Integrated Pest Management

B.C. Pest Monitor — Former Newsletter of IPM in British Columbia

Vol. 5 No. 1

by David F. Polster, Polster Environmental Services, Duncan, BC

Ecological Vegetation Management

Managing vegetation has been practiced in British Columbia since aboriginal peoples started fires to promote the growth of desirable species such as camus. More recently, managing vegetation has become part of most of our lives, whether it is controlling dandelions in lawns or managing woody vegetation under powerlines. With the advent of synthetic chemical herbicides, we have become increasingly reliant on these chemicals to "solve" our vegetation management problems. However, changes in public attitudes towards chemical herbicides and the realization that, in many cases, the herbicides were failing to produce the desired results, have led vegetation managers to look for alternatives.

Ecological and physiological processes dictate what vegetation grows on a site. Ecological vegetation management seeks to use these natural plant processes to achieve management objectives. To effectively manage the vegetation we must understand what these plant processes are and how they work to affect the vegetation on a site.

Ecological Needs of Plants

All plants need "space" in which to grow, whether this is actual physical space or whether it is a share of resource "space", such as water, nutrients, light, etc. Ecologists use the term niche to describe the multi-dimensional space where the species completes its life cycle. Management of a species may be affected by modifying the space in which it grows. For instance, a species that needs certain moisture conditions to grow can be managed by simply changing the moisture conditions. A knowledge of the ecological requirements of the species being managed can help in designing appropriate management systems (1).

Ecological Roles of Plants

Natural vegetation occurs in communities as groups of plants respond similarly to their environment (2). For example, vegetation patterns around a wetland clearly show the response of different groups of plants to moisture conditions. Communities of plants change over time, in a process called succession, until a steady state (climax) is reached (3). The first plants to become established on a bare site are called pioneers. For example, an old field, which was initially bare, might be colonized by annual weeds. These will eventually be replaced by a more permanent vegetation cover of perennial grasses and other plants. This would in turn be replaced by shrubs and pioneering trees, which would eventually be replaced by later successional trees, until eventually a climax forest develops (4). We can manage vegetation by understanding the role the particular species we are trying to manage plays in this successional series.

Successional Distance

Successional distancing is the term applied to maintaining two distinct type of vegetation cover on adjacent sites. For instance, you may wish to have a flower bed with open, bare ground between the flowers, next to a lawn. The bare ground is one vegetation cover (or lack of cover) while the lawn is the other. This generally works well because the bare ground represents a very early stage of succession while the lawn is several steps along in succession. The first plants to invade the bare ground will be weeds such as chickweed, not the perennial grasses making up the lawn. In effect, you have created successional distance between these two vegetation types and this "distance" keeps the grass out of the flower bed with only minor maintenance. However, if instead of the lawn, you had a yard full of weeds, then, because the weeds represent the next successional stage after the bare ground, you would soon find that there were weeds in your flower bed. There would be no successional distance between the two vegetation types. Successional distancing keeps the mature forest out of the hay field with only minor maintenance (cutting the hay every year), while if you let the hay field grow up into shrubs and pioneering trees (red alder, poplar, etc.) you would soon see the forest trees invading.

Seasonal Changes in Food Reserves

How do physiological processes in the plant fit into the picture? By understanding some basic physiological processes we can provide effective treatments. For instance, a foliar herbicide such as glyphosate needs to be applied when the plants are actively growing. It will be most effective when leaves are moving the products of photosynthesis down into the roots. By understanding the patterns of movement of materials in a plant we can determine when a herbicide will be moved from the leaves down into the roots. Understanding the seasonal changes in the levels of stored food reserves allows us to design treatment programs that will be most effective. Cutting a woody plant such as willow or maple in the late fall when carbohydrate levels are high will result in vigorous regrowth in the spring. If the same plant is cut in late June when root reserves are low, regrowth will be far less. In fact, repeatedly cutting the regrowth every three or four weeks will prevent the willow or maple from accumulating much, if any, food reserves, and it may die over the winter. Plant food reserves tend to be lowest when the plant has spent a lot of energy growing new shoots and leaves, but before it has a chance to gain much energy through photosynthesis.

