"Biological
Insect Control
in Nursery and
Landscape Settings"
By Mario Lanthier and Tania Jensen, CropHealth Advising & Research,
July 2001.
Prepared for the B.C. Ministry of Agriculture, Fisheries and Food.
A modified version was published in the 2002 version of the "Nursery
& Landscape Pest Management & Production Guide".
- Tips to build
a resident population of beneficial insects;
- Using pesticides with minimal impact
on beneficials;
- Other resources on beneficial
insects
A favorable environment will attract beneficial insects to a nursery or
a landscape setting. With most
predator species only the immature stages feed on pests such as aphids and
thrips. The adults prefer to feed
on flower pollen. For example, the
female syrphid fly requires flower nectar to produce eggs.
Thus, the fly will be attracted to a site with flowers, will feed, and
then search for an aphid colony to lay eggs within.
Techniques that can be used to build a resident population of beneficial
insects include diversifying the garden landscape, planting appropriate flowers,
retaining banker plants, and releasing commercially reared beneficial insects.
Diversifying the garden
landscape
A crop or landscape with low plant diversity is less desirable to
beneficial insects. A diversified
landscape with a variety of flowers, shrubs and trees, and small sources of
water will provide shelter, alternative food sources, overwintering sites, and
water for predator insects. A
succession of flowers over the season will provide a continuous supply of pollen
and nectar for feeding adults.
Planting appropriate
flowers
Many researchers have examined the value of different flowers to attract
predator insects. For example,
clover, buckwheat, and yarrow are excellent flowers to attract Orius
(minute pirate bugs), an important predator of nursery and flower production,
whereas dill, fennel and yarrow will attract lady beetles, syrphid flies and
parasitic wasps.
On another page is a list of flowers
and shrubs to attract beneficial insects in British Columbia.
Retaining banker plants in the nursery
Plants already colonized by aphids, thrips, or spider mites will attract
beneficial insects. Keeping a few
infested plants will allow the predator population to increase and disperse over
the rest of the site. If a large area is
infested by a pest problem, the site manager can treat one section first,
wait a few days, then treat the other section. This will preserve
some of the resident predator population.
It is important to be patient and allow nature to do its work.
The goal of sound pest management is to keep the situation under control
and prevent plant damage, not to wipe out all insects.
Releasing
commercially-raised beneficial insects
Purchasing beneficial insects is a good method to augment the resident
population of predators and parasites. This
practice is commonly used for greenhouse crops, in propagation areas, and in
specific landscape situations.
However, not all situations are favorable to this practice. For instance many species of lady beetles sold by
insectaries, such as the convergent lady beetle Hippodamia convergens,
will instinctively fly away upon release and will provide little benefit to a
small outdoor landscape. The aphid
midge Aphidoletes, another excellent predator of aphids, requires open
soil that is not disturbed at the base of the plant and is more appropriate in
greenhouses or rose gardens than in field production or street plantings.
On another page is a list of Canadian
suppliers of beneficial insects.
Pesticides are important in pest management programs.
They can also be harmful to naturally occurring predators and parasites.
In many situations, an outbreak of aphids or spider mites can be traced
back to a pesticide application that destroyed the beneficial insect population.
Treating problems early in the season and using pesticides of low
toxicity to beneficials are two techniques to preserve the resident population
of beneficial insects.
Treating problems
early in the season
It is important to treat some pest problems early in the season and to be
more tolerant later in the spring and summer.
For example, a pesticide treatment to Malus and Prunus early in the
season may be sufficient to bring the aphid numbers to a low level that
predators and parasites can easily control during the summer.
In other situations, the aphids become active many weeks before the
predators arrive. For example, the
aphid winter eggs will hatch at bud break on Viburnum and Cornus
well before any predator insect is active. On
these plants, it is important to treat at the time of bud break to prevent
serious plant damage.
On plants such as Potentilla and Spiraea, the aphids will
appear during summer months when a large number of predators are already
present. A pesticide application
may not be necessary during this period.
Using pesticides of low
toxicity to beneficials
Pesticides vary in their toxicity to predators and parasites. Generally, broad-spectrum products, which control a large
variety of pest problems, will kill beneficial insects whereas
narrow-spectrum products and short-residual products are less harmful.
On another page is a list of pesticides
commonly used on ornamental plants and their impact on beneficial insects.
