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Re: Question about natural control of aphids

  • Subject: Re: [cg] Question about natural control of aphids
  • From: "Deborah Mills" deborah@greencure.org
  • Date: Tue, 29 Oct 2002 09:35:15 -0800

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.

What 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.
What 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.
And from The Organic Gardener's Handbook of Natural Insect and Disease Control, Barbara Ellis and Fern Bradley, Eds...
"For 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 Green
The Pennsylvania Horticultural Society
100 North 20th Street, 5th floor
Philadelphia, PA  19103-1495
Phone: 215-988-8885; Fax 215-988-8810

-----Original Message-----
From: Jon Rowley [mailto:rowley@nwlink.com]
Sent: Tuesday, October 29, 2002 10:22 AM
To: community_garden@mallorn.com
Subject: [cg] Question about natural control of aphids

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?
Thank you!
Paul  Revier
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,
Jon Rowley
Interbay P-Patch

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