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ALTERNATIVE PEST CONTROL AGENTS

Rick Besson, Entomologist

Spraying with any insecticide, organic or not, should be a
last resort. Effective pest management begins with prevention.
Their are several good farming practices which can prevent pest
problems. These include using raised beds (controls the spread
of disease) and crop rotation (disrupts the cycles of insects in
the soil).

1. Steps to Successful Pest Control

Detection. A key to successful pest control is early
detection. Walk the fields regularly, being observant. This can
help avoid getting caught in situations that require difficult
decisions.

Identification. It is very important to be able to identify
pests. Problems cannot be managed if they are not recognized.
This cannot be stressed enough.

Evaluation. It is important to evaluate the significance
of the pest. The simple presence of a pest in the field does not
necessarily warrant concern. Before it is considered a problem,
populations must be at certain levels and the crop at a
vulnerable stage.

Consider the alternatives. There will generally be several
alternatives for dealing with problems. Many of these begin with
prevention. When problems are discovered, preventative tactics
should be initiated to prevent them from happening again.

2. Properties of a Desirable Insecticide

1. Selective-- controls a certain pest but does not affect
other beneficial or innocuous species.

2. Degrades rapidly

3. Low human and environmental toxicity

Unfortunately, these standards are not fully satisfied by
any synthetic, biological or botanical insecticide.

3. Biological Insecticides

Biological or microbial insecticides are derived from
microbes growing in the environment. They have some definite
advantages:

* non-toxic to humans -- in fact many are less toxic than
coffee or aspirin;

* very specific -- they target a single species or a group
of closely related species;

* degrade rapidly;

* can often be used right up to harvest without the required
field entry intervals.

However, they also have several disadvantages:

* very specific -- This can be a disadvantage if the plant
is being affected by a complex f several species;

* degrade rapidly;

* costly - There are few distributors and the cost can be
expensive;

* slow acting -- Some biological insecticides have a slow
response time. This needs to taken into account in deciding when
to treat.

Common Types of Biological Insecticides

* Bacillus thurgiensis (bBt) -- There are over sixty
recognized varieties of this bacteria, but only four are
available on the commercial market. Bt is actually just like a
regular insecticide; by the time one sprays it the bacteria has
been killed and all that's left is the little protein, called a
delta endotoxin. It is used like any other insecticide. Insects
can develop resistance to Bt like they can to synthetics.

* Bacillus thurgiensis (Bt) var. kurstaki -- [NOTE: All
commercial brands of this strain are not the same. Some work
better than others.] Kurstaki is the strain used to kill
caterpillars, the larvae of moths and butterflies. It is not
effective on other pests. Bt var. kurstaki is a stomach poison
and must be ingested by the insect. It works by tearing up the
paratrophic membrane in the insect's stomach. The insect stops
feeding almost immediately and dies within a few days.

* Bt var. Israelensis (Bti) -- This strain kills fly
larvae. It is used in greenhouses to kill fungus gnats. It is
also used in the control of black fly larvae. Bti doesn't kill
caterpillars or beetles, only specific types of fly larvae.

* Bt var. tenebrionis -- This strain is used to kill some
types of beetle larvae, including the Colorado potato beetle and
elm leaf beetle. There is evidence of some resistance developing
in the Colorado potato beetle in the Northeast where large potato
production occurs. It has only taken about two years to see
resistance in the beetle. To be effective, Bt var. tenebrionis
requires a high pH in the gut. Most beetles, such as the lady
beetles and other beneficials are unaffected because of the low
pH in their stomachs. This strain is used in control of about
six beetle species. [NOTE: The Colorado potato beetle is
somewhat unique among insects. It has an amazing ability to adapt
to just about anything humans develop to kill it].

* Bt var. aizawai -- This strain was marketed years ago and
has recently been reintroduced. In this area it is sold under
the trade name, XenTari. It is more effective than the kurstaki
on some pests. As with kurstaki it kills only caterpillar
larvae. It is used in the control of some of the most
troublesome species including the diamondback moth and the beet
armyworm.

