Tree‐mediated interactions between the jack pine budworm and a mountain pine beetle fungal associate

1. Coniferous trees deploy a combination of constitutive (pre‐existing) and induced (post‐invasion), structural and biochemical defences against invaders. Induced responses can also alter host suitability for other organisms sharing the same host, which may result in indirect, plant‐mediated interactions between different species of attacking organisms. 2. Current range and host expansion of the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) from lodgepole pine‐dominated forests to the jack pine‐dominated boreal forests provides a unique opportunity to investigate whether the colonisation of jack pine (Pinus banksiana Lamb.) by MPB will be affected by induced responses of jack pine to a native herbaceous insect species: the jack pine budworm (Choristoneura pinus pinus Freeman; JPBW). 3. We simulated MPB attacks with one of its fungal associates, Grosmannia clavigera Robinson‐Jeffrey & Davidson, and tested induction of either herbivory by JPBW or inoculation with the fungus followed by a challenge treatment with the other organism on jack pine seedlings and measured and compared monoterpene responses in needles. 4. There was clear evidence of an increase in jack pine resistance to G. clavigera with previous herbivory, indicated by smaller lesions in response to fungal inoculations. In contrast, although needle monoterpenes greatly increased after G. clavigera inoculation and continued to increase during the herbivory challenge, JPBW growth was not affected, but JPBW increased the feeding rate to possibly compensate for altered host quality. 5. Jack pine responses varied greatly and depended on whether seedlings were treated with single or multiple organisms, and their order of damage.     

Population structure of a lodgepole pine (Pinus contorta) and jack pine (P. banksiana) complex as revealed by random amplified polymorphic DNA.

We studied the population structure of a lodgepole (Pinus contorta Dougl.) and jack pine (Pinus banksiana Lamb.) complex in west central Alberta and neighboring areas by assessing random amplified polymorphic DNA (RAPD) variability in 23 lodgepole pine, 9 jack pine, and 8 putative hybrid populations. Of 200 random primers screened, 10 that amplified 39 sharp and reproducible RAPDs were chosen for the study. None of the 39 RAPDs were unique to the parental species. RAPD diversity ranged from 0.085 to 0.190 among populations and averaged 0.143 for lodgepole pine, 0.156 for jack pine, 0.152 for hybrids, and 0.148 for all 40 populations. The estimated population differentiation based on G(ST) was 0.168 for hybrids, 0.162 for lodgepole pine, 0.155 for jack pine, and 0.247 across all 40 populations. Cluster analysis of genetic distances generally separated jack pine from lodgepole pine and hybrids, but no division could be identified that further separated lodgepole pine from hybrids. The observed weak to mild trend of "introgression by distance" in the complex and neighbouring areas was consistent with the view that introgressive hybridization between lodgepole and jack pines within and outside the hybrid zone may have been through secondary contact and primary intergradation, respectively.     

Spatial genetic structure of the mountain pine beetle (Dendroctonus ponderosae) outbreak in western Canada: historical patterns and contemporary dispersal

Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population.     

Population structure and migration pattern of a conifer pathogen, Grosmannia clavigera, as influenced by its symbiont, the mountain pine beetle

We investigated the population structure of Grosmannia clavigera (Gc), a fungal symbiont of the mountain pine beetle (MPB) that plays a crucial role in the establishment and reproductive success of this pathogen. This insect-fungal complex has destroyed over 16 million ha of lodgepole pine forests in Canada, the largest MPB epidemic in recorded history. During this current epidemic, MPB has expanded its range beyond historically recorded boundaries, both northward and eastward, and has now reached the jack pine of Alberta, potentially threatening the Canadian boreal forest. To better understand the dynamics between the beetle and its fungal symbiont, we sampled 19 populations in western North America and genotyped individuals from these populations with eight microsatellite markers. The fungus displayed high haplotype diversity, with over 250 unique haplotypes observed in 335 single spore isolates. Linkage equilibria in 13 of the 19 populations suggested that the fungus reproduces sexually. Bayesian clustering and distance analyses identified four genetic clusters that corresponded to four major geographical regions, which suggested that the epidemic arose from multiple geographical sources. A genetic cluster north of the Rocky Mountains, where the MPB has recently become established, experienced a population bottleneck, probably as a result of the recent range expansion. The two genetic clusters located north and west of the Rocky Mountains contained many fungal isolates admixed from all populations, possibly due to the massive movement of MPB during the epidemic. The general agreement in north-south differentiation of MPB and G. clavigera populations points to the fungal pathogen's dependence on the movement of its insect vector. In addition, the patterns of diversity and the individual assignment tests of the fungal associate suggest that migration across the Rocky Mountains occurred via a northeastern corridor, in accordance with meteorological patterns and observation of MPB movement data. Our results highlight the potential of this pathogen for both expansion and sexual reproduction, and also identify some possible barriers to gene flow. Understanding the ecological and evolutionary dynamics of this fungus-beetle association is important for the modelling and prediction of MPB epidemics.     

