Table 1.— Description of iierbicide treatments tested for effects on ectonnycorrhizal 

 development of conifer seedlings at major forest nurseries in the Central 

 and Northern Rocky Mountains 



Herbicide 



Formulation 

 (trade name) 



Rate of active ingredient 



Timing 



Bifenox 



DCPA 



Modown 80% WP^ 



Dacthal. 75% WP 



Napropamide Devrinol, 50% WP 



Lb/acre (kg/ha) 

 3 and 6 (3.4 and 6.7) 

 3 and 6 (3.4 and 6.7) 

 3 + 3 (3.4 + 3.4) 



10.5 and 21 (11.8 and 23.5) 

 10.5 and 21 (11.8 and 23.5) 

 10.5 + 10.5 (11.8 + 11.8) 



3 and 6 (3.4 and 6.7) 

 3 and 6 (3.4 and 6.7) 

 3 + 3 (3.4 + 3.4) 



Postseeding 

 Postgermination 

 Postseeding plus 



postgermination 

 Postseeding 

 Postgermination 

 Postseeding plus 



postgermination 

 Postseeding 

 Postgermination 

 Postseeding plus 



postgermination 



Control 



No treatment 



^WP is wettable powder formulation; total active ingredient is based on the manufacturer s 

 recommendation. 



Field Procedures 



Each plot was bed-wide 4 ft by 3 ft (1.2 m by 0.9 m) 

 along the bed. Each herbicide was applied at two rates 

 (IX, at recommended rate and 2X, at twice the recom- 

 mended rate), and at two times (postseeding, postgermi- 

 nation of tree seed). In addition, we tested the multiple 

 appUcations of a IX postseeding spray followed by a IX 

 postgermination spray. Herbicides were applied with a 

 pressurized sprayer in a water carrier at a volume 

 equivalent to 85 gal/acre (100 mL/plot). Postsowing 

 treatments were applied within 2 days after sowing; 

 postgermination sprays were apphed 28 to 35 days after 

 seedling emergence. Emergence is defined as the time 

 when most seedlings had shed their seed coats. Five 

 herbicide treatments plus a control were represented for 

 each herbicide. A total of 155 treatment combinations 

 (465 plots) were evaluated for ectomycorrhizal develop- 

 ment. Other details on the herbicide treatments are 

 available in Ryker (1981). 



Sampling Procedures 



Thirteen to 15 adjacent seedlings representing each 

 plot were hfted in June 1979 (planted April-May 1978, 

 except at Montana where beds were sown in fall 1977). 

 Seedlings were hfted carefully with a digging fork to 

 avoid root loss and damage. In all cases sample seed- 

 hngs were adjacent, located two rows from the edge, and 

 well away from the end of the plot. Use of adjacent seed- 

 lings (seedling groups) minimized damage to the plots, 

 which were also used for phytotoxicity and weed-control 

 evaluations and standardized general sample location to 

 avoid border effects. Within these confines, the exact 

 positioning of the seedhng group was random. Seedling 

 rows were uniform except for occasional missing 

 individuals. All seedlings were placed directly into a 

 plastic bag, with no attempt to separate or clean roots 



on the site. Plastic bags were put on ice or refrigerated 

 at 34 °F (1 °C) for transport to and storage at the 

 laboratory location. All evaluations were completed 

 within 90 days. 



Ectomycorrhizal evaluation procedures.— All ectomycor- 

 rhizal evaluations were done with no foreknowledge of 

 plot treatments by three examiners working at least two 

 at a time. Root systems from each of 10 seedlings ran- 

 domly selected from each plot sample were carefully 

 separated and washed in running water prior to exami- 

 nation. Spot checks on loss of small roots caused by 

 washing indicated such losses were small. Three tj^pes of 

 root evaluations were made for each seedling: (1) The 

 total root system was scanned and percentage of 

 ectomycorrhizal roots was estimated to the nearest 10 

 percent. (2) Excised from each seedling were 10-cm seg- 

 ments of major lateral roots (accumulative if necessary) 

 from the uppermost root system and from the lowermost 

 part of the root system. In each case, the 10-cm seg- 

 ments were cut to include just the first short root 

 nearest the originating major root and to just exclude 

 the last short root. Total number of ectomycorrhizal 

 short roots were counted and recorded separately for the 

 upper and lower 10-cm lengths. (3) Each ectomycorrhizal 

 short root was categorized into an arbitrarj- morphologi- 

 cal type based on external appearance (color, branching 

 habit, etc.). In cases of doubt, thin sections of short 

 roots were examined microscopically to determine if a 

 Hartig net and mantle were present. 



Soil Properties 



Because of the wide variation in the soUs at some of 

 the nurseries, basic properties (soU type, physical 

 makeup, pH, CEC. and organic matter content) were 

 determined for the study site at each nursery (Ryker 

 1981). 



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