Seed Physiology

A knowledge of seed physiology can be used to manage vegetation. The seeds of many pioneering plants will germinate when exposed to sunlight (5). The rapid flush of pioneering herbaceous vegetation on recently logged sites is an example. Weeds that magically appear on a cleared lot may have come from seeds in the soil seed bank. They were dormant as long as vegetation was covering the lot. Clearing the vegetation cover created an environment in this case that allowed the weeds to grow. In contrast, the seeds of many later successional species, such as wolf-willow, will not germinate in full sunlight (6). It may be possible to control the growth of such plants by reducing the canopy closure of the vegetation on the site.

Ecological Disturbance

Weeds thrive under conditions of disturbance. A vacant lot or untended garden patch will soon become full of weeds. These could be killed with a timely application of the right herbicide, but because the conditions that allowed the weeds to establish in the first place have not been changed, the weeds will soon be back. Ecological vegetation management seeks to minimize the disturbance associated with management activities and therefore change the outcome. In the vacant lot, a herbicide application would have created a disturbance in the vegetation which is exactly the condition the weeds need to establish (7). Repeated herbicide applications to keep sites bare, such as around electrical substations, along a fence lines or railroad tracks, will encourage the growth of weeds. The herbicides create a disturbance, both in the vegetation, and, depending on the herbicide, in the soil--which then encourages weed invasion. This disturbance is not limited to the area of application, but may be felt in the vegetation for some distance away (8). Other disturbance creating conditions, such as salt along highways, or even the repeated trampling by the feet of school children along a path, will encourage weed invasion. When we maintain the conditions of disturbance, the pioneering vegetation (generally weeds) is maintained. Minimizing herbicide use can reduce weed growth and result in cost effective vegetation management systems (9).

Applied Ecological Vegetation Management

Each vegetation management problem will have its own unique set of ecological solutions as objectives and sites differ. However, by understanding how plants respond to treatments, we can design management systems that work with nature rather than against it.

Control of individual plants won't work unless we change the conditions that allows the plant to establish. For example, dandelions in a lawn can be pulled out or sprayed, but unless the conditions that allowed the dandelion to become established are changed, there will soon be new dandelions. In the case of dandelions, it may be our continual disturbance with the blades of a lawn-mower set too low that helps them establish. Cutting the lawn at 10 cm instead of 5 cm and fertilizing so that it grows well may provide enough competition to reduce invasion by dandelions. Keeping the grass longer also conserves water and reduces the need for summer watering. Taken one step further, clover can be seeded into the lawn to reduce the need for fertilizer, because it fixes nitrogen from the air, which eventually becomes available to the turfgrass.

Ecological vegetation management principles apply to other types of sites. For example, steam and/or hot water may be used to kill vegetation where bare ground is needed without creating a disturbance in the vegetation or soils adjacent to the bare ground. Heat is an effective means of controlling vegetation without damaging nearby ecosystems (10). Successional distancing can be used to maintain the bare ground while the adjacent vegetation is allowed to develop past the weed stage. A dense grass and legume cover can be established under power lines to preclude growth of the adjacent forest species which might invade if the vegetation was composed of woody pioneers (11). In some cases, it may be best to prune the later successional species, such as the spruce trees along residential power line, than to cut them down and encourage the growth of pioneers, such as aspen, which will grow into the lines more rapidly.

An understanding of ecological processes as well as the physiology and ecology of the plants involved can lead to effective, innovative solutions to traditional vegetation management problems. By working with natural processes we can reduce our management costs, both in dollars and to the environment.

References

1. Haeussler, S. C. Coates and J. Mather. 1990. Autecology of Common Plants in British Columbia: A literature review. Forestry Canada and B.C. Ministry of Forests, Research Branch. Victoria, B.C. 272 pp.

