TERMINAL WEEVILS OF LODGEPOLE PINE AND THEIR PARASITOID
COMPLEX IN BRITISH COLUMBIA
by
ERVIN KOVACS
B.Sc.(Agr.), University of Kiev, 1983
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
in
THE FACULTY OF GRADUATE STUDIES
(Department of Forestry, Forest Entomology)
We accept this thesis as conforming
to the required standard
(3.0 units)
THE UNIVERSITY OF BRITISH COLUMBIA
April 1988
© Ervin Kovacs, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced
degree at the University of British Columbia, 1 agree that the Library shall make it
freely available for reference and study. I further agree that permission for extensive
copying of this thesis for scholarly purposes may be granted by the head of my
department or by his or her representatives. It is understood that copying or
publication of this thesis for financial gain shall not be allowed without my written
permission.
Department of Forest Sc.lfmf.eB
The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3
Date April 21r1988
DE-6(3/8-n ii
Abstract
A study has been conducted with the objectives of
(1) identifying weevils and their parasitoids emerging from infested lodgepole pine leaders, (2) determining emergence patterns of hosts and their parasitoids, and (3) obtaining further information on the biologies of the terminal weevils and their natural enemies in British Columbia.
The major experiments and biological observations were carried out in young spaced lodgepole pine, (Pinus contorta
Dougl. var. latifolia Engelm.), stands at Ellis creek, near
Penticton, B.C. A total of 1046 infested leaders were collected. One-third of the terminals were dissected and the numbers of weevils and parasitoids at developmental stages were recorded. The remainder of the leaders were set up for individual rearing. Observations were also made on the feeding and ovipositional behavior of the weevils.
Feeding habits of the parasitoids were also studied.
Dissections showed that a few adult weevils emerge in the fall of the year of attack. The majority of adults overwinter as larvae but pupation also may occur prior to winter. In addition, dissections indicated that parasitism plays an important role in larval mortality of weevils. iii
Weevils which emerged in the laboratory were identified as being of the following species: Pissodes terminalis
Hopping, Magdalis gentilis LeC. and Cylindrocopturus sp.
(COLEOPTERA: Curculionidae). M. gentilis is the first weevil species to emerge, in late May. This emergence is
followed by that of P. terminalis from early June through mid-July, while Cylindrocopturus sp. emerges from early June
through mid-July.
P. terminalis attacks the current year's leaders, whereas adult M. gentilis and Cylindrocopturus sp. feed on
foliage. All three weevil species utilize lodgepole pine
terminal shoots for breeding. Larval feeding under the bark almost always results in the death of the terminal.
The terminal weevils have a complex of natural enemies
in British Columbia. Parasitoids belong to six families of
the order Hymenoptera. The pteromalid Rhopalichus pulchripennis Crawford is the most widely distributed parasitoid species in the province. Two species of Eurytoma
(Eurytomidae) ranked second in abundance. Emergence patterns of adult parasitoids are closely synchronized with
that of their hosts. iv
Parasitoids were observed feeding on pollen of flowering weeds in the field. This observation suggests that natural parasitoid populations could be enhanced by cultivating lupin, Lupinus sp., in lodgepole pine stands.
It was concluded that every effort should be made to minimize weevil numbers in order to prevent formation of crooks, forks and stag-heads. Early emergence of
M. gentilis suggests that leader clipping projects should be carried out by early spring. Further research is recommended to ensure correct association between parasitoids and host weevil species and to develop or establish methods for preservation of parasitoids for clipped leaders for release in the forest. V
TABLE OF CONTENTS
PAGE TITLE PAGE i ABSTRACT ii TABLE OF CONTENTS V LIST OF TABLES vi LIST OF FIGURES viii LIST OF APPENDIX xi ACKNOWLEDGEMENT x i i
1. INTRODUCTION 1.1 Current Knowledge 1 1.1.1 The Insects 1 1.1.2 The Host 1 2 1.1.3 Biology of Pissodes terminalis 17 1.1.4. Biology of Maqdalis gentilis 29 1.1.5. Biology of Cylindrocopturus sp. 30 1.2 Objectives of the Study 34
2. METHODS 2.1 Location of the Study 35 2.2 Dissection of Infested Leaders 35 2.2.1. Sampling Techniques 39 2.3 Incubation of Infested Leaders 40 2.4 Direct Observations and Measurements 43 2.5 Data Analysis 45
3. RESULTS AND DISCUSSION 3.1 Summer Collections in 1986 46 3.2 February Leader Collection in 1987 46 3.3 Summer Activities in Penticton in 1987 54 3.3.1 Dissection of Attacked Leaders 54 3.3.2 Individual Incubation of Infested Leaders 62 3.3.3 Observations on the Biologies of P.terminalis 66 3.3.3.1. Longevity and Fecundity of Pissodes terminalis 66 3.3.3.2. Duration of Egg and Pupal Stages of 69 3.3.4.Observations on the Biology of M. gentilis and Cylindrocopturus sp. 71 3.3.5 Parasitoids Associated with the Weevils 81 3.3.6 Adult Parasitoid Food Plant 84 3.3.7 Weevil Attack and Attack History Survey 87
3.4 Management Implications 91 3.5 Other Strategies for Weevil Control 92
4. GENERAL DISCUSSION AND CONCLUSIONS 93 5. RECOMMENDATIONS 94 BIBLIOGRAPHY 95 APPENDIX 100 vi
LIST OF TABLES
TABLE PAGE
I Area infested and losses caused by the Mountain Pine Beetle, Dendroctonus ponderosae Hopkins infestations in British Columbia in 1983-1987 2
II Total number of trees of major species planted 15 on Crown Land in British Columbia in 1984-1986
III Insects recorded as being associated with leaders of young lodgepole pine in western North America 18
IV Parasitic Hymenoptera of Pissodes terminalis 28
V Parasitic Hymenoptera of Cylindrocopturus spp. 33
VI Summary of terminal weevils and parasitoids reared from infested lodgepole pine leaders collected throughout British Columbia in June,1986 47
VII Summary of the insect life stages found in infested leaders of lodgepole pine collected near Williams Lake in February,1987 50
VIII Numbers of terminal weevils and parasitoids reared from infested leaders collected at Riske Creek, near Williams Lake between February 25 and April 2,1987 52
IX Summary table of leaders collected for dissection and incubation in southern British Columbia in May,1987 55
X Insect life stages found during dissection of damaged lodgepole pine leaders collected in southern British Columbia in May,1987 56
XI Summary table of the results of weekly dissection of lodgepole pine terminals attacked during 1987 from Ellis Creek 58
XII Summary table of insects reared from weevil infested lodgepole pine terminals collected at Ellis Creek and along the Big White Road in May,1987 63
XIII Longevity and oviposition characteristics of ten female Pissodes terminalis reared at 20+2°C at UBC 83 TABLE
XIV Hymenopterans found associated with terminal weevils in British Columbia, 1986-1987
XV Results of the weevil attack incidence and attack history survey conducted on a 33ha young spaced lodgepole pine stand at Ellis Creek in July,1987 (n=!088) viii
LIST OF FIGURES
FIGURE PAGE
Crook in the main stem of lodgepole pine 4
2 Lodgepole pine exhibiting fork in the stem 5
3 Replacing the dead terminal by three or more laterals results in formation of a stag-head 6
4 Generalized relationship of growth rate to temperature 11
5 Distribution of P. terminalis and its hosts in North America 1 3
6 Adult Pissodes terminalis on elongating lodgepole pine leader 21
7 Dorsal view of the last abdominal segment of the lodgepole terminal weevil 22
8 Generalized life cycle of P. terminalis on lodgepole pine 24
9 Second instar P. terminalis larva mining beneath the epidermis of the current year's terminal shoot 26
10 Larva (A) and pupa (B) of genus Cylindrocopturus 31
11 Map showing the locations of collections of infested leaders in south-central British Columbia in the summer of 1986 36
12 Locations of the collection plots in the southern interior of British Columbia in the summer of 1987 37
13 Locations of the study and survey plots at Ellis Creek, near Penticton, B.C. 38
14 Mass rearing of infested lodgepole pine leaders in modified seedling boxes. Note emergence jar set into the side of the box at top left 41
15 Individual rearing of infested lodgepole pine leaders in mailing tubes. Note the vial entered into the lower half of the cap 42 ix
FIGURE PAGE
16 Two types of symptoms of infested lodgepole pine leaders by terminal weevils. The terminal still has its apical dominance but its needles have already changed color (A). The terminal is still green but has lost its apical dominance and laterals have caught up with the it (B) 48
17 Emergence of leader weevils and their parasitoids from infested lodgepole pine leaders collected at Riske Creek, near Williams Lake, B.C. in February,1987 53
18 Frequency distribution of headcapsule widths of dead weevil larvae resulted from weekly dissections of infested terminal shoots 60
19 Frequency distributionof headcapsule widths of live weevil larvae resulted from weekly dissections of infested terminal shoots 61
20 Temporal emergence of Magdalis gentilis and Cylindrocopturus sp. from infested lodgepole pine leaders collected in the southern interior of British Columbia in May,1987. Rearing started on May 7,1987 64
21 Temporal emergence of Pissodes terminalis and parasitoids from infested lodgepole pine leaders collected in the southern interior of British Columbia in May,1987. Rearing started on May 7,1987 65
22 Schematic diagram of terminal weevil emergence and oviposition in relation to leader elongation of Pinus contorta 67
23 Survivalship and fecundity of ten Pissodes terminalis females 70
24 Maqdalis gentilis adult on elongating lodgepole pine terminal shoot 72
25 One healthy lodgepole pine needle and 11 needles affected by the feeding of adult M. gentilis. The apical part of the needles have dessicated, discolored and curled up along the longitudinal axis. Apical portion of the last three needles had been broken either by wind or rain 73
26 Ovipositon site made by M. gentilis female in the current year's terminal shoot. Oviposition was at the very base of the needle 74 PAGE
27 Oviposition site made by P. terminalis female into the elongating terminal
28 Cylindrocopturus sp. adult
29 Feeding punctures on lodgepole pine needles caused by Cylindrocopturus sp. adults
30 Lodgepole pine terminal damaged by Magdalis qentilis larvae
31 Lodgepole pine terminal damaged by larvae of Cylindrocopturus sp.
32 Fireweed, Epilobium anqustifolium L. in young lodgepole pine stand
33 Lupin, Lupinus sp. growing in young lodgepole pine stand
34 1985 and 30-year monthly minimum and maximum average temperatures at the Penticton airport
35 1986 and 30-year monthly minimum and maximum average temperatures at the Penticton airport LIST OF APPENDIX
APPENDIX
I Form used for recording insect life stages found during dissection
II Form used for recording emerged specimens from rearing boxes
III Projected field emergence of weevils calculated with three methods of degree-day calculation for different developmental minimum temperatures (TMIN) when the maximum developmental temperature (TMAX) was unknown and set at 30°C
IV Weekly measurements of 25 elongating lodgepole pine leaders ACKNOWLEDGEMENT
I would like to acknowledge the help and criticism received from my supervisor, Dr. J.A. McLean, committee members, Drs. M.B. Isman, and J.W.E. Harris; and Dr. M.A.
