2019 YUKON FOREST HEALTH REPORT TABLE OF CONTENTS YUKONHEALTH FOREST REPORT 2017

Published under the authority of the Minister of Energy, Mines and Resources, Why We Have a Forest Health Program in Yukon...... 1 Government of Yukon Yukon Forest Health Monitoring Strategy...... 1 Rotational Monitoring of Forest Health Zones...... 1 All photographs: Government of Yukon Aerial Surveys and Ground Truthing as the Primary Tools for Monitoring...... 2 ISSN 1708 - 9360 Standards for Conducting Aerial Surveys...... 2 Identifying Yukon’s Major Forest Health Concerns...... 3 Printed in Whitehorse, Yukon, March 2020 Summary of 2019 Forest Heath Initiatives...... 6 © Minister of Energy, Mines and Resources, Government of Yukon Annual Forest Health Aerial and Ground Surveys...... 8 Weather and Biotic and Abiotic Disturbances...... 12 FOR FURTHER INFORMATION, PLEASE CONTACT: 2019 Yukon Weather Summary...... 12 Energy, Mines and Resources, Government of Yukon Summary of 2019 Biotic and Abiotic Disturbances...... 17 Forest Management Branch Biotic Disturbances...... 18

Physical Address: Forest Insects...... 18 Mile 918.07 Alaska Highway Aspen Serpentine Leafminer (Phyllocnistis populiella)...... 18 Whitehorse, Yukon Large Aspen Tortrix (Choristoneura conflictana)...... 21

Reception: Spruce Beetle (Dendroctonus rufipennis)...... 25 Phone: 867.456.3999 Western Balsam Bark Beetle (Dryocoetes confusus)...... 28 Toll free in Yukon: 1.800.661.0408 ext. 3999 Willow Blotch Leafminer (Micrurapteryx salicifoliella)...... 29 Fax: 867.667.3138 Forest Diseases...... 31 Email: [email protected] Pine Needle Cast (Lophodermella concolor)...... 31 Mailing Address: Abiotic Disturbances...... 33 Box 2703 (K-918) Flooding and High Water Tables...... 33 Whitehorse, Yukon Y1A 2C6 Other Abiotics...... 33 Pest Complexes...... 33 www.yukon.ca/forestry Aspen Decline...... 33 Porcupine and Bark Beetles...... 40 Proactive Management of Mountain Pine Beetle...... 41 Monitoring Mountain Pine Beetle in 2019...... 42 Border Zone...... 43 British Columbia Observations...... 43 Using Bait Traps...... 46 Special Projects...... 47 Assessment of Spruce Beetle Risk in the Kusawa Lake Area...... 47 Spruce Beetle Pheromone Trapping...... 50 Forest Health Extension...... 53 Other Noteworthy Disturbances in 2019...... 53 References...... 59 WHY WE HAVE A AERIAL SURVEYS AND FOREST HEALTH PROGRAM GROUND TRUTHING AS THE IN YUKON PRIMARY TOOLS FOR MONITORING

The Government of Yukon’s Forest Management Branch (FMB) manages Yukon forests for sustainability and Aerial overview surveys and ground field checks are a relatively simple and low-cost method for effectively monitors and reports on forest health, a major component of forest management. The Forest Resources Act monitoring forest health over large areas (Ciesla, 2000; Mitton J.B. and M.C. Grant, 1980). Aerial overview (FRA) supports forest health monitoring and recognizes that the long-term health of Yukon’s forests must be surveys are also adequate for regional and provincial summaries and to meet national requirements for the maintained and protected for the benefit of Yukon people and future generations. Forest Health Network (BC Ministry of Forests, Lands and Mines and Canadian Forest Service, 2000). Under section 34-2 of the FRA, the Forest Management Branch director may develop research, monitoring As a result, aerial overview surveys are the primary tool for monitoring forest health in Yukon. The forest plans and programs to: health aerial overview survey standards used by the BC Ministry of Forests, Lands and Natural Resource a) investigate the spread, effect and control of insects and pests as it relates to the protection of forest Operations are also used in Yukon, which ensures continuity across jurisdictions. Field checks are important resources; and, for validating the data collected from the aerial surveys. Researchers check a portion of surveyed areas to confirm the identity and severity of the pest or disease disturbance. b) support the advances in forest resource management. This includes monitoring plans such the risk-based Yukon Forest Health Monitoring Strategy adopted by Standards for Conducting Aerial Surveys FMB in 2009 The following standards are used to conduct aerial surveys in Yukon:

Yukon Forest Health Monitoring Strategy • Use a Cessna 206 or equivalent high wing single engine airplane. The Yukon Forest Health Monitoring Strategy focuses on Yukon’s forest stands that are most susceptible to • Flying height of 800 m above ground level. the 10 forest health agents of greatest concern. Since its implementation in 2009, the strategy has met the • Aerial surveyors use 1:100,000 scale maps. three priorities described below each year. • Two qualified aerial surveyors (one positioned on each side of plane). The objectives of the Yukon Forest Health Monitoring Strategy are: • Each surveyor oversees a 4 km wide corridor (8 km gridlines) – in 2014 FMB modified this to a 6 km wide 1. To provide a Yukon-wide overview of forest health issues; (12 km gridlines) corridor given that baseline data has been captured for each forest health zone. 2. To focus monitoring activities on high-risk forest health concerns across forested landscapes that are • In 2017, given the size of FHZ 4, the gridlines were increased to 14 km, or 7 km for each surveyor. considered most valuable to Yukon residents; and • Fly aerial surveys on clear days with sunny skies. 3. To monitor and assess forest health concerns and to determine and evaluate forest management responses. • Aerial surveyors map and record the severity and type of disturbance, such as: The FRA regulations (sections 81 and 82) commit the director to provide a written report on the status of • Dead and dying trees caused by bark beetles. forest health in Yukon (the annual Forest Health Report) to the Minister of Energy, Mines and Resources • Defoliation from insects and diseases such as budworm, leafminers or needle diseases. (EMR). • Stressed or dead trees from climatic factors such as flood, drought or wind-throw. Rotational Monitoring of Forest Health Zones • Trees damaged by animals such as porcupines.

Yukon is divided into five forest health zones (FHZ) (Map 1). In these areas, monitoring focuses on forest Aerial surveyors also use on-the-ground checks to confirm the type of disturbance recorded from the aerial stands that are the most susceptible to the ten forest health agents of greatest concern. Each year since surveys and digitize recorded mapping data to store in the Government of Yukon Geographic Information 2009, researchers have completed aerial surveys of one of the five zones, with FHZ 5 combined with another System. FHZ given its small size. This year marks the third year that FHZ 2 has been resurveyed. Given that baseline data has already been captured in each of the forest health zones, the mapping resolution from 2014 forward will be based on previous pest levels, FHZ size, and visibility. In 2019, a combination of grid and drainage flying was conducted, using a 14km grid. Forest health reports are produced annually by FMB. These reports summarize the results of forest health monitoring and related-activities and draw on historical data to access population trends. This historical data lies in both the FMB reports and Forest Insect and Disease Survey (FIDS) reports. In 2018 an additional source of historical FIDS spatial data was made available and will be used for interpretation of population trends going forward. This FIDS data generally represents point-source sampling for specific pests or that of permanent sample plots using a three-tree beating method to identify and quantify forest defoliators. This information will not only assist with assessing population trends but also help identify climate-induced 1 changes to pest distribution. 2 IDENTIFYING YUKON’S MAJOR FOREST HEALTH CONCERNS

4a In 2009, FMB determined the top 10 concerns that pose the greatest 4. Budworms (Choristoneura spp.) risk (i.e. extensive mortality or defoliation) to Yukon forests – ones The budworm guild, comprising of eastern spruce budworm, fir-spruce that can be effectively monitored as part of a risk-based forest health budworm, two-year cycle budworm and western black-headed budworm, monitoring program. Eight are insects, one is a pathogen, and the last cause similar defoliation damage to spruce, subalpine fir and larch (Larix is an environmental effect called drought stress. laricina) forests in Yukon. In 2008, eastern spruce budworm damage All these concerns can effectively be monitored with aerial surveys was mapped across 1,000 ha in Yukon, primarily near Stewart Crossing. 1a because their damage to trees is very visible. Historically, eastern spruce budworm damage has been mapped in the 4b extreme southeast portion of Yukon (Garbutt, 2013). The following is a rationale (based on Ott, 2008) for the identification of major forest health concerns that pose the greatest risks to Yukon 4a Defoliation to tips of mature spruce trees, Spruce budworm, forests: Stewart Crossing, Yukon. 4b Spruce budworm larva.