Acid-catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol

Utilization of ethanol produced from biomass has the potential to offset the use of gasoline and reduce CO(2) emissions. This could reduce the effects of global warming, one of which is the current outbreak of epidemic proportions of the mountain pine beetle (MPB) in British Columbia (BC), Canada. The result of this is increasing volumes of dead lodgepole pine with increasingly limited commercial uses. Bioconversion of lodgepole pine to ethanol using SO(2)-catalyzed steam explosion was investigated. The optimum pretreatment condition for this feedstock was determined to be 200 degrees C, 5 min, and 4% SO(2) (w/w). Simultaneous saccharification and fermentation (SSF) of this material provided an overall ethanol yield of 77% of the theoretical yield from raw material based on starting glucan, mannan, and galactan, which corresponds to 244 g ethanol/kg raw material within 30 h. Three conditions representing low (L), medium (M), and high (H) severity were also applied to healthy lodgepole pine. Although the M severity conditions of 200 degrees C, 5 min, and 4% SO(2) were sufficiently robust to pretreat healthy wood, the substrate produced from beetle-killed (BK) wood provided consistently higher ethanol yields after SSF than the other substrates tested. BK lodgepole pine appears to be an excellent candidate for efficient and productive bioconversion to ethanol.     

Phylogeographic insights into an irruptive pest outbreak

Irruptive forest insect pests cause considerable ecological and economic damage, and their outbreaks have been increasing in frequency and severity. We use a phylogeographic approach to understand the location and progression of an outbreak by the MPB (Dendroctonus ponderosae Hopkins), an irruptive bark beetle that has caused unprecedented damage to lodgepole pine forests in western North America and is poised to expand its range across the boreal forest. We sampled MPB populations across British Columbia and Alberta and used phylogeographic methods to describe lineage diversification, characterize population structure, investigate expansion dynamics, and identify source populations of the outbreak. Using 1181 bp of mitochondrial DNA sequence from 267 individuals, we found high haplotype diversity, low nucleotide diversity, and limited lineage diversification. The overall pattern was consistent with isolation by distance at a continental scale, and with reduced diversity and population structure in the northerly, outbreak regions. Post-Pleistocene expansion was detected, however more recent expansion signals were not detected, potentially due to the size and rapid rate of range expansion. Based on the limited genetic structure, there were likely multiple source populations in southern British Columbia, although the magnitude of the demographic expansion and rate of spread have obscured the signature of these source populations. Our data highlight the need for caution in interpreting phylogeographic results for species with similar demographics.     

Differences in defence responses of Pinus contorta and Pinus banksiana to the mountain pine beetle fungal associate Grosmannia clavigera are affected by water deficit

We tested the hypotheses that responses to the mountain pine beetle fungal associate Grosmannia clavigera will differ between the evolutionarily co‐evolved host lodgepole pine (Pinus contorta var. latifolia) and the naïve host jack pine (Pinus banksiana) and that these responses will be influenced by water availability. G. clavigera inoculation resulted in more rapid stem lesion development in lodgepole than in jack pine; water deficit delayed lesion development in both species. Decreased hydraulic conductivity was observed in inoculated lodgepole pine seedlings, likely because of tracheid occlusion by fungal hyphae and/or metabolite accumulation. Drought but not inoculation significantly impacted bark abscisic acid levels. Jasmonic and salicylic acid were implicated in local and systemic responses of both species to G. clavigera, with salicylic acid appearing to play a greater role in jack pine response to G. clavigera than lodgepole pine. Water deficit increased constitutive levels and/or attenuated induced responses to G. clavigera for several monoterpenes in lodgepole but not jack pine. Instead, inoculation of well‐watered but not water deficit jack pine resulted in a greater number of xylem resin ducts. These findings reveal mechanisms underlying differences in G. clavigera‐induced responses between lodgepole and jack pine hosts, and how water availability modulates these responses.     