Hulme during the research. I also would like to thank the
Forest Research Development Agreement for providing the grant for this research. I would like to express my appreciation to the scientists of the Biosystematics
Research Institute in Ottawa for the identification of the specimens. I dedicate this thesis to my parents who encouraged me during the study; to my Aunt and Uncle, Mrs. and Mr. M. Kovacs who provided financial support for my expenses during my University years. I also would like to thank my friend, Aldo Intrieri for his encouragement I received while at University. 1
1. INTRODUCTION
1.1 Current knowledge
1.1.1 The insects
Lodgepole pine, Pinus contorta Dougl. var. latifolia
Engelm. has become an important component of the annual allowable cut in British Columbia and in 1986 it accounted for 23% of all timber harvested (MOF 1986). Much of the timber was harvested as a result of mountain pine beetle,
Dendroctonus ponderosae Hopk. (COLEOPTERA: Scolytidae), infestations. Mature lodgepole pine stands have suffered enormous losses from attacks by this insect pest throughout the province for the past five years (Table I). In outbreak situations sanitation logging is recommended (Safranyik et al. 1974). The intensive salvage operations have resulted in large clearcuts which are now being regenerated.
Young stands of lodgepole pine are vulnerable to attack by many insect pests (Amman and Safranyik 1984). Among the numerous insects attacking open-grown regeneration, twig weevils, belonging to the family Curculionidae (order
Coleoptera), often cause serious damage to the terminals of young coniferous trees (Keen 1952). In British Columbia, one of the most important twig weevils is the lodgepole terminal weevil, Pissodes terminalis Hopping but other weevils such as Maqdalis gentilis LeConte (Furniss and
Carolin 1977; Wood et a_l. 1987) and Cyl indrocopturus spp. 2
Table 1: Area infested and losses caused by Mountain pine beetle, Dendroctonus ponderosae Hopkins infestations in British Columbia in 1983-1987.
Forest 1983-1987 Region area # of trees volume killed infested killed (million m3) (ha) (millions)
Cariboo 1,063,000 72. 1 21.4 Kamloops 214,410 21.9 11.8 Nelson 107,300 7.5 2.7 Prince Rupert 73,400 4.2 3.6 Prince George 10,225 7.4 0.25
Total 1,468,335 113.1 39.75 1 1983 data are not available 3
(Furniss and Carolin 1977) are also known as damaging agents.
Terminals attacked by P. terminalis change color from a healthy green to a dull brown. Dying and dead leaders are clearly recognizable by early August (Drouin e_t al. 1963).
The loss of the terminal leader results in competition between the laterals in the whorl below the dead leader.
If only a single lateral assumes apical dominance the .stem develops a permanent crook (Fig.1). Sometimes two laterals compete for dominance which results in a fork in the stem
(Fig. 2). If weevil attack reoccurs on the same tree for three or more consecutive years or as a result of a single year's attack, three or more laterals can assume apical dominance, and the tree becomes multi-leadered or stag-headed (Fig. 3). Maher (1982) estimated that every time the terminal is attacked by P. terminalis and the dead leader is replaced by one of the laterals, the tree suffers a 42% height growth loss.
Salman (1935) stated that the impact of Pissodes terminalis on lodgepole pine is similar, in some respects, to that caused by the Sitka spruce weevil, Pissodes strobi
Peck. (Coleoptera: Curculionidae) in eastern white pine,
Pinus strobus L. Marty (1959) indicated two types of losses due to P. strobi attack. The first type of loss is reduction in recoverable volume which is due to formation of Figure 1 Crook in the main stem of lodgepole pine. 5
Figure 2 Lodgepole pine exhibiting fork in the stem. Figure 3 Replacing the dead terminal by three or more laterals results in formation of a stag-head. 7 crooks, forks and stag-heads. The second type of loss is lumber degrade in the remaining volume.
M. gentilis causes damage from California to British
Columbia and in Montana (Keen 1952; Furniss and Carolin
1977). Damage caused by M. gentilis is not restricted to any particular portion of the crown (Fellin and Schmidt
1966) and Fellin (1973) does not consider it to be serious.
Adult weevils puncture the needles with their mandibles and feed on the palisade and other tissues (Fellin 1973).
Sometimes the feeding is so extensive that a hole is punctured through the needle. Distal portions of the needles, in relation to the feeding site, dessicate and discolor (Fellin and Schmidt 1966), and are broken off by wind, rain or snow (Plumb 1950; Fellin 1973). Such injury resembles that caused by the feeding of larvae of
Lepidoptera or Tenthridid sawflies (Plumb 1950). Fellin
(1973) stated that defoliation was the only type of damage he had observed and "there was no indication that adults oviposit nor that larvae feed in or on the shoots or any other portions of the standing tree".
Approximately 35 weevil species described from North
America belong to genus Cylindrocopturus but only a few species have been reported to be of economic importance
(Eaton 1942). Several species in this genus attack the twigs and boles of young coniferous trees, such as pine,
Pinus spp., larch, Larix spp., and true fir, Abies spp. in 8
North America (Buchanan 1940). Weevils cause damage in both the adult and larval stages (Eaton 1942). Excellent accounts of the biology and feeding habits of these weevils are given by Eaton (1942) and Buchanan (1940). Adult weevils puncture the epidermis of the needle and eat the mesophyll tissue. In exceptional cases, defoliation is so extensive that it leads to the death of the whole tree.
Adults also feed on the tissues of the current year's growth. Eaton (1942) pointed out that larval feeding in the stem and twigs would be more serious than feeding by adults on the foliage, because the former was usually followed by the death of the tree.
All the previously mentioned weevil species prefer young, open-grown trees. The impact of these weevils on young stands urges us to make every effort to reduce weevil populations. The only control method currently used against the lodgepole terminal weevil is leader clipping (MOF 1987) followed by immediate burning of infested terminals (McLean,
J.A.1 personal communication). However, clipping is an expensive, time consuming operation and it does not give
100% control. In contrast, losses caused by M. gentilis and
Cylindrocopturus sp. are not considered important (Furniss
1942; Fellin 1973; Furniss and Carolin 1977) and therefore no practical measures have been developed for the control of these weevils. Eaton (1942) and Furniss (1942) suggested
1 Professor of Forest Entomology, University of British Columbia, Vancouver, B.C. 9
some control measures to control Cylindrocopturus species which included destruction of the immature stages of weevils
by removing and burning infested trees, collecting and destroying adult weevils and using concentrated sprays (lead arsenate and cryolite) to prevent attack. In the absence of effective control methods, it seems that natural control will play the most important role in reduction of numbers of
these pests. Natural control includes all physical and
biological factors which have an effect on pest population densities (DeBach 1964). Parasitism is one of the most
important natural mortality factors.
Enhancement of natural parasitoid populations already
present in the environment could lead to reduction in pest
numbers. Greathead (1986) distinguishes manipulations
intended to enhance the impact of natural enemies from the
term "classical biological control" which includes
introduction and establishment of exotic species to suppress
pest populations. Perhaps the knowledge of emergence
patterns of hosts and parasitoids and an understanding of
the phenologies of hosts and their parasitoids could result
in the development of method(s) for enhancing natural enemy
populations. However, emergence patterns of insects reared
artificially in laboratories often do not match those in the
field because development of most organisms is temperature-
dependent (Allen 1976) and the higher temperatures in 10 controlled conditions may cause development of organisms to be unnaturally accelerated.
In 1735, Reaumur attempted to integrate temperature and time into describing poikilothermy of insects and development of plants for the first time (Allen 1976; Higley et al. 1986). Although this approach has been developing ever since, the assumptions of calculating degree-days have not changed (Higley et al. 1986). Allen (1976) stated that
"the most general assumption is that the rate of development is some function of temperature". According to Higley et al. (1986) the relationship of temperature to growth is complex as a result of various temperature-dependent biochemical reactions in organisms, such as the availability of enzymes and their substrates.
Fluctuations in temperature can greatly affect the rate of larval development. Usually, the actual curvilinear relationship between temperature and growth rate (Fig. 4) is calculated as a linear relationship. This approach is acceptable if the considered temperatures are in the linear section of the function (Higley et al. 1986). The type of approximation becomes important when we take the developmental minimum and maximum temperatures into consideration. Techniques for calculating developmental maxima are not precise and most often, they are not determined. Calculations of the minimum and maximum Temperature
FIGURE 4. Generalized relationship of growth rate to temperature (from Higley et a_l. 1986). 12 developmental thresholds are not precise and may make degree-day calculations less accurate.
A common problem is when to begin calculations.
Usually, calculations start when temperatures exceed the lower threshold. However, development of the organism may not occur at this time (Higley et al. 1986). Degree-day estimates include various errors, such as differences between ambient and microhabitat temperatures, or differences between measurements of different weather stations. There are several approaches for calculating degree-days. The rectangle method is the most frequently used method which calculates the area under the time- temperature curve as a rectangle (Arnold 1959), whereas the modified triangle method and sine wave methods calculate the area under the curve on a half-day basis (Higley et al.
1986).
1.1.2 The host
Lodgepole pine is the most widely distributed conifer
in western North America (Fig. 5) where it spans 33 degrees of latitude (Wheeler and Critchfield 1985) from southeastern
Alaska and the interior of Yukon Territory to the Baja peninsula in California (Maher 1982). Its longitudinal
range spans from the North Coast to the Black Hills in South
Dakota (Maher 1982) over 3900m of elevation (Wheeler and
Critchfield 1985). FIGURE 5. Distribution of P. terminalis and its hosts in North America (from Maher 1982). 14
The natural range of lodgepole pine is subdivided into three principal regions: (1) the Pacific coast, (2) the mountain chain comprising the Cascade Range, Sierra Nevada and the high mountains of southern California, (3) the
Intermountain region and Rocky mountain system from the
Yukon to southern Colorado (Wheeler and Critchfield 1985).
Patterns of variation in morphological, physiological and biochemical traits coincide with these major geographic subdivisions (Wheeler and Critchfield 1985). Pinus contorta
Dougl. var. latifolia Engelm. will be referred to as lodgepole pine throughout this study.
In Canada, lodgepole pine grows in three regions:
British Columbia, Alberta and the Yukon (Kennedy 1985), and
in B.C. it accounts for 15% of the the total standing volume of mature timber (McDougal 1973; Kennedy 1985). Lodgepole pine ranked second among tree species planted in British
Columbia in 1984-1986 and was exceeded only by spruces
(Table II).
Lodgepole pine exhibits a large ecological amplitude with respect to climate as is seen from its wide growing
range. This tree species is quite variable in its response
to climatic factors such as wind, humidity and day length.
However, with regard to light, its requirements are quite constant (Satterland 1973). Weetman et al. (1985) stated
that lodgepole pine is not a nutrient demanding tree species 15
Table II. Total number of trees of major species planted on Crown Land in British Columbia in 1984-1986
Total number of trees planted (thousands) Spec ies 1 984- 1985 1985-1986
Engelmann, White Spruce 64, 052 57,832 Lodgepole Pine 25, 289 29,981 Douglas-Fir 15, 840 13,800 Amabalis Fir 2, 635 1 ,381 Western Red Cedar 2, 244 2,385 Sitka Spruce 2, 144 2,082
Source: Ministry of Forestry, Annual Reports 1984-1985, 1985-1986. 16 and it grows well on poor sites but also responds quickly to nitrogen fertilization.
Fire plays an important role in the establishment and
structure of lodgepole pine stands. Brown (1973) stated that in stands dominated by lodgepole pine fire usually
leads to the establishment of pure lodgepole pine stands due to its serotiny. Lodgepole pine readily establishes itself on cutover and burned-over sites (Brown 1973) but it often
reproduces overabundantly (Alexander 1960). As many as
100,000 seedlings may establish per acre (Woodhead 1934) and
Tackle (1959) reported 2.5 million seedlings per hectare.
Rapid rates of juvenile growth help lodgepole pine to
overtop most of competing tree species for the first two-
three decades of its growth (Schmidt and Alexander 1985).
Intensive intraspecific competition for nutrients, water,
light and living space slows the rate of growth in
overstocked stands (Woodhead 1934; Alexander 1960).
