Insect Defoliation Studies on Red Alder (Alnus Rubra Bong)
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INSECT DEFOLIATION STUDIES ON RED ALDER (ALNUS RUBRA BONG.) ON BURNABY MDUNTAIN, B.C. Peter Muthigani B.Sc., University of East Africa, 1967 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Biological Sciences @ Peter ~uthigani Simon Fraser university August, 1971 APPROVAL Name : Peter ~uthigani Degree : Master of Science Title of Thesis: Insect defoliation studies on Red Alder (Alnus rubra ~ong.)on Burnaby Mountain, B.C, ~xaminingcommittee: Chairman: G .H, Geen Senior Supervisor J.H. Borden --. R.C. Brooke Date Approved: z(&~PI/ ABSTRACT Defoliation of A-lnus rubra Bong. saplings on Burnaby Mountain, B.C., between August 1970 and August 1971 was mainly caused by two chyrsomelid beetles, Pyrrhalta punctipennis (Mannerheim) and Altica ambiens Le Conte and one sawfly, EZiocampa ovata L. (Hymenoptera, ~enthredinidae). Insect damage was low until August. Between mid-~une and the autumn there was a progressive decline in the numbers of leaves per tree. The number of leaves damaged increased steadily from June on, but the proportion of each leaf damaged remained small until mid-August. After mid-August the damage per leaf increased rapidly, and by early September severe leaf damage was apparent. NO relationship was established between leaf surface lost to defoliators and stem wood volume increment or between residual leaf surface in the autumn and stem growth. iii TABLE OF CONTENTS Paqe Examining Committee Approval ......................... ii Abstract .............................................. iii Table of Contents .................................... iv List of Tables ....................................... vi List of Figures ..................................... vii Acknowledgements ..................................... x Introduction .......................................... 1 Alnus rubra Bong. ............................... 1 I. Taxonomy ................................. 2 11. Range .................................... 2 111. Salient Features of A_. rubra ~cologyand Life History ............................. 3 IV. Red Alder and Nitrogen ~ixation..\......,. 5 V. Growth and yield ......................... 7 VI. characteristics as a Tree and a Wood; Present Uses; Potential Uses .......,..... 10 VII, Pests and ise eases ....................... 13 ' Red Alder on Burnaby Mountain ................... 16 I. Site characteristics ..................... 16 Project on ~efoliation ......................... 21 Scope and objectives ......................... 21 Methods and ater rials ................................ 24 I . The Sampling Site .......................... 24 I11 . Check of Visual ~stimationof Defoliation .. 25 IV . Revised Defoliation ~stimates .............. 28 V. Measurements of Seasonal Growth ............ 29 VI . Sampling for the Vertical Distribution of the ~ainDefoliators .................... 31 Results ............................................. 37 Notes on Insects Occurring on Red Alder on Burnaby Mountain ............................... 58 I . Pyrrhata punctipennis (Mannerheim) ...... 58 I1 . Altica ambiens Le Conte ................... 63 IV . Hemicroa crocea Fourcroy ................. 69 V . Malacosma pluvialis Dyar ................ 69 Discussion ......................................... 71 Conclusions ......................................... 78 Literature cited .................................... 80 LIST OF TABLES Paqe Table 1. Examples of yield tables for red alder 9 Table 2. Visual estimates of the degree of de- 83 foliation on red alder leaves in the fall of 1970 Table 3. Data on mean leaf areas, mean damaged leaf areas and the mean defoliation per- centages for &. rubra saplings in 1970 Table 4. Data on mean leaf areas, mean leaf areas damaged and the mean defoliation percen- tages for A_. rubra saplings in 1971 Table 5. The seasonal change in the mean number of leaves per stem and the mean total photosynthetic surface per stem Table 6. Seasonal change in the mean percentage of the total foliage per sapling that is damaged by defoliators Table 7. Seasonal wood volume increments in red alder saplings aged 2 - 4 years Table 8. Seasonal wood volume increments in red alder saplings expressed as proportional incre ase LIST OF FIGURES Fig. I The range of red alder ~ig.11. Mean monthly precipitation over a period of 5 years on Burnaby Mountain Temperature regime in the Lower Fraser Valley Fig. IV. Cross section of A_. rubra stem under low power magnification to show the overall appearance of growth rings Fig. V. Cross section of A. rubra stem stained with safranin Fig. VI. Cross section of A_; rubra stem stained with safranin . Fig. VII Cross section of A. rubra stem stained with safranin to show the hazy