Claire
West
EHUF
490 – Native Plant Production
Spring
2004 – Prof. Kern Ewing
Guidebook
for Native Plant Propagation:
Herbivore
and Insect Protection in Restoration Nurseries
Herbivory in the Pacific Northwest
Restorationists and gardeners alike
in the
Protection Methods
Physical Barriers
Fences are
an obvious precaution, especially important where populations of deer, rabbits,
and other herbivorous rodents and mega fauna are prominent. A seven-foot fence
is sufficiently tall to keep out more aggressive predators, but it is important
to choose the appropriate materials for the nursery’s location and goals. The
wire mesh/metal stakes approach is practical for smaller nurseries; it is
advisable to use a mesh with spaces no larger than four inches wide, and secure
that to support stakes placed approximately six feet apart. This technique is
inexpensive while allowing for quick construction and disassembly, as well as
enabling the nursery and stock to remain visible to passers-by. Chain link also
serves these purposes, but is more costly. Synthetic fencing products are also
available, and are specially designed for durability in constant UV exposure;
while this option is not sturdy enough to protect plants from wildlife, it may
be useful around walkways and parking lots to prevent plant damage from human
negligence. A comprehensive guide to fencing options, expenses, and
construction is available at the Home Depot website.
Often, the physical placement of
nursery ‘furniture’ can influence predator behavior; landscape elements like
rock structures and hedge plantings around the fence make the material inside
less appealing, and the fencing less passable. Also, strategic placement of
benches, polyhouses, and wet/capillary beds a few feet inside the fence deny
potential fence-hoppers a safe landing spot. The most efficient design in product
protection should be considered from initial conception of nursery layout.
Netting is frequently necessary to
prevent interference from bird species, which are most commonly crows and geese
in our region. Container plants are especially vulnerable to uprooting and
vegetative structural damage from hungry and curious birds, inhibiting healthy
establishment. Birds are also a threat to the on-site seed source, grazing on
maturing fruits of nursery plants, and in this way reduce a nursery’s
production potential. Products like Gardnet Anti-Bird Netting, as promoted by
Hummert International, is a ¾ in. sturdy plastic mesh, and is available for
approximately $20.00 for 700 square feet. Netting is a necessary investment for
nursery success.
Mateirals like remay or a
poly/plastic covering is more frequent on a restoration site or in an
agricultural setting where seeds are sown directly. But if seedlings are
started outdoors, removable, versatile protection such as this may be a
necessity. Such barriers are effective against insect invasion as well.
Entrances to greenhouses and poly houses are a common oversight when
considering paths for insect introduction; screens on fans, doors, and
ventilation can save time, resources, and seedlings. Hummert offers Green-Tek
and Econet screens, which are fine enough to prevent passage of most winged
pests, like thrips, whiteflies and aphids. A product called ‘Envriomesh’ is new
on the market and relatively inexpensive, and is specifically designed to
inhibit insect infestation of young plants. Floating row covers are popular and
serve the same function, not just for sensitive seedlings but established
plants as well.
Chemical Applications
Fencing and netting are more permanent and very necessary structural components to the successful nursery, but sometimes it is advisable to topically apply chemical amendments to local target species. Commercial products like Bobbex have been consistently successful in deterring deer herbivory, but organic substances like blood meal and egg whites are an effective alternative for the more environmentally conscious nursery site. Similarly, replacing chemical slug bait, which poses potential harm to pets and small children, with diatomaceous earth (or even cheap beer) solves the problem of gastropods in a safe, non-toxic fashion.
Protection from Insects, Bacteria
and Fungus
Individual plant health, as
affected by insects, fungal infections, and bacterial presence is another large
component of nursery stock defense. The screens and portable covers mentioned
earlier are a more ecologically friendly approach to deter insects, but are
only one option when it comes to plant protection. Pesticides, fungicides, and
bactericides are commonplace and effective throughout the nursery system, and
come in many forms.
Conventional pesticides are
typically harsh chemicals that can pollute local water supplies, have
unintended consequences for other animal life, and breed genetically enhanced
‘super bugs.’ They tend to be used as reactive tactics against infestations
that, using more holistic, planned production methods, can be prevented from
initial stages. The Appropriate Rural Technology Transfer suggests a
Biointensive Integrated Pest Management (IPM) strategy that involves a broad
range of preventative measures to ensure that nursery stock stays pest, fungus,
and bacteria-free from seed start to restoration site. For the greenhouse, they
suggest in-house weeding as a means of sanitation (as insects can and do live
on the weedy species), in conjunction with screening of the house (mentioned
above), and implementing biological controls if and when harmful insects
surface. For example, if an aphid infestation should occur, beneficial insects
like ladybugs or praying mantis would be introduced to eradicate the problem.
To ensure that soil used in production is bacteria and fungus-free, the IPM
strategy is insistent on soil sterilization (when soilless medium is
unavailable). A suggested eco-friendly approach is a technique called
solarization, where soil is covered in clear polyethylene tarps, trapping
sunlight and heating soil to 212° F, at which temperature all harmful pathogens
are eradicated after 30 minutes. Beginning with disease-suppressive potting
mixes can remove the need for this process, but this is a good technique to
make the best of available materials.
Powdery mildew on
a flowering currant
Climate
control of the greenhouse is integral in preventing vegetation damage from mold
and other fungal damage; constant surveillance of humidity levels and
temperature is the best preventative against moisture buildup and disease
outbreak, and is an easier task than having to start a new crop or nurse
damaged plants back to health. An innovative, low-cost solution to fungal
infection (again, if and when it occurs) is baking soda, which, when combined
with horticultural oil is effective against powdery mildew and, as recent
research claims, leaf spots, scab, anthracnose, phoma, botrytis and
phytophthora. The Rural Technology Transfer also suggests using compost teas as
a further means of disease control.
Alternative, largely organic
approaches are, in most cases, more financially viable options for the small
nursery budget, and are better for the plants overall. These pest control
measures, in conjunction with a good, sturdy fence and enough bird exclosure
netting, make for a productive, prosperous and pest-free nursery.
SOURCES
The
Home Depot Fencing advice web page:
Hummert
International: Distributor of Horticultural Products
Business:
http://oregonstate.edu/dept/nurserystartup/new/Web_Files/home.htm
Rural
Technology Transfer website, Integrated Pest Management page:
http://attra.ncat.org/attra-pub/nursery.html#IntPestMgmt