Woodhead (1934) pointed out that later natural thinning
takes place which results in the death of less vigorous
trees. However, this natural thinning process is not
efficient in terms of silviculture (Alexander 1960).
Overstocked stands result in reduction in diameter and
height growth (Alexander 1960), total and merchantable
volume, in increased length of rotation and high cost of
harvesting (Johnstone 1985). Effects of overstocked stands 17 can be reduced by juvenile spacing. Precommercial thinning
(spacing) is accomplished through different operational practices which includes chemical, mechanical and selective thinning. Johnstone (1985) indicated that thinning has a direct effect on diameter and height growth of young trees.
Thus spacing is increasingly recognized as important as a silvicultural technique to improve the growth and merchantable yield of dense lodgepole pine stands.
Beside twig weevils, elongating lodgepole pine terminals are susceptible to attack by different insects.
The degree of impact varies from agent to agent. Table III summarizes phytophagous insects damaging young leaders.
1.1.3 Biology of Pissodes terminalis
Hopping (1920) gave a description of Pissodes terminalis for the first time in 1907, when he observed the insect and its damage in young lodgepole pine stands in Kern
County, California. Only three short articles concerning the weevil's distribution, biology and damage (Keen 1928;
Salman 1935; Keen 1952) were published until the early
1960's. Studies on P. terminalis commenced in the early
1960's when Drouin e_t al. (1963) reported the occurrence and life history of the weevil in young stands of jack pine,
Pinus banksiana Lamb., from the prairie provinces of Canada.
Beside the prairie provinces, damage caused by the lodgepole terminal weevil was observed in other parts of Canada, 18
Table III. Insects recorded as being associated with leaders of young lodgepole ptne in western North America
Order Fam i1y Genus/specles Reference
COLEOPTERA Curculionidae P i ssodes radlatae Hopk. Furniss and Carol In ( 1977)
P. term 1 na 11s Hopp. Stark and Wood (1964) Stevens and Knopf (1974) Furniss and Carol in ( 1977) Undgren (1980) Evans (1982). Bella (1985)
Wagda11s h1spo1des LeC. Keen (1952) Furniss and Carol1n (1977) M. gent ills LeC. FelUn and Schmidt ( 1966) Fell in ( 1973) M. 1econtei Horn. Keen ( 1952), Fel11n ( 1973)
Scolyt i dae P i tyophthorus opimus Blm. Stevens (1973) Stevens and Knopf (1974)
LEPIDOPTERA 01ethreut1dae Eucosma sonomana Kft. Grant (1958) Petrova alblcapitana Busck.Furniss and Carol in ( 1977) P. metal 1 lea Busck. Furniss and Carolm ( 1977) Rhyacionia buoliana Sclff. Furniss and Carol in ( 1977) Undgren (1980) 19
including Alberta, British Columbia and the Northwest
Territories (Stevenson and Petty 1968; Bella 1985a, 1985b),
and in the USA, including Oregon and Washington (Stark and
Wood 1964), Colorado and Idaho (Stevens and Knopf 1974) and
California, Wyoming and South Dakota (Furniss and Carolin
1977). Figure 5 shows the distribution of P. terminalis in
North America. Within British Columbia the annual Forest
Insect and Disease Survey (FIDS) has reported weevil damage
from different parts of the province.
Stevens and Knopf (1974) described the egg of P.
terminalis as being sub-globose, having thin, translucent
chorion and measuring 0.5x0.8 mm in size. In 1911, Hopkins
gave a full generic description of the larval form of the
genus Pissodes, but no actual generic diagnosis. He stated
that "all of these characters (i.e. presence or absence of
eyespots, the form and proportion of several anatomical
parts, etc) have not been sufficiently studied to present
them in tabular form for the identification of these
species". Diagnostic features for P. terminalis larvae have
not been published and it is difficult to distinguish them
from other weevil larvae such as those of Maqdalis. In
general, larvae of P. terminalis are creamy white in color
and have tan head capsules and lack abdominal prolegs (Maher
1982). Fully developed larvae tend to be longer than adults
by approximately 1-3 mm (Stevens and Knopf 1974). 20
Pupae are creamy white (Stevens and Knopf 1974), or white
(Duncan 1986), are approximately the same size as the adult, and bear a prominent snout.
Adult weevils are easily recognizable from their prominent rostrum with a pair of clavate antennae. Length of adults ranges from 5.5 mm to 6.3 mm (Hopping 1920). The weevils are mottled yellowish-brown (Stevens and Knopf 1974)
(Fig. 6). The pronotum is gradually restricted anteriorly.
The anterior part of the elytra is covered with yellow scales, whereas there is a more or less fused posterior band of white and yellow scales near the vertex of the declevity.
These white bands also extend across the median portion of the femora of both the mid and legs (Hopping 1920). Adult males and females of genus Pissodes can be separated by different characteristics (Hopkins 1911). The most convenient and most precise way to separate the sexes is by examination of the seventh and eighth abdominal tergites after removing the elytra and membranous hindwings. In males there are eight visible abdominal tergites; the seventh is distinguished by the broadly retuse posterior margin, while the eighth tergum is prominent with the apex rounded (Fig. 7). In females there are only seven visible abdominal tergites, -the eighth being completely covered by the seventh (Fig. 7) (Hopkins 1911). Hopkins (1911) mentioned other distinguishing characteristics between males and females as well. According to him, the rostrum of the male is stout, shorter, less shining and more distinctly Figure 6 Adult Pissodes terminalis on elongating lodgepole pine leader. 9
A A
)
FIGURE 7: Dorsal view of the last abdominal .segment of the lodgepole terminal weevil. 23 punctured, whereas in the female the beak is longer, smoother and more slender than in males. The inner apical tooth of the tibiae is usually more prominent.
Chromosomal polymorphism also exists between males and females of genus Pissodes which was documented by Manna and
Schmidt (1958) and then by Smith and Takenouchi (1969).
Stark and Wood (1964) reported that there are considerable differences in the life history of P. terminalis on jack pine in the prairie provinces of Canada and on lodgepole pine in California. Since the natural range of jack pine did not include the study areas the following description will deal only with P. terminalis populations attacking lodgepole pine. When the host is lodgepole pine the life cycle of the weevil is completed in one year.
In the genus Pissodes the lodgepole terminal weevil is the only species which "consistently lays its eggs into the developing terminal" (Stark and Wood 1964). Consequently, the life of the weevil must be synchronized with the phenology of the terminal shoot. Adult weevils emerge presumably from hibernation sites in the ground (Stark and
Wood 1964) and infested leaders from late April to late June
(Fig. 8). Adult emergence is followed by maturation feeding during which weevils feed on the phloem of elongating terminals. After mating the female excavates a cylindrical ovipositional puncture into which it deposits up to three 24
FIGURE 8. Generalized life cycle of P. terminalis on lodgepole pine (from Price 1980) 25 eggs (Drouin et al. 1963) and then seals the hole with foecal pellet (Stark and Wood 1964). The tissue surrounding the puncture is characterized by purple-brown discoloration.
Oviposition occurs on the main stem of the current year's terminal growth which makes P. terminalis unique in the genus in terms of oviposition.
Eggs hatch within two weeks (Stevens and Knopf 1974) and first instar larvae begin random mining under the epidermis. Second instar larvae are characterized by negative geotropism (Drouin et a_l. 1963) as they mine toward the apical bud (Fig. 9). As a result of rupturing resin ducts larval feeding tunnels fill with resin and these areas become purplish (Stevens and Knopf 1974). The spiral fashion of feeding in the cambium region kills the current year's leader. Later instars move into the pith and continue tunneling. Larvae reach maturity during the fourth instar. Fall temperatures affect larval development and they might pupate and adults even emerge and overwinter probably in the duff. However, the majority of the weevils overwinter in the pith as larvae and complete their development and pupate in the following spring (Stevens and
Knopf 1974) (Fig. 8).
Different factors contribute to weevil mortality throughout the life cycle of the weevil. High mortality from drowning in resin occurs among early larval stages when larvae rupture resin ducts of the elongating leader while 26
Figure 9 Second instar P. terminalis larva mining beneath the epidermis of the current year's terminal shoot . 27 attempting to establish feeding sites (Drouin et a_l. 1963).
Another factor which contributes to high larval mortality is parasitism, especially among early instar larvae (Stark and
Wood 1964). Maher (1982) stated that weevil mortality is greatest during the larval and pupal stages. When later instar larvae move into the pith, the role of parasitism decreases and starvation plays an important role in reducing larval survival. Sometimes 5-6 larvae enter the pith and there may not be sufficient food for all larvae to complete their development. This results in starvation and death.
Although Finnegan (1958) reported 90% predation of Pissodes approximatus Hopkins (Coleoptera: Curculionidae) by the downy woodpecker, Dendrocopus pubescens medianus (Swainson), the role of bird predation in regulating P. terminalis populations has not yet been determined.
Some parasitism also occurs during the pupal period. A list of parasitoids associated with the lodgepole terminal weevil is presented in Table IV.
There are insects, other than parasitoids found in association with P. terminalis. Stevens (1973) found a small scolytid beetle, Pityophthorus opimus Blackman
(COLEOPTERA: Scolytidae) living commensally with the weevil.
P. opimus utilizes portions of the phloem and xylem of the terminal after it starts to dessicate as a result of weevil activity. Stevens (1973) collected three species of parasitic Hymenoptera from P. opimus galleries:
Acerocephala atroviolacea Cwfd. (Pteromalidae), Eurytoma Table IV. Parasitic Hymenoptera1 of Pissodes terminalis
Order/Family Spec ies
HYMENOPTERA BETHYLIDAE Cephalonomia (?) hyalinipennis
BRACONIDAE Brachistes sp. Bracon pini Mues. Eubadizon strigitergum (Cushman) Tr iaspi s pi ssodes Viereck
EULOPHIDAE Tetrastichus sp.
EURYTOMIDAE Eurytoma piceae Bugbee Eurytoma pi ssodes Girault Eurytoma sp. nr. cleri
ICHNEUMONIDAE Dolichomitus terebrans nubilipennis Vier Helcostizus subrectus Townes
PTEROMALIDAE Habrocytus sp. Mesopolobus sp. Rhopalichus pulchripennis (Cwfd.)
1 From Stark and Wood (1964), Stevenson and Petty (1968), Stevens and Knopf (1974). 29
tomici Ashmed (Eurytomidae) and Rhopalichus pulchripennis
Cwfd. (Pteromalidae). The latter two species are also
parasitoids of P. terminalis (Table IV).
1.1.4. Biology of Magdalis gentilis
The genus Magdalis includes 25 species in Europe but
only fragmentary information is available about their
biology and economic importance in the literature (Bukzeeva
1965). Although a few collections of Magdalis spp. had been made prior to 1963, there were no records that any species
of this genus had caused any significant amount of damage in
the Northern Rocky Mountains (Fellin 1973). The first
significant damage caused by M. qentilis LeC. was recorded
in the Lewis and Clark National Forest in west-central
Montana in 1965 (Fellin and Schmidt 1966). This weevil
occurs from California to British Columbia and Montana
(Furniss and Carolin 1977). Hosts of the weevil include
ponderosa pine, Pinus ponderosae Dougl., Jeffrey pine, Pinus
jeffreyi Greville and Balfour (Furniss and Carolin 1977),
and lodgepole pine (Fellin and Schmidt 1966).
Beside its damage, M. qentilis has not been studied in
detail and there is no available information on its biology
or life cycle in the literature. Generic diagnostic
features of adults and larvae also have not yet been
described. The literature also lacks information on
insects, such as parasitoids, associated with this weevil. 30
1.1.5. Biology of Cylindrocopturus spp.
The genus Cylindrocopturus is widely distributed in western North America. Different representatives of the genus can be found from Alberta and British Columbia to
Washington and California and from Oregon to Montana
(Furniss and Carolin 1977). Hosts include many species of pines but weevils also attack Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Furniss 1942; Eaton 1942; Furniss and Carolin 1977).