Publications
- “Field Guide to Harmful and
Beneficial Insects and Mites of Tree Fruits”
H.G. Philip and Linda Edwards, B.C.
Ministry of Agriculture, Fisheries and Food, 2001.
An excellent pocket-size publication
with colour pictures of common predators of tree fruit, often the same predators
that are found on landscape plants.
Available from the B.C. Ministry of Agriculture, Fisheries and Food in
Kelowna, 250-861-7211. See more information at the website
http://www.al.gov.bc.ca/cropprot/fieldguide/preface.htm.
-“Integrated Pest Management Manual
for Landscape Pests in British Columbia”
L.A. Gilkeson and R.W. Adams, B.C.
Ministry of Environment, Lands and Parks, 2000.
This recent publication has a section on
biological control, including a description of insect parasitic nematodes,
predatory midges, lady beetles and predatory mites, as well as natural enemies
commercially available for various pest problems.
Available from the Office Products Centre in Victoria, 1-800-282-7955, or
on-line at
http://wlapwww.gov.bc.ca/epd/epdpa/eripm/landtoc.htm.
-“Floriculture Production Guide for
Commercial Growers”
Christine Koch, B.C. Ministry of
Agriculture and Food and the B.C. Horticultural Coalition, 1999.
Commercial growers rely extensively on
biological control for the production of flowers inside covered structures.
The section on biological control agents consists of a pest-by-pest list of
biological control agents available for planned releases, such as the aphid
midge Aphidoletes aphimyza, the predatory mite Hypoaspis miles,
and the minute pirate bug Orius species.
Available from the B.C. Ministry of Agriculture in Abbotsford,
604-556-3001.
- “Natural Enemies Handbook: The
Illustrated Guide to Biological Pest Control”
M.L. Flint and S.H. Dreistadt,
University of California Press, 1998.
An excellent book at a very affordable
price, it includes numerous colour pictures and pages of technical details.
Available from the Communication Services of the University of
California in Oakland, 510-642-2431 or visit the web site http://danrcs.ucdavis.edu
-“Organic Tree Fruit Management”
Linda Edwards, Certified Organic
Associations of British Columbia, 1998.
A publication written for growers, it
includes practical information on naturally-occurring beneficial insects.
Available from the Certified Organic Associations of British
Columbia, Box 577, Keremeos, B.C. Canada, V0H 1T0, or on-line at
http://www.certifiedorganic.bc.ca/Booksand/OrganicTreeFruitManagement/OrganicTreeFruitManagement.htm
-“A Field Guide to Beneficial
Insects and Arachnids in British Columbia Seed Orchards”
Michelle J. A. Hall, British Columbia
Ministry of Forest, 1996.
A well-researched publication based on
field monitoring by the author and an extensive literature review.
Each predator insect is fully described, along with colour photographs.
-“Beneficial Insects and Common
Pests On Strawberry and Raspberry Crops”
D.E. Henderson and D.A. Raworth,
Agriculture Canada, 1991.
This pocket-size publication has a
strong description of beneficial insects, along with colour photographs and
details on insect prey.
Available from the Communications Branch of Agriculture Canada in Ottawa,
Ontario, K1A OC7.
-“Applied Bio-nomics Ltd.:
Biological Technical Manual”
A technical publication aimed at
individuals wishing to purchase beneficial insects for commercial releases.
For more information contact Applied Bio-nomics Ltd., 11074 West Saanich
Road, Sidney, B.C., V8L 3X9, 604-656-2123.
Web sites
- “InfoBasket”
http://infobasket.gov.bc.ca/Infoman/
A web site maintained by the B.C.
Ministry of Agriculture, Food and Fisheries with links to a large number of
other websites on beneficial insects.
- “Harmful and Beneficial Insects and Mites of
Tree Fruits”
http://www.al.gov.bc.ca/cropprot/fieldguide/main.htm
A web site maintained by the B.C. Ministry of Agriculture, Food and
Fisheries. Predator insects commonly found in tree fruit orchards of
the Okanagan Valley are illustrated, along with a short technical
description.
- “Biological Control: A Guide to
Natural Enemies in North America”
http://www.nysaes.cornell.edu/ent/biocontrol/
A web site maintained by Cornell
University, it includes information and pictures of many predators, parasites
and pathogens.
- “World Wide Web Biological Control Sites”
http://www.nysaes.cornell.edu/ent/biocontrol/websites.html
Links to a large number of web sites on this topic.
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