1. Spruce bark beetle (Dendroctonus rufipennis) This bark beetle is the most damaging forest pest of mature spruce (Picea 5. Larch sawfly (Pristiphora erichsonii) 1b spp.) forests in Yukon. A spruce bark beetle outbreak in southwest Yukon This defoliator is the most damaging agent of larch in North America. 5 that began around 1990 has killed more than half of the mature spruce In the mid and late 1990s, mature larch stands in southeast Yukon were forest (primarily white spruce [P. glauca]) over approximately 400,000 heavily defoliated and experienced some mortality. hectares (ha). 5 Larch sawfly larva. 1a Grey trees stand level damage, Spruce bark beetle Haines Junction, Yukon. 6. Large aspen tortrix (Choristoneura conflictana) 1b Adult spruce bark beetle. 2a This defoliator of trembling aspen (Populus tremuloides) periodically 6a erupts into outbreaks that result in severe defoliation, branch dieback 2. Northern spruce engraver (Ips perturbatus) and, at times, extensive tree mortality. Outbreaks of large aspen tortrix The northern spruce engraver acts as both a secondary bark beetle that have occurred in several places throughout Yukon, including Teslin Lake, attacks trees infested with spruce bark beetle, as well as a primary pest Braeburn, Haines Junction, Pelly Crossing and Champagne. that attacks and kills stressed spruce trees (primarily white spruce). The 6a Stand Level defoliation, Large aspen tortrix, Haines Junction, Yukon. population of the northern spruce engraver beetle has increased in 6b Adult moth, Large aspen tortrix. Yukon as a result of the increased availability of host trees associated with 2b the spruce bark beetle outbreak in southwest Yukon. In 2008, infestations 6b by the northern spruce engraver were at their greatest level since the 7. Aspen serpentine leafminer (Phyllocnistis populiella) beginning of forest health recording in Yukon. Spruce engraver beetle infestation was mapped in southwest Yukon at over 3,000 ha (Garbutt, This insect pest occurs throughout the Yukon range of trembling aspen 2013). and also defoliates balsam poplar (Populus balsamifera). Starting in the early 1990s, a massive outbreak of aspen serpentine leafminer extended 2a Single tree attack, Northern spruce engraver. from Alaska through Yukon, and into British Columbia. 2b Young adults and larva, Northern spruce engraver. 7a Stand level damage, Aspen serpentine leafminer, Dawson City, Yukon. 3a 7b Leaf mining, Aspen serpentine leafminer. 7a 3. Western balsam bark beetle (Dryocoetes confusus) This beetle attacks subalpine fir (Abies lasiocarpa). Western balsam bark beetle moved north from BC. in the late 1980s and has become an active disturbance agent in mature subalpine fir stands in southern Yukon. 3a Single tree attack, Western balsam bark beetle, Watson Lake, Yukon. 3b Adults, Western balsam bark beetle. 3 3b 7b 4 8. Pine needle cast (Lophodermella concolor) SUMMARY OF 2019 This pathogen is the most common cause of premature needle loss of lodgepole pine (Pinus contorta) in Yukon (Garbutt, 2009). Pine stands in southeast Yukon are chronically infected and the disease is becoming FOREST HEALTH INITIATIVES increasingly common in central Yukon. In 2008, pine needle cast occurred The following four initiatives were completed by FMB in 2019: from the British Columbia border to the Continental Divide, Yukon. The 8a most northern observation of needle cast was observed in young pine stands in the Minto Flats-McCabe Creek area in the Yukon interior (Ott, COMPONENT 1: Annual Forest Health Aerial and Ground Surveys 2008). The most severe damage in these pine stands covered 477 ha In 2019, aerial surveys were undertaken in central Yukon, Forest Health Zone 2 (FHZ 2), in order to map (Garbutt, 2014). Yukon forest disturbances as described in the Yukon Forest Health Monitoring Strategy (Map 1). The survey 8a Stand level damage, from Pine needle cast, Minto, Yukon. took five days to complete. Weather conditions in 2019 were rather unsettled with rain, mist and low clouds as well as smoke, all of which made for less than optimum lighting conditions. 8b Damage to needles of young pine, Pine needle cast.

COMPONENT 2: Proactive Management of Mountain Pine Beetle 8b 9. Mountain pine beetle (Dendroctonus ponderosae) FMB continues to take a proactive approach to monitoring the northward expansion of the mountain Though endemic to North America, this bark beetle is not present in Yukon. pine beetle (MPB). A half-day aerial survey was undertaken to monitor the northward movement of the Most western pines in North America are suitable hosts, but lodgepole MPB along the Yukon/B.C. border near Watson Lake, as per the monitoring strategy. pine and ponderosa pine (P. ponderosa) are the most important host species (Logan and Powell, 2001). In western Canada, lodgepole pine is The Five Year Mountain Pine Beetle Monitoring Strategy, implemented in 2013, describes and outlines the primary host of this beetle (Campbell et al., 2007; Li et al., 2005). monitoring activities for the next five years in the Yukon. This plan has provided effective and efficient management for tracking the northern expansion of the MPB population. Since 2014 surveys have been Mountain pine beetle (MPB) is currently the most important forest health undertaken along the BC border using a 30 km east-west grid. The grid was adaptive in that it was based 9a concern in western Canada. The current outbreak in BC is responsible for killing over 13 million ha of pine forests (Carroll, 2007). Cold-induced on the MPB risk in BC; initially the grid was 300 km*30 km (5 km north of border in Yukon, and 25 km south mortality is considered the most important factor controlling MPB of border in BC), but was reduced to 300*25 km over the last few years given the decreasing populations dynamics (Régnière and Bentz 2007). A warming climate is expected in BC. to allow MPB to expand its range into higher elevations, eastward, and This will be the last year that FMB monitors the border zone given the diminishing MPB risk in northern northward (Carroll et al., 2003; Régnière and Bentz 2007), potentially as far British Columbia, extensive wildfires in the border zone, and 10 years of monitoring with no MPB detected. north as Yukon. Monitoring for MPB is a high priority because of its severe This decision will be revisited if and when MPB poses a risk to Yukon pine forests as determined by annual impact on pine forests during outbreaks and because of its confirmed surveys conducted by the British Columbia Ministry of Forests, Lands, Natural Resource Operations and proximity (80 km) to the Yukon border in 2011. 9b Rural Development. 9a Mature pine tree attack, Mountain pine beetle, Rocky Mountain Trench, British Columbia. COMPONENT 3: Special Projects: Enhancing Knowledge Base to Inform Risk Management 9b Surviving larva at base of tree, Mountain pine beetle, Rocky FMB undertakes special projects to gain a better understanding of hazard, risk and host-pest interactions Mountain Trench, British Columbia in Yukon Forests to help minimize the risk where possible. These surveys are often triggered by an abiotic event, such as extensive flooding, drought, wind events; or widespread presence of a biotic agent (pest or 10. Tree dieback due to drought stress disease). 10 Trembling aspen tends to occupy the driest sites in Yukon. Because of this, Two special projects were undertaken in 2019; one a continuation of a 2018 project. dry site aspen stands are expected to be the first to exhibit dieback due 1. In 2018 and 2019, spruce beetle pheromone trapping was undertaken in the Haines Junction area to 1) to drought stress in a warming climate. In 2008, aspen stands exhibiting monitor populations of spruce beetle in Haines Junction Timber Harvest Planning areas, 2) understand dieback were scattered along the North Klondike Highway between the timing of the spruce beetle flight period in the Haines Junction area; and 3) and to determine the Whitehorse and Stewart Crossing. Most of these stands were on dry, rocky spatial distribution of the spruce beetle populations in Haines Junction area slopes and bluffs with south and west aspects, although some were located on level ground with well-drained gravel soil. Aspen stands experiencing 2. Helicopter reconnaissance and ground surveys of spruce beetle populations in the Kusawa Lake area dieback tended to be in an open canopy and were often stunted. Those and eastward towards Carcross. on the rocky slopes and bluffs typically were adjacent to treeless steppe plant communities which are found on sites too dry for trees to grow COMPONENT 4: Extension – Community Engagement (Ott, 2008). FMB prepares and delivers presentations regarding forest health, either for special projects - e.g. mountain 10 Tree dieback of aspen due to drought stress, Mayo, Yukon. pine beetle, or general information. These are conducted upon request or as required to communicate FMB programs. For further information on these and other Yukon forest health disturbances please FMB also responds to general forest health and pest incident reports from the public and from government refer to the EMR forest health website at http://www.yukon.ca/forestry agencies throughout Yukon. These reports are often incidental in nature. Pest incident reporting is covered 5 This website contains forest health brochures and annual reports prepared by EMR. under the section titled Other Noteworthy Disturbances in 2019, contained in this forest health report. 6 ANNUAL FOREST HEALTH B E A U F O R T ( A R S E A C T I C O H C E A N ) AERIAL AND GROUND SURVEYS A M A C K E N Z I E In 2019 forest health surveys were directed at biotic and abiotic disturbances in FHZ 2. A five day aerial survey B A Y of the forested area within FHZ 2 was undertaken using an extended Cessna 206 fixed-wing aircraft (Photo 1). Nunavut The area was flown in an east-west grid pattern with 14 kilometres between grids, allowing each surveyor to map seven km on either side of the plane. In 2019 two additional FMB staff accompanied the primary aerial Primary Highway observer for one or two days each for the purposes of mentoring (Photo 2). Secondary Highway FHZ 2 includes a section of the Porcupine River drainage basin. This is a large area bounded on the south Old Crow Map Grid (1:100,000/map) P! (approximately) by latitude 61° 00’ North, extending northward to latitude 64° 10’ North. To the north it runs Zone 5 Forest Monitoring Zones along the Hess River, south towards the Glenlyon Range and then to Mount Black. To the west it is bordered Zone 1 - Surveyed 2009, 2014, 2018 by Kluane National Park and to the NE from Kluane to Ogilvie Mountains. It falls mostly into the northern boreal cordillera ecozone but also includes western boreal cordillera, Mackenzie-Selwyn Mountains, and a A L A S K A Zone 2 - Surveyed 2011/12, 2016, 2019 very small portion in the Wrangell Mountains in Kluane National Park (Map 2, Photo 3-7). (U.S.A.) Eagle Plains Zone 3 - Flown 2009, 2015, Scheduled for 2020 P! G r e a t B e a r L k . Zone 4 - Flown 2010, 2017

