Skip to Content.
Sympa Menu

market-farming - Aphids in greenhouses

market-farming AT lists.ibiblio.org

Subject: Market Farming

List archive

Chronological Thread  
  • From: Adriana Gutierrez & Dennis LaGatta <gutierrez-lagatta AT home.com>
  • To: market farming <market-farming AT franklin.oit.unc.edu>
  • Subject: Aphids in greenhouses
  • Date: Sun, 06 Feb 2000 05:49:49 -0500


Aphids are the cockroaches of the greenhouse world. If I'm not
mistaken ALL aphids are female, are born pregnant and bear at least 250
live young over their life span. Let me preface this by saying that
while I am not certified organic I believe in using the least-toxic
methods of pest control. I can tell you that I've tried all of the
suggestions reported to date and many others including: ladybugs,
lacewings, kelp strays, molasses and Safer soap, all with limited
success. The beneficials tend to fly away over time, even the so-called
"Stay-at-Home" lady beetles. I continue to use these occasionally but
the most consistently effective treatment for me is a spray of:

1 part Murphy's Oil Soap
1 part alcohol
9 parts water

I can not tell you if this is kosher with the certifiers but I know of
an "organic" grower in our area who uses this. One of our local retail
nurseries swears by Ultra Fine Oils (which if I'm not mistaken are not
allowed for those of you who are certified?), however I have repeatedly
had bad results with them. I get black spots on all of the plants.
However, I believe part of my problem is my inability to spray in the
late afternoon (my greenhouse is not near my home). The official line
is not to spray oils when it is hotter than 90 degrees - in my belief if
the sun is shining it magnifies through the droplets and burns the
plants regardless of temperature. Therefore, try spraying in the
afternoon.

THE most effective treatment is cool weather. If your plants can take
it drop the temperature in the greenhouse into the forties or even
thirties for a couple of days and it will slow down the reproduction
rate dramatically. Forceful spraying with a hose also provides good
knockdown - in my case I grow mesclun greens, densely seeded and this is
usually not an option. I did do this on an infested lemon tree with
good results.

Whatever treatment you select, especially sprays, you will need to
repeat it every three days for a couple of weeks. If you're not
certified organic, natural pyrethrins will help, as will neem. Rotating
the sprays will keep the critters from building a resistance. I have
also read that keeping a couple of finches in the greenhouse cuts down
on bug problems considerably, I suspect more the slug, snail, cutworm
crowd but maybe aphids too.

The long term management of aphids in the greenhouse requires a good
impervious insect netting (I believe an ultra-fine one is now
available), a healthy supply of beneficials, extraordinary precautions
in the introduction of outside plants, controlling the entrance of
outsiders, especially people who work with plants, into your
greenhouse. If you have an ant problem you will need to take care of it
as they have a symbiotic relationship with the aphids. I'm in a
temporary greenhouse situation now which doesn't allow me a lot of these
controls, but in my next, permanent greenhouse I plan to grow a band of
beneficial attractant plants around the entire perimeter of the
greenhouse. Gardens! Alive and other suppliers sell mixes of seed or
you can make up your own.




Archive powered by MHonArc 2.6.24.

Top of Page