Terminal Weevils of Lodgepole Pine and Their Parasitoid
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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.