Eggs are ovoid (Furniss 1942) or pear-shaped (Eaton
1942) and 0.48mm long and 0.30mm wide (Furniss 1942; Eaton
1942). Fine diagnostic features of larvae of
Cylindrocopturus were given by Anderson (1941). He described the larva (Fig. 10) as stout, curved and cylindrical. Approximately one-half of the head is retracted into the prothorax and its anterior part contains a few setae. The posterior half of the prothorax contains many asperities which make this part conspicuous. The color of the body ranges from white to cream-colored depending upon the age of the larva (Eaton 1942), and the body length varies between 3.0-3.5mm (Furniss 1942). The pupa (Fig.
10), is cream-colored as are mature larvae but slightly
longer than the adult.
Adults are covered with light and dark scales which makes them appear gray in color. Length of males and 31
FIGURE 10. Larva (A) and pupa (B) of genus Cylindrocopturus (from Anderson 1941). 32 females ranges from 2.5mm to 2.6mm (Eaton 1942; Furniss
1942). Eaton (1942) gave some external distinguishing characters which separate males and females: "the most reliable character is the median impression of the first visible abdominal sternite". This sternite is strongly impressed in the centre in the males while it is "convex and only slightly flattened in the females".
Different species of the genus emerge at different times from May through August (Furniss 1942; Eaton 1942;
Furniss and Carolin 1977). After some maturation feeding the female oviposits a single egg into each ovipositional puncture and seals each with a faecal pellet. Oviposition occurs in stems and branches. When eclosion occurs larvae start feeding which results in girdling of the branches. As larvae age, feeding tunnels run together and the entire phloem-cambium region is destroyed (Eaton 1942). Most of the larvae overwinter in the wood and pupation takes place the following spring.
Parasitism of Cylindrocopturus spp. occurs throughout their life cycle. A list of insects associated with these weevils is presented in Table V. 33
Table V. Parasitic Hymenoptera1 of Cylindrocopturus spp.
Order/Family Spec ies
HYMENOPTERA BRACONIDAE Dendrosoter scaber Mues. Microbracon pini Mues. Microtonus n. sp. Urosigalphus pini Cush.
EULOPHIDAE Euderus argyresthiae (Cwfd.) Euderus subopaca (Gahan) Tetrastichus sp.
EUPELMIDAE Euphelmella vasicularis (Retz.)
EURYTOMIDAE Eurytoma tomici Ashm.
ICHNEUMONIDAE Calliephialtes comstockii (Cress.)
PTEROMALIDAE Amblymerus near verditor (Nort.) Caenacis sp. Cecidostiba dendroctoni Ashm. Rhopalichus pulchripennis Cwfd.
SCELIONIDAE Telenomus sp.
TRICHOGRAMMATIDAE Zagella sp.
1 From Eaton (1942) and Furniss (1942). 34
1.2 The major objectives of the present study were:
1. To determine the insects infesting lodgepole pine
terminals.
2. To identify emerging parasitoids from infested
lodgepole pine leaders in British Columbia.
3. To determine weevil and parasitoid emergence
patterns from infested lodgepole pine leaders in
order to evaluate leader clipping strategies to
minimize weevil numbers and enhance natural
parasitoid populations. 35
2. METHODS AND MATERIALS
2.1. Location of the study
In 1986, locations of the preliminary studies were chosen on the basis of annual reports of those Forest
Regions where lodgepole terminal weevil attacks had been reported by the Canadian Forestry Service's Forest Insect and Disease Survey (FIDS). Samples of infested lodgepole pine terminals were collected from six locations in south central British Columbia (Fig. 11). One third of these infested leaders were dissected and the remainder were set up for mass rearing in waxed seedling boxes at UBC. Based on the results of the rearing experiment, sampling plots were chosen at Riske Creek, 80km west of Williams Lake in
February,1987. The 1987 summer research was carried out in the southern interior of British Columbia (Fig. 12-13).
This study was supported by the availability of the
facilities of the Agriculture Canada Research Station in
Summerland (Fig. 12).
2.2. Dissections of infested leaders
One third of the collected leaders from each site were dissected in the laboratory using a dissecting microscope. The 1987 winter dissection was carried out to:
- determine overwintering stages of the weevils and
parasitoids. Figure 11. Map showing the locations of collections of infested leaders in south-central British Columbia in the summer of 1986.
u> FIGURE 12. Locations of the collection plots in the southern interior of British Columbia- in the sur.rr.er cf 19B7. 38
) 4u
\
.'X418 \
•' { i
v v 428
"slash i _ —. I -.T. r,r^
(-<3^ r i 209
road !
) /
/ / /
Figure 13. Locations of the.study and survey plots at Ellis creek, near Penticton, B.C. 39
The 1987 summer dissections aimed to:
- determine the overwintering success of weevils
and parasitoids, and
- monitor the development of host weevils and their
parasitoids.
2.2.1. Sampling techniques
The 1987 summer dissection included weekly collections and dissections of current year's terminals showing symptoms of weevil attack. Six randomly chosen infested leaders were collected weekly from June 5 to June 30,1987 followed by 10 leaders weekly between July 8 and Sept. 30,1987. There were insufficient infested terminals at the beginning of the study to collect 10 leaders every week. As emergence of adult weevils continued, the number of attacked terminals increased which allowed the collection of 10 infested terminals/week. Infested leaders were clipped with a hand pruner and taken back to the laboratory where they were dissected.
A special data form was created for this dissection on which leader length, basal and apical leader diameter, number of weevil and parasitoid emergence holes, and all host and parasitoid developmental stages were recorded
(Appendix I). All data were grouped according to the type of dissection (May dissection or weekly dissection of 40 current year's attacks). Totals were summed for presentation in Tables.
A 33ha young, spaced lodgepole pine stand (site 209,
Fig. 13) was surveyed for weevil attack incidence and attack history. A systematic sampling system was used in the survey. The distance between the transect lines was 15m and a tree was sampled at 10m intervals along the transect line.
If there was no tree at the 10m point, the closest tree within a 5m radius was chosen for sampling. If two trees were equally far from the 10m sign a coin toss was used to decide which tree would be sampled.
2.3. Incubation of infested leaders
Two thirds of the collected attacked terminals from each site were set up for either mass or individual rearings in modified waxed seedling boxes (Fig. 14) and paper mailing tubes (Fig. 15), respectively. A small jar or vial was inserted into the upper half of each box (Fig. 14) or into the lower half of one of the caps of the mailing tubes (Fig.
15). Boxes and tubes were kept at room temperature and emerging specimens were collected and recorded daily.
Emerged specimens were kept either in 70% alcohol or were pinned. Pinned specimens were sent to the Biosystematic
Research Institute in Ottawa for identification. A collection of pinned specimens is maintained in the Forest
Entomology laboratory of the Faculty of Forestry at UBC. 41
Figure 14 Mass rearing of infested lodgepole pine leaders in modified seedling boxes. Note emergence jar set into the side of the box at top left. 42
Figure 15 Individual rearing of infested lodgepole pine leaders in mailing tubes. Note the vial entered into the lower half of the cap. 43
Rearings and leader elongation measurements aimed to compare the relationship between weevil emergence patterns and leader phenology. Twenty-five lodgepole pine trees were randomly chosen on site and marked with red plastic ribbons.
A number was assigned to each ribbon so that measurements could be taken from the same trees repeatedly. Leader elongation was measured and recorded every 7 days.
Rearings also helped to:
- describe emergence patterns of the weevils and their
associated parasitoids from infested lodgepole pine
leaders,
- provide specimens for identification,
- describe the relationship between host and parasitoid
phenologies.
2.4. Direct observations and measurements
Direct observations were carried out in the field and in the laboratory to:
- obtain a better understanding of the biology of the
weevils by observing feeding habits, oviposition and
damage caused by different weevil species,
- obtain information on the feeding habits of the
parasitoids, and
- measure the longevity and fecundity of P. terminalis. 44
Ten pairs of P. terminalis adults were placed in 0.5 L
jars covered with cheese cloth and kept at room temperature
(20+2°C). Each day a 10-cm-long section of lodgepole pine
terminal was placed in each jar. The leaders were kept in plastic bags in a refrigerator until used. Diameters of the
removed terminals were measured at mid-point and the number
of needle fascicles counted. Numbers of feeding punctures and oviposition sites were counted with the aid of a
dissecting microscope. Oviposition sites were opened and
the number of eggs per site counted and recorded.
Direct observations also included measuring the
duration of the egg stage of P. terminalis. Incubation was
determined only for those eggs which were kept under
laboratory conditions. Sections of current year's terminal
growth with oviposition sites were obtained from the
longevity and fecundity experiment described earlier.
These leader sections were placed on moist (but not wet)
paper towels in paper boxes which were closed and kept at
room temperature. Dessication of leaders was prevented by
moistening the paper towels in the bottom of the boxes
daily. Eggs were checked daily under a dissecting microsc•
ope in order to record hatching of the eggs. After
examination, oviposition sites were closed to prevent
dehydration of eggs. Date of oviposition and date of
hatching were recorded. Widths of head capsules of newly 45 hatched larvae were measured using an ocular micrometer in a dissecting microscope.
Observations were also carried out to measure the pupal
period of P. terminalis. Twenty weevil larvae were obtained from the May dissection. Each larva was kept in a separate numbered petri dish. Dates of pupation and adult emergence were recorded for all 20 larvae.
2.5. Data analysis
Incubation of infested leaders in the laboratory accelerated the development and emergence of weevils and parasitoids. To calculate the number of accumulated degree- days, a degree-day program, (DEGDAY) (Higley et al. 1986) was used. The program calculated the number of heating degree-days using the rectangle, triangle and sine-wave methods. Minimum developmental threshold temperatures,
(TMIN) for the weevils are not known, so heating degree-days were calculated for arbitrarily chosen TMIN values
(TMIN=4,5,6,7 and 8°C). The maximum developmental threshold temperature, (TMAX) was unknown and when TMAX was also unknown and DEGDAY allowed for an "unknown" setting and it was also run with TMAX=30°C. The program was run on an IBM-
AT personal computer at UBC. 46
3. RESULTS AND DISCUSSION
3.1. Summer collections in 1986
A total of 1100 infested leaders were collected throughout the province in June,1986. Incubation of infested terminals showed that beside the lodgepole terminal weevil, another weevil, Magdalis gentilis, is also present in the Prince George and Williams Lake areas (Table VI).
3.2. February leader collection in 1987
As a result of high weevil attack incidence and easy availability, infested terminals (335) were collected at
Riske Creek, near Williams Lake in February,1987. Two types of symptoms of weevil attack were observed during collecting. Figure 16A shows an infested terminal which still has its apical dominance but its needles are dead and had changed color to dull brown. In Figure 16B the terminal is still green but it has lost its apical dominance. This observation suggests that this terminal grew slowly after the attack and the laterals had a chance to catch up with the terminal. If the attack is not heavy or larvae had been successfully pitched out the terminal manages to maintain its moisture content and it remains green but its growth is slowed down. This raises the question, "Does each symptom specifically result from one of the weevil species?" To 47
Table VI. Summary of terminal weevils and parasitoids reared from infested lodgepole pine leaders collected throughout British Columbia in June,1986
Location P. terminalis M. gentilis Parasites
Prince George 6 1 56 Penticton 418 19 — 3 Penticton 421 4 2 Kelowna 14 - 31 Kamloops 1 3 - 13 Kamloops 2 1 —- 18 Williams Lake 1 4 1 15 Williams Lake 2 1 1 Merritt -— —- 19
Total 51 2 168
< 48
A B
Figure 16 Two types of symptoms of infested lodgepole pine leaders by terminal weevils. The terminal still has its apical dominance but its needles have already changed color. (A). The terminal is still green but has lost its apical dominance and laterals have caught up with the it (B). 49
test this hypothesis, infested leaders exhibiting either of
these symptoms would need to be reared individually.