Zone 5 - Flown 2013, 2018

Mountain Pine (MPB) Border Zone Aerial Survey 2009 - 2019

Spruce Bark Beetle Monitoring Aerial Survey 2018, 2019 Ongoing

Zone 3

P! Dawson City P! Keno City

P! Mayo P! Stewart Northwest Crossing Territories Beaver P! Creek Pelly P! Zone 2 Crossing PHOTO 1 Two-person aerial survey crew and extended Cessna 206.

Faro P! Carmacks P! P! Ross River

Burwash P! P! Destruction Bay Landing Zone 4 Zone 1 P! Haines Junction P!Whitehorse

Carcross P! Teslin Watson Lake P! P!

a MPB Survey Are P A C I F I C O C E A N British Columbia 1:5,250,000 North American Datum 1983 Yukon Albers 0 50 100 200

Km

7 MAP 1 Yukon Forest Health Aerial Surveys by year (2009 – 2019) and planned surveys for 2020. PHOTO 2 Aerial survey trainee, primary aerial surveyor, and pilot. 8 PHOTO 3 White River drainage NW of Haines Junction with predominantly spruce forests.

PHOTO 5 Predominantly white spruce PHOTO 6 Spruce, lodgepole pine, and trembling stands with pockets of trembling aspen near aspen mixed forests near Ragged Lake, SE of Coghlan Lake, north of Whitehorse. Pelly Crossing.

PHOTO 7 Treeless hillside in the Russell 9 PHOTO 4 Stewart River east of Mayo with mixed forest types including spruce and trembling aspen. Range east of Mayo. 10 S N I A T

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WEATHER STATIONS 1 WEATHER STATIONS 1 ˚ CELSIUS

WEATHER STATIONS 1 WEATHER STATIONS 1

FIGURE 4 May 2019 temperature and precipitation anomalies (top) and April – August 2019 temperature and precipitation anomalies (bottom). Source: Climate.weather.gc.ca and Yukon Wildland Fire Management.

1 OC = Old Crow CA = Carmacks HJ = Haines Junction TE = Teslin DA = Dawson FA = Faro XY = Whitehorse WL = Watson Lake MA = Mayo BU = Burwash ATL = Atlin

FIGURE 3 April 1 snow water equivalent. 15 Source: Yukon Water Resources April Snow Survey and Water Supply Bulletin. 16 SUMMARY OF 2019 BIOTIC AND ABIOTIC DISTURBANCES

Given that FHZ 2 was surveyed in 2011/2012 and in 2016 it is possible to assess trends over time by comparing pest activity in these years (Table 1). In addition, special surveys were conducted in FHZ BIOTIC DISTURBANCES 1 to follow-up on the spruce beetle infestation mapped in 2018 in the Kusawa drainage area; all forest health factors were mapped during this survey and are included in Table 1. FOREST INSECTS

TABLE 1 Summary of forest health disturbances in a portion of FHZ 1, and FHZ 2 in 2011/2012, 2016, and 2019. Note some stands had a combination of pests – the most dominant pest is noted first. Aspen Serpentine Leafminer (Phyllocnistis populiella)

FHZ 1 FHZ 2 The aspen serpentine leafminer is a defoliator of with elevated risk of ongoing mortality (Cahoon trembling aspen (Populus tremuloides) and is et al. 2018). Based on their findings they speculate

DISTURBANCE TYPE 2019 (ha) 2011/12 (ha) 2016 (ha) 2019 (ha) common throughout the host range in Yukon. that aspen may be eliminated on the warmest Biotic The leafminer’s activities were first recorded in the and driest sites. This is due to a combination of early 1950s along the Alaska Highway. At endemic a warmer and drier climate which increases the Aspen serpentine leaf miner - 181,900 32,884 96,132 levels, single leaf infestation is common but vulnerability to defoliators or initiates/exacerbates Large aspen tortrix 342 730 6,106 726 whole tree infestation occurs during outbreaks. the severity of an aspen serpentine leaf miner Current outbreaks in Alaska and Yukon have outbreak. While the role of aspen serpentine leaf Birch leaf roller - 468 847 - impacted hundreds of thousands of hectares of miner in the aspen decline complex has not been mature and immature aspen. Ten to 20 years of studied in the Yukon it is speculated that this Spruce beetle 709 (old) 48 - 54 unprecedentedly severe leafminer defoliation has biotic factor is indeed a contributing factor (see Western balsam bark beetle 34 6 27 10 occurred in stands of aspen along the Silver Trail aspen decline section). between Mayo and Stewart Crossing. The tell-tale Willow blotch miner 28 168 526 5,823 signs of silvery foliage and reduced growth can be In Yukon this leafminer has been present every Northern spruce engraver beetle - - 36 - seen along most of the highways in Yukon. year for the last two decades with variation in annual levels, severity and extent. In 2019 FHZ Pine needle cast - 7,116 85 629 Aspen serpentine leaf miners affect photosynthesis 2 had a slight increase from 2016 and 2011/2012. by mining the leaf tissue and impairing the Infested areas accumulated to 186,215 ha in 2019, Abiotic functioning of the stomata on the bottom of the 178,603 ha in 2016 and 181,900 ha in 2011/2012. Aspen decline - 906 513 4,769 leaves (Wagner et al. 2008; Doak and Wagner 2015). This can lead to premature leaf loss, up to 4 Silvery leaves characteristic of this defoliator (Photo Flooding - 213 48 132 weeks earlier on severely mined foliage (Wagner 8) were noted throughout the host range in FHZ 2, and in combination with aspen decline (Photo 9 Drought - spruce - - 35 - et al. 2018), reduced growth, and tree mortality (Wagner and Doak 2013; Doak and Wagner 2016). and Photo 10) in 48% of the stands (Map 3). Drought - aspen - 20 - - Tree ring analysis of several tree species in Alaska Landslide - 234 - 5 found that if the warming trend of the last several Windthrow - - - 5 decades persist aspen productivity will remain low Pest Complexes Aspen serpentine leaf miner/aspen decline - - 145,719 90,083 Large aspen tortrix/aspen decline - - 12,648 - Pine needle cast/abiotic - - - 767 Porcupine/lodgepole pine beetle 0.5 26 15 3

17 18 PHOTO 8 Moderate aspen serpentine leaf miner west of Wellesley Lake. PHOTO 10 Severe aspen serpentine leaf miner with light aspen decline along Donjek River.

