Agr.) University of British Columbia 1970

THE BIOLOGY AND CONTROL OF CENTAUREA DIFFUSA LAM. AND CENTAUREA MACULOSA LAM. by- Alan Kemball Watson B.Sc. (Agr.) University of British Columbia 1970 A Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Science in the Department of Plant Science / accept this thesis as conforming to the required standard The University of British Columbia May, 1972 In presenting this thesis in. partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I 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 representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my Written permission. Department of The University of British Columbia 8, Vancouver Canada Date 2-^ (i) ABSTRACT Centaurea diffusa was found to infest 64,079 acres in the semiarid interior of southern British Columbia. C. maculosa has infested an additional 8,420 acres. These weedy plant species are common along roadsides-and in waste places and are spreading rapidly over vast areas of semiarid rangeland. The density of the knapweed species could only be correlated with the degree of soil disturbance and was not correlated with any chemical property of the soil. The knapweeds are not generally grazed by domestic livestock and substantially reduce the forage yields in heavily infested areas. C. diffusa and C. maculosa prevent soil erosion on disturbed sites as these pioneer species are capable of rapid colonization of these sites. These species are utilized to some extent as honey plants. However, the losses attributed to knapweed infestations generally override any potential use of the knapweeds. Seeds of C. diffusa and C. maculosa germinate readily over a wide range of conditions. Continuous light was found to significantly retard the gemination of both species. The optimum temperature for germination of C. maculosa was found to be lower than that for C. diffusa seed. The optimum soil depth for emergence of both species was on the soil surface. C. diffusa seed did not emerge from soil depths below 3 cm. C. maculosa seed emerged from a soil depth of 5 cm. Phenological data were recorded for both species. C_. maculosa begins to flower in early July with C. diffusa flowering approximately one or two weeks later. The annual reproductive capacity of C. diffusa was determined to be 665 with C. maculosa exhibiting an annual reproductive capacity of 298. (ii) Dual mechanisms of seed dispersal were observed for both species. Propagule dispersal is mainly by wind. Cultural methods of control were generally found not to be beneficial in controlling the knapweeds. The knapweeds can be adequately controlled by using the herbicide picloram, 4-.amino - 3,5,6 - trichloropicolinic acid, however, the high cost of this herbicide has greatly limited its use. Phytophagous.insects, Urophora affinis and Metzneria paucipunctella, have been studied as potential biocontrol agents for the knapweeds. Initial releases of Urophora affinis indicate that the insect is capable of survival in the southern interior of British Columbia. The population has increased substantially since the initial release in 1970. It will take up to 10 years or more, however, before the releases of U. affinis are sufficiently well established to reduce the knapweed infestations. Two fungal organisms, Sclerotinia sclerotiorium and Microsphaeropsis centaureae, were isolated from diseased C_. diffusa in the Vernon area. The potential of these organisms as biotic agents has, as yet, not been determined. Weed control methods must be associated with other appropriate manage• ment practices to produce increases in forage yields. Such an integrated approach to the control of diffuse and spotted knapweed will substantially reduce the extent of the knapweed infestation in the southern interior of. British Columbia. (iii) TABLE OF CONTENTS Page ABSTRACT • i LIST OF TABLES - ........... iv LIST OF FIGURES ........ • vii ACKNOWLEDGEMENT , ........ •••••• viii I. INTRODUCTION • • • 1 II. DISTRIBUTION 2 A. Literature Review ....... .• 2 B. Experimental Methods 5 C. Results and Discussion ...... 7 III. WEED ECOLOGY ... : 16 A. Literature Review •.... 16 B. Experimental Methods • • • • • 28 C. Results and Discussion • • . 33 IV. CONTROL , 51 A. Literature Review 51 B. Experimental Methods ••• • , 70 C. Results and Discussion ' 72 V. BIBLIOGRAPHY 91 VI. APPENDIX • • 100 (iv) LIST. OF TABLES,. Table Page I Density scale utilized in the Centaurea survey ' 5 II Methods of soil analysis ,• 6 III. Acreage infested with Centaurea species in B.C 7 IV Plant density of knapweed infestations 9 V Average monthly and annual mean temperatures of selected sites .. .• ,.• 10 . VI Average monthly and annual precipitation and altitude of selected sites ', 11 VII Precipitation and mean temperatures of selected sites in 1971 ... 12 VIII Chemical analysis of knapweed infested soils 14 IX Chemical composition of the above ground parts of Centaurea diffusa .(% dry wt.) ............. 