Drouin et al. (1963) reported that needles of terminal
shoots attacked by P. terminalis changed color and were clearly recognizable by early August. In the current study
it was observed that needles of attacked leaders turned brown (with a few exceptions) only in January-February of the following year. In August, identification of dying terminals was possible only by close examination of the terminals.
Results of dissections are summarized in Table VII. It
is not known which weevil species completed its development and emerged in the previous fall leaving the four emergence holes. Weevil larval mortality ranged from 54% to 60% on the three sites. As diagnostic features of the larvae of P. terminalis and M. gentilis were not available it was not possible to determine the ratio of the live and dead larvae of the two species. Advanced decay of the two dead pupae
indicated that these pupae must have died in the previous
fall. The majority of the weevils overwintered as larvae
rather than as pupae.
Incubation of infested lodgepole pine terminals was very successful. Only one dead P. terminalis adult was
found in one of the boxes after the rearing had finished. 50
Table VII. Summary of the Insect life stages dissected from Infested leaders of lodgepole pine collected from stands on the Palmer Lake Road, Riskle Creek, near Will1ams Lake In February 1987 .
5 LocatIon Number of Emergence Weevil life Paras 1 to Id life stages stages leaders holes1 dissected W P adult pupae 1arvae adult pupae 1arvae L D L D L D L D L D L D
15km left 36 1 2 30 40 - -
15km right 27 - - 24 29 - -
21km right 50 4 1 3 30 42 4 1-1 -
1 W = weevil , P = parasitoid 2 L = 11ve, D = dead 51
Fifty three M. gent ilis and only two P. terminal is adults emerged from the boxes (Table VIII). The first weevil species to emerge was M. genti1is (Fig. 17). Emergence started on March 16,1987 (20 days after rearing was initiated on February 25,1987) and finished on March
23,1987. The two P. terminalis adults emerged 23 days after
M. gentilis had completed its emergence (Fig. 17). As a result of incubation of infested leaders at room temperature emergence of the weevils was accelerated compared to that in the field but the number of accumulated heating days has not been calculated.
Many parasitoids were also reared (Table VIII).
Samples were dominated by the ectoparasitoid Rhopalichus pulchripennis Crawford (HYMENOPTERA: Pteromalidae) and the endoparasitoid Allodorus sp. (HYMENOPTERA: Braconidae), and to a lesser extent by two species of eurytomids. Figure 17 shows the emergence patterns of the parasitoids. All species, except the eurytomids, started emerging on March
17,1987, after 21 days at 20°C. Allodorus sp. finished its emergence within 8 days but R. pulchripennis and the eurytomids emerged until April 10,1987. Delomerista japonica Cushman (HYMENOPTERA: Ichneumonidae) was also present on the sites. 52
Table VIII. Numbers of terminal weevils and parasitoids reared from leaders of lodgepole pine collected from stands on the Palmer Lake Road. Rlske Creek, near Williams Lake, between February 25 end April 2,1987.
Locat ton Number of Number of specimens reared leaders P. terminal is M. qentilis Parasitoids reared
15km left 521+102 1 6 2
15km right 501*102 - 33 3
21km right 901-M02 1 14 11
1 number of leaders set up for mass rearing 2 number of leaders reared individually Figure 17 Emergence of leader weevils and their parasitoids from infested lodgepole pine leaders collected at Riske creek, near Williams Lake, B.C. in February,1987. 54
3.3. Summer activities in Penticton in 1987
3.3.1. Dissections of attacked terminals
The research was continued in Penticton between May
4,1987 and Sept. 30,1987. During this study a total of 1046 infested terminals showing symptoms of weevil attack were collected on 12 sites at Ellis creek (Fig. 13) and on two sites along the Big White Road. Of the 1046 leaders collected, 309 were dissected and 737 were set up for individual rearing (Table IX). Results of the dissections are summarized in Table X. These dissections showed that M. gentilis is present also in the southern Interior of British
Columbia.
It was not known which weevil species left the four emergence holes, therefore adult mortality could not be determined. However, it was noted that one terminal collected on site 120 near Kelowna contained seven live and one dead adult and one live larva of M. gentilis. This indicates that high numbers of M. gentilis are able to survive in a single terminal which can lead to high weevil attack incidence.
When individual incubation of infested terminals was completed at the end of July, reared leaders were dissected to check the success of rearing. In the 737 dissected leaders 11 dead P. terminalis adults, 17 live 55
Table IX. Summary table of leaders collected for dissection and rearing in Penticton and Kelowna in May,1987
Number of leaders collected Site for dissection for rearing
6 5 - 10 - 15 32 24 51 34 10 17 36 30 61 71 40 82 414 29 90 418 north 40 62 418 south 22 47 421 1 1 23 428 46 1 03 114 (Kelowna) 19 47 120 (Kelowna) 15 49 road 18 70 slash - 20 Total 309 737 Table X. Insect lire stages found during dissection of damaged lodqepole pine leaders collected In Penticton and Kelowna in May,1987
Weevil life stages Parasitoid Emergonce Site adult pupae 1arvae mortality adult pupae larvae _ holes L D L D L D 1t W Pa
6 - - - - - 6 75. 0 - - 1 2 - 32 - - - - 10 18 64, 3 - - 3 - - 34 - - - - 4 4 44 . 4 - - 1 1 - 3S - - - - 16 19 54, 3 - 1 2 - - 71 - - - - 18 15 45.. 5 - - - - 4 14 - IP - - 5 16 66.. 7 - 1 - 2 - 4 18 north - - - - 8 18 60.. 0 - 3 1 4 - 4 18 south - 3P - - 3 11 50. 0 - 2 - 5 2 421 - - - - 5 6 46. 1 - - - 2 - 428 - IP - - 9 35 77. 7 - 3 12 - - 114 Kelowna - 2P - 1 8 24 68. 6 2 1 - - - 120 Kelowna 1M t - 3 12 48. 0 - 1 - 1 1 road - - - 1 2 9 75. 0 - 2 - 1 2
Total 7M 7P 1 2 91 195 60 .5 2 15 22 IB 5 1M
1 L • 11 vs, 0 • dead. P " P- terminal 13, M - M. aentIlls 2 w « weevil. Pa • parasitoid 57
Cylindrocopturus sp. larvae, 768 dead weevil larvae, 4 dead
weevil pupae, 17 dead parasitoid adults and 23 live and 17
dead parasitoid pupae were found. Weevil larval mortality
was 75% which is much higher than that found in the May,1987
dissection (Table X). This high larval mortality might be
the result of high temperatures and low air humidity in the
laboratory which led to rapid dessication of the leaders.
The room temperature averaged 23^C during the rearing.
Humidity of the air was not measured.
It was interesting to note that 23 live parasitoid
pupae were still in the leaders. This raises the following questions, "Do these parasitoids overwinter for a second
year or do they emerge later in the current year? If they
emerge later what are they going to feed on?". These
parasitoid pupae were kept in petri dishes at room
temperature but by the end of September only three
R. pulchripennis, one Mesopolobus sp. and two
D. japonica emerged. The rest of the pupae dehydrated and
died.
Weekly dissections of current year's attacks started on
June 5,1987 which showed the development of the weevils
during the summer. Table XI shows the results of these
dissections. As a result of the weevil complex the relative
numbers of larvae of the different weevil species is unknown
but this data still provides some insight into the 58
Table XI. Summary table of the results of weekly dissection of lodgepole pine leaders attacked at Ellis creek during the summer of 1987
Number of Number of Eggs* Larvae Pupae Adults Date feeding oviposition punctures s 1 tes L D P L D P L D P L D
June 5 6 44 27 c c c 10 6 90 48 43 - 7 - - - - - 16 6 84 76 55 6 14 - - - - - 23 6 90 48 19 10 17 2 30 6 46 39 3 11 19 6 July 8 10 129 81 33 18 24 6 14 10 ?d 7d 1 4 30 7 22 10 10 47 10 29 10 12 18 22 2 Aug. 5 10 7 45 6 1 12 10 21 9 1 19 10 17 2 26 10 16 2 Sept.2 10 19 3 3 9 10 17 2 5 17 10 22 6 3 1 - - 23 10 26 2 4 1 - - 30 10 17 3 8 - - 1 a number of leaders collected b L=live. D=dead, P=parasitized c number of eggs was not counted d it was not possible to identify the feeding punctures after July 8., 1'987. 59 development of the weevils. Extensive resin flow and larval mining made counting the number of feeding punctures and oviposition sites impossible after July 8,1987. The last live egg was found on July 14,1987. It was not possible to determine how many live eggs were attacked by egg parasitoids. An egg was considered dead if it appeared greyish or the chorion was wrinkled.
The mean number of larvae per leader (160 leaders dissected) was 3.4 (S.D.=2.79, range=1-17). Stark and Wood
(1964) dissected leaders (n=305) collected in lodgepole pine stands infested by P. terminalis only. They found 4.2 larvae per leaders (range=1 - 19) .
Headcapsule widths of dead and live larvae (n=115 and 376, respectively) obtained from the dissections were measured.
The frequency distributions are presented in Figs. 18-19.
Stark and Wood (1964) measured the headcapsule widths of the four instars of P. terminalis and the arrows (Figs. 18-19) designate the mean headcapsule width of each instar measured by them. The slight differences in the measurements in the two experiments also indicate the presence of the terminal weevil complex in Penticton. 60
12 16 20 24 28 32 36 40 44 46 52 micrometer divisions
Figure 18 Frequency distribution of headcapsule widths of dead weevil larvae resulted from weekly dissections of infested terminal shoots ( 1 micrometer division = 0.025mm). 61
12 16 20 24 28 32 36 40 44 48 52 micrometer divisions
Figure 19 Frequency distribution of headcapsule widths of live weevil larvae resulted from weekly dissections of infested terminal shoots ( 1 micrometer division - 0.025mm). 62
3.3.2. Individual incubation of infested terminals.
Numbers of accumulated degree-days were calculated
(Appendix III). Since the lower developmental thresholds of
the weevils are unknown the exact number of accumulated degree-days cannot be determined. Therefore all emergence dates throughout this study represent emergence dates in the
laboratory.
Individual rearing, which started between
May 7-11,1987 , revealed that, beside P. terminalis and
M. gentilis, a third terminal weevil species from the genus
Cylindrocopturus is also present in the Penticton area
(Table XII). The first weevil species to emerge was
M. qentilis which started emerging on May 12,1987 and
finished seven days later, on May 19,1987 (Fig. 20). The
rapid emergence of M. gentilis was similar to that recorded
from the earlier Williams Lake rearings (Fig. 17).
Cylindrocopturus sp. emerged between June 9,1987 and
July 9,1987 (Fig. 20). Although the pattern of the
emergence was scattered it suggests that the majority of
the adults emerge in the first two weeks of July or later
allowing for elevated rearing temperatures. On June 3,1987
(30 days in rearing) P. terminalis started to emerge and
reached its peak on June 7,1987 (34 days in rearing) (Fig.