discon- tinuous aspect of two false rings under low power magnification Fig. VIIL. elations ship between visual and measured damage to leaves Fig. IX. Seasonal change in mean percentage leaf area damaged by insects Fig. XA. Change in mean surface area per stem Fig. XB. Change in mean number of leaves on stem Fig. XI. Seasonal distribution of percentage of red alder leaves damaged by defoliators Fig. XII. elation ship between the number of dam- aged leaves and percent area damaged Fig. XIII. Frequency distribution of damage to leaves of red alder (21 vi 71) vii ~ig.XIV. Frequency distribution of damag leaves of red alder (28 vi 71) ~ig.XV, Frequency distribution of damage to leaves of red alder (8 vii 71) Fig. XVI . Frequency distribution of damage to leaves of red alder (15 vii 71) Fig. XVII. Frequency distribution of damage to leaves of red alder (22 vii 71) ~ig.XVIII. Frequency distribution of damage to leaves of red alder (6 viii 71) Fig. XIX. Frequency distribution of -P. puncti- pennis first instars on stems Fig. MC Frequency distributim of late in- stars of 2. punctipennis on stems Fig. MCI. Frequency distribution of E. ovata larvae on stem ~ig,XXII. elations ship between mean percent defoliation and wood volume increment Fig, XXIII. elations ship between wood volume in- crement and residual leaf area in 3- year old stems Fig. XXIV. elations ship between wood volume in- crement and residual leaf area in 4- year old stems ~ig.XXV. Eggs of g. punctipennis Fig. XXVI. Top: Characteristic circular holes eaten off by large larvae of P. puncti- Bottom: A third instar larva of z. punc t i~ennis viii Z + Paqe Fig. XXVII. comparison of leaf damage caused by adult 62 Chrysomelids. Leaves marked (A) show isolated holes eaten off by A_. ambiens. Leaves marked (B) show the concentrated feeding of P. punctipennis ~ig.XXVIII A. Dorsal view of adult P. punctipennis 64 B. Ventral view of adult g. puncti- pennis showing the cleft on the last sternite of the male Fig. XXIX. Top: .Third instar larva of Altica ambiens 65 Middle: Brown patches on leaf surface indicate epidermal damage by young A_. ambiens larva Bottom: Holes made by older A.- ambiens larva tend to be more rectangular than circular Fig. XXX. A. Adult A. arnbiens specimen with the 67 tachinid parasite pupa still attached to the lateral posterior side of the abdomen B. Dorsal view of the tachinid imago Fig. XXXI. A. id-instar larva of Eriocampa ovata 68 L. showing the characteristic white exuviathat larval instars except the last one exhibit. B. Early damage by E. ovata larva. C. Extreme damage by E. ovata larva ~ig.XXXII. Mature larva of Hemichroa crocea Fourcroy 70 I am grateful to Dr. A.L. Turnbull for his generous assist- ance, Mr. R.G. Long for the photography and Drs. B.P. Beirne, J.H. Borden, G.R. Lister for their willingness to render assist- ance. Finally, many thanks to the Canadian Commonwealth Scholar- ship and Fellowship Administration for awarding me the scholar- ship and smooth handling of everything. -1- INTRODUCTION Little work has been done on methods of measuring damage to either forest or agricultural crops by defoliating insects (Strickland et al., 1970). Judging by the scarcity of reviews and papers, the manner in which defoliation influences the growth of crop plants and forest trees has not been studied adequately (Kulman, 1971). One result of this deficiency is that it is difficult to assess objectively the need for con- . trol measures, ~onspicuousbut superficial damage may elicit excessive and uneconomical controls while cryptic but signifi- cant damage may go untreated, Economic injury levels of pest density must be determined carefully; there are factors that influence the market value of the crop that must be considered entirely apart from total productivity (Stern et al., 1959). Crop loss assessments must be devised before pest control costs and the market value of the crop can be superimposed (Stern et al., 1959). This thesis attempts to assess the effects of defoliating insects on the productivity and growth of red alder (Alnus rubra Bong.) ALNUS RUBRA BONG, Red alder is the most abundant hardwood in the Pacific -2- Northwest and coastal Alaska. The total red alder volume was estimated in 1957 to be about 12.5 billion board-feet, about 900k of which was in Washington and Oregon (Worthington, 1957). The volume of red alder is only about 3% of the conifer volume in the ~ac5ficNorthwest. In Washington and Oregon, increasing amounts of red alder are being used for pulpwood and lumber (Worthington, 1957). Red alder is generally relegated to the status of a weed tree in conifer forests, on roadsides and along power lines, among other locations, It is probable that it will be regarded as an economically important tree in the future. I, Taxonomy Alnus rubra Bong.