Paternally Inherited Chloroplast Polymorphism in Pinus: Estimation of Diversity and Population Subdivision, and Tests of Disequilibrium with a Maternally Inherited Mitochondrial Polymorphism

We have surveyed a chloroplast DNA restriction fragment length polymorphism in 745 individuals, distributed rangewide in eight allopatric natural populations of jack pine (Pinus banksiana Lamb.) and eight allopatric natural populations of lodgepole pine (Pinus contorta Dougl.). The polymorphic region of the chloroplast genome is located near duplicated psbA genes. Fourteen length variants were found in the survey, and these variants distinguished the two species qualitatively. Variant diversities were high in both species (h(es) = 0.43 in jack pine; h(es) = 0.44 in lodgepole pine). Population subdivision was weak within and among lodgepole pine subspecies and in jack pine (i.e., θvalues were less than 0.05). This weak subdivision is compatible with theoretical predictions for paternally inherited markers in wind-pollinated outcrossers, as well as for polymorphisms with high length mutation rates. If these populations are at a drift-migration equilibrium, the chloroplast DNA restriction fragment data and previous mitochondrial frequency data from the same individuals are consistent with gene flow that is differential through seeds and pollen. The new data have permitted the first empirical tests of disequilibrium between maternally and paternally inherited factors. As expected, these tests failed to detect convincing evidence of non-random association between chloroplast and mitochondrial variants.     

Asynchrony in larval development of the pine beauty moth, Panolis flammea, on an introduced host plant may affect parasitoid efficacy

In the United Kingdom, Panolis flammea (Den. and Schiff.) (Lepidoptera: Noctuidae) is an important pest species of the introduced lodgepole pine but not of its natural host Scots pine. The timing of P. flammea larval growth must be synchronized with its host tree if the larvae are to succeed. We collected field data during 1990 which revealed that the phenological window starts earlier in Scots pine and is shorter than that observed in lodgepole pine. The larvae are found in the field earlier and within a narrower time frame within a Scots pine forest than in a lodgepole pine forest. The larval developmental period is significantly longer on lodgepole pine than on Scots pine. The synchrony/asynchrony of P. flammea to its natural host (Scots pine) and an introduced tree (lodgepole pine) results in the parasitoids having a different impact on the larvae of the two hosts. At any one time, the host plant, caterpillars and parasitoids are more synchronous on the ancestral Scots pine than on lodgepole pine, resulting in a higher percentage of larvae in the optimal instar for parasitism at that time. In lodgepole pine, the percentage of suitable instars available to parasitoids is lower at any given time. The information presented here furthers our understanding of the possible mechanisms for the observed differential population dynamics of the insect on Scots pine and lodgepole pine in the UK. Handling editor: Robert Glinwood.     

Glyphosate-induced changes in the attack success and development of the mountain pine beetle and impact of its natural enemies

Roundup (active ingredient glyphosate) administered into the sapwood around the root collar of lodgepole pine trees, Pinus contorta var. latifolia Engelm., was investigated as a tool for creating trap trees for the mountain pine beetle (MPB), Dendroctonus ponderosae Hopk. MPB's attacked semiochemical-baited, glyphosate-treat trees before attacking baited control trees. Bark samples disclosed an increase in survival of MPB eggs and early instar larvae, enhanced larval development and increased attacks by insect parasites and predators in treated trees. The braconid wasp, Coeloides dendroctoni Cush., parasitized MPB larvae found at high densities in treated trees two months following attack. The dipteran predator, Medetera aldrichii Wh., was only found in treated trees. Increased competition by Ips pini (Say) had a negative impact on MPB survivorship. The enhanced impact of insectan agents apparently offset any glyphosate-induced gains in MPB survival or development, but did not cause a significant reduction in MPB emergence.     