2. Daubenmire, R. 1968. Plant Communities: A Textbook of Plant Synecology. Harper and Row. New York. 300 pp.

3. Oosting, H.J. 1956. The Study of Plant Communities: An Introduction to Plant Ecology. W.H. Freeman and Co. San Francisco. 440 pp.

4. Meuller-Dombois, D. and H. Ellenberg. 1974. Aims and Methods of Vegetation Ecology. John Wiley and Sons. Toronto. 547 pp.

5. Salisbury, F.B. and C. Ross. 1969. Plant Physiology. Wadsworth Publishing Company Inc. Belmont, California.

6. Young, J.A. and C.G. Young. 1992. Seeds of woody plants in North America. Dioscorides Press. Portland, Oregon. 407 pp.

7. Loucks, L.O. 1985. Looking for surprise in managing stressed ecosystems.
BioScience. 35(7): 428-432.

8. Herbel, C.H., H.L. Morton and R.P. Gibbens. 1985. Controlling shrubs in the arid southwest with Tebuthiron. J. Range Mange. 38(5):391-394.

9. Lybecker, D.W., E.E. Schweizer and R.P. King. 1988. Economic analysis of four weed management systems. Weed Science. 36:846-849.

10. Stapleton, J.J. and J.E. DeVay, 1986. Soil solarization: a non-chemical approach for management of plant pathogens and pests. Crop Protection 5: 190-198.

11. Green, J.E. 1982. Control of Vegetation Damage by Small Rodents on Reclaimed Land. Proceedings of the Sixth Annual British Columbia Mine Reclamation Symposium, Vernon, B.C., Technical and Research Committee on Reclamation, Ministry of Energy Mines and Petroleum Resources, and The Mining Association of British Columbia, Victoria, B.C.

Treatment Thresholds for Landscape Pests

In January, BC Environment and Environment Canada co-sponsored a workshop on setting treatment thresholds for managing pests in landscape plantings. The workshop was held in Nanaimo, B.C. and over 65 participants came from Vancouver Island and the Lower Mainland to pool their experience in making treatment decisions for common landscape pests.

A treatment threshold is the point at which control steps must be taken to prevent an unacceptable level of economic or aesthetic injury. Plants or sites are injured when the population of insects, diseases, weeds or other pests reach a certain level. The workshop participants listed the many factors that a pest manager takes into account when deciding what constitutes an unacceptable level of injury and when treatment must be used (see box). They then pooled their knowledge to come up with some treatment thresholds useful for coastal landscapes.

Decisions on when to treat may be based on qualitative information or quantitative information (see box). Little research has gone into establishing quantitative thresholds for landscape plantings. There is, however, an increasing effort to use sampling and measuring methods to establish consistent thresholds for treatment thresholds. Such thresholds are more easily applied by others and are less dependant on the judgement of experienced individuals.

The idea of classifying the type of landscape site with respect to the degree of pest management required has proven useful in producing landscape pest management plans. Typical classifications are:

Class A - High profile sites or those requiring an intensive level of service; e.g., display gardens, high traffic areas, playing courts, golf greens.

Class B - Medium profile sites or those with a moderate level of service; e.g., boulevards and medians, general park and playground area, parking lot perimeters.

Class C - Low profile sites or those needing little service; e.g., utility areas, works yards, naturalized parks areas and trails.

Treatment Thresholds for Insects

Aphids on Boulevard Tulip Trees:

Research on treatment thresholds has been conducted in Burnaby and Vancouver. The following thresholds are based on counting the droplets of honeydew falling on cards over a specific length of time.

Cards clipped to a branch for 4 hours: 1-2 drops of honeydew/cm²

Cards placed on the ground below tree for 1/2 hour: 9 drops of honeydew/cm²

The differences in the honeydew index depends on the method used to count. Also, the high count was considered a possible acceptable maximum that people may tolerate in what, historically, had been a very bad infestation.

Aphids on Roses:

When over 10% of the roses in the bed have over 50% leaves infested with aphids.

Spider Mites:

In the absence of predatory mites, 2-3 spider mites/leaf. Predators may be adequate for control if there is > 1 predator mite/10 spider mites.

