«by Angela D. Hughes Submitted in partial fulfilment of the requirements for the degree of Master of Science at Dalhousie University Halifax, Nova ...»
An Ecological Study on Red Sorrel (Rumex acetosella L.) in Wild Blueberry Fields in
Angela D. Hughes
Submitted in partial fulfilment of the requirements
for the degree of Master of Science
Halifax, Nova Scotia
in co-operation with
Nova Scotia Agricultural College
Truro, Nova Scotia
© Copyright by Angela D. Hughes, 2012
NOVA SCOTIA AGRICULTURAL COLLEGEThe undersigned hereby certify that they have read and recommend to the Faculty of Graduate Studies for acceptance a thesis entitled “An Ecological Study on Red Sorrel (Rumex acetosella L.) in Wild Blueberry Fields in Nova Scotia” by Angela D. Hughes in partial fulfilment of the requirements for the degree of Master of Science.
Dated: April 18 2012 Supervisor: _________________________________
NOVA SCOTIA AGRICULTURAL COLLEGE
The author reserves other publication rights, and neither the thesis nor extensive extracts from it may be printed or otherwise reproduced without the author’s written permission.
The author attests that permission has been obtained for the use of any copyrighted material appearing in the thesis (other than the brief excerpts requiring only proper acknowledgement in scholarly writing), and that all such use is clearly acknowledged.
Table of ContentsList of Tables
List of Figures
List of Abbreviations and Symbols Used
Chapter 1 Introduction
1.1 Introduction to the Problem
1.2 Wild Blueberry History
1.2.2 Blueberry Management
1.3 Weeds in Blueberries
1.3.1 General Weed Management
1.4. Red Sorrel
1.5 Botrytis Blight
1.5.2 Impact of Weeds on Disease
1.6 Honey bee
1.6.3 Foraging on Non-Native Weeds
Chapter 2 Red Sorrel Management with Pronamide
2.2 Material & Methods
2.2.1 Study Sites
2.2.2 Experimental Design
2.3 Statistical Analysis
2.4 Results & Discussion
2.4.1 Impact of Kerb Applications on Blueberries
iv Chapter 3 The Impact of Red Sorrel (Rumex acetosella L.) on Honey Bee (Apis mellifera L.) Activity and Botrytis cinerea Spore Germination in a Wild Blueberry Field
3.2 Materials & Methods
3.2.1 Study Sites
3.2.2 Timing of Blueberry & Red Sorrel Flowering and Sorrel Pollen Release.......... 33 3.2.3 Impact of Red Sorrel Density on Pollinator Activity
3.2.4 Effect of Red Sorrel Pollen on B. cinerea Spore Germination and Floral Infection
220.127.116.11 Effect of Red Sorrel Pollen on Infection of Wild Blueberry Flowers by B. cinerea
3.3 Statistical Methods
3.4 Results and Discussion
3.4.1 Timing of Blueberry and Red Sorrel Flowering and Sorrel Pollen Release....... 38 3.4.3 In Vitro Germination of Botrytis cinerea Spores and Red Sorrel Pollen............ 45 3.4.4 Infection of Mature and Immature Blueberry Flowers by B. cinerea Spores and Red Sorrel Pollen
3.4.5 Honey Bee Observations
Chapter 4 Conclusions
4.1 Overall Conclusions
4.3 Management recommendations
Table 2.1 Average blueberry stem height and floral bud counts at Mt.
Thom and Kemptown Nova Scotia in 2009 and 2010….............. 24 Table 2.2 Density and biomass of red sorrel ramets and blueberry stems at two sites for the 2-year blueberry production cycle in Nova Scotia…………………………………………………………… 26 Table 2.3 Percent ground cover of blueberry and red sorrel in two Nova Scotia fields in 2009 and 2010………………
Table 2.4 Blueberry yield and profit after applications of Kerb in the fall and sprout year at two crop year fields in Nova Scotia………… 29 Table 3.
