Development of a Program forReintroducing White Pine to the

Lower St. Lawrence Region

Phase I Report PMVRMF (01-01-128)

by

Pierre BelleauStéphanie Rioux

Mike Roy

Bas-Saint-Laurent Model Forest

2

April 200

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SCIENTIFIC ADVISOR

n Bérubé: Laurentian Forestry Centre, Canadian Forest Service

n-Yves Blanchette: Faculty of forestry, Université de Moncton

ëtan Daoust: Laurentian Forestry Centre, Canadian Forest Service

ston Laflamme: Laurentian Forestry Centre, Canadian Forest Service

bert Lavallée: Laurentian Forestry Centre, Canadian Forest Service

y Prégent: Research branch, Ministère des Ressources naturelles du Québec

Introduction ................................................................................................................................................................... 4

Phase 1 Objectives ............................................................................................................. ........................................... 5

Distribution Area and Factors ........................................................................................................................................ 6

Insect Pests and Diseases of White Pine ....................................................................................................................... 7

Material and Method....................................................................................................................................................10

Results and Discussion ......................................................................................................... .......................................15

Conclusion and Recommendations ..............................................................................................................................20

Bibliography

TABLE OF CONTENTS

4

White pine has tremendous ecological, economic and aesthetic value. When the first settlers arrived in eastern NorthAmerica, the volume of wood contained in white pine stands was estimated at around 3.4 billion cubic metres(Wendel and Smith 2000). In the late 1800s, most of these vast expanses of forest had been harvested. It is hard toimagine what these 300- to 400-year-old white pine forests looked like, with their trees boasting diameters of overtwo metres. There is no question that this species contributed greatly to the economic development of severalcommunities, as attested by various documents from that period (Langelier 1884). In the Lower St. Lawrence region,as elsewhere in the province, the popularity of white pine led to overharvesting and today’s very low population.

The loss of white pine is causing significant forest biodiversity depletion in the Lower St. Lawrence region. Yet, thehigh demand for this species and its rapid growth make it a very judicious choice in terms of economic and forestvalue. However, white pine trees in a natural setting require considerable care during their early years to enablethem to withstand insect pests and disease. The losses caused by blister rust and white pine weevil in recentdecades explain why people now hesitate to plant this species on a wide scale. Today’s context is very different fromtimes past and it is practically unthinkable that these forests could be restored to their former glory.

The Bas-Saint-Laurent Model Forest is committed to finding sustainable solutions for forest-reliant communities. Tothat end, it decided to spearhead a project aimed at reintroducing white pine to the Lower St. Lawrence region.Depending on whether the objective is economic or ecological, the method used will be adapted to the situation,combining pure plantations and low-density planting. The project blueprint was based on the recommendations madeby a group of scientists with whom the Model Forest partnered from day one. After discussion, it was decided todivide the program into two phases. The first phase, the subject of this report, consists of an exploratory studycovering the entire Lower St. Lawrence region. The second phase will most likely be carried out during 2002-2003; itshould include a new inventory and focus on preparing and implementing an action plan for reintroducing white pine.The project presents a unique challenge in that it requires mapping out a strategy and coordinating actions that willsucceed in controlling the two primary harmful agents of this species.

The following report provides the reader with an overview of the problems associated with white pine in Québec andthe Lower St. Lawrence region, including a description of the ecological characteristics, control methods andresearch under way for each of the main insect pests. The first step of the project – an inventory completed in 2001-2002 – is then presented, along with the method and results. Finally, recommendations are made regardingcontinuation of the project.

INTRODUCTION

5

In keeping with the proposal submitted in April 2001, four objectives were established for Phase 1 of the project to

reintroduce white pine to the Lower St. Lawrence region. They would be achieved through an inventory of

plantations:

1. Assess all white pine plantations (health, quality, potential);

2. Verify the silvicultural approaches adopted during planting;

3. Provide basic data to determine the sampling plan for Phase 2;

4. Define quantifiable objectives for the reintroduction program (abundance and distribution).

PHASE 1 OBJECTIVES

6

The white pine’s distribution area largely depends on the length of the growing season. Its northern limit follows the

average annual 2OC temperature isotherm. White pine occurs in most American states and some varieties are even

found in Mexico. The climate in this distribution area is cool and damp, with temperatures in July ranging from 18°C

to 23°C (Wendel and Smith 2000).