19 PHOTO 9 Moderate aspen serpentine leaf miner with light aspen decline northeast of Wellesley Lake. PHOTO 11 A vibrant and healthy aspen stand; an uncommon sighting. 20 e l i n

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Large Aspen Tortrix (Choristoneura conflictana)

Native to North America, the large aspen tortrix is they fail to flush. At the third instar stage of larval found throughout the trembling aspen’s range. development, they roll the leaves and continue Before 1990 and the onset of the spruce bark beetle until they complete larval development. Pupation infestation in the southwest Yukon, it was the single occurs normally at the leaf edge in late June. Adults most common cause of insect-based disturbance emerge after about ten days and mate. Then, in Yukon forests. In FHZ 1 the last outbreak was females lay eggs in small masses on the upper prior to 1990, and occurred in forest stands north surfaces of leaves. Eggs hatch in early August. After of the village of Haines Junction. In FHZ 2 and FHZ hatching, early instar larvae feed on leaf surfaces 3 the last recorded outbreak occurred from 1975 until late August. Then at the second instar stage, to 1981, in aspen stands between McQuesten and they hide in the bark crevices. Here they spin webs Dawson City. (hibernacula) for overwinter shelter and enter a hibernation stage known as diapause. At this The most recent outbreaks began in FHZ 1 in 2012, and in FHZ 2 and FHZ 3 in 2015. In This insect completes its life cycle in a single stage, the water in their cells is replaced with glycol FHZ 4 sporadic defoliation has been noted between Francis Lake to Ross River, and year. During that time, larvae pass through five (antifreeze) which allows them to withstand winter Little Salmon Lake, but there has not been any recorded landscape-level events. developmental stages, known as instars, before temperatures as cold as -27°C. While it appeared that populations had collapsed in FHZ 1 in 2017, 1,060 hectares of reaching maturity. At the end of each instar, larvae defoliation was recorded in 2018 in the Whitehorse-Haines Junction corridor. In 2019 shed their skins and re-emerge as the next larger The life history of this insect places it in direct no defoliation was noted in this corridor, however 726 hectares of trembling aspen stage. Small second instar larvae emerge from the competition with the aspen serpentine leafminer, forests were infested near Annie and Alligator Lakes (Photo 12). Defoliation was also tents they have spun for winter quarters in late May such that in years when aspen serpentine leafminer noted south of Minto near Big Creek, Rosebud and Scroggie Creek west of Pelly or early June. They then feed on the emerging buds populations are low, large aspen tortrix feeding is Crossing, and McQuesten River and Lake Creek (Map 4) between McQuesten and and leaves of the aspen trees. In some instances, more significant. Stewart Crossing (Map 5). Dieback associated with successive years of defoliation 21 initial feeding damages the buds to the extent that persists in previously defoliated stands. 22 Y U C k r K C Legar e k e

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e n 0 10 Large Aspen Tortrix u e s t M c Q Light Kilometres Moderate McQuesten K ree k Severe lo C nd o o se ike M T il ra R T er A ilv S W Reid E Lakes T P S ir La a k e te E the Stewart Crossing l L C C r r e Ros ebu e e d e k k

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23 PHOTO 13 Light large aspen tortrix defoliation near Rosebud Creek. MAP 5 Large aspen tortrix defoliation southwest of McQuesten. 24 Spruce Beetle (Dendroctonus rufipennis)

The spruce beetle is a natural disturbance agent In 2018 spruce beetle was recorded over 1,196 Normally between 12 to 18 months following attack the foliage of dying trees will turn yellow-orange/red. throughout the geographical range of spruce hectares in FHZ 1, the majority of which was found Discolouration may vary between branches on the same tree over time. Needles usually drop from the (Picea spp.) in North America. At endemic levels, near the south end of Kusawa Lake and eastern tree 14 to 20 months following attack. The exposed twigs of the upper crowns have a yellowish-orange/red spruce beetle normally infest downed trees, drainages including Two Horse Creek, West Arm hue and later, turn to grey. In Yukon depending upon the site and climatic factors, discolored foliage can logging debris, decked timber, dying or stressed of Teslin Lake, and Primrose and Rose Lakes. At be retained for a few years, although duller in colour than the initial colour fade (Table 2). This phenomena trees and only occasionally cause tree mortality. the end of the last outbreak populations were makes it more difficult to assess outbreak stage based on the ratio of reds to greys. It is possible that some During periods of outbreak, beetles will attack persisting, albeit at very low levels, in the Devilhole of the red trees are two-year old attack with adult beetles overwintering in the root collar. Duller red trees and kill live trees causing widespread mortality. In Creek/Kusawa Lake area. At that time ground are three-year old attack with no beetle present. Yukon, spruce beetle is the most damaging agent assessments found very low survival and fecundity of mature spruce forests. The earliest recorded rates. In 2012, the last year this area was mapped, outbreak occurred in the late 1930s and early populations were very low with only light polygons TABLE 2 Life stages and associated tree discoloration in a spruce beetle two-year life cycle. 1940s around Dezadeash Lake when 50,000 ha (<10% infested) mapped. This marked a significant were infested with the beetle. It is thought that reduction in severity from the outbreak years and LIFE STAGE TREE COLOUR logging during the building of the Haines Road thus signaled the decline of the local populations. Spring 2017 Attacking adult/lays eggs Green foliage contributed to this outbreak. In the mid-1970s a Based upon the proximity of the last known smaller (100 ha) outbreak occurred during the infestation and the current levels it is possible Fall 2017 Overwinter as larvae Green foliage construction of the Aishihik Power Project. Both of that spruce beetle found an endemic niche, Summer/Fall 2018 Develop to adult and Yellowing foliage can also appear-orange- these outbreaks were likely caused or exacerbated with populations persisting in stressed trees and overwinter in root collar Trees showing this color are referred to as “Faders” by human activities as trees were felled and left expanding into the homogeneous spruce forests Spring 2019 Emerging Adult Red foliage-before needle drop during construction, providing ideal breeding at the south end of Kusawa Lake, Takhini River and Foliage may appear bright red habitat for beetle populations. Primrose Lake. Summer 2020 No longer contains Dull red foliage, (as trees begin needle drop), to grey The most recent spruce beetle outbreak started The life cycle of the spruce beetle typically takes Spruce beetle. (all needles completely off tree) in Kluane National Park and Reserve around 1990. one to three years depending on site position, The outbreak was first observed in 1994 by which temperature and elevation. In the two- year cycle, time the beetle had already caused over 32,000 early instar larvae overwinter and mature the In 2019, 709 hectares of old spruce beetle attack was mapped in the same area that was mapped in 2018 ha of mortality. The beetle then moved into public following summer. In the late summer or early near Kusawa Lake (Map 6). No recently attacked trees were recorded. The ratio of reds to greys at the south and First Nations forest lands north and south fall two years after the initial attack, brood adults end of the lake indicates declining spruce beetle populations; however, there is much greater variation of Haines Junction in the Shakwak Trench. Over may emerge from the bole and crawl to the base on the east side of the lake making the ratio of reds to greys more difficult to interpret. As mentioned the next 15 years, the beetle continued to kill vast where they enter at the root collar to hibernate. above, some of the ‘brighter’ red trees may have overwintering adults at the base which will emerge tracts of spruce within and west of Kluane National During one-year cycling, larvae grow throughout and attack new trees in the spring of 2020. Ground assessments in 2019 were limited to one site which Park. During the outbreak more than half of the the summer months, pupate in late summer (July/ indicated poor recruitment and survival, and no overwintering adults. As a cautionary measure FMB will mature spruce had been killed over approximately August) and overwinter as adults. Regardless of the continue to monitor this area annually, weather permitting, as part of a proactive approach to forest health 400,000 hectares. length of the life cycle, a beetle must overwinter as management (see Special Projects section for more information). an adult before it can reproduce. One of the main differences between the recent In FHZ 2, four spot infestations and 2 polygons totaling 54 hectares were mapped east of Mayo Lake (Map 7). and historic outbreaks was the mode of initiation. In the past, outbreaks were associated with certain stand-level, abiotic disturbances such as windthrow, fire or right-of-way clearing. The recent outbreak is unique in that climate moderation was the initiation factor. These climatic conditions also favoured increased beetle fecundity. Over the same period, warmer winters resulted in reduced brood mortality.

25 26 M

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C k i a C t n the host range in Yukon. Over the past two affected areas have been high elevation stands BE r a n C e a v h te e AV N a es k h r S u it L e g Q C ER R Sou th Mc a E

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l K l c e G Keno City decades, light to moderate infestations have been with concentrated subalpine fir components. k e k A M n a C Cre o Fla t l e Ligh tning R n R o a t ss ar C C w k k e St k Elsa Cr observed in the southern part of the territory. The In the mid-1990s, hundreds of hectares of light e ee e n

r k R a o C c s C n s ork k u k e e D C ry Cre W e illia C n ms a C beetle works in concert with a symbiotic fungal (<10%), current-year mortality were mapped

k k d l ra nite Cree k R oo a P G p H arent Cree k k ee Tiny Island u Cr a La e Ck C r ke t ld e e la pathogen to overcome tree defense mechanisms. in the LaBiche River area in southeast Yukon. k ie e R P Halfw ay F k n oop g o L Lakes n C t akes o s p y g e n K k i g Ck P n e E s i At endemic levels, the beetles prefer trees Years of successive attacks have removed a large k e d n r r w a o C L F r a e rd v s n g i d e R k r in u r r C a M weakened by age or climatic stress (e.g., drought, proportion of the subalpine fir overstory. In 2007, B a n o to Penap e R n o k m D C d Lake MA YO E C a l ree k v i w k d C R s O M wind damage or snow-damage), but during an extensive area of light, current-year mortality M E u into o on rr C n s ay k Cre r V e k e I d Cal n la R gha n C Wareham A C r ee Ck Lake Janet k k E outbreaks healthy trees are susceptible to attack. was mapped in the hills south and west of Teslin LAK E Ck dw ards Lake e Lake g ds d Edw ar e o Five Mile L y Lakes W a k Endemic beetle populations can cause single Lake. Light scattered mortality has also been seen i lliam illiamson Lake so k W C M n e k re e C C d t a T e s c n C a N R a e A J tree mortality; however, outbreak populations can on both sides of Tagish Lake (Windy Arm), south l s o n W E S C r Mayo e e T T k S cause extensive group tree or stand-level mortality of Carcross. Similarly in 2017 significant increases E W