To use Bts or other Microbials Correctly

1. Identify the pest correctly -- If pests are not
properly identified, the microbials cannot be
effective.

2. Remember that Bts only attack certain life stages.
They are not effective against adults, only larvae.
Also, keep in mind that the smaller the instar the
smaller dose it will take to kill it. NOTE: Instar --
A small number of insect species, (grasshoppers, for
example) develop in a pattern called incomplete
metamorphosis. This pattern involves a succession of
molts. After the embryo develops into a nymph, which
is a small version of the adult, it feeds, molts and
continues this sequence several times. The periods
between these molts are called instars. Usually after
about six instars the fully mature adult emerges.
These insects do not have radically different life
behaviors between stages of maturity, as do those
undergoing complete metamorphosis (e.g. butterflies).

3. Remember that although the Bts may not instantly kill
the insect, they will cause them to stop feeding almost
immediately.

4. All biologicals are subject to UV degradation, so spray in
the evening.

*Encapsulation -- There are new types of Bt available,
which have been encapsulated (MVP-kurstaki). The gene is placed
in the bacteria pseudomonas fluorescence. The bacteria produces
the Bt protein crystal. The bacteria is then killed. When it
dies it forms an envelope around the crystal. This helps reduce
the UV degradation. There is some uncertainty about the organic
restrictions on genetically altered bacteria. With this
particular strain, while there is a small improvement in its
performance, there is a large increase in the cost.

Nematodes. Nematodes are tiny roundworms. These sucking
organisms feed with a small stylet. When they are inside the
insect they fit the stylet into various organs. Beneficial
nematodes are classified as entomophagus (ento - insects, phagus
(feeding). They are very selective, feeding only on certain
types of insects. They are typically effective against insects
that occur in the soil or bore into plant material. This is
because nematodes are extremely sensitive to desiccation. They
need to be in a very moist environment, such as soil or in a tree
or shrub.

NOTE: Many packages of commercial nematodes have a short
shelf-life. Make sure nematodes purchased are fresh. Most
advertised brands are guaranteed for two months after purchase.
In tests there was no viability after three months. Try to buy
them from the manufacturer. Nematodes are effective against many
insects including cutworms and white grub species.

Viruses. There is a naturally occurring virus which is
used in control of the beet armyworm. The beet armyworm comes
from the South, where it is a major pest on cotton. Having been
a pest on cotton (heavily treated with chemicals for years) the
beet armyworm is resistant to all synthetic insecticides. There
are encouraging results with the virus nuclearpolyhedrosus (NPV).
It only kills one species and has no effect on closely related
varieties in the same genus. It took 10 - 17 days to effect 70%
control. There two strains of the virus.

The virus has two positive features:

1. very selective -- It is non-toxic to almost everything
but the target species.
2. very low use rates -- Typical application is 5 grams of
the virus per acre.

Bacteria. Bacillus popillae is used against white grubs.
It is not recommended anymore because Ringer, the company that
marketed it, tested the product and found it had no active
ingredient. These bacteria are produced commercially by loading
vats full of insects and fermenting them with the bacteria.
Ringer found they were fermenting some non-pathogenic species.

4. Botanical Insecticides

Botanicals insecticides are used almost as much as
biological insecticides. They are derived from plants.

There are several advantages to using botanicals:

1. degrade rapidly --They are not as selective as
biological, so it is necessary that they degrade quickly;

2. fast acting -- Some work very quickly to stop feeding or
kill the insect;

3. low human toxicity -- This is true for some. Others need
to be handled carefully to avoid unnecessary risk;

4. low phyto-toxicity -- They are safe to plants.

There are also disadvantages:

1. degrade rapidly -- This helps beneficials, but shortens
the length of time the pest population is exposed;

2. toxicity -- Some types are very toxic to the applicator.
As with all insecticides they need to be handled carefully,
taking no unnecessary risks;

3. cost/availability -- Most are available by mail, but can
be expensive. Some can be difficult to obtain. When
ordering by mail it would be good to find out if the product
is registered for use in one's own state;

4. lack of test data -- Unlike synthetics, there has been
little research into the most effective dosages and
frequency. There is still a lot of experimentation in
organic gardening and farming.

Types of Botanicals

* Pyrethrum/Pyrethrins -- Pyrethrum/Pyrethrins are derived
from the pyrethrin daisy flowerhead. Pyrethrum is a fast acting
nerve poison, which has an immediate knock down