The Relative Abundance of Mountain Pine Beetle Fungal Associates Through the Beetle Life Cycle in Pine Trees

The mountain pine beetle (MPB) is a native bark beetle of western North America that attacks pine tree species, particularly lodgepole pine. It is closely associated with the ophiostomatoid ascomycetes Grosmannia clavigera, Leptographium longiclavatum, Ophiostoma montium, and Ceratocystiopsis sp.1, with which it is symbiotically associated. To develop a better understanding of interactions between beetles, fungi, and host trees, we used target-specific DNA primers with qPCR to assess the changes in fungal associate abundance over the stages of the MPB life cycle that occur in galleries under the bark of pine trees. Multivariate analysis of covariance identified statistically significant changes in the relative abundance of the fungi over the life cycle of the MPB. Univariate analysis of covariance identified a statistically significant increase in the abundance of Ceratocystiopsis sp.1 through the beetle life cycle, and pair-wise analysis showed that this increase occurs after the larval stage. In contrast, the abundance of O. montium and Leptographium species (G. clavigera, L. longiclavatum) did not change significantly through the MPB life cycle. From these results, the only fungus showing a significant increase in relative abundance has not been formally described and has been largely ignored by other MPB studies. Although our results were from only one site, in previous studies we have shown that the fungi described were all present in at least ten sites in British Columbia. We suggest that the role of Ceratocystiopsis sp.1 in the MPB system should be explored, particularly its potential as a source of nutrients for teneral adults.     

Target-specific PCR primers can detect and differentiate ophiostomatoid fungi from microbial communities associated with the mountain pine beetle Dendroctonus ponderosae

The aim of this study was to develop DNA probes that could identify the major fungal species associated with mountain pine beetles (MPB). The beetles are closely associated with fungal species that include ophiostomatoid fungi that can be difficult to differentiate morphologically. The most frequently isolated associates are the pine pathogens Grosmannia clavigera and Leptographium longiclavatum, the less pathogenic Ophiostoma montium, and an undescribed Ceratocystiopsis species (Cop. sp.). Because growing, isolating and extracting DNA from fungi vectored by MPB can be time and labour intensive, we designed three rDNA primer sets that specifically amplify short rDNA amplicons from O. montium, Cop. sp. and the pine Leptographium clade. We also designed two primer sets on a gene of unknown function that can differentiate G. clavigera and L. longiclavatum. We tested the primers on 76 fungal isolates that included MPB associates. The primers reliably identified their targets from DNA obtained from pure fungal cultures, pulverized beetles, beetle galleries, and tree phloem inoculated with G. clavigera. The primers will facilitate large-scale work on the ecology of the MPB-fungal-lodgepole pine ecosystem, as well as phytosanitary/quarantine sample screening.     

Mountain pine beetle develops an unprecedented summer generation in response to climate warming

The mountain pine beetle (MPB; Dendroctonus ponderosae) is native to western North America, attacks most trees of the genus Pinus, and periodically erupts in epidemics. The current epidemic of the MPB is an order of magnitude larger than any previously recorded, reaching trees at higher elevation and latitude than ever before. Here we show that after 2 decades of air-temperature increases in the Colorado Front Range, the MPB flight season begins more than 1 month earlier than and is approximately twice as long as the historically reported season. We also report, for the first time, that the life cycle in some broods has increased from one to two generations per year. Because MPBs do not diapause and their development is controlled by temperature, they are responding to climate change through faster development. The expansion of the MPB into previously inhospitable environments, combined with the measured ability to increase reproductive output in such locations, indicates that the MPB is tracking climate change, exacerbating the current epidemic.     

Non-equilibrium succession dynamics indicate continued northern migration of lodgepole pine

Because species affect ecosystem functioning, understanding migration processes is a key component of predicting future ecosystem responses to climate change. This study provides evidence of range expansion under current climatic conditions of an indigenous species with strong ecosystem effects. Surveys of stands along the northern distribution limit of lodgepole pine (Pinus contorta var. latifolia) in central Yukon Territory, Canada showed consistent increases in pine dominance following fire. These patterns differed strongly from those observed at sites where pine has been present for several thousand years. Differences in species thinning rates are unlikely to account for the observed increases in pine dominance. Rates of pine regeneration at its range limits were equivalent to those of spruce, indicating a capacity for rapid local population expansion. The study also found no evidence of strong climatic limitation of pine population growth at the northern distribution limit. We interpret these data as evidence of current pine expansion at its range limits and conclude that the northern distribution of lodgepole pine is not in equilibrium with current climate. This study has implications for our ability to predict vegetation response to climate change when populations may lag in their response to climate.     