1 Crop year blueberry stem density counts in plots with and without red sorrel in a Nova Scotia blueberry field…………….. 54
Figure 3.1 Percent open blueberry and red sorrel flowers in blueberry fields in A) Collingwood 2009 B) Debert 2009 C) Collingwood 2010 and D) Debert 2010.
Error bars represent standard errors.……………
Figure 3.2 Red sorrel pollen grain release from 20 stems in A) 2009 and B) 2010 in two Nova Scotia blueberry fields……………….
Figure 3.4 Percent germination of B.
cinerea spores in the presence of increasing concentrations of red sorrel pollen………………. 46 Figure 3.5 Percent infected blueberry flowers following inoculation at the F4 or F7 stage of development with suspensions of B.
cinerea (B.C.) alone or with red sorrel pollen………………. 47
Red sorrel is a perennial weed in wild blueberry fields that decreases yield. Multiple experiments were conducted to evaluate its impact on blueberry pollination, Botrytis blight incidence, and berry yield. Kerb applications did not significantly impact blueberry stem or floral bud formation. Removal of red sorrel with Kerb increased blueberry yield at both sites. However a double application had no difference than one application. Blueberry and red sorrel flowering overlapped and red sorrel pollen grains were found on blueberry flowers in both years at all sites. Red sorrel pollen grains increased the incidence of germinating spores in Petri dishes and this relationship was adequately modeled with a three parameter, exponential rise to a maximum. Red sorrel pollen significantly increased disease incidence on immature blueberry flowers. Honey bees foraged from blueberry and red sorrel flowers, but there was no evidence to suggest that they favored red sorrel flowers over blueberry flowers.
First of all I would like to thank my supervisor Nathan Boyd for all your patience and encouragement without your time an understanding I would not be where I am today. A sincere thank you to my committee members Paul Hildebrand and Chris Cutler for all your guidance, time and knowledge without you this project would not have been possible. I would like to send a large bear hug out to the blueberry growers and field scouts. Thank you for allowing me to tromp around in the blueberry fields of NS.
Without you and your hard work and dedication to this industry where would we be?
Thank you to Nancy MacLean, and Anna Fitzgerld for their expertise and help with and use of lab material. Thank you to Scott White for all his interest and input over the years.
To my family and friends, thank you for your encouragement and love throughout this entire journey.
1.1 Introduction to the Problem Wild blueberry (Vaccinium augustifolium Ait.) is the number one fruit crop in Nova Scotia in terms of total acreage, export sales, and total value to the province’s economy (Robichaud 2006; Strik and Yarborough 2005). In 2010, the wild blueberry industry produced 16, 500 tones of blueberries and contributed over $13 million dollars to the annual farm-value in Nova Scotia alone (Stats Canada 2010).
Wild blueberries are grown in six Canadian provinces and 36 U.S. states (Moore
1993) and are continuing to expand. They are a unique horticultural crop as they are not planted but developed from native stands. They are an increasing popular crop grown in many parts of the world (including Canada, United States, Norway and China) for their antioxidant properties and health benefits (Howatt 2008). In 1996, blueberries were found to be the highest in antioxidant activity out of 41 fruits and vegetables tested (Prior et al. 1996).
Weed control is the most important and most common challenge in commercial production. Weeds compete with the wild blueberry for nutrients, light and moisture.
They also impede harvest activities, decrease berry quality, and may be a crop contaminant. There are many problematic weeds that occur in the blueberry fields (Esser 1995; Sampson et al. 1990), but red sorrel (Rumex acetosella L.) is one of the most common. In a survey from 1984-1985 it was found that red sorrel was the third most common weed in wild blueberry fields (McCully et al. 1991). In 2000-2001 sorrel was the most abundant weed out of 125 weed species recorded and it had increased 43% since the 1984-1985 survey (Jensen and Sampson 2001, unpublished data). It is a
copious seed production. It is a concern due to its impact on yields, interaction with the disease Botrytis blight and possible interaction with honey bees.
