CULT:Beneficial insects
- Subject: CULT:Beneficial insects
- From: B* S*
- Date: Thu, 04 Apr 2002 13:06:12 -0500
On 4/3/02 6:19 PM, "Janet" <janett@telusplanet.net> wrote:
> I've finally had the opportunity to look at the site. It is wonderful and
> coming from Alberta, I can appreciate the work you have done as years back I
> worked with archeologistst and paleontologists associated the Tyrell Museum
> of Palentology.
>
> With your specialization in entomology can you share your thoughts about
> introducing certain insects that may be beneficial to the irises and the
> garden beds themselves? I'm curious if you have found it easier to use
> pesticides or if you use some of the methods which use one variety of insect
> to combat others - such as ladybugs against aphids. I know that irises have
> the boring insects and I would be very interested in hearing your thoughts on
> this. Because I do not use pesticides, I find at times my yard is crawling
> with insects. I really don't know if that means my
> yard is healthy or not, but I'm not a big fan of insects. I always let
> spiders live because they eat other insects and I love the birds nesting
> around my yard because they eat the mosquitos in summer. Bees are always
> welcome in my garden, but I'm frightened silly of the things as I've never
> been stung and am allergic to other insects. I've tried planting some garlic
> around fruit trees to ward off those little red spider mites, but I would love
> to know what things I could use to deter insects from my irises.
Introducing beneficial insects is something that has been way oversold to
the backyard gardener. The introductions often fail to survive or simply
fly away somewhere else. Also, most of the available species are generalist
predators that do not specialize on particular pests. Not to say that they
can't be of use, but if you are concered about one or a few pest species,
you would getter better results using a specialist species for control.
The introduced Asian ladybug has become a pest itself in some parts of the
country, including here, where thousands invade buildings every fall. They
smell bad and make stains when crushed.
Much greater success has been had in small plots by manipulating the
envirornment to improve the chances of the native predatory and parasitic
insects that might be present. Researchers at the University of Tennessee
have found that simply providing a loose mulch and planting companion
flowers significantly reduced the damage to broccoli plants. The main
predators responsible were spiders, which hid in the mulch from their own
predators. The flowers attracted and fed predatory and parasitic wasps and
bees, which attacked cabbage worms and other pests. The key to using
generalists seems to be in building up very large populations, something
difficult to do with introductions.
The only really significant insect pest of irises is the iris borer. The
damaging part of its life cycle takes place INSIDE the plant where predators
can't get at it. For control measures, see THE GARDENER'S IRIS BOOK.
Aphids are unsightly and also can reduce the vigor of iris plants. A major
predator of aphids is the Daddy Longlegs, a spider-like creature common in
most gardens. Lacewings and lacewing larvae can also reduce aphid numbers.
If these predators are not present, spraying with a soap solution quickly
elminates aphids, as well as mites and scale insects. I favor Murphy's oil
soap, about a teaspoon to a quart of warm water (even this is probably
stronger than needed). It quickly biodegrades.
So far as I know, there is no evidence that planting garlic deters any
pests, including spider mites. Unfortunately, while there is often a lot of
value in folk wisdom, there is also a lot of nonsense.
The nonsense is not limited to folk remedies. Many firms offer sonic pest
repellers, which have been shown repeatedly to have no effect whatsoever on
insect populations, yet there is this veneer of "science" and technology
which promises success. In fact I just got a catalog today from an outfit
headed by Jerry Baker, "America's Master Gardener," and it included the
useless sonic devices at the usual high price. Makes me wonder about some
of Jerry's other advice!
Bill Shear
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