A review of factors affecting the population dynamics of jack pine budworm (Choristoneura pinus pinus Freeman)

Jack pine budworm (Choristoneura pinus pinus Free.) (Lepidoptera: Tortricidae) is a native insect that periodically defoliates areas of jack pine (Pinus banksiana Lamb.) in the subboreal forests of North America east of the Rocky Mountains. Outbreaks of jack pine budworm generally occur at 6- to 12-year intervals and collapse after 2–4 years. Periodicity of outbreaks varies and is associated with site-related factors. Survival of early-instar larvae during spring dispersal is tied to the abundance of pollen cones (microsporangiate strobili), which provide a refuge for larvae until current-year needles expand. Jack pine trees that have been heavily defoliated produce few pollen cones in the following year, often resulting in high mortality of early-stage larvae. A diverse guild of generalist parasitoids attack jack pine budworm, but only a few species account for most mortality in any area. Collapsing jack pine budworm populations are characterized by sharp declines in early instar survival, coupled with an increased rate of parasitism in the late larval and pupal stages. The reciprocal interaction between heavy defoliation and low pollen cone production, and increased parasitism of late-stage larvae or pupae, are consistent with second-order density dependence factors identified in analysis of a long-term population data set. Since the 1950s, several jack pine budworm outbreaks have been roughly synchronous over a large geographic area, suggesting that Moran effect processes, as well as moth dispersal or other factors, may be involved in jack pine budworm dynamics. Although the short duration of outbreaks enables most trees to recover, over time dead trees and top-killed trees accumulate in jack pine stands. Jack pine is well adapted to fire and when fires ignite, the accumulation of dead trees and woody debris often leads to intense wildfires followed by prolific regeneration. The three-way interaction of jack pine, jack pine budworm, and fire ultimately serves to maintain vigorous stands and ensures continued hosts for jack pine budworm. Received: October 1, 1999 / Accepted: September 22, 2000     

Variation on reaction norm in lodgepole pine natural populations

Variations on the norm of reaction among ten natural lodgepole pine populations sampled from three lodgepole pine subspecies (Pinus contorta ssp. contorta, ssp. latifolia and ssp. murrayana) were studied by using 20 year heights measured in 57 provenance test sites across interior British Columbia (B.C.). There were significant population by site interactions. Concurrent joint regression and the AMMI model were used to dissect these population by environmental interactions. Joint regression analysis indicated that three populations (from the northwest) had a negative linear regression coefficient with environmental deviation, three (from central and southeast sites) had a positive regression coefficient and four (from the southwest) had a zero regression coefficient. The AMMI model revealed a similar pattern of reaction norm among the ten populations. But the three significant IPCA axes, which captured twice as much of the G × E sum of squares than joint regression, were more effective in separating the ten populations and associating their performance with the climate of test sites and their origin. The variation patterns of reaction norm in lodgepole pine populations demonstrated that adaptation of lodgepole pine natural populations to the various physical environments, at sub-species as well as at population level, was due largely to a balance between selection for high growth potential in less severe environments and selection for high cold hardiness in severe environments. Received: 4 May 2000 / Accepted: 10 November 2000     

Relationship between respiratory depletion of sugars and loss of cold hardiness in coniferous seedlings over-wintering at raised temperatures: indications of different sensitivities of spruce and pine

Long-term effects of elevated winter temperatures on cold hardiness were investigated for Norway spruce (Picea abies L. Karst.), lodgepole pine (Pinus contorta Dougl.) and Scots pine (Pinus sylvestris L.). Two-year-old seedlings with the same pre-history of growth and cold hardening in the field were maintained from early December to late March at two field sites in northern Sweden and in a cold room. The temperatures at these locations averaged –13·5, –8·9 and 5·5°C, respectively. Following treatments, carbohydrate contents and cold tolerances were assessed. Needle respiration was also analysed during the 5·5°C treatment. Cold tolerance of lodgepole pine and Scots pine was much reduced following the 5·5°C treatment. Cold tolerance was somewhat reduced in lodgepole pine following the –8·9 °C treatment, but was essentially maintained in spruce throughout all treatments. The cold tolerance of needles was strongly correlated with their soluble sugar contents. Spruce maintained cold hardiness by having larger reserves of sugars and lower rates of respiration which decreased more rapidly as sugars were depleted. Tolerance of lodgepole pine to frost desiccation was also much reduced following the 5·5°C treatment.     