21 X Chemical analysis of C. diffusa and C. maculosa in flower (% dry wt. ) .... •. / 22 • XI Effect of C_. maculosa water extract on crop seedlings (7 days after sowing) 27 XII Effect of C. diffusa water extract on crop seedlings (7 days after sowing) ... ... ... 28 XIII Yield of forage and knapweed from knapweed infested rangeland in the southern interior of British Columbia 34 XIV Weight of C. diffusa and C_. maculosa seed gathered in British Columbia' , 39 XV The effect of light on germination of C. diffusa -and C. maculosa seed (adjusted means).. 40 XVI Optimum germination temperatures for C. diffusa-and C. maculosa ,. • 43 XVII • Average seed production of C. ..diffusa and C. maculosa . .•. 46 XVIII Shallow plowing (7 cm) on C. diffusa in the fruiting stage (% cover) .... 51 ,(v) Table Page XIX- Plowing- (18 cm) on C. diffusa in the fruiting stage (%' cover) ._. -. 52 XX • Mowing of C. diffusa in the bolted stage (% cover) ..... 52 XXI Effect of burning on C. diffusa in the fruiting stage (% cover) .. .. ..' 53 / • . XXII Effect of picloram, reseeding, and complete protection from grazing by domestic animals on the control of C. - diffusa ..< ... • : • 54 XXIII 2,4-D (1 kg/hectare) applied to pasture infested with with diffuse knapweed in the rosette stage (% cover) . 54 XXIV Potential insect agents for the biological control of C. diffusa , ..... 59 XXV, Potential insect.agents for the biological control of C. maculosa ........ 60 XXVI Factors and responses involved in the host specificity of ovippsition in U. affinis • • •' • 63 XXVII Length of ovipositor; .and dimensions of oviposition site of some Urophora spp. • •••• ........ 64 XXVIII Urophora affinis. attack of Centaurea at B.C. release sites' ........... • 66 XXIX Effects of soil disturbance on C. diffusa populations ... 72 XXX Shallow plowing with later fertilizer application (10T fresh horse manure/hectare) (% cover) 73 XXXI The effects of mowing on knapweed • 74 XXXII Results of the East Kootenay Knapweed Control Program oc 1970-1971 75 XXXIII Treatments utilized to break sclerotia dormancy ? 80 XXXIV Determination of pathogenicity of Sclerotinia sclerotiorium and Microsphaerosis centaureae- on Centaurea diffusa and C. maculosa .................... 82 XXXV- Plant diseases observed on Centaurea species in North America 777777777. ,83 (vi) Table - . Page XXXVI Evaluation of biological control measures against weeds in Canada ' 87 Appendix Table I. Effect of temperature on germination of C. diffusa and C. maculosa ...................... 100 Appendix Table II. Effect of sowing depth on seedling emergence of C. diffusa and C. maculosa • 101 (vii) LIST OF FIGURES Figure Page 1 Distribution of C. diffusa in the U.S.A 4 2 Distribution of C.\ maculosa in the U.S.A. .• 4 3 Distribution of C. diffusa in British Columbia .. 8 4 Distribution of C. maculosa in 'British Columbia ;. 8 5... Temperature gradient bar ,. 31 6j C. diffusa and C. maculosa seeds on temperature gradient bar 31 7 Pollen grains of C. nigra, C. maculosa and C. diffusa ... 38 8 C. maculosa, (upper) and C. diffusa seeds .. .. 38 9 The effect.of temperature on germination of C. diffusa and C. maculosa seed • 42 10 Seedling emergence of C. diffusa and C. maculosa 24 days after sowing at different soil depths ........ 43 11 C. maculosa, (left) and C. diffusa flower heads ......... 50 12 Fusiform gall in the receptacle of a C. maculosa flower, head , 61 13 Sclerotium in a C. diffusa, root 61 14 Apothecia produced from cold treated sclerotia 79 15 Plate culture of S_. sclerotiorium. 79 16 Plate culture of M. centaureae 81 17 Leaf spot on C. diffusa 85 18 Leaf spot on C. maculosa 85 19 Re-establishment of C. diffusa-after herbicide treat• ment at OK Falls, B.C 89 . 20 Re-establishment'of C. maculosa after herbicide treat• ment 'at Chase, B.C. •••• • 89 (viii) . ACKNOWLEDGEMENT I thank Dr. A.J. Renney for his interest and supervision throughout this study. The assistance of the other members of the committee: Dr. V.C. Runeckles, Dr. W.G. Wellington and Dr. R.J.'.Copeman is gratefully appreciated. •In particular,.I am indepted to Dr..'R.J. Copeman for advice and materials in regard to the work with the fungal organisms. • I also thank Dr. G.W. Eaton, for assistance with statistical problems and Dr. R. Taylor for obtaining herbarium specimens. I thank Dr..R.J. Bandoni, Department of Botany, University of British Columbia; Miss M.E. Elliott, Plant Research Institute, Ottawa; and Dr. G. Morgan-Jones, Department of Biology, University of Waterloo for their valuable assistance in the identification of the fungal isolates. I gratefully appreciate the co-operation of Dr. J.E. Miltimore, W.A. Hubbard'''and other members of the staff at the Canada Department of Agriculture Research Stations at Kamloops and Summerland. The interest and advice of Dr. P. Harris,.Research Institute, Belleville, Ontario is gratefully acknowledged.

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