S A o u

T t k R

a h C over successive years of attack. were noted in SE Yukon where previously mapped lb T o t

Nel W so n s a e ts t spot infestations expanded into trace polygon o t n k u ree B k C C re e Fraser Falls R E Over the last 20 years, the western balsam bark Tw o Pl V ea I sa R n infestations. This persistence and expansion of t C R r I V E e R

e k beetle has advanced north from British Columbia Three M ile Rapid Talb S C western balsam bark beetle confirms that climate ot r Lake S ee E k H Francis into southern Yukon. Surveys from the mid-1980s Lake s Five Mile Rapid Fran ci suitability has improved such that this bark beetle

k H VER orseshoe e I R C k Slough e r r to the early 1990s recorded the beetle’s northerly e e C e e M S k r e is now established in Yukon forests. C a ES d H o w h e a spread across the 60th parallel. With the change d o l d Ethel o g N k k e e k e Lake r r C Highland e s o s Lake f r e k a k C in climatic conditions, extensive amounts of In 2019 in FHZ 2, western balsam bark beetle Cre P the l c E O l d o R C

k S S C H E Narrow an o e mature and semi-mature trees, and successive populations declined to 10 hectares from 27 Lake 27 MAP 7 Location of spruce beetle polygons east of Mayo Lake. years of attack, the balsam bark beetle has hectares in 2016. 28 Willow Blotch Leafminer (Micrurapteryx salicifoliella)

This common leaf miner was first recorded in Yukon in 2007 adjacent to the Stewart River at Stewart Crossing. In 2019 willow leaf blotch miner damage increased tenfold from 526 hectares in 2016 to 5,823 hectares. Infested willow were noted throughout most riparian zones in FHZ 2 (Map 8 and Map 9; Photo 15 and Photo 16). Studies in Alaska have found branch dieback and mortality associated with successive years of defoliation such that there are concerns regarding the impacts to vertebrate populations including moose (Wagner and Doak 2018).

s a

C z Diamain Litt l n r le Lake Kalzas a 0 a 10 Willow Blotch e Leaf Miner K l e Lake l

k i M a c m Kilometres Pelly Crossing N e e d l e r o c k

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e

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K k PHOTO 16 Severe willow blotch leaf miner defoliation near Needlerock Creek. u lo T n Ess d L Lake ik Tadru L Ma e yo 0 10 e e k Willow Blotch Leaf Miner e n Jane C r u e s t t Lake M c Q Kilometres Drury Tatchun Lake McQuesten ek L Cre o ose M l T Mayo Li t.tle S al m o i Frenchman wy n L a k e ra Lake H T R K r ll ve A Carmacks Ro e lo il Fraser R b b S o e p R n W F w rt m n d alls li a o Reid ns l m i E o C a L k n S akes e Ck l e T tt L i P S i k r La e a k e t e r N e E C t o he k r Stewart Crossing l k Manda h e e d nn W e a a l s L Cr e

e M Lake C

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K C D z iamain Little l n r Lake Kalzas a a e La K l Fox e ke i l k m L a c Hutshi M Lak e Otter Falls Lakes Lab e rg e Pelly Crossing N e e Moraine d l e Lake r o c Taye k PHOTO 15 Severe willow blotch leaf miner defoliation MAP 8 Willow L leaf blotch miner defoliation between MAP 9 Willow leaf blotch miner defoliation southwest of Stewart Crossing and Pelly Crossing. along the shoreline of Braeburn Lake. Pelly Crossing and southwest of Carmacks.

29 30 C

r N o ed o r ok V th o C ro Crystal a k La l le e ke y C d

R o s e bu d k Willow N k k Lake e C e d o e ok r Cro C g 0o 10 l PC ine Needle Cast/Abiotic Damage t a l ys d r Cr FOREST DISEASES e e k Wi C Ck ll o C k r g w Light e Co ldsp rin e C k r e Si J ek d e a Gr a n d Kilometress li n p e V a C l l re e eModerate y k k e Cre W oo d bu rn G r m e Pine Needle Cast (Lophodermella concolor) a y C C R r C r J e e

Seanvere r e e e k k k e k C e W c k k o o a d l Ck c b a u l rn B H B Summit Woodbu rn

C re e k u k Lake C Lake C n

a Winter Damage k Pine needle cast is a fungal disease of two-needle pines. In Yukon, it occurs throughout the range of the l t l e e h a k al La Ck r W Gran n g d Gra ek r i yling Lakes re p Va C ts lle o y Ck rn H host species, lodgepole pine. The disease is prevalent in the southeast and is increasingly common in k e bu C a Grayling d L r L i e Cre oo t t l B ek W e e l Ka l k a Lakes za s R i v c L e k a va C r re ek W central Yukon. In 2008, severe infections were found in young pine that regenerated following the Minto o L i y o t G d t Hunte r le C k r a b y k u C li a r R a n g e n e r r i C L b k it C t o le Fire. This was the northernmost incidence of the disease yet found in Yukon. Crown dieback, branch kill, w

u K a C lz h D a r s ia s C e m L

e a r ai o g n z k l s i b a defoliation and tree mortality (rarely) occur as a result of infection. Pine needle cast can infect all age B y C K C re L e e a r n k k e H e o e K

t a k l za C I L s C k M L A classes of pine. Outbreaks of pine needle cast tend to be more severe following successive wet summers k C N A R Y M L w P E L o l i l when conditions have been optimal for spore production, dispersal and infection. The disease spores are W R E V transferred during periods of wet weather from the year-old needles to the newly flushed needles at the R I

Pelly Crossing Ne ed le branch tips. Pine needles infected the previous year turn red in early summer as needle necrosis takes ro ck Fort Selkirk Ck

place. These one-year-old needles are then shed later in the year, making it challenging to identify from E L P L e Y

M kirk k igan the air later in the summer. Hence annual infected area figures likely underrepresent the actual area given S el H i i r m k ellsga te Tthe c ta C e Ndu P C re Rapid a k d Lake Von Wilczek n La ke these conditions. Successive years of severe infection results in only the current years needles remaining o Tow hata l C n e k Lake r r i e e e e v Lhútsäw re k l K C o Y Lake W U on the tree. This phenomena is commonly referred to as “lions tailing”. Ck C r K Ck Legar e k e L k e ake

O z ile r m H c a rmile r l g Fou u i o k e F C a N L Ck y W e Ragg s ed n o Lake In FHZ 2 pine needle cast led to foliage discoloration over 1,396 hectares up from 85 hectares in 2016 (Photo V k e a L N e i n e Ta a d tlm m le a i l r n a t M o 17). Abiotic (winter drying) damage was also suspected in 55% of the affected stands due to the retention of Lak T ic c e a k T a Minto t C l k re ek m C r k a a C r pex D in Ck A e older needles. Stands with pine needle cast were found west of the Stewart and Pelly Crossing area (Map e k

M c C ab e C r 10), while those combined with abiotic damage were found SW of Minto and south of Little Salmon Lake Cre ek C e k e k (Map 11). Recorded precipitation at the Mayo weather station in June 2018 was 283% above normal. These

B i g E s s

moist conditions provide ideal conditions for dispersal and spread of pine needle cast spores. Ground L

k a k

C surveys will be conducted in 2020 to confirm the causal factor(s). e MAP 10 Location of pine needle cast and abiotic damage.

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C Frenchman k Ri v Winter Damage e r Highway M ek L S u re ake A L rra C M O y T L E N L A K E L I T h g u o r l iv e S M y R a gu n d 's r e e Co b i v al Mine a R Lake a R ell R pb N o o n o L m r b it tle lm C d a Sa r e e e e k n C s Carmacks r

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d 31 PHOTO 17 Barely discernible pine needle cast south of Stewart Crossing. MAP 11 Location of pine needle cast and abiotic damage. R 32 ABIOTIC DISTURBANCES

Flooding and High Water Tables Other Abiotics

Flooding affects trees by reducing the supply Shallow-rooted tree species, such as spruce, of oxygen to the soils and roots, sediment are more prone to wind throw. In 2019 only five accumulation which can lead to poor soil aeriation, hectares of spruce windthrow was mapped near exposure to toxic compounds that accumulate Caribou Creek, Pelly River area. Also in 2019 a five in waterlogged soils, and in some cases physical hectare landslide was recorded at Owl Creek, near damage to the roots or sudden exposure to the Mayo Lake. elements (Iles and Gleason 2008).