Comparisons of mountain pine beetle (Dendroctonus ponderosae Hopkins) reproduction within a novel and traditional host: effects of insect natal history,colonized host species and competitors

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Stand‐replacing fires reduce susceptibility of lodgepole pine to mountain pine beetle outbreaks in Colorado

Aim As climate change is increasing the frequency, severity and extent of wildfire and bark beetle outbreaks, it is important to understand how these disturbances interact to affect ecological patterns and processes, including susceptibility to subsequent disturbances. Stand‐replacing fires and outbreaks of mountain pine beetle (MPB), Dendroctonus ponderosae, are both important disturbances in the lodgepole pine, Pinus contorta, forests of the Rocky Mountains. In the current study we investigated how time since the last stand‐replacing fire affects the susceptibility of the stand to MPB outbreaks in these forests. We hypothesized that at a stand‐scale, young post‐fire stands (< c. 100–150 years old) are less susceptible to past and current MPB outbreaks than are older stands. Location Colorado, USA. Methods We used dendroecological methods to reconstruct stand‐origin dates and the history of outbreaks in 23 lodgepole pine stands. Results The relatively narrow range of establishment dates among the oldest trees in most sampled stands suggested that these stands originated after stand‐replacing or partially stand‐replacing fires over the past three centuries. Stands were affected by MPB outbreaks in the 1940s/1950s, 1980s and 2000s/2010s. Susceptibility to outbreaks generally increased with stand age (i.e. time since the last stand‐replacing fire). However, this reduced susceptibility of younger post‐fire stands was most pronounced for the 1940s/1950s outbreak, less so for the 1980s outbreak, and did not hold true for the 2000s/2010s outbreak. Main conclusions Younger stands may not have been less susceptible to the most recent outbreak because: (1) after stands reach a threshold age of > 100–150 years, stand age does not affect susceptibility to outbreaks, or (2) the high intensity of the most recent outbreak reduces the importance of pre‐disturbance conditions for susceptibility to disturbance. If the warm and dry conditions that contribute to MPB outbreaks concurrently increase the frequency and/or extent of severe fires, they may thereby mitigate the otherwise increased landscape‐scale susceptibility to outbreaks. Potential increases in severe fires driven by warm and dry climatic trends may lead to a negative feedback by making lodgepole pine stands less susceptible to future MPB outbreaks.     

Comparative detection,density, and reproductive performance of Kirtland's warbler in jack and red pine

The formerly endangered Kirtland's warbler (Setophaga kirtlandii) is among a growing number of conservation-reliant species that depend on active management to avoid reverting to endangered status. Because the Kirtland's warbler is a habitat specialist of young, even-aged jack pine (Pinus banksiana), managers of the recovery effort stressed creating new jack pine stands and monitoring numbers of singing males through an annual census using single visits to individual stands. Kirtland's warbler will occupy and breed in red pine (P. resinosa), but red pine has not been surveyed for Kirtland's warblers in the annual population census. Furthermore, the current monitoring approach cannot determine their species detection probability or individual detection probability, which is essential to evaluate both red pine use and the accuracy of the census. From 2016–2018 we estimated density and detection probabilities in jack pine and red pine stands through repeated visits to a limited number of stands rather than single visits to many stands. Estimates of species detection probability indicated that ≥1 male Kirtland's warbler would be detected on most sites when any were present, but individual detection probabilities were less and varied by stand type, indicating that single visits to sites would underestimate numbers and that accurate estimation of detection probability was important for estimation of density in different stand types. We offer quantitative estimates of detection probabilities for determination of Kirtland's warbler population size in jack pine versus red pine stands in the same areas and breeding seasons. Managers of Kirtland's warblers should incorporate detection probabilities into population surveys to achieve more accurate estimates of population size.