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market-farming - insecticidal soaps and cabbage pest control - long

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  • From: Marcie Rosenzweig <fullcircle AT jps.net>
  • To: market-farming post <market-farming AT franklin.oit.unc.edu>
  • Subject: insecticidal soaps and cabbage pest control - long
  • Date: Sun, 29 Apr 2001 08:43:02 -0700


Hi folks,

One of the problems with getting the digest is that there's a delay in the
interaction, so please bear with me if these things were covered before I
got the originals.

The key to least toxic pest control is first to identify the pest correctly
then to understand the life cycles and physiology involved. Insecticidal
soaps work best on soft-bodied sucking insects like aphid, white fly, and
mites. Their actions are 1) smothering the insect by plugging the
breathing apparatus and 2) dessication by removing the waxy coating that
keeps them from drying out on their own. They must make contact with and
cover the pest in order to be effective. They work on aphid and mites in
part because these pests are fairly immobile even in the adult egg-laying
stage and in part because you miss enough of the territory to knock their
population down without taking out the preditory mites, lacewing and lady
beetle larvae that feed on them.

These soaps, alone or in combination with cayenne pepper are not
particularly effective for chewing insects like imported cabbage moth or
cabbage loopers because 1) the adult egg-layer is quite mobile so you are
not significantly reducing the populations by spraying and 2) because these
insects are difficult to cover thoroughly enough to smother- you may as
well hand-pick these critters if you've got time to do try this approach,
and 3) these guys will crawl to a leaf thats newer of more palitable if
they "don't like the taste" of the one they're munching on. If you have a
plot of any size and you are growing crops to make a living, soaps aren't
the solution for you.

Two other points to consider. If you are growing crops and plan to sell
them as organic, you must use only approved materials. Soaps are not
generally labeled for use against cabbage worms. Also, you will not be
able to use homemade soap sprays under this circumstance. Homemade sprays
may be phytotoxic and actually kill your crop if you use the wrong soap to
make them. Organic weed control sprays like the one Safers used to make
are actually soaps made with long-chain fatty acids. If you're a
backyard gardener and you're not selling commercially as organic, you might
look into the old Palmolive and Murphy's as both used to be made with
vegetable oils and were generally safe for plants. This may have changed -
do your homework first.

The best controls against wormy cabbage pests are timing, barriers, and
biocontrols. Loopers are a pest that is predictable so you can time crops
- again, this is a better solution for home gardeners than production
farming. Barriers have already been mentioned. I've used row covers very
effectively on crucifers. Personally, I think biocontrols are the best
resource for holdings of any size.

Bt is still the fastest and most effective weapon we have against
lepidopteran pests. To help avoid resistance, I mixed that with other
biocontrols like releasing or fostering habitate for trichogramma wasps.
If you release trichogrammas, you'll need about
100,000 per acre. I also don't disturb paper wasps or yellow jackets
unless they are outside the door to my house or barn. They will take out a
significant number of larvae. Birds do too. There's also the homemade
virus spray. Nuclear polyhederosis virus attacks cabbage loopers. They get
really chauky white then turn black and liquify. If you can find them in
the white stage, you can put about 10 of them in a blender with some water
then dilute this solution in even more water in a 2 gallon sprayer and take
care of about an acre of cabbage, broccoli, lettuce and the like.



Marcie A. Rosenzweig
Full Circle
Auburn, CA






  • insecticidal soaps and cabbage pest control - long, Marcie Rosenzweig, 04/29/2001

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