21). Emergence continued until July 7,1987. 63
Table XII. Summary table of insects reared frore weevil infested lodgepole pine leaders collected on Cartni Road at Ellis Creek and on the Big Wnite Road in May,1987
Number of Site leaders P. terminal is M. gent 111s Cylindrocopturus sp. Parasitoids reared
10 15 - 1 - 2 32 51 6 5 6 9 34 17 - 3 - 4 36 61 8 - - 12 71 82 4 1 3 6 4 14 90 8 2 - 13 418 north 62 3 5 - 13 418 south 47 - - - 13 421 23 - 5 - 8 428 103 6 2 - 14 1 14 47 10 - - 10 120 49 7 7 - 15 road 70 7 - - 7 slash 20 - - 3 1
Total 737 59 24 12 127 10
9 -
8 -
7 -
6 -
5 -
4 -
3 -
1 -
' I i »» • I i i i » I i i i i I i i i i'|'i i i i | i i i i | i i i I ' '1 ' 4 9 14 19 24 29 34 39 44 49 54 59 64 69
DAYS IN REARING AT 20*C V~7\ MAGDAUS GENTILIS CYUNDROCOPTURUS SP
FIGURE 20: Temporal emergence of Magdalis qentilis and Cylindrocopturus sp. from infested lodgepole pine leaders collected in the southern interior of British Columbia in May,1987. Rearing started on May 7,1987. o V) C 15 ™™HJ^^ terminalis 0 R. pulchripennis 10 D. terebrans Eurytoma spp. 2 D D n-n /Allodorus sp. U_U_D D LMesopolobus sp.
D. japonica Hyssopus sp. 0 1 i 1 1 1 1 i 1 1 1 1 i 1 1 1 1 i 1 1 1 1 i 1 1 1 1 i * 1 1 1 i • 1 • 1 i 10 15 20 25 30 35 40 45 50 55
Days in Rearing at 20 °C
Figure 21 Temporal emergence of Pissodes terminalis and parasitoids from infested lodgepole pine leaders collected in the southern interior of British Columbia in May,1987. Rearing started on May 7,1987. 66
Since females oviposit into the elongating terminal shoot, leader elongation is critical for successful oviposition. Measurements were taken from 25 elongating lodgepole pine leaders. Elongation began at the beginning of May,1987. Although a slight increase in leader length occurred in mid-August, terminal growth was practically completed by early August,1987 (Fig. 22) (Appendix IV). The period of rapid leader elongation is the period when the epidermis is the most vulnerable to insect feeding.
Figure 20 shows the emergence of the terminal weevils in relation to tip elongation. It is clear that weevil emergence coincides with leader elongation.
3.3.3. Observations on the biologies of P. terminal is
3.3.3.1. Longevity and fecundity of Pi ssodes
terminal is
Longevity and fecundity of 10 female P. terminalis were determined. Average longevity of females was 112.8 days; one female lived for 226 days (Table XIII). It was observed that female P. terminalis are able to lay eggs as soon as 2 days following emergence and therefore do not require longer maturation feeding. In this study, the preoviposition period averaged 10.1 days (S.D.=+6.8, range=2-22 days). Oviposition began on day 2 and thereafter increased until day 21, declined to about two-third its peak overwintering LARVAE/pupae/adults
adult emergence 1 1 dispersal to new oviposition terminals c I 1 overwintering LARVAE/pupae/adults i
Leader O * lOOr-
Cn c 5 3 B 50
0 « * o Bud Elongation of the terminal of P. contorta.
Jan Feb Mar Apr May Jun Jul Aug Sep. Oct Nov, Dec
Figure 22: Schematic diagram of terminal weevil emergence and oviposition in relation to tip elongation of Pinus contorta. Table x111 . Longevity and oviposition characteristics of 10 female P i ssodes terminal 1s reared at 20°C+2°C at UBC.
Characteristics Mean S.D. Range
Longevity (days) 112.8 74.9 32-226 Preoviposition period (days) 10.1 6.8 2-22 Total eggs per female 115.0 67.5 9-216 Eggs per oviposition site 0.94 -1 0-2 Eggs per female per day2 1.57 1.34 0.39-4.62
1 S.D. has not been calculated 2 from first day of oviposition to death of female 69 value on day 28, and then increased until day 35 (Fig. 23).
Oviposition started to decrease sharply after day 49, although only three females had died. Fecundity averaged
115 eggs per female (S.D.=+67.5, range=9-216). A total of
1246 oviposition sites were counted and 1150 eggs were found giving a mean number of eggs per oviposition site of 0.94.
Females most often laid one egg per pit (91.8% of pits), but sometimes they oviposited two eggs (0.5%) or none (7.7%).
Five eggs were laid directly on the bark surface (0.4%).
These results are in general agreement with observations that generally only one egg is deposited in each pit (Drouin et al.; Stark and Wood 1964). Females laid 1.57 eggs per day on an average basis (S.D.=1.34, range=0.39-4.62)
(Table XIII).
3.3.3.2. Duration of egg stage and pupal stages of
P. terminalis
Terminals with oviposition sites from the longevity and fecundity experiment were evaluated for the duration of the egg stage of P. terminalis. Observation of 54 eggs revealed that the average duration of the egg stage is 8 days (S.D.=+0.98, range=5~l8). This is in agreement with the findings of Stevens and Knopf (1974) who reported that eggs of P. terminalis hatched within two weeks. Two eggs hatched 5 days after oviposition and 9 took 18 days to hatch. Head capsules of 36 first instar larvae were 7 21 35 49 63 77 91 105 119 133 147 161 175 189 203 217 231
days • egg/female/week + number of females
Figure 23: Survivalship and fecundity of ten Pissodes o terminalis females. 71 measured indicating that the average head capsule width was
0.371mm (S.D.=+0.022, range=0.300-0.400).
Observations on the pupal stadium of 20 P. terminalis pupae showed that on average it takes 15 days (S.D.=+2.5, range=11-20) from pupation to adult emergence at 20°C.
3.3.4.Observations on the biology of M. gentilis
and Cylindrocopturus sp.
M. genti1is is a black weevil (Fig. 24). Measurements showed that the average length of 7 males was 3.94mm
(S.D.=+0.13) whereas the average length of 13 females was
4.92mm (S.D.=+0.23). Adults are defoliators (Fig. 25).
Fellin (1973) stated that "there was no indication that adults of M. qentilis oviposit nor that larvae feed in or on the shoots or any other portions of the standing tree". In the present study, however, M. gentilis adults were reared from current year's infested lodgepole pine leaders (Tables
VI, VIII and XII). Furthermore, oviposition by M. gentilis was also observed. Ovipositional sites were always at the base of the needles (Fig. 26). P. terminalis never oviposited at the base of the needles (Fig. 27). It is not known if oviposition is restricted to the terminal or also occurs on other portions of the crown. Plumb (1950) and
Keen (1952) reported that larvae of certain Magdalis species are twig miners. Furniss and Carolin (1977) also recorded Figure 24 Maqdalis gentilis adult on elongating lodgepole pine terminal shoot. 73
Figure 25 One healthy lodgepole pine needle and 11 needles affected by the feeding of adult M. gentilis. The apical part of the needles have dessicated, discolored and curled up along the longitudinal axis. Apical portion of the last three needles had been broken either by wind or rain. 74
Figure 26 . Oviposition site made by M. qentilis into the current year's terminal shoot. Oviposition was made at the very base of the needle. Figure 27 Oviposition site made by P. terminalis female into the elongating terminal. 76 larvae of M. gentilis mining branches of ponderosa pine and
Jeffrey pine.
Although larvae of P.terminalis and M. qentilis are indistinguishable, leaders damaged by the two weevil species can be separated examining the following characteristics.
Larval boring of M. qentilis is powdery and fine-grained, whereas P. terminalis larvae produce shredded borings.
Larvae of M. gentilis tend to work into the wood deeper than do P. terminalis larvae. Furthermore, pupal chambers of M. gentilis are smooth, whereas those of P. terminalis are lined with some shredded wood (Keen 1952; Furniss and
Carolin 1977; Hulme, M.A.2^ personnel communication).
Like adults of M. gentilis, Cylindrocopturus sp. adults
(Fig. 28) also feed on needles (Fig. 29). Larvae of both M. genti1is and Cylindrocopturus sp. mined beneath the bark of the terminal feeding in the phloem region (Figs. 30-31), but they never entered the pith. Larvae of these two weevil species pupate between the bark and the wood of the terminal. Larvae of neither species construct cocoons.
Breeding by more than one of the terminal weevil species in the same terminal was never observed.
2 Research scientist, Pacific Forestry Centre, Victoria, B.C. 77
Figure 28 Cylindrocopturus sp. adults. Figure 29 Feeding punctures on lodgepole pine needles caused by Cylindrocopturus sp. adults. 79
Figure 30 Lodgepole pine terminal damaged by Magdal qentilis larvae. 80
Figure 31 Lodgepole pine terminal damaged by larvae Cylindrocopturus sp. 81
A small black beetle, Pityophthorus prob. boycei Sw.
(COLEOPTERA: Scolytidae) was also found associated with the terminal weevils during this study. It was observed that the majority of P. prob. boycei utilized untouched portions of previously attacked leaders. However, this beetle also attacked healthy terminal shoots.
3.3.5. Parasitoids associated with the weevils
A large number of parasitoids was also reared. All samples were dominated by the pteromalid R. pulchripennis.
Two species of Eurytoma collectively ranked second in abundance. The first parasitoids to emerge were two ichneumonids Polichomitus terebrans nubilipennis (Viereck), and Delomerista japonica Cushman and the braconid Allodorus sp. (Fig. 21). Emergence patterns show that, although the two species of Eurytoma started to emerge among the first parasitoids, they had an extended emergence during the rearing. All other early emerging species completed emergence within 7-14 days and were followed by the pteromalids R. pulchripennis and Mesopolobus sp. and the eulophid Hyssopus sp.
Rearing parasitoids in the laboratory accelerated emergence relative to the field situation, presumably owing to the higher temperatures in the laboratory. Minimum developmental temperatures of the parasitoids are unknown 82 and thus the number of accumulated degree-days could not be determined. Emergence patterns of the parasitoids coincided with those of P. terminalis and Cylindrocopturus sp. (Figs.
20-21). Emergence of M. gentilis preceeded that of the parasitoids but probably by the time newly emerged adult weevils finished maturation feeding and oviposition, parasitoids were also ready to attack. Figs. 20 and 21 show that phenology of the weevils is closely followed by that of the parasitoids. Close relationships between host and parasitoid phenologies is one of the criteria for successful biological control of the pest (Ehler and Andres 1983;
Murdoch et al. 1985).
Incubation of infested lodgepole pine leaders collected throughout British Columbia for the last two years has made
it possible to summarize data on parasitoids of the terminal weevils (Table XIV). Parasitoids belong to 6 families in the order Hymenoptera. As a result of the terminal weevil complex, correct associations between hosts and parasitoids cannot be ensured. In the course of this study neither predators nor entomophagous fungi were found in association with any of the weevils. 83
Table XIV. Hymenoterans found associated with the terminal weevils in British Columbia, 19B6-1987.
Fam i1y Genus/Spec i es Locat1 on Relat ive Type of abundance paras i to i d
Braconidae A11odorus sp. Kelowna Endo Pent icton Prince George Williams Lake Coeloides Kelowna Ecto ruf ovar jepatus (Prov.) Eu1oph i dae Hyssopus sp. Kelowna Endo Pent icton Eurytom i dae Eurytoma spp. Kami oops Ecto Kelowna Merritt Penticton Prince George Will lams Lake Ichneumonidae Poli chom i tus Penticton Ecto terebrans nubi1ipennis Williams Lake (Ratzeburg) Delomer i sta japonica Penticton Ecto Cushman Pteromalidae Rhopa1i chus Kamloops Ecto pu1chr ipenni s Cwfd. Kelowna Merritt Penticton Prince George Will lams Lake Mesopc1obus sp. Kamloops unknown Merr1tt PentIcton Scellonidae Te1enomus sp. Kami oops Endo Will lams Lake
very abundant frequent in samples rare 84
3.3.6. Adult parasitoid food plants
Pollen or honeydew are essential for adult parasitoid nutrition (Hagen and Hale 1974) and reproduction
(DeBach 1974). DeBach (1974) indicated that experiments of
Russian scientists have shown the need for supplementary food for adult parasitoids. Hagen and Hale (1974) suggested that the application of supplementary food where non-prey food is lacking can be used to attract or retain natural enemies. DeBach (1974) reported that in order to provide food for adult parasites of the codling moth, Laspeyresia pomonella (L.) (LEPIDOPTERA: Olethreutidae), nectar- producing plants should be planted in orchards.