According to Horton and Brown (1960), the specie’s current range is more the result of past forest fires than of the

weather or soil conditions within its potential range. In fact, white pine is classified as a fire species, which means that

it is adapted to conditions created by fire (Vachon 1980). White pine itself plays a role in fire frequency because of

its highly combustible bark. According to Maissurrow (Petitclerc 1974), the decline of white pine in Eastern Canada is

not attributable to logging, but rather to the lack of synchronism between seed production and fire occurrence,

therefore causing seeds to disappear. In any event, the few maps consulted (Horton and Brown 1960; Lavallée

1973; Stiell 1985; Clark and Perera 1995), which show the boundaries of the specie’s distribution area, all include

the Lower St. Lawrence region.

It is hard to say, however, how abundant white pine was in the region’s forests of yesteryear. In Quebec, the largest

expanses of forest occurred in the western part of the province. We are anxiously awaiting the results of a study on

the natural disturbance cycles of mixedwood forests, which the Model Forest has supported financially for four years

running. The study should describe the composition of our heritage forests. Some of these data are currently being

processed and compiled.

DISTRIBUTION AREA AND FACTORS

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INSECT PESTS AND DISEASES OF WHITE PINE

7

are 277 species of insects and 110 types of disease that can harm white pine, in addition to the seemingly

pread problem of grazing deer in the United States. However, among these harmful agents, a few are especially

ed, namely, blister rust, the white pine weevil and, to a lesser extent, armillaria root disease (caused by

aria sp.).

er rust (Cronartium ribicola)

r rust is caused by a fungus that originated in Asia and was introduced here in the early 20th century. It was

bserved in Quebec in 1916 and is today found throughout the white pine’s distribution area.

lister rust’s cycle is highly complex. It involves a primary host, in this case white pine, and an intermediate host

ging to the Ribes genus (currants and gooseberries). All five-needled pines are susceptible to the disease,

enters by the needles and works itself toward the branches and ends up in the trunk. Orange-yellow fruiting

s appear after a certain period of time and are easily detected in the spring. The foliage above the infected part

y becomes chlorotic. Within the space of three years, the disease can kill subjects with a stump diameter of less

5 cm by girdling. Individual trees of all ages are at risk, although most targets are under 25 years old. Even if

ee is harvested before it dies, the presence of cankers on the trunk lowers its quality.

ective strategy against blister rust combines various measures, some preventive in nature, others curative. At

tset, it is important to choose an appropriate location for the plantation, i.e. in the natural range of white pine,

altitude of less than 300 m, with relatively low humidity, at the top of a slope, with good drainage and without

esence of any Ribes species. Inspections are crucial in order to detect any signs of cankers. The frequency of

tions varies, but in general they should be carried out every two or three years, until the trees are 15-20 years

ortality can be prevented by pruning the lower half of the crown at around eight years old, thereby removing

fected parts and diseased branches. Ribes may also be eradicated within a radius of 300 m, but this operation,

nitary felling, can only really be considered in relatively small areas, such as private woodlots.

al solutions for reducing the susceptibility of plantations are currently under study. One such solution is a

ical control method that consists in inoculating white pine seedlings with fungi. An experimental plantation of

8

this type was established in summer 2000 in the Est du Lac Témiscouata area of the Model Forest by Jean Bérubé, a

researcher with the Laurentian Forestry Centre (LFC), in conjunction with the Model Forest. Another promising

avenue is the selection of resistant lines of pine offering superior growth. Progeny tests aimed at identifying plus

trees are currently under way at two forest tenant farms belonging to the Model Forest. This genetic improvement

work is being supervised by the LFC’s Gaëtan Daoust. Pines are not the only species that have drawn the attention of

genetic specialists. Studies are being conducted to develop blister rust-resistant Ribes cultivars for the purpose of

supplying commercial currant plantations (Zambino 2000). Pruning studies are also under way to determine in what

conditions the technique is most effective.