In 2019 in FHZ 2 flooding was recorded at 11 different sites, totaling 132 hectares. This is up from 48 hectares in 2016. The majority occurred in spruce stands but lodgepole pine was also affected in a few areas.

PEST COMPLEXES PHOTO 18 Microclimate effects on trembling aspen with healthy hillside stands versus stands with aspen decline along Mayo River. Aspen Decline

Aspen decline or dieback refers to mortality were found in 2016 in ground assessments of As the climate warms the likelihood of ongoing to 94,852 ha from 158,880 ha in 2016. Symptoms or damage to forests due to multiple causes, symptomatic stands between Dawson City and decline is possible given the potential for increased mapped throughout the host range were often in including a possible combination of biotic and Whitehorse. In the Northwest Territories aspen frequency of drought events, particularly since association with areas with a history of defoliation abiotic factors. Symptoms include thin crowns, decline has been linked to high water tables from trembling aspen has a low tolerance for water (Map 12). Poor lighting due to smoke and haze top dieback, stem mortality, and stem breakage. melting permafrost. Observations from aerial deficit. Warmer springs could also result in early may be partially responsible for this decrease, In Western Canada decline has been observed surveys also suggest microclimate effects, such as spring flush followed by late spring frosts. as decline symptoms are difficult to detect in on a number of tree species including yellow those associated with inversions or cold air pooling less than optimum lighting conditions. Another cedar, birch, aspen, and cottonwood. According to (Photo 18), and clonal resistance (Photo 19); some Changing climate will also lead to changes possibility is that stands with advanced symptoms Canadian Forest Service Forest Insect and Disease clones may be more resistant to defoliators or in biotic factor regimes including changes deteriorate such that they are barely visible (Photo historical records for the Yukon dating back to phenological or genetic characteristics may make to pest distribution, severity, and frequency 20, Photo 21). 1952, aspen dieback was first detected in 1987 near them less vulnerable to abnormal or extreme which could also contribute to aspen decline. Swift River. Since then dieback has been recorded weather events. Ongoing monitoring of these forests, and ideally The area with the most extensive and pronounced intermittently on a variety of tree species, including establishment of permanent sample plots, using damage was near Wellesley Lake, where many cottonwood and trembling aspen. In 2016 158,367 In the United States and Canada widespread protocol developed by Canadian Forest Service of the aspen stands were affected (Photo 22, 23). ha exhibited symptoms of aspen decline in FHZ dieback and mortality of trembling aspen for examination of climate impacts on health and This area is within the Klondike Plateau Ecoregion 2. In 2017 damage was mapped over 4,618 ha in occurred between 2000 and 2010. Research in productivity of aspen (CIPHA), will help determine and is known for its weather extremes. The coldest the highway corridor between Mendenhall and both countries has found that drought was a the factors involved and extent and changes in January and warmest July temperatures are Dezadeash Lake, up from 2,130 in 2016. The vast major predisposing and contributing factor, damage levels. recorded in the lowest topographic settings in the majority of decline in 2016 was in combination with along with multi-year defoliation by forest tent ecoregion with extreme temperatures in the lower Given recent and historical observations of defoliator activity. In 2015 5,621 ha were affected caterpillar, and to a lesser extent stem damage valleys range from –60 to 35°C (Yukon Ecoregions decline and the potential for continuation and in FHZ 3, some of which had visible snow and ice by fungi or insects (Worrall et al. 2013). Frost, Working Group 2004). These temperature possibly expansion of decline, FMB is conducting damage. Decline was also observed aerially in particularly late spring frost, was also found to be fluctuations and potential for cold air pooling, work to gain a better understanding of potential 2009 (2,488 ha), 2010 (11 ha), and 2011 (529 ha). a contributing factor on some sites in Utah. Based given the terrain, are undoubtedly a factor in the on these findings, a retrospective spatial analysis contributing factors. This includes the retrospective extent and severity of aspen decline in this area. Ground assessments of aspen mortality in 2008 was conducted to determine if such was the case spatial analysis of defoliation events and ground between Whitehorse and Stewart Crossing found for Yukon trembling aspen stands. Results of the reconnaissance to identify potential causal agents. that site and stand conditions also played a role. analysis indicated a strong relationship between In 2019 in FHZ 2 the area of aspen decline decreased Open grown and/or sites with poor water retention cumulative defoliation severity and aspen decline had a high incidence of pests, such as poplar symptoms, thereby confirming the findings in borers (Saperda calcarata), which contributed Alberta and United States. 33 to decline of the stands. Similar relationships 34 PHOTO 21 Advanced symptoms of aspen decline with only a few stems remaining; near Britannia Creek.

PHOTO 19 Healthy aspen clone within a stand affected by aspen decline near Janet Lake.

PHOTO 22 Landscape level aspen decline (with aspen serpentine leaf miner) near Wellesley Lake.

35 PHOTO 20 Advanced symptoms of aspen decline with only a few stems remaining; near Aishihik Lake. 36 S N I A T

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e W 37 PHOTO 24 Discontinuous aspen decline symptoms SW of Mayo. MAP 12 Location of aspen decline in relation to areas with defoliator history and severity. 38 A spatial analysis was completed to determine if aspen decline was a function of stand age - e.g. stands Porcupine and Bark Beetles naturally deteriorating as they age rather than biotic and abiotic causal agents. Looking at the age distribution of stands with aspen decline in 2016 and in 2019, this does not seem to be the case, as 74% and Porcupines feed on the nutrient-rich inner bark of all species of coniferous and deciduous trees, but they 56% respectively of the affected stands are <60 years old (Figure 5 and 6). prefer pine. This feeding generally takes place in the winter, when their favoured foods are scarce, but can occur throughout the year. Some of the trees are girdled by the feeding and subsequently die, or are Age Class Distribution of Aspen Stands with predisposed such that secondary bark beetles, such as lodgepole pine beetle (Dendroctonus murrayane) Decline in 2016 or pine engraver beetle (Ips pini) attack and further weaken or kill the trees. FIGURE 5 Age Class Distribution of Aspen Stands with Decline in 2016 In 2014 ground checks were conducted on pockets of lodgepole pine that had a signature similar to stands infected with mountain pine beetle. Several ground checks revealed mortality or damage due 2% AGE SUM OF 5% 2% to porcupine solely (Photo 25), porcupine and lodgepole pine beetle, and in some cases pine engraver CLASS HECTARES 1-20 beetle. Hence similar damage is now deemed affected by this pest complex.

1-20 2,092 21-40 In 2019 only three hectares of this mammal/bark beetle complex was recorded. 19% 21-40 44,611 38% 41-60 41-60 40,285 61-80 61-80 22,651 81-100 81-100 6,145 34% >100 >100 2,772

FIGURE 6 Age Class Distribution of Aspen Stands with Decline in 2019

AGE SUM OF CLASS HECTARES 1-20 208 21-40 16,154 41-60 21,269 61-80 22,117 81-100 5,406 >100 1,700

39 PHOTO 25 Top-kill due to porcupine feeding on main stem of lodgepole pine. 40 PROACTIVE MANAGEMENT OF MONITORING MOUNTAIN PINE BEETLE MOUNTAIN PINE BEETLE IN 2019