There are several diseases that impact blueberry growth and yields. Botrytis blight caused by Botrytis cinerea Pres.:Fr. is an occasional but destructive fungal disease (Hildebrand et al. 2001) that overwinters as a dormant mycelium or sclerotia on blueberry and other plant debris including red sorrel (Lambert 1990; Hildebrand et al.
2001). On blueberries, B. cinerea appears mostly on expanded corollas under favorable conditions (Hildebrand et al. 2001) and outbreaks of Botrytis blight tend to occur in coastal areas where fog is prevalent.
Wild blueberry pollination is essential for increased fruit and larger berry formation. There are numerous species of native pollinators which are associated with pollination of the wild blueberry (Finnamore and Neary 1978; Morrissette et al. 1985) and their efficiency is well documented (McGregor 1976; Fisher et al. 1993). However, these native pollinators are not sufficiently abundant to ensure adequate pollination of all flowers in blueberry fields (Boulanger et al. 1967; Mohr and Kevan 1987). Thus, introduced bees such as bumble bees (Bombus impatiens Cresson.), alfalfa leafcutter bees (Megachile rotundata F.), and honey bees (Apis millifera L.) are frequently used to enhance blueberry fruit set.
There is a lack of published peer-reviewed literature on the interaction between red sorrel, Botrytis blight and honey bee activity in wild blueberry fields. I hope to broaden our understanding of the ecological impacts of these interactions and determine if they are detrimental or beneficial to the crop.
Wild blueberries are native to northeast North America and are an important food source for birds and other wild animals. Native Americans enjoyed them long before the first Europeans discovered them in North America (Wood 2004). Early explorers such as Samuel de Champlain documented that Native Americans gathered and dried wild blueberries for use in the winter months and would add them to meals (Wood 2004).
They encouraged the growth of blueberries by periodically burning fields which would quickly regenerate new shoots (Howatt 2008). The first European settlers found them to be similar to types of berries that grew in their homeland such as the blueberry in Scotland, whortleberries in Ireland, bilberries in Denmark, blabar in Sweden, and bickberren and blauberren in Germany (Howatt 2008).
The commercial development of today’s wild blueberry industry began in the late nineteen forty’s and early nineteen fifties (Kinsman 1993). In Yarmouth County Nova Scotia during the early 1800’s specific areas were repeatedly burned due to forest fires and the land soon filled in with blueberry and other plants that thrive in acidic soils (Wood 2004). Early records of harvesting and selling wild blueberries date back to the1800’s. At that time, berries were handpicked and sold in baskets in nearby towns and shipped in barrels or cans to the Boston market (Kinsman 1986).
Today, commercial production of wild blueberries is limited to a rather small area in eastern Canada and the north-eastern United States, in the provinces of Nova Scotia, New Brunswick, Prince Edward Island, Newfoundland & Labrador, Quebec and Maine (Howatt 2008). Nova Scotia is the third largest producer of wild blueberries in the world and frozen blueberries are one of Canada’s major exports (USDA 2012). In recent years,
rich in antioxidant compounds that fight free radicals that are associated with cancer, heart disease and premature aging (Howatt 2008).The industry has seen many changes along the way and continues to evolve today.
1.2.1 Species The blueberry plant is a member of the Ericaceae or heath family, genus Vaccinium, subgenus Cyanococcus. There are three main blueberry species of economic importance: (1) the highbush blueberry, V. corymbosum L., (2) the wild ‘lowbush’ blueberry, V. angustifolium, Aiton, and (3) the rabbiteye blueberry, V. ashei Reade (Gough and Korcak 1995). Commercial wild blueberry fields consist of native clones of V. angustifolium and/or V. myrtilloides (Strik and Yarbourough 2005.) The plant is a perennial that spreads vegetatively by roots (Vander Kloet 1998) and by seed. Shoots are low growing reaching 10 to 60 cm in height. New shoots of maturing plants develop from dormant buds on underground stems called roots (Kinsman 1993).