Maritta Perry Grau
Frederick County Master Gardener
(6/8) One of the best practices
you can add to your gardening repertoire is IPM, "a
research-based holistic approach to pest management
that emphasizes biological (e.g., attracting natural
enemies, cultural (e.g., planting disease-resistant
varieties), and physical (e.g., hand removal of insect
pests) approaches to prevent problems and control
pests and diseases at acceptable levels….Monitoring
and using organic or other low-risk pesticides only
when pest or disease levels are unacceptable are also
part of this management approach" (https://extension.umd.edu/hgic/topics/how-id-prevent-and-manage-plant-problems).
Many predators and parasitoids
are your friends: they pollinate your plants and
attack destructive pests, whether larvae or adult. For
example, ladybugs will eat aphids, white flies, potato
beetles, mites, and other bugs. According to Chris
McLaughlin’s "Predatory
Insects in the Garden" in the magazine Fine
Gardening, the Green Lacewing insect is the "Aphid
lion" of the garden, its larvae eating as many as 60
aphids in one hour. Lacewings also eat mealybugs,
spider mites, scale, and thrips, etc. Tiny
Trichogramma wasps "lay eggs inside the larvae of
garden pests such as cabbage worms, cutworms, and
borers," McLaughlin notes. As the eggs hatch, they eat
the larvae from the inside.
As I’ve advised before, take
at least a weekly walk around your garden to spot
problems early on: Closely study visible plant parts,
including undersides of leaves. Where you see a pest,
are you looking at an egg, a larva, an adult? Once
you’ve identified the pest or plant problem, try using
physical and cultural methods first to resolve the
problem. You may pick off destructive pests by hand,
wash them off with a hose, or wipe them away with a
cloth. Remove dead, diseased, and infested plant parts
as needed (be sure to clean/disinfect your tools
afterward). Of course, avoiding all-kill sprays means
that your flowers, vegetables, and fruits may not look
perfect. Learn to live with that. When I find a big
yellow and black-striped caterpillar munching a
milkweed leaf, I’m happy—that means a monarch
butterfly will eventually emerge.
So when should you use a
pesticide? When you’ve tried everything else to
eradicate the problem. For example, one IPM control
for bagworms is handpicking. Next, you may opt to lop
off the branch to which the bag is attached. However,
if the worms are crawling around on branches, and you
can’t get them all, you may need to spray. The
University of Maryland Extension Service
recommends using the microbial insecticide, B.t.
(Bacillus thuringiensis), against bagworms between now
and mid-July, as it works well only on immature
bagworms.
As reassurance, the Minnesota
Department of Natural Resources states that studies
show that "In
general, Bt is very safe for use. The U.S.
Environmental Protection Agency has found no hazards
to human health associated with the use of Bt…. The
EPA has exempted it from food residue tolerances,
groundwater restrictions, endangered species labeling
and special review requirements. Bt has no known
effect on … bees, fish, birds, and wildlife. It is the
pesticide of choice for use near lakes, rivers, and
dwellings."
Another effective IPM tool is
knowing whether the plant is right for your zone, for
the soil, for the amount of water, sun/shade that it
gets. According to the UMD extension service, "The
best management method is prevention. When you focus
your time, attention, and efforts on growing ‘the
right plant, in the right place, in the right way,’
you can greatly reduce plant problems."
Biodiversity is also an
important part of IPM. With a variety of plants, you
will attract a greater variety of insects. Using
companion plantings helps, too. Much like using
predator insects and parasitoids, planting different
crops near one another makes IPM easier, helps with
pollination, and provides habitat for those beneficial
insects mentioned above. Amy Grant,
notes that all types of onions and peppers, as
well as spinach, lettuce, carrots, asparagus, and
arugula, can be planted alongside tomatoes. A number
of herbs and flowers are also good at deterring pests
from tomatoes—for example, borage, parsley, mint,
marigolds, and nasturtiums.
However, some plants don’t do
well together. For example, the Brassicas (broccoli,
cabbage, etc.) should not be planted with tomatoes;
nor should corn, as corn tends to attract the tomato
fruit worm. Having potatoes near tomatoes increases
the chance of potato blight disease.
All of these elements will
affect how well the plant grows and how susceptible it
is to disease and pests.
Read other articles about controlling insects & garden pests
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