Concerned about the northward expansion of the Mountain Pine Beetle (MPB), the Government of Yukon This marks the tenth consecutive year that the threat of MPB invasion of Yukon forests was addressed has developed a risk analysis and subsequent monitoring strategy to track the northern movement of this by aerial surveys in mid-August (Map 1). In 2010 when aerial surveys were initiated, MPB populations and bark beetle. Below is a history of response to MPB: subsequent pine mortality within the Rocky Mountain Trench (RMT) of B.C. were very high (within 150 kilometers of Yukon border). Given the beetle pressure and risk associated with active MPB populations • A National Risk Assessment of the threat of The Mountain Pine Beetle (MPB) is a native in the RMT, aerial surveys were expanded in 2014 to assess the ongoing risk in two areas; a 30 by 300 MPB to Canada’s boreal and eastern pine North American bark beetle that is distributed kilometer border zone straddling the Yukon/B.C. border, as well as the Rocky Mountain Trench in British forests was completed in 2007 by the Canadian throughout most of the range of lodgepole pine in Columbia. The border zone stretches from the Rancheria River in the west to nearly as far east as the Forest Service. British Columbia. Historically climate has impeded Northwest Territories border, and encompasses areas with lodgepole pine as the dominant species. its expansion northward, not host, and until the Since 2010, severe winter cold has killed beetle broods within the trees in the RMT. That, combined with • In 2009, the Forest Management Branch current outbreak was only recorded south of 56°N. declining populations in northern BC, has arrested significant northward movement of MPB populations. (FMB) implemented the Yukon Forest Health The MPB is currently the single biggest forest Hence in 2015, aerial surveys in the RMT were discontinued following two years of insignificant northward Strategy that is in line with the National Forest health concern in western Canada. The current movement of MPB in the RMT. Pest Strategy (NFPS). MPB outbreak is responsible for killing over 13 million ha of pine forest in BC alone. • From 2009 until the present, both FMB and BC’s Ministry of Forests, Lands and Natural The MPB is one of ten forest health agents that Resource Operations have been conducting pose the greatest risk to Yukon forests. It can aerial surveys. be effectively monitored as part of a risk-based forest health monitoring program. As such, FMB • Since 2009 FMB has been setting and has taken a proactive approach to managing the monitoring MPB bait traps in southern threat posed by the northward expansion of the Yukon to detect presence of MPB. (To date no MPB from British Columbia. Although the MPB presence of MPB has been detected.) has not expanded into Yukon yet, it moved quickly • The Government of Yukon Interdepart- northwards within the Rocky Mountain Trench in mental Mountain Pine Beetle Committee, northern BC, during the peak of the BC outbreak. formed in 2011, provided direction and This represents a potential pathway of MPB into developed strategies to monitor and Yukon given the availability of susceptible host manage MPB in the future. and lack of geographic barriers.

• In 2012 the MPB committee completed a Climate plays an important role in the population Yukon-specific pest risk analysis: Mountain of MPB. One of the most important factors in Pine Beetle Pest Risk Analysis for Yukon controlling the northern movement of MPB is Lodgepole Pine Forests. cold weather and an inner bark temperature of -40˚C for at least one week. Mild winter weather • From this risk analysis, a five year MPB allows overwintering MPB populations to thrive monitoring plan and strategy was developed and the outbreak to continue. Unseasonably and implemented in 2013: Mountain Pine warm, dry springs and summers have likely also Beetle Monitoring Plan for Yukon Lodgepole played an important role in the expansion of the Pine Forests 2013 - 2018 (Refer to Forest Health beetle, possibly allowing for earlier emergence Report 2013 (Garbutt 2013), Appendix 2). and mating in the spring and summer (Mitton and Ferrenberg, 2013).

41 PHOTO 26 Legacy of the 2018 wildfires in northern BC: a discontinuous landscape of lodgepole pine. 42 Border Zone s e 0 r t 2

In 2019 no MPB was detected in the border zone. Similar to previous years scattered single red lodgepole e n m

pines were observed in this area, suggesting attack by either the lodgepole pine beetle (Dendroctonus o o 0 s l i murrayanae) or pine engraver beetle (Ips pini), and possibly porcupine. The beetles are indigenous to l e Yukon and generally attack old or weakened trees, as such they pose no significant threat to forest health. K N

A “typical” attack from MPB usually involves small groups of trees rather than one single tree. Currently, t r

MPB is not present in Yukon. o e g F ! ( A

Given the diminishing MPB risk in northern British Columbia, extensive wildfires in the border zone, and d 10 years of monitoring with no MPB detected, FMB will no longer monitor the border zone as per the 0 n 2 1 0 a 0 t

2013 MPB Monitoring Plan. The 2018 wildfires in northern BC burned vast expanses of mature lodgepole 6 - d 2

- S r 1 1 pine in the northern Rocky Mountain Trench, thereby altering the homogeneity and continuity of the Highway 1 6 > a e i d pathway into Yukon, and the amount of hazard within border monitoring zone (Map 13, Photo 26). FMB r n L i

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In 2019 only portions of northern BC were flown, i 2 2

o r than that east of the Alaska Highway. Given the t o s including the area where the highest risk MPB has o t right climatic conditions small populations could p N S occurred for the last several years. This area, north- a become established and slowly move northward west of Fort Nelson, BC, has a discontinuous corri- W and cross the B.C./Yukon border into southeast ! ( dor of lodgepole pine but a more favorable climate Yukon, killing scattered individual trees or small (Hodge 2012) contributing to the persistence of groups of trees. 43 local populations. MAP 13 Mountain pine beetle in northern BC from 2017-2019 and extent of 2018 BC wildfires. 44 Using Bait Traps

Since 2009, FMB has been setting up and monitoring 15 pheromone bait tree stations in southern Yukon and northern B.C. to detect the presence of MPB (Map 14, Photo 28 and 29). These pheromone baits do not attract MPB over long distances, but will draw them to the baits if they are already in the area. They also do not attract other species of bark beetles. No presence of MPB was found in 2019.

PHOTO 27 Vast expanse of mature lodgepole pine; looking north to the Yukon border southwest of Watson Lake. PHOTO 28 Pheromone placed on the north side of PHOTO 29 MPB bait tree. the tree.

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45 MAP 14 Mountain pine beetle monitoring bait trap locations in southern Yukon and BC, conducted by FMB. 46 SPECIAL PROJECTS

Two special projects were undertaken in 2019. The first was an assessment of spruce beetle risk in the Kusawa Lake area that had been mapped in 2018. The second is an ongoing project that was initiated in 2018 to better understand pest disturbances and inform risk management.

Assessment of Spruce Beetle Risk in the Kusawa Lake Area

In order to better understand the origin and risk of the Kusawa Lake spruce beetle infestation, a reconnaissance helicopter survey and ground survey was undertaken by FMB. The helicopter provided better visual assessments of crown colors and infestation age, as well as facilitating landing for ground surveys.

Lack of landings only allowed for ground assessments at one site on the east shore of Kusawa Lake, where red trees were observed from the air. Ground assessments confirmed spruce beetle but no new attacks were found, nor was there any evidence of live adults, pupa, or larva, including overwintering adults at the base of the tree. The red trees examined had short adult galleries and no larval galleries (Photo 30, 31, 32), indicating poor recruitment rates and survival. Assessing infestation age is challenging in the colder Yukon climate as red foliage can be retained for a number of years. This complicates the ability to predict the likelihood of emerging spring beetles at the base of red trees throughout Yukon (see spruce beetle section).

Overall based on the lack of progeny, and/or ratio of reds (recent attack) to greys (older attack) it appears as though populations are declining. The uncertainty is higher on the east side of Kusawa Lake, where the ratio of reds to greys is variable (Photo 33, Photo 34). Given a two-year life cycle, adults could emerge from the base of red trees in the spring of 2020. Hence FMB will continue to monitor this area because of this variation and the presence of suitable host material. PHOTO 30 Woodpecker activity on dead tree PHOTO 31 Spruce beetle adult galleries with no larval PHOTO 32 Two-to-three-year old recent spruce attacked by spruce beetle. galleries. beetle red attacked tree.

47 48 Spruce Beetle Pheromone Trapping

In the summer of 2019, spruce beetle (Dendroctonus rufipennis) monitoring plots were established in the Haines Junction, Yukon area. The objective of the monitoring plots were to collect information on spruce beetle populations.

Background – Spruce Beetle Life History and 1990-2000’s Attack

The spruce beetle is a natural forest disturbance and lay eggs. During the outbreak, the primary throughout the range of spruce (Picea spp.) in North tool for monitoring spruce beetles was annual America. In Yukon, spruce beetle has been the most aerial surveys. Between 2005 and 2007, additional damaging agent of mature spruce forests. The most ground-based monitoring was conducted using a recent major spruce beetle outbreak was located in series of pheromone-baited Lindgren© funnel traps Southwest Yukon (Kluane region) and started in the to determine flight periods and the spatial variation early 1990’s. The outbreak lasted well over a decade, in population levels. This work indicates that the peaking in 2004. It is the largest, most severe and flight period occurs from May to the beginning long-lasting spruce beetle infestation in Canada, of August. In the summer of 2018 and 2019, the affecting over 400,000 hectares of white spruce Forest Management Branch implemented similar PHOTO 33 High ratio of red trees (recent attack) to grey (older attack) on east side of Kusawa Lake. (Picea glauca) forest. During the outbreak, annual ground-based monitoring plots with the following aerial surveys were conducted from 1994 to 2012 objectives: to monitor insect activity and map white spruce mortality. At the peak of infestation in 2004, nearly 1. To monitor populations of spruce beetle in 100,000 hectares of newly attacked spruce forests Haines Junction Timber Harvest Planning areas; were detected. After 2004, the area of newly infested 2. To understand the timing of the spruce beetle forest steadily declined to 263 ha of light infestation flight period in the Haines Junction area; in 2012. Aerial surveys (specific to spruce beetles in southwest Yukon) ceased in 2013 because the 3. To determine the spatial distribution of spruce infestation had returned to endemic levels (Garbutt beetle populations in the Haines Junction area; 2013). While spruce beetle populations remain at and, endemic levels in southwest Yukon, monitoring high hazard spruce forests is a proactive measure 4. To detect increases of spruce beetle populations that will give early warning should accelerated should they occur. population increase occur. The Forest Management Branch uses these findings Spruce beetles have a dynamic and multi-phase as indicators of forest ecosystem function and life cycle, which typically takes one to three years to ability to maintain natural processes, both of which complete. The majority of the life cycle occurs under are goals outlined in the Champagne and Aishihik spruce bark, adults briefly emerge (for the flight Traditional Territory Strategic Forest Management period) from trees and search for new host material Plan. (new live trees) where they mate, excavate galleries,