Decision-support models are also being developed to help tree growers select the best planting sites. This approach

requires a near-perfect understanding of the disease and its contributing factors, something this study is helping to

do. In this respect, regional variations may be observed, which explains why investigative research is required before

making recommendations for a reintroduction program. For now, there are no clear guidelines regarding

reforestation prescriptions. Some studies opt for high-density plantings, others for either plantations under cover or

mixed plantations. The quest for better silvicultural options will be one of the main objectives of the second phase of

the project, as it is for similar initiatives in the United States (Ostry 2000).

White pine weevil (Pissodes strobi [Peck])

The white pine weevil is a native insect. It appears to attack up to 20 species of trees in the United States, including

ornamental trees. Among them, white pine is at the top of the list. The weevil is found everywhere in eastern North

America and throughout the range of the white pine. This species is the weevil’s preferred target in the Montérégie,

Lanaudière and Laurentides regions of Québec. Not only do trees lose value because of deformed stems, but also

because this pest greatly stunts their growth.

The adult insect overwinters in the forest litter near its host. Early in the spring, the adults mate and feed on the

terminal shoots of young pine. Females lay their eggs on the upper portion of the shoot, which is sometimes also

occupied by other females. The eggs hatch and the larvae feed under the bark, causing the terminal shoot, and in

some cases the lateral buds, to die. More than one whorl may be attacked during a given year. In natural forests,

weevils attack white pines regardless of tree size and it has been reported that even individual trees over 25 m in

height have been attacked. The weevils react to sensory stimuli caused by their outside environment (Boulet 1995).

9

Like blister rust, the white pine weevil is best controlled using an approach that combines several tactics. At least,

that is what is recommended by researchers in western Canada who are helping develop integrated pest

management systems for Sitka spruce (Alfaro et al. 1995). IPM systems take into account site conditions, silvicultural

regimes, the genetic resistance of seedlings and, last but not least, more direct control methods. However, this type

of tool is not yet available for the conditions in Quebec or for solving the problem specific to white pine.

The easiest and most effective control technique for white pine consists in trimming and discarding the affected

shoots, the objective being to produce at least one saw log. However, this technique will only be successful if it is

carried out when most of the insect population is still under the bark, i.e. around mid-July. Specialists have proposed

a phenological indicator for determining the ideal time, which is the period when wild raspberries begin to ripen. The

shoot must be cut down to the whorl below. Competition among the lateral shoots for apical dominance causes some

deformation to occur; however, this situation can be corrected the following year with selective pruning. Monitoring

and pruning become more difficult when plantations are around 15 years old, which is why it is important to maintain

insect populations at a low level during the plantation’s early years. The first signs of infestation usually appear

around the age of five or six. Weevils spread rapidly and when 20% of stems are affected, it is already too late to

bring the situation under control. As regards the silvicultural regime, very dense plantations with rows spaced 2.5 m

or less apart and maintenance of the dominant trees’ upper story and wide crowns are recommended. Maintenance

and clearing operations should be carried out as late as possible.

When choosing a plantation’s location, certain precautions can help reduce the risk of an epidemic. Studies have

shown that sites with heavy soils and poor drainage, along with wooded border areas, should be avoided. Boulet

(1995) subdivided Quebec into five susceptibility zones, each representing a different probability level of weevil

infestation. Generally speaking, the higher the infestation risk, the earlier damage occurs in the stand’s life. In the St.

Lawrence Valley, the risk is greater in the Appalachian foothills. Most of the Lower St. Lawrence region belongs to the

moderate-risk zone, where the proportion of plantations affected by weevils ranges from 21.1% to 40.0%.

In Quebec, research on white pine weevil is mainly geared toward a better understanding of the factors that stimulate

egg-laying so that resistant stock can be chosen. It has been noted that the predilection for white pine varies widely

depending on the family to which the insect belongs. These variations in behaviour suggest that promising advances

can be made in terms of control. In the meantime, ongoing efforts are needed to ascertain the best time to apply

proven control methods for maximum effectiveness – a parameter that varies according to the region affected. The

study at hand should provide answers in this area.