Scale:

15-20 adult females/15 cm at the tip of a terminal branch. May depend on the amount of sooty mould that appears. Depends on parasitism rate.

Fungus Gnats:

15-20 gnats per yellow sticky cards, set 20 cm apart.

Tent Caterpillars:

Most treated on the basis of complaints received.

European Cranefly (Leatherjacket) in Turf:

Up to 20 larvae per 900 cm is usually tolerable if turf is receiving good management.

Treatment Thresholds for Weeds and Vegetation

For vegetation to be controlled selectively, such as in shrub beds and annual display plantings:

Class A - 10% coverage of site most often used - <10% might be appropriate for higher profile areas; >10% for some sites

Class B - 10% to 30% coverage

Class C - over 30% coverage — depends on proximity to higher profile sites

For weeds in turf:

Class A - 5-20% considered by most to be acceptable — depends on kind of weed and patchiness

Class B - good turf management can maintain site quality and keep weed levels from increasing

Class C - not likely to use herbicides on these sites — noxious weeds would be an exception — usually would use mechanical methods

Treatment Thresholds for Plant Diseases

Powdery mildews and rusts, on roses and other plants:

Class A - 0-10% of foliage affected — thresholds will vary depending on host / disease

Class B - a range of 1-5% might be tolerable — will depend on proximity to a Class A site

Class C - treat when health of plant is threatened

Complete notes from the workshop are available from the Pesticide Management Section, BC Environment, 2nd Floor, 777 Broughton St., Victoria, V8V 1X4

News of Pest Management News

The first issue of a new national pest management publication came out last month. The purpose of the Pest Management News (PMN) is to facilitate communication and technology sharing among pest management practitioners. The new journal arises from a combination of pest management and biological control publications that used to be funded by Agriculture and Agri-Foods Canada. While the PMN still has some start-up support from federal funds, it is expected to become self-supporting from subscription and advertising revenues and corporate donations.

Each issue is divided into sections on IPM, biological control, plant protection, and the Pest Management Alternatives Office. Articles in the first issue range from IPM alternatives for methyl bromide and information on diatomaceous earth and ivermectin, to electronic databases, integrated fruit production and international biological control. Announcements and a Market Place section round out the publication.

PMN is published quarterly in March, June, September and December.

Subscription Rates

Within Canada (taxes and postages included)

$25 Cdn per year

$15 Cdn for registered students

$70 Cdn for businesses, libraries and institutions

Outside of Canada (postage included)

$20 US per year

$50 US for businesses, libraries and institutions

Make cheques or money orders out to PMN. For a free introductory copy write or fax:

PMN
Box 35009
Ottawa, Canada K1Z 1A2
Fax: 819-772-1197

Products are listed for reader information only. This does not constitute an endorsement of either quality or effectiveness by B.C. Environment.

New Products

Invisible Fencing

Off Limits^® Crop Protection Systems has taken their underground fencing system for keeping pets in their yards, one step further. The electronic system has been adapted to enable growers to keep dogs in their orchards to chase deer. The dogs chase the deer out of the orchard, but the dogs themselves do not leave the limits of the property because they are restrained by the invisible fencing system. The underground fence works by sending a radio signal to a receiver on the dog's collar, which gives the dog a slight shock if it goes off the property. The deer leave the orchard, while the dogs learn to stay.

For more information, contact:
Jeff Myles
410 Memorial Drive NE.,Calgary, AB T2E 4Y7
403-290-0099 or 1-800-668-2812
e-mail: jmyles@freenet.calgary.ab.ca

Textured Street Pavement

StreetPrint^TM Pavement Texturing is an innovative method for imprinting freshly laid asphalt with a grid pattern that looks like hand laid brick or cobblestone. The asphalt is then coated with a coloured expoxy emulsion. The paved area has the look and design appeal of decorative pavers, but without the cracks that allow weeds to grow between the blocks. Using this type of surface could prevent the weed problems seen with brick or paver surfaces. Invented in Kelowna, B.C., it has been distributed since 1993.