Description of monitoring plots & duration

Lindgren© funnel traps were used to monitor spruce beetles (Dendroctonus rufipennis) through the spring and summer of 2018 and 2019. These funnel traps are specifically designed for monitoring and sampling insect populations (BC FLNRO 2016). Ten traps were erected across locations surrounding Haines Junction (Photo 35). Traps were established in locations with a 30-meter buffer between traps and live spruce trees to reduce the risk of attacks on live trees. Traps were set on stand-alone metal posts, and chemical lures were attached to the traps to attract spruce beetles. Two different chemicals (lures) were used to attract spruce beetles to traps; Englemann spruce terpene blend, and frontalin, both developed by Synergy Semiochemicals Corporation of, Burnaby, BC. The Englemann spruce terpene blend has a similar chemical composition as the natural volatile organic compounds released by spruce trees, which is attracts spruce beetles. Frontalin is an aggregation pheromone common to many insect species. Spruce beetles emit Frontalin to signal others to attack a specific tree. Traps 4 and 9 were discontinued in 2019 and replaced by setting traps in more 49 PHOTO 34 Closer 1:1 ratio of reds (recent attack) to greys (older attack) on the east side of Kusawa Lake. preferable sites. Trap 12 was removed due to the proximity of the Bear Creek forest fire. 50 There was considerable variation in the number of Summary and Considerations for Next Year spruce beetles collected between traps (Table 2). At the minimum, Trap 7 and Trap 11 each collected The 2019 spruce beetle monitoring plots provided further insight into spruce beetle populations, spatial one spruce beetle over the entire season, at the distributions and spruce beetle flight period in Southwest Yukon. Given the biennial flight pattern observed maximum, Trap 6 collected 27 beetles over the in the previous infestation and the potential effects of climate change on flight periods, it is recommended season. Based on trap catches, spruce beetle to continue the spruce beetle pheromone trapping project to inform best management practices, such as populations are highest in the Pine Canyon and timing of harvesting, transport of timber and milling operations. Mackintosh East areas, which are currently active commercial harvest areas. There are several TRAP LOCATION (TIMBER HARVEST TOTAL NUMBER TABLE 3 Location information and harvesting considerations and best management NUMBER PLANNING AREA) OF SB COLLECTED total number of spruce beetles practices used to reduce spruce beetle risk, collected for each Lindgren© funnel including timing harvesting operations outside the 1 Pine Canyon 4 traps established near Haines flight period (informed by Lindgren trap monitoring 2 Pine Canyon 12 Junction in spring/summer 2019 plots), minimizing large (>20 cm) logging debris left 3 Haines Junction Fuel Abatement 2 on site, minimizing stump heights, not stacking infested firewood next to healthy trees, and 5 Quill Creek 4 removing any stacked green wood prior to the next 6 Bear Creek 27 beetle flight. 7 Pine Canyon 1 The Lindgren© funnel traps collected many other 8 Mackintosh East 7 insect species of over the summer, including other bark beetles, moths, flies, bees, etc. Northern 10 Pine Canyon 18 spruce engraver beetle or Ips (Ips perturbatus) was 11 Quill Creek 1 commonly found in the traps. Ips is a secondary bark 12 Mackintosh East N/A beetle that attacks stressed or predisposed trees, including those already infested with spruce beetle. Total 76 The traps collected a lower number of Ips compared to spruce beetles, however Ips catchment is incidental and may be not be representative of the population. Across all traps for the entire collection period, 35 northern spruce engraver beetles were collected.

The 2019 pheromone trap catches are considerably lower than the results from the 2005-2007 pheromone trapping results from the decline of the last outbreak and the 2018 pheromone trapping results. The 2019 pheromone trap catches had an average of 9 spruce beetles per trap, compared to the 2018 trap catches with an average of 15 spruce PHOTO 35 Lindgren© funnel trap # 5 (Pine Canyon). beetles per trap. Figure 7 compares weekly trap results from 2018 and 2019. In several traps, this decrease may be due to the availability of Findings stacked green trees nearby, which spruce beetle preferentially attacked over the pheromone traps. Traps were established during the first two weeks The stacked trees had been harvested while of May, and were checked on a weekly basis for 12 addressing the 2019 Bear Creek forest fire. More weeks. Trap catches indicated that spruce beetle data is required to further understand spruce flight began during the last week of May and beetle dynamics at a harvest site level. Another continued to increase with peak activity observed in observation relates spruce beetle flight to daily mid-June (June 6th - June 14th). After June 14th, trap high temperatures. Spruce beetle flight occurs catches decreased, and by the beginning of August when under bark temperatures reach 15 °C. Figure the flight period had ended. The pheromone traps 7 also shows that in 2018 and 2019 more spruce were removed after several weeks where few spruce beetles were caught after experiencing daily high beetles were observed. Overall, a small number (76) temperatures greater than 15 °C and subsequent FIGURE 7 Catchment of spruce beetles per trap and daily high temperature over the spring/summer of 2018 spruce beetles were collected for all traps over the catches decreased after reaching a threshold and 2019. Bars represent spruce beetle catches per trap by study week. The trend lines represent daily high spring and summer. temperature. temperatures. Dates indicate the month and week when traps were checked. There were 10 traps in 2018 and 9 51 traps in 2019. 52 FOREST HEALTH EXTENSION

Forest Management Branch made several presentations to various stakeholders in 2019 to familiarize them with various aspects of the forest health program. OTHER NOTEWORTHY DISTURBANCES IN 2019

As part of the forest health program FMB assists both the public and other government agencies in the identification of forest pests (Table 3). This section includes those pest which are either mostly urban in their occurrence, or those observed on the ground but not visible during aerial surveys.

TABLE 4 Summary of pest incident reports in 2019.

DISTURBANCE HOST SETTING LOCATION PICTURES

Environmental; White Conifer trees adjacent to road right of Marsh Lake Photo 36, 37 discolored needles spruce ways can be susceptible to calcium Dump Purplish colour of spray from dust abatement in summer access road needles can be a and salting in winter. This can cause sign of pollutants. stress and mortality to roadside trees.

Environmental or White Mature white spruce on residential Country Photo 38, 39 disease. spruce property with frequent watering. Residential Branch flagging; Cause of decline of trees is uncertain. discoloured and Damage to trees caused by unknown reddish needles pest, pathogen or environmental stress. PHOTOS 36 and 37 Spruce trees adjacent to road right of ways can be susceptible to calcium Roundheaded White Recently dead white spruce with Country Photo 40, 41, spray from dust abatement, the purplish color woodborer in spruce woodborer larvae. Woodborers gen- residential 42 of needles can be a sign of pollutants. dead conifer erally attack weakened or dead and Monochamus spp down trees of most conifer species.

Comandra blister Lodgepole Young lodgepole pine with Comandra Chadburn Photo 43 rust Cronartium pine blister rust. Lake area comandrae The blister rust can cause cankers on stems and branches of infected trees. However this rust rarely causes signifi- cant damage to pine forests.

Eastern spruce White Defoliation of upper crown and branch Stewart Photo 44 budworm spruce tips on mature white spruce along Crossing/ Choristoneura roadside. Silver Trail fumiferana Highway Pine needle cast Lodgepole Young lodgepole pine. Defoliation, Country Photo 45 Lophodermella pine straw coloured and red needles on the Residential, concolor previous year’s foliage. Ibex Valley During successive years of attack only the current years foliage remains on 53 the tree resulting in “lions tailing”. 54 PHOTOS 38 and 39 Unknown pest, pathogen or environmental damage to mature Spruce on a private, rural property.

PHOTOS 40, 41 and 42 Roundheaded woodborer larvae in dead mature Spruce at private residence in the 55 Haines Junction area. 56 PHOTO 45 “Lions tailing” and straw coloured needles on Lodgepole pine caused by needle cast near the Ibex Valley, Whitehorse.

PHOTO 43 Comandra blister rust in the PHOTO 44 Spruce budworm damage on Chadburn Lake area, Whitehorse. Note the White spruce near Stewart Crossing/Silver Trail. orange yellow pustules are visible.

57 58 REFERENCES

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59 60 Published March 2020 www.yukon.ca/forestry