10

Population

We decided to begin by making a list of all white pine plantations found in the Lower St. Lawrence region, using forest

and administrative data from three different sources. First, the data base for the Eastern Quebec Forestry

Development Program was retrieved and reactivated by the consultants group SYGIF, at the request of the Bas-Saint-

Laurent Model Forest. Additional technical information, this time describing the work carried out in private woodlots

whose owners belong to the group management program, was obtained from the regional office of the Ministère des

Ressources Naturelles du Québec (MRN), on the condition that it remain confidential. Lastly, digital coverage of all

forest-related work carried out between 1990 and 1997 in the area overseen by the Groupement forestier de l’Est

du lac Témiscouata (GFELT) was consulted. This coverage was produced by the Model Forest for the purpose of

tracking its performance indicators. These three data banks did not use the same fields to describe plantation

prescriptions, and a given plantation could be registered in more than one data bank.

Based on the compiled data, we estimated the number of white pine plantations in the area extending from

Kamouraska to Matane at just over 950, all categories combined (pure and mixed). This number includes cases,

however infrequent, where the same plantation was entered under more than one prescription number owing to the

different white pine sources it contained. Information was sufficiently detailed for almost half the trees, making it

possible to establish the breakdown of plantations by percentage of white pine. Of ten plantations: one is pure, seven

are mixed (5-95% white pine) and two have only a few pines. In addition, close to 60% of plantations are

concentrated in the western part of the Lower St. Lawrence region.

Between 1976 and 1987, an average of four white pine plantations were established annually. Thereafter, the rate

increased to an average of 82 plantations per year, with peaks in excess of 200 plantations in 1994 and 1995. As of

1988, the number of white pine plantations in the region rose, most of them being mixed. The increase resulted from

a review of the overall objectives of the Eastern Quebec Forestry Development Program immediately prior to starting

Phase 2, with the aim of better targeting the program’s participation in regional forestry in a context of

overharvesting. Thus began a “shift” toward softer silviculture. Because of the high incidence of epidemics and

disease in single-species plantations, a panel of experts recommended that white pine be dispersed during planting

and combined with companion species. The program guidelines recommended planting 625 white pine seedlings

MATERIAL AND METHOD

11

(25%) with 1875 seedlings of other species in rows spaced 4 m apart. Mixed plantations combining white pine with

hardwood species subsequently became much more frequent. The seedlings available from nurseries were a good

size and there were no constraints in terms of supply (Denis Pineault, personal communication, 2000). This measure

had the added benefit of reducing losses suffered by owners whose plantations became infested.

Sampling

Due to the large number of plantations and vast study territory, sampling had to be restricted. First, plantations

established before 1996 and containing at least 50% white pine were singled out. Three criteria were then applied to

select the final plantations. The first was that plantations had to be old enough to be affected by blister rust and be

such that signs of infection would probably be more noticeable. The second criterion was aimed at eliminating

plantations where sampling would be too tedious owing to the dispersed nature of the white pine present.

The percentage of white pine was calculated based on the number of trees of each species contained in

“reforestation reports.” This statistic served as the primary basis for plantation selection, even though it was highly

inaccurate. On several occasions, the actual percentage of white pine, based on visual assessments in the field, was

considerably different from the initial figure due to mortality. Furthermore, the reforestation reports did not provide

any information as to the distribution of seedlings, which would have made it possible to evaluate the homogeneity of

the plantation beforehand. The pine trees were sometimes in groups rather than dispersed throughout the

plantation, resulting in the rejection of 31 plantations and many wasted trips. For analysis purposes, two density

values (calculated and actual) were recorded. The third selection criterion was that plantations had to contain the

minimum number of white pine trees (200) for the necessary measurements to be taken.

The inventory was carried out in 57 plantations established between 1982 and 1996, 80% of which were less than

10 years old. A small number of plantations were studied even though the percentage of white pine was below the

critical level. The lowest density recorded was roughly 40%, according to our estimates. The final sample was evenly

distributed between the eastern and western parts of the Lower St. Lawrence region (Figure 1). Of the study group

of plantations, 10 had been previously pruned. For those particular plantations, fewer measurements were required.

