in this trial using a due to recruitment of stems through completely randomized design; these Mortality of Tagged Aspen Cohorts suckering and stump sprouting. included two carrier formulations, one Cut stump application of both Release® from Ontario and the other from British and the British Columbia formulation Stem Height, Stem Diameter, Columbia, in combination with two with the isolate (B) resulted in Stem Basal Area, and Stem Volume fungal isolates, JAM and , for a the highest mortality of tagged aspen Stem height, stem diameter, stem total of four treatments plus a brushed (Figure ). All other treatments resulted basal area, and stem volume were treatment and a triclopyr herbicide in responses that were not statistically calculated for each treatment. In the (Release®) treatment. Three control significant from one another. tagged cohorts, the only significant treatments, consisting of applications The response of all living aspen response to the treatments was that of the British Columbia and Ontario stems in the treatment plots, including observed between the non-brushed formulations without C. purpureum, the tagged stems, was also recorded and control and all other treatments. as well as a non-brushed treatment, analyzed on a stems/ha basis. Three Further analysis of data collected from were also included in the experimental years after treatment there were no non-tagged stems demonstrated no design (Table ). The treatment plots statistically significant effects of treat- significant differences between any of were manually brushed to provide the ments on the total number of aspen the treatments (Table ). cut stem surface required for inocula- tion of the fungus. Each treatment was table Treatment key replicated five times. One of the objectives of this trial was Treatment I.D. Composition of treatment formulation to observe the response of cohorts of aspen stems to the applied treatments. B2139 B.C. carrier formulation + fungal isolate from B.C. (2139) A simple criterion was set by which the O2139 Ontario formulation + fungal isolate from B.C. (2139) cohort was selected and which included BJ6 B.C. formulation + fungal isolate from Ontario (JAM6) all aspen stems greater than cm in OJ6 Ontario formulation + fungal isolate from Ontario (JAM6) diameter and cm in height. These ONf Ontario formulation only (no fungal isolate) stems were tagged and their mortality BCf B.C. formulation only (no fungal isolate) assessed annually. This method of Rlse 30% Release® (triclopyr) herbicide in mineral oil selecting sampling units resulted in Brsh Brushed only non-uniform plot sizes that were m notrt Non-brushed control wide, but of varying length. This was necessary because of the variability in distribution of cohort stems within the treatment plots. The plot areas were also measured and recorded for the purpose of weighting responses to the treatments on a “per-area” basis (e.g., total stems per hectare). The data contained in this note were analyzed using a one-way analysis of variance (proc glm with the lsmeans command) and Tukey’s hsd procedure for comparison of the treatment means (Harper et al. ). For further details on the mode of application, formulations used, and the experimental design, please see Harper et al. (). figure Mean number of dead stems (with error bars) in 25-stem cohorts in response to treatment. Letters signify statistically significant differences using Tukey’s HSD (α = 0.05). Suckered Shoots vs. Stump Sprouts All non-cohort stems were categorized according to whether they originated as a sucker or as a stump sprout growing from the base of a decapitated stem. The mean densities of suckers and sprouts in response to treatment is shown in Figure , which illustrates some of the differences in vegetative reproductive strategies. Brushing increased the mean number of sprout stems, indicating that this treatment was not effective at inducing stem mortality because terminal growth was replaced by lateral shoot growth. It also appeared that a large number of suck- ers were subsequently recruited into the brushed plots following the year of figure Mean number of total aspen stems/ha in response to the applied treatments. treatment. On the other hand, the use There were no significant differences between treatment means. of Release® reduced the mean numbers of sprouts, but did not affect mean table Treatment means (s.e.) of total stem diameter, total stem height, total stem sucker densities, which were similar to basal area, and total stem volume per square metre for untagged stems. those of the brushed treatment. Treat- There were no significant differences between treatment means (Tukey’s HSD ment B appeared to have reduced where α = 0.05). mean stem numbers of both aspen sprouts and suckers, indicating that it Sum of stem Sum of stem Sum of stem Sum of stem may be the better candidate for control diameters heights basal areas volumes of aspen growth. These data also sug- Treatment (cm /m2 ) (cm /m2 ) (cm2 /m2 ) (cm3 /m2 ) gest a reason for the higher number of aspen stems found in plots treated with the O formulation: brushed stems B2139 10.1 (4.4) 93.6 (39.5) 1.18 (0.65) 63.8 (50.2) appeared to have suffered the same O2139 22.9 (4.4) 207.4 (39.5) 3.25 (0.65) 179.8 (50.2) mortality as those treated with B, BJ6 26.6 (4.4) 249.3 (39.5) 3.52 (0.65) 204.9 (50.2) but mean sucker numbers were higher OJ6 21.5 (4.4) 175.2 (39.5) 2.70 (0.65) 130.4 (50.2) than in the other brushed treatments, ONf 15.6 (4.4) 139.3 (39.5) 1.94 (0.65) 94.0 (50.2) suggesting that the efficacy of the BCf 15.0 (4.4) 154.4 (39.5) 1.76 (0.65) 111.5 (50.2) Ontario strain was restricted to the Rlse 17.0 (4.4) 148.1 (39.5) 2.83 (0.65) 220.0 (50.2) season of application. Brsh 19.6 (4.4) 178.3 (39.5) 2.01 (0.65) 94.4 (50.2) notrt 16.4 (4.4) 154.2 (39.5) 2.39 (0.65) 156.6 (50.2) Summary Measurements in the third year to treatment. The mean number of and Mycologic Inc. Numerous persons following treatment showed that both vegetatively produced shoots per treat- were involved in the conception and B and Release® significantly ment (root suckers vs. stump sprouts) design of the project and in the collec- increased mortality of the treated stems. appeared to be dependent upon the tion of data. They included: Ron Wall However, despite the responses shown kind of treatment applied. and Raj Prasad, Pacific Forestry Centre, by these stems, these treatments did Victoria; Doug Pitt, Canadian Forest not significantly reduce aspen density Acknowledgements Service, Great Lakes Forest Centre, because of subsequent stem recruit- Sault Ste. Marie; Will Hintz, Brad ment through suckering and stump The data for this extension note were Temple, Louise Hahn, Holly Williams, sprouting. Stem height, stem diameter, derived from a cooperative effort of the Katherine Oliver, and Jim Meldrum, stem basal area, and stem volume did B.C.