It was observed that one of the sites (site 418) had particularly high numbers and a wide variety of parasitoids.
This site supported an abundance of fireweed, Epilobium angustifolium L. (Fig. 32) and one species of lupin, Lupinus sp. (Fig. 33). Neither of these two weed species grew on any of the other study sites. It was noticed that adult parasitoids fed on pollen of these flowering weeds. This observation suggests that pollen plays an important role in adult parasitoid nutrition (Hagen and Hale 1974). 85
Figure 32 Fireweed, Epilobium angustifolium L. in young lodgepole pine stand. 86
Figure 33 Lupin, Lupinus sp. growing in young lodgepole pine stand. 87
3.3.7. Weevil attack incidence and attack history
survey
A weevil attack incidence and attack history survey was conducted at Ellis creek on a 33ha lodgepole pine stand.
A total of 1088 trees were sampled. Results of the survey are presented in Table XV. Weevil attack started in 1983 and the number of infested trees was 13 times higher in 1984 than in the previous year. The infestation rate doubled in
1985 compared to 1984. Attack incidence declined in 1986.
This decline was probably a result of the unusually cold winter of 1985 (Fig. 34). The mild winter of 1986 (Fig. 35) may have resulted in an increase in adult and larval survival rates as there was an almost 4-fold increase in the number of weevilled trees in 1987. Of the 1088 trees sampled, 21 trees (1.9%) were attacked twice. No tree was found with more than two attacks. 88
Table XV. Results of the weevil attack incidence and attack history survey conducted on a 33ha, 14-year-old spaced lodgepole pine stand at Ellis Creek in July,1987 (n=l088).
Tree condition Number of Percentage of trees total
Healthy (never attacked) 842 78.9
Attacked in 1983 2 0.2 Attacked in 1984 26 2.4 Attacked in 1985 53 4.9 Attacked in 1986 36 3.3 Attacked in 1987 129 1 1.9
Total 1088 100.0 Figure 34: 1985 and 30-year monthly minimum and CO maximum average temperatures at the Penticton airport (Courtesy of Environment Canada). 1 1 1 1 1 Oct Nov D«c Jan Feb Mar Apr
months
1986 average maximum + 30-year average maximum
1986 average minimum A 30-year average minimum
Figure 1986 and 30-year monthly minimum and maximum average temperatures at the Penticton airport(Courtesy of Environment Canada 91
3.4 Management implications
Emergence patterns of the weevils showed that timing is important in planning leader clipping projects. Early emergence of M. gentilis suggests that leader clipping should be carried out by early spring. Observations suggest that the best time for leader clipping is February. Most of the attacked leaders have changed color by this time and recognition of infested terminals is relatively easy.
Experience has also shown that the top of the snow is hard in February which facilitates easy access to stands. In addition, the height of the snow helps a person reach the terminals and in many cases bending the tree (which might lead to breakage) can be avoided.
As mentioned earlier, a wide variety of parasitoids have been observed on flowers of weeds. Flowering weeds in lodgepole pine stands could provide nectar or pollen to parasitoids enhancing natural parasitoid populations already present in the field. Cultivating fireweed, E. angustifolium, is impractical because this weed is a serious competitor for moisture and space, which could suppress smaller trees. However, cultivating lupin, Lupinus sp., would be beneficial not only for the parasitoids but also for the trees as lupin fixes nitrogen enhancing the nitrogen content of the soil. 92
3.5. Other strategies for weevil control
Hulme et al. (1987) suggested new methods for the control of the Sitka spruce weevil, Pissodes strobi (Peck).
They suggested putting infested Sitka spruce leaders into containers with a fine screen on the top with openings
1.7x1.7mm wide. Emerging parasitoids and predators are able to crawl through the screen but P. strobi is prevented from escaping. Although this method is simple and inexpensive, it is not as applicable for the control of terminal weevils in lodgepole pine stands because of the variety of weevil species and their parasitoids. The three weevil species and the parasitoids vary in size which makes this method inapplicable.
Hulme et §_1. (1986) utilized the relative lack of cold- hardiness of P. strobi to kill the weevil and maintain parasitoid populations. When infested terminals were cooled to -26°C, weevils of all developmental stages were killed damaging the parasitoids or predators. This method may be applicable for the control of terminal weevils on. lodgepole pine . However, the cold-hardiness of P. terminalis,
M. gentilis and Cylindrocopturus sp. have yet to be determined. Further experiments should be carried out to address this question. 93
4. GENERAL DISCUSSION AND CONCLUSIONS
The major findings of the present study can be summarized as follows:
a. A terminal weevil complex consisting of three weevil
species, Pissodes terminalis Hopping, Maqdalis
gentilis LeConte and Cylindrocopturus sp., is present
on lodgepole pine in British Columbia.
b. Beside killing elongating terminals
M. gentilis and Cylindrocopturus sp. adults also
feed on needles.
c. Biology of P. terminalis differs slightly from that
of the two other weevil species. Third instar
P. terminalis larvae migrate into the pith , whereas
M. gentilis and Cylindrocopturus sp. larvae feed and
pupate between the bark and the wood.
d. M. gentilis emerges in mid-May and is followed by
P. terminalis and Cylindrocopturus sp. The latter
two weevils emerge from early June through mid-July.
e. The terminal weevils have a parasitoid complex in
British Columbia.
f. The most widely distributed parasitoid is Rhopalichus
pulchripennis Cwfd. Two species of Eurytoma
collectively rank second in abundance.
g. Emergence of the parasitoids closely follows that of
the weevils. 94
5. RECOMMENDATIONS
The following recommendations are made based on the results of the study:
a. Early emergence of M. gentilis suggests that leader
clipping projects should be carried out before the
spring. The best time for this is February when
attacked leaders have already changed color and
dead terminals are easily recognized.
b. Research should be carried out on the taxonomy of the
weevils to ensure species identification when
larvae alone are available, and to ensure correct
association between parasitoids and host weevil
spec ies.
c. Lupin, Lupinus sp., might be amenable to cultivation
near or at young lodgepole pine stands to enhance
parasitoid survival by providing a feeding site for
adults.
d. Further research is needed to demonstrate how the
parasitoid complex from clipped leaders could be
preserved and returned to the forest. 95
BIBLIOGRAPHY
Alexander, R.R. 1960. Thinning lodgepole pine in the Central Rocky Mountains. J. For. 58:99-104
Allen, J.C. 1976. A modified sine wave method for calculating degree days. Environ. Entomol. 5:388-396
Amman, G.D. and L. Safranyik. 1984. Insects of lodgepole pine: impact and control. IN: Baumgartner, D.M. R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.): Lodgepole pine - the species and its management. Symposium Proceedings. Wash. State Univ. pp.107-124
Anderson, W.H. 1941. The larva and pupa of C. furnissi Buchanan (Coleoptera: Curculionidae). Proc. Ent. Soc. Wash. 43:152-155
Arnold, C.Y. 1959. The determination and significance of the base temperature in a linear heat unit system. J. Am. Soc. Hortic. Sci. 74:430-435
Bella, I.E. 1985a. Pest damage incidence in natural and thinned lodgepole pine in Alberta. For. Chron. 62:233-238
Bella, I.E. 1985b. Western gall rust and insect leader damage to tree size in young lodgepole pine in Alberta. Can. J. For. Res. 15:1008-1010
Brown, J.K. 1973. Fire cycles and community dynamics in lodgepole pine forests. IN: Baumgartner, D.M. (ed.) Management of lodgepole pine ecosystems. Baumgartner, D.M. (Ed.) pp.429-456
Buchanan, L.L. 1940. Three new species of the lonqulus group of Cylindrocopturus (Coleoptera: Curculionidae). Proc. Entomol. Soc. Wash. 42:177-181
Bukzeeva, O.N. 1965. Biology of Maqdalis frontalis Gyll. Zoologicheski Zhournal 46:55-59 (in Russian).
DeBach, P. 1964. Biological control of insect pests and weeds. Chapman and Hall Ltd., London, 844pp.
DeBach, P. 1974. Biological control by natural enemies. Cambridge University Press. 323pp.
Drouin, J.A., C.R. Sullivan, S.G. Smith. 1963. Occurrence of Pi ssodes terminalis Hopping (Coleoptera: Curculionidae! in Canada: Life history, behavior, and cytogenetic identification. Can. Ent. 95:70-76 96
Duncan, R.W. 1986. Terminal and root-collar weevils of lodgepole pine. Pest Leaflet FPL 73, Pac. For. Centre 6pp.
Eaton, C.B. 1942. Biology of the weevil Cylindrocopturus eatoni Buchanan, injurious to ponderosa pine and Jeffrey pine reproduction. J. Econ. Entomol. 35:20-25
Ehler, L.E. and L.A. Andres. 1983. Biological control: exotic natural enemies to control exotic pests. IN: Wilson, C.L. and C.L. Graham (eds.): Exotic plant pests and North American agriculture. Academic Press, New York, pp.395-413
Evans, D. 1982. Pine shoot insects common in Canada. Pac. For. Res. Centre, BC-X-233 56pp.
Fellin, D.G. 1973. Weevils attracted to thinned lodgepole pine stands in Montana. USDA Forest Service, Research Paper INT-136 20pp.
Fellin, D.G. and W.C. Schmidt. 1966. Magdalis gentilis LeC. A newly discovered pest of forest regeneration in Montana. Mont. Acad. Sci. Proc. 26:59-60
Finnegan, R. 1958. The pine weevil, Pissodes approximatus Hopk. in Southern Ontario. Can. Ent. 90:348-354
Furniss, R.L. 1942. Biology of Cylindrocopturus furni ssi Buchanan on Douglas-fir. J. Econ. Entomol. 35:853-859
Furniss, R.L. and V.M. Carolin. 1977. Western forest insects. USDA Forest Service Misc. Publ. No.1339 654pp
Grant, J. 1958. Observations on a pine shoot moth, Eucosma sonomana. J. Entomol. Soc. B.C. 55:26-27
Greathead, D.J. 1986. Parasitoids in classical biological control. IN: Waage, J. and D. Greathead (eds.) Insect parasitoids. 13th Symposium of the Royal Entomological Society of London, Academic Press, New York pp.289-318
Hagen, K.S. and R. Hale. 1974. Increasing natural enemies through use of supplementary feeding and non-target pray. IN: Maxwell, F.G. and F.A. Harris (eds.): Proceedings of the Summer Institute of Biological Control of Plant Insects and Diseases. Jackson, pp.170-181 97
Higley, L.G., L.P. Pedigo and K.R. Ostlie. 1986. DEGDAY: A program for calculating degree-days, and assumptions behind the degree-day approach. Environ. Entomol. 15:999-1016
Hopkins, A.D. 1911. Contribution toward a monograph of the bark weevils of the genus Pissodes. Technical Series, No.20, Part I, Bur. of Entomology
Hopping, A. 1920. A new species of the genus Pissodes (Coleoptera). Can. Ent. 52:132-134
Hulme, M.A., A.F. Dawson and J.W.E. Harris. 1986. Exploiting cold-hardiness to separate Pi ssodes strobi (Peck) (Coleoptera: Curculionidae) from associated insects in leaders of Picea sitchensis (Bong.) Carr. Can. Ent. 118:1115-1122
Hulme, M.A., J.W.E. Harris and A.F. Dawson. 1987. Exploiting adult girth to separate Pi ssodes strobi (Peck) (COLEOPTERA: Curculionidae) from associated insects in leaders of Picea sitchensis (Bong.) Carr. Can. Ent. 119:751-753
Johnstone, W.D. 1985. Thinning lodgepole pine. IN: Lodgepole pine - the species and its management. Baumgartner D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.); Symposium Proceedings. Wash. State University, pp.251-262
Kennedy, R.W. 1985. Lodgepole pine as a commercial resource in Canada. IN: Baumgartner D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.): Lodgepole pine - the species and its management. Symposium Proceedings. Wash. State University, pp.21-23
Keen, F.P. 1928. Insect enemies of California pines and their control. Calif..Dept. Nat. Res., For. Div., Bulletin No.7. 113pp.