12

Figure 1: Geographic distribution of sampled plantations

Measurements

The sampling method used for the inventory was developed by Bruno Boulet of the MRN for studies involving insect

and disease monitoring. It was subsequently used by Gaston Laflamme of the Laurentian Forestry Centre to carry out

work related to white pine blister rust. A total of 100 trees are assessed in each plantation using this method. The

number of rows in the plantation is determined first. The number of cruise lines (between two and six) is then chosen

according to the size and shape of the plantation. In general, four cruise lines of 25 trees are completed. The

number of the row and the first tree are determined using a random number table. One tree out of two is examined

in each cruise line.

It was not possible to systematically apply the method described above to all plantations. For example, it could not

be used in plantations where the number of trees to be measured was too low due to either a high mortality rate or a

highly irregular layout. The alternate procedure used in both these cases consisted in examining one out of two

trees, trying to cover the entire plantation.

22

1

1

8

6

5

41

13

Each tree was first examined for signs of blister rust infection. If any signs were detected on the trunk or on a branch

less than 10 cm away from the trunk, the height of the highest infection was recorded as a “trunk infection.” If,

however, the infection was on one or more branches, but at a distance of over 10 cm from the trunk, the height of

the highest infection was recorded as a “branch infection.” The height of infection is a basic datum used to

determine the pruning prescription. The percentage of trees affected determines the incidence of disease in the

plantation. In this regard, each region establishes its own rules for warranting sanitary pruning. Currently, the Agence

régionale de mise en valeur des forêts privées du Bas-Saint-Laurent (private forest development agency for the

Lower St. Lawrence region) sets the minimum level at 5% of affected trees, and the plantation must have a good

future potential.

The causes of seedling mortality are wide-ranging: poor planting technique, competing vegetation, errors committed

during stand tending, attack by harmful agents, etc. For the purposes of this study, the only mortality cases

considered were the ones directly attributable to blister rust. The statistics presented below give a fairly accurate

picture of the situation in terms of damage caused by this disease. Total mortality can only be equal to or over these

values.

As previously mentioned, in the case of mixed plantations, it is impossible to know the initial distribution of white pine

based on the information contained in the reforestation reports. However, this information is essential for calculating

the mortality rate. In addition, unless the plantation is composed solely of white pines, an inventory using cruise lines

does not lend itself very well to assessing mortality without considering what was there initially. During the second

phase of the project, permanent sample plots are planned. All trees within these plots will be counted so that this

variable can be measured where deemed essential. It will also be possible to measure several other parameters,

some related to white pine growth in relation to site characteristics.

Each tree was then visually assessed for signs of weevil occurrence. An insect that causes the terminal shoot to die

leaves telltale signs. The year of the attack was noted (2001, 2000, 1999, and before 1999). When several attacks

occurred, only the most recent one was recorded because of the difficulty in distinguishing successive events. The

presence of trunk deformations was also noted, without considering when they were caused.

Several other measurements were also taken during the inventory, according to the established sampling protocol

(Appendix 1). In keeping with the protocol, pine tree height was measured for every tenth tree sampled. The slope

was then measured using a clinometer, with values divided into six classes (A: 0-3%, B: 4-8%, C: 9-15%, D: 16-

14

30%, E: 31-40%, F: 41% and higher). Site exposure was determined using a compass. The plantation’s position on

the slope was determined two ways: based on the general topography (high, mid-slope, low) and—the more

accurate way—based on the “point d’observation écologique” (ecological point of observation) method (Saucier et

al. 1994), which uses sample plots for ecological surveys and considers irregularities of landforms. The extent of

competing vegetation was assessed visually and deemed either high, medium or low. This variable is known to

influence the moisture level near the ground and, therefore, has a direct impact on the blister rust’s development.

The susceptibility zone was determined using the map produced by Lavallée (1986). The year the plantation was

established and the percentage of white pine were taken from the reforestation reports. Values for parameters such

as drainage class, initial disturbance and ecological type were taken from the MRN’s digital ecoforest coverage so

they could be subsequently validated in the field. For altitude, the topographical cover was consulted. The

plantation’s geographic coordinates were obtained with a global positioning system (GPS) and, finally, a few other

observations were made, such as whether pruning had been carried out. Analyses were done with SYSTAT software,

setting the probability level at 95%.

Two people were assigned to this inventory, which was carried out from October 5 to December 6, 2001. Members of

the team led by LFC researcher Gaston Laflamme provided the necessary training to personnel before sampling

started. The late onset of winter made it possible to extend the inventory period until funds ran out. Only one major

snowfall temporarily interrupted the work. In the end, 88 plantations were visited in 55 days. The time required to

sample a plantation varied between 0.7 and 3 hours, with several factors affecting productivity.

15

It is important to remember two major characteristics of the sample plantations: they had to be composed of 50% or

more white pine and have been established after 1982.

For blister rust, three parameters were studied: the number of trees that have died from blister rust, the number of

trees with infected trunks and the number of trees with infected branches only. The plantation’s predisposition to

disease was determined by the total number of infected trees. Therefore, for this segment, only plantations not

having been pruned were compiled (n=47).

The average mortality rate for white pine in the plantations visited was 2.3%. In the worst case recorded, blister rust

destroyed nearly one fifth of standing timber. The disease was fairly widespread, as losses were recorded in six out

of ten plantations. In all the plantations studied, the percentage of white pine had no effect on the mortality rate,

which appears to contradict the theory that low-density planting can limit damage caused by blister rust. The

mortality rate in pure plantations actually averaged 2.9%, compared with 4.0% in plantations with less than 50%

white pine. Nonetheless, except for the lower percent class, blister rust problems seemed to increase with the

abundance of white pine. The mortality rate is very closely related to the age of the plantation, i.e. how long ago the

seedlings were planted (p=0.001), to the susceptibility zone (p=0.018) and, to a lesser extent, to the degree of

competition (p=0.062).

Observations showed that 6.6% of white pines had infected branches, compared with 18.8% with infected trunks.

Symptoms were seen in 90% of cases when it came to infected branches, whereas all plantations showed signs of

infected trunks. In the most severely affected plantations, the disease respectively reached 32.0% and 71.4% of

pines for these two indicators. The occurrence of infected trunks is higher in plantations established on logged areas

than in those established on wild land—an important fact in the case of private woodlots. This may be due to the

absence of Ribes on recent wild land. Considering the late date of the inventory, it is possible that cankers may have

gone unnoticed, thus leading to an underestimated infection rate. However, based on the data collected, the

probability of this error is low, since when the mortality rate was high, branch infection was also high (r=0.70).

A plantation’s age greatly influences the degree of branch and trunk infection from blister rust. The same thing was

observed for the number of dead trees. The number of infected trees also varies with the susceptibility zone. As for

RESULTS AND DISCUSSION

16

the successional series, it highlights the effect biophysical characteristics have on the site (p=0.05). According to

our observations, the incidence of blister rust increases on sites where the vegetation will potentially become a sugar

maple-yellow birch stand (Table 1). This conclusion goes somewhat against the generally accepted view that

hardwood sites offer good conditions for the establishment of white pine.

Table 1: Effect of the successional series on the degree of infestation byTable 1: Effect of the successional series on the degree of infestation byTable 1: Effect of the successional series on the degree of infestation byTable 1: Effect of the successional series on the degree of infestation by

white pine blister rustwhite pine blister rustwhite pine blister rustwhite pine blister rust

Successional Series

RS1-4 MS1 FE3

NumberNumberNumberNumber 3 18 5

Infected branchesInfected branchesInfected branchesInfected branches 8.3% 4.6% 11.9%

Infected trunksInfected trunksInfected trunksInfected trunks 28.0% 16.5% 34.9%

Infected treesInfected treesInfected treesInfected trees 36.3% 21.1% 46.8%

The moisture regime is not an issue, since all FE3 sites were on soils with good drainage. However, the presence of a

higher percentage of Ribes could explain the phenomenon. It is worth noting that the number of replicates is not the

same for all series.

Without intervention, losses in the coming years are expected to affect around 25% of trees (one in four) in the

types of plantation studied (Figure 2). This does not take into account current losses. Whereas nothing can be done

to save trees with infected trunks, all trees with infected branches can be saved through proper pruning, provided

that it is done quickly. On average, the highest infected branch is located roughly 0.5 m from the ground, with

extremes ranging from 0.3 m to 1.8 m. If the height of the infected area is compared with the average height of trees

in the plantation, the average height of infection is between one-tenth and half of the total height of the tree. In

almost 90% of plantations (not pruned), the infected areas were actually found in the lower third of the tree. Pruning

half the crown, as suggested by researchers, should sufficiently slow down the disease’s progress. The percentage of

affected trees meets the minimum conditions required by the Agence régionale de mise en valeur des forêts privées

du Bas-Saint-Laurent to be eligible for a sanitary treatment. The number of plantations having benefited from pruning

nevertheless remains low.