For more information, contact:
John Simmons, President
Integrated Paving Concepts Inc.
1480 Foster St., Suite 90
White Rock, B. C. V4B 3X7
Tel: 604-535-8961
Fax: 604-535-8962
Or visit the company's Internet site

Publications

Safe and Sensible Pest Control
1992 - 1994. By L. Gilkeson

This is a series of brochures developed by BC Environment to encourage the use of safe, practical alternatives to the overuse of pesticide against common pests of home and garden. Titles available: Aphids; Beneficial Insects; Carpenter Ants; Caterpillars; Fleas; Household Pests; Rats and Mice; Turf Weeds; Yellowjackets; Bats

Available from:
Environmental Management Branch
PO Box 9342 Stn Prov Govt, Victoria, BC V8W 9M1
Fax: 250-387-9935

All About Moles and How to Control Them
1994. By David W. Fraser

This small, fact filled booklet gives detailed and helpful information on controlling moles in B.C. It covers what works as well as what does not work and why. It would be useful for farmers and groundskeepers as well as home gardeners.

Available from:
Rising Sun Publications
PO Box 31705, Pitt Meadows, B.C. V3Y 2H1
Tel: 604-465-6764 Fax: 604-465-6734
Cost CDN$5.99 plus shipping and handling

Turfgrass Disease and Pest Management Guide for Professional Turfgrass Managers in B.C.
1996. By Leslie MacDonald and Henry Gerber

This excellent new publication replaces the older Ministry of Agriculture publication "Diseases of Lawns". It is written for British Columbia turfgrass managers and contains information about contributing factors and IPM approaches to over 40 diseases and insect pests. The manual is well-organised, easy to use and contains many colour pictures of damage. It was a joint effort, written by Ministry of Agriculture, Fisheries and Food staff, and published by the Western Canada Turfgrass Association.

Available from:
Bob Wick
WCTA
22097 Isaac Cres. Maple Ridge, B.C. V2X 0V9
Cost CDN $20.00 (taxes and postage included)
(Cost to WCTA members is $15.00)

Seedling Barrier Protection from Deer and Elk Browse
1996. By Ian Booth and John Henigman

This new publication from the Ministry of Forests discusses methods of detecting and assessing deer and elk browse problems and describes the physical protection devices available for protecting trees seedlings from browse damage. These range from protective tubes for individual trees to area fences and barriers. Useful tables show the common commercial trees species ranging from most preferred to least preferred by elk and deer.

Available at no charge from:
Forestry Division Services Branch
Production Resources Department
Ministry of Forests
2nd Floor, 1205 Broad St., Victoria, B.C. V8W 3E7
Tel: 604-387-6719
Fax: 604-356-2093

Copies of Back Issues of B.C. Pest Monitor are Still Available

From: Environmental Management Branch, PO Box 9342 Stn Prov Govt, Victoria, BC V8W 9M1 Fax: 250-387-9935 or online at Brochures.

May 1992 Vol. 1 (1): * Integrated Pest Management in B.C. * IPM in Vancouver Parks * District of Coquitlam's Vegetation Management Plan

Nov. 1992 Vol. 1(2): * Using Sheep for Vegetation Management in B.C. * CP Rail System Vegetation Steam Car

May 1993 Vol. 2 (1): * Developing IPM on Pears in B.C. * Apple Pest Management in B.C.

Nov. 1993 Vol. 2(2): * Tree and Ornamental Disease Control in the City of Victoria * Turf Disease Control Through Integrated Turf Management * Pest Management Plans in B.C.

May. 1994 Vol. 3(1): * IPM for Structural Pests * IPM for Cockroaches

Nov. 1994 Vol. 3(2): * IPM Programs in B.C. Cranberries * IPM in B.C. Blueberries

June 1995 Vol. 4 (1): * Garry Oak Pest Update * Biological Control of Aphids in Vancouver * Ladybugs * IPM in BC Agriculture

Dec. 1995 Vol. 4(2): * Preventing Deer Damage * Living with Raccoons * Bats