Keen, F.P. 1952. Insect enemies of western forests. USDA Misc. Publ. 273 280pp.
Lindgren, B.S. 1980. Pests of lodgepole pine, Pinus contorta, with particular reference to potential impact in Sweden. Forest Entomology Reports No.3, Swedish Univ. of Agric. Sci.-, Uppsala, 125pp. Maher, T.C. 1982. The biology and impact of the lodgepole terminal weevil in the Cariboo Forest Region. M.Sc. Thesis, Univ. of B.C. Vancouver, 63pp.
Manna, G.K. and S.G. Smith. 1958 Chromosomal polymorphism and interrelationships among bark weevils of the genus Pissodes German. The Nucleus. 2:179-208 98
Marty, R.J. 1959. Predicting weevil-caused volume loss in white pine. For. Sci. 5:269-274
McDougal, F.W. 1973. The importance of lodgepole pine in Canada, pp.10-26. IN: Baumgartner, D.M. (ed.) Management of lodgepole pine ecosystems. Wash. State University, pp.10-26
Ministry of Forests. 1981-1986. Annual Report. Province of B.C.
Ministry of Forests and Lands. 1987. Pest Management Progress. 6(2):25
Murdoch, W.W., J. Chesson and P.L. Chesson. 1985. Biological control in theory and practice. Amer. Nat. 125:344-366
Plumb, G.H. 1950. The adult feeding habit of some conifer- infesting weevils. Can. Ent. 82:53-57
Price, D.S. 1980. The major entomological pests of young lodgepole pine in the Cariboo. B.S.F. Thesis, Faculty of Forestry, Univ. of British Columbia, 74pp.
Safranyik, L., D.M. Shrimpton and H.S. Whitney. 1974. Management of lodgepole pine to reduce losses from The mountain pine beetle. For. Techn. Report 1, Pac. For. Centre 24pp.
Salman, K.A. 1935. The effects of attack by Pissodes terminalis Hopping on lodgepole pine in California. J. Econ. Entomol. 28:496-497
Satterland, D.R. 1973. Climatic factors and lodgepole pine. IN: Baumgartner, D.M. (ed.): Management of lodgepole pine ecosystems. Wash. State University, pp.297-309
Schmidt, W.C. and R.R. Alexander. 1985. Strategies for managing lodgepole pine. IN: Baumgartner, D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.) Lodgepole pine - the species and its management. Symposium Proceedings. Wash. State University, pp.201-210
Smith, S.G. and Y. Takenouchi. 1969. Chromosomal polymorphism in Pi ssodes weevils: Further on incompatibility in P. terminalis. Can. J. of Genetics and Cytol. 11:761-782
Stark, R.W. and D.L. Wood. 1964. The biology of Pissodes terminalis Hopping (Coleoptera: Curculionidae! in California. Can. Ent. 96:1208-1218 99
Stevens, R.E. 1973. Association of Pityophthorus opimus Blackman with Pi ssodes terminali s in Colorado lodgepole pine (Coleoptera: Scolytidae and Curculionidae). Coleopt. Bull. 27:141-142
Stevens, R.E. and J.A.E. Knopf. 1074. Lodgepole terminal weevil in interior lodgepole pine forests. Environ. Entomol. 3:998-1002
Stevenson, R.E. and J.J. Petty. 1968. Lodgepole terminal weevil (Pissodes terminalis Hopping) in the Alberta/ Northwest Territories Region. Can. Dept. of For. Bi-monthly Res. Notes 24:6
Tackle, D. 1959. Silvics of lodgepole pine. USDA Forest Service, Intermountain Forest and Range Experimental Station Misc. Publ. No.19 24pp.
Weetman, G.F., R.C. Yang and I.E. Bella. 1985. Nutrition and fertilization of lodgepole pine. IN: Baumgartner, D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.): Lodgepole pine - the species and its management. Symposium Proceedings. Wash. State University, pp.225-232
Wheeler, N.C. and W.B. Critchfield. 1985. The distribution and botanical characteristics of lodgepole pine. IN: Baumgartner, D.M., R.G. Krebill, J.T. Arnott and G.F. Weetman (eds.): Lodgepole pine - the species and its management. Symposium Proceedings. Wash. State University, pp.1-13
Wood, G.S., G.A. VanSickle, L. Humble. 1987. Forest Insect and Disease Conditions, British Columbia and Yukon 1987 Can. For. Service, Pac. For. Centre BC-X-1987 32pp.
Woodhead, P.V. 1934. Thinning lodgepole pine stands in the Central Rocky Mountain Region. J. For. 32:594-597 APPENDIX I
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2merg loles o o n r*i 55 H m > T0T 102 APPENDIX II Form used for recording emerged specimens from rearing boxes 103 (NJ IT) (Nl CNI CNI 1— (Nl 3 i—! C- (Nl o (NJ 3 CM i—! 3 00 p_ tH 3 r- C- i—I 3 i—l i- 3 iH 3 C-. ro i—l 3 CNI 1—! 3 I—lC - i—l 3 3- c 3 1—1 ON 3 C- cc 3 C~ 3 C- 3 CM NT 3 ro 3 En1 :NI CM -i 3 «-i CNI ro -a uo vD r~ i-l (N| uo vC ao o> O ro No . T i-H i—i r-l —I i—I i-H •H i-H I-H CNI CNI CNI (NJ CN CNI CN CN CNI CNI CO c- CI CI APPENDIX III Projected field emergence of weevils calculated with three methods of degree-day calculation for different developmental minimum temperatures, (TMIN) when the maximum developmental temperature, (TMAX) was unknown and set at 30°C 105 Projected field emergence based on Penticton Airport data Start of lab TMIN2 Accumulated 1 3 emergence heat units TMAX unknown Rectang. Triang. Sine Rectang. Triang. Sine Magda1i s gent i1i s May 12 4°C 7G May 13 May 15 May 14 May 13 May 15 May 14 May 12 5°C 72 May 13 May 16 May 15 May 13 May 16 May 16 May 12 G°C €8 May 13 May 18 May 16 May 13 May 18 May 16 May 12 7°C 64 May 13 May 20 May 18 May 14 May 20 May 18 May 12 8°C 60 May 14 May 2 1 May 20 May 14 May 22 May- 20 P1ssodes term i na1 is June 3 4°C 532 June 19 June 2 1 June 20 June 19 June 19 June 19 June 3 5°C 504 June 20 June 20 June 20 June 2 1 June 21 June 2 1 June 3 6°C 476 June 21 June 22 June 22 June 2 1 June 22 June 22 June 3 7°C 448 June 22 June 23 June 23 June 22 June 23 June 23 June 3 8°C 420 June 23 June 25 June 24 June 23 June 26 June 25 CylIndrocopturus sp June 9 4°C 627 June 26 June 27 June 26 June 26 June 27 June 27 June 9 5°C 594 June 26 June 28 June 27 June 27 June 28 June 28 June 9 €°C 561 June 27 June 29 June 28 June 28 June 29 June 29 June 9 7°C 528 June 27 June 30 June 29 June 28 June 30 June 30 June 9 B°C 495 June 30 July 1 July 1 June 29 July 2 Ju 1 y 1 Specimens set up for rearing on May 7, 1987. TMIN - minimum developmental temperature TMAX - maximum developmental temperature APPENDIX IV Weekly measurements of 25 elongating lodgepole pine leaders 107 Date May 141 May 24 Jun 4 Jun 14 Jun 24 Jul 4 Jul 14 Jul 24 Aug 3 Aug 13 No. Length of leader 1 8 .2 15 . 7 23 .0 36 .0 38 .6 46 .4 49 .4 49,. 5 49 .8 50.. 4 2 6 . a 16 . 2 21 .4 33 .2 38 .O 47 .2 50 .2 51 ,9 53 . 1 53 ., e 3 7 . 1 1 1. 5 15 .9 27 . 1 31 .5 37 .2 40., 6 42 .3 44 .0 44 ,9 4 6 . 3 22 .8 29 .6 42 . 1 47 .9 55 .6 56,. 5 57 .8 58 .6 58,. 8 5 7 .6 9 .9 14 . 3 29 .9 37 .4 44 .7 47 .6 50 .6 54 .3 54 .,8 6 18 .9 25 .3 41 .4 47 .3 56 .8 59,. 0 59 .5 60 .0 60 .8 7 13 .0 18 .6 32 .6 37 .2 45 .5 49 .7 52 .3 53 .5 53 .5 8 16 .8 24 .6 39 .6 41 .5 45 .9 47 .3 47 .5 47 .5 47 .8 9 17 .9 24 .9 39 .2 42 .2 49 .6 50 .8 51 . 1 52 .3 52 .4 10 8 .4 11 .2 20 .7 24 .4 28 .6 29 .6 29 .6 29 .6 29 .6 11 14 . 4 20 .3 31 .4 34 .5 39 .2 41 .9 42 .5 42 .5 42 .8 12 13 .5 17 .7 25 .2 28 .5 28 .7 28 .7 28 .7 29 .6 29 .6 13 13 . 1 19 .2 33 . 1 37 .0 44 .4 46 .6 46 .8 49 .5 49 .5 14 20 .3 26 .9 38 .5 43 .6 54 .2 58 .2 59 .5 60 .0 60 .8 15 18 .3 24 .2 36 .3 4 1. 0 45 .6 46 .7 46 .8 4S .3 48 .5 1G 19 . 7 26 .5 35 .9 38 .9 48 .3 51 .0 51 .6 52 .8 53 .4 17 21 .0 26 .5 40 .0 45 .8 53 .5 56 .9 57 . 3 56 . 4 59 . 4 18 17 .9 24 . 1 37 .7 42 .6 52 .0 55 .2 56 .4 58 .0 58 .0 19 14 .0 17 .7 29 .8 35 .0 41 . 1 41 .5 41 .6 42 .8 43 .6 20 1 1. 2 14 .9 25 .4 28 .7 34 .9 37 .8 39 .8 4 1. 4 4 1. 8 21 18 .5 26 .4 39 .5 44 .6 53 .8 58 . 1 61 .2 63 . 1 64 .0 22 15 . 1 22 .0 37 .0 42 .9 51 .3 53 .0 56 .0 58 .8 59 .5 23 16 .8 21 .2 33 .5 36 .8 39 .2 39 .5 39 .7 39 .7 39 .7 24 20 .7 25 .9 37 .9 4 1. 2 48 .8 51 .4 53 .7 53 .7 54 . 1 25 20 .7 27 .6 43 .5 48 . 1 59 . 1 62 . 1 65 .8 68 .8 70 .2 1 leaders were collected on site 120 near Kelowna