17

The amount of time before intervention is a key factor in the survival of young trees. What this project confirms, as

other studies have done, is that the incidence of disease and mortality increases with time. Each year, the mortality

rate rises by 0.7% and the percentage of infected trees, by 4.5% (Figure 3).

FIGURE 2: EXTENT OF DAMAGE CAUSED BY BLISTER RUST

DEAD

ON BRANCH

ON TRUNK

INFECTED0

10

20

30

PER

CE N

TAG

E

18

The weevil problem was analyzed in all 57 sampled plantations. Damage was noted on 10.4% of trees. Within the

sample, 41 plantations, or 72%, showed signs of weevil damage. As previously mentioned, the Lower St. Lawrence

region belongs mainly to the moderate-risk susceptibility zone (Boulet 1995), where the percentage of weevil-

infested plantations should range between 21.1% and 40%. It was also noted that 82% of attacked plantations had

less than 20% of their trees affected.

The white pine weevil did not show any clear preference for a specific area of the Lower St. Lawrence region. In the

western part of the region, 76.7% of plantations were affected, with damage being observed on 17.6% of trees, with

a maximum of 78.0% in one specific case. The percentage of plantations affected was lower in the east, at 66.7%,

with damage occurring on 10.5% of trees and the maximum reported, 47.0%. These differences are not significant,

however.

FIGURE 3: INCREASE IN BLISTER RUST DAMAGE

1980 1985 1990 1995 2000YEAR OF PLANTING

0

20

40

60

80

100PE

RC

E NTA

GE

INFECTED TREESDEAD TREES

19

Despite literature stating that the risk of a weevil attack decreases with age (Lavallée et al. 1997), no such trend was

observed in this study. The age of the study plantations ranges from 5 to 19 years old, which may account for why a

similar effect was not observed. In 2001, four times as much damage was recorded as in the previous three years.

This situation may have been related to natural variations in local weevil populations. However, due to the protocol

followed, only the most recent attack was recorded.

Sustained weevil attacks since 1982 are the cause of multiple deformations suffered by white pine trees in

plantations. Based on our inventories, the problem is not that serious, considering that it was only observable in

36.8% of plantations and 1.3% of trees. The deformations observed were in the trunk and not the shoot. They are

also of varying nature.

20

This study allowed us to meet the main objective of Phase 1 of the project, i.e. to describe the state of white pine

plantations in the Lower St. Lawrence region. The results confirm the urgency of implementing an appropriate

strategy to protect and increase the forest capital of this species. Special attention must be given to blister rust,

because it can kill trees. To date, mortality from this disease has been relatively low. However, much higher mortality

rates are anticipated if no sanitary measures are put in place soon. With prompt action, it would be possible to

preserve up to 7% of trees otherwise doomed to disappear. The white pine weevil is also fairly widespread, with

seven in ten plantations being affected in the Lower St. Lawrence region. The extent of the damage remains low.

However, in young plantations, which were not considered in this study, the problem could be more acute. The weevil

situation currently warrants control measures, especially since plantations are virtually impossible to treat once they

are 15 years old.

These conclusions enable us to make a few recommendations concerning a second phase of the project, including a

new inventory and the content of the required strategy:

1.1.1.1. To complete the project, the inventory plan should include sampling in young plantations,To complete the project, the inventory plan should include sampling in young plantations,To complete the project, the inventory plan should include sampling in young plantations,To complete the project, the inventory plan should include sampling in young plantations,

given their high susceptibility to the white pine weevil. This approach will also make itgiven their high susceptibility to the white pine weevil. This approach will also make itgiven their high susceptibility to the white pine weevil. This approach will also make itgiven their high susceptibility to the white pine weevil. This approach will also make it

possible to determine the age at which blister rust sets in;possible to determine the age at which blister rust sets in;possible to determine the age at which blister rust sets in;possible to determine the age at which blister rust sets in;

2.2.2.2. The region would benefit from a decision-support system for integrated pestThe region would benefit from a decision-support system for integrated pestThe region would benefit from a decision-support system for integrated pestThe region would benefit from a decision-support system for integrated pest

management for the white pine. This issue was not included in the initial objectives;management for the white pine. This issue was not included in the initial objectives;management for the white pine. This issue was not included in the initial objectives;management for the white pine. This issue was not included in the initial objectives;

however, future planning could include criteria that would contribute to the developmenthowever, future planning could include criteria that would contribute to the developmenthowever, future planning could include criteria that would contribute to the developmenthowever, future planning could include criteria that would contribute to the development

and validation of such a tool by scientists.and validation of such a tool by scientists.and validation of such a tool by scientists.and validation of such a tool by scientists.

3.3.3.3. Despite incentive measures to encourage sanitary treatments such as pruning, thisDespite incentive measures to encourage sanitary treatments such as pruning, thisDespite incentive measures to encourage sanitary treatments such as pruning, thisDespite incentive measures to encourage sanitary treatments such as pruning, this

intervention is still not very popular. This confirms the need to take various actions tointervention is still not very popular. This confirms the need to take various actions tointervention is still not very popular. This confirms the need to take various actions tointervention is still not very popular. This confirms the need to take various actions to

promote awareness and inform technical personnel and woodlot owners of the existencepromote awareness and inform technical personnel and woodlot owners of the existencepromote awareness and inform technical personnel and woodlot owners of the existencepromote awareness and inform technical personnel and woodlot owners of the existence

of control methods and their use.of control methods and their use.of control methods and their use.of control methods and their use.

CONCLUSION AND RECOMMENDATIONS

21

4. The regional office of the Ministère des Ressources naturelles should notify localThe regional office of the Ministère des Ressources naturelles should notify localThe regional office of the Ministère des Ressources naturelles should notify localThe regional office of the Ministère des Ressources naturelles should notify local

nurseries of the project under way and ask them to increase production of white pine innurseries of the project under way and ask them to increase production of white pine innurseries of the project under way and ask them to increase production of white pine innurseries of the project under way and ask them to increase production of white pine in

order to meet future demand.order to meet future demand.order to meet future demand.order to meet future demand.

The challenge that lies ahead is clearly to develop a strategy that includes ways to prevent both blister rust and

weevil damage. However, there appears to be no precedent to this type of model. The solution lies in combining

preventive and curative measures. Regional priorities will have to be established and then treatments planned in the

light of the differences and similarities in pest cycles during a stand’s life. Until all the required information is

available, genetic improvement and biological control efforts will continue in the Lower St. Lawrence region, as will

efforts to improve sanitary pruning techniques.

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Cahier d’instructions techniques. Version finale 2000-2001. Agence régionale de mise en valeur de la forêt privée duBas-Saint-Laurent. 2000. 37 pages.

Clark, T.D. and A.H. Perera. 1995. An overview of old-growth white and red pine ecology in Ontario. Report no 19.Ontario Ministry of Natural Resources. Forest Research Institute. 2-25.

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L’amélioration génétique en foresterie : où en sommes-nous? 1999. Proceedings of the symposium held in Rivière-du-Loup, September 28-30, 1999. Conseil de la recherche forestière du Québec.

Langelier , J.C. 1884. A sketch on Gaspesia. Joseph Dussault. Quebec. 104 pages.

Lavallée A. 1978. La rouille vésiculeuse du pin blanc. 2nd Edition. Laurentian Forestry Centre. Forestry Service. 8pages.

Lavallée, A. 1986. Les risques d’infection par la rouille vésiculeuse du pin blanc. Laurentian Forestry Centre. ForestryService. Newsletter LFC 23E.

Lavallée, A. 1986. Zones de vulnérabilité du pin blanc à la rouille vésiculeuse au Québec. For. Chron. 62: 24-28.

Lavallée, R. and J. Morissette. 1989. Le contrôle du charançon du pin blanc. Forestry Canada. Laurentian ForestryCentre. Newsletter no 25.

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