Excellent advice. Using less-toxic products as a
last resort is always the best way. If using neem oil, be sure to apply in the
evening since it is highly toxic to bees. Keep in mind that pyrethrum
(synthetic or natural) is toxic to aquatic life. I know both are used in
organic practices but remember, even though something is considered "safer" or
"less toxic" it does have a toxicity because it is "killing" something. Even a
toilet bowl cleaner is considered a pesticide. Always follow the instructions
on the label.
I found very helpful this year was to examine all my brassica plants when
aphids first started showing up, and squishing them then. It seemed to curb
population expansion, since the nymphs mature in 1-2 weeks. Prevention is
really the key with any pest/disease, starting with healthy soil. Pests go for
the weaker plants (generally). Pest prevention begins with healthy transplants
going into healthy soil.
homemade "soap" sprays won't include that commercial insecticidal soap does is
pyrethrum, a botanical toxin. True insecticidal soap works well in my
experience. Anticipate repeated applications.
from The Organic Gardener's Handbook of Natural Insect and Disease Control,
Barbara Ellis and Fern Bradley, Eds...
vegetable crops and small ornamentals, spray smaller plants frequently with a
strong stream of water to knock aphids off; attract native predators and
parasites by planting pollen and nectar plants; release purchased aphid
midges, lady beetles, lacewings, or parasitic wasps; use homemade garlic,
quassia, or tomato-leaf sprays; spray insecticidal soap; as a last resort,
spray infested plants with neem or pyrethrum. For fruit or shade trees, spray
dormant oil to kill over wintering eggs, and plant flowering groundcovers in
home orchards to attract predators and parasites."
Paco John Verin
City Wide Coordinator - Philadelphia
The Pennsylvania Horticultural Society
100 North 20th Street, 5th
Philadelphia, PA 19103-1495
Phone: 215-988-8885; Fax
We have a small organic community garden
plot in Berkeley, California. Lately we have been experiencing
ever-increasing numbers of aphids which are doing considerable damage to our
winter greens. We've tried spraying them off with a high-pressure nozzle,
hand-picking them, and just recently, applying a mild soap solution. Can
anyone recommend any other successful strategies for dealing with these
critters, or ways of maintaining our plot that will make it less desirable
for them to inhabit?
Aphids seem to be attracted to stress of one kind or another. In
community gardens where space is limited, stress is often from
over-crowding. If spacing is the problem, it can often be
overcome by removing/thinning every other plant or even more. Over-watering,
under-watering, and soil deficiency are other stress inducers, but
overcrowding is the most common in a community garden. Remove the
stress and the aphids will usually disappear. When
planting winter greens put yourself in the seed's shoes. How large do
you want to be when you grow up? Give the seed enough space to become
all that it can be and it usually will. When the plant is growing
whenever the leaves touch the neighbor plant's leaves, try removing the
neighbor plant. Roots don't like to intrude on another plants root
zone...very stressful for a brassica.
Add a good amount of compost and/or a brown/green mulch around all the
plants. The mulch will retain moisture and will feed plants when
decomposed. Add mulch layers regularly.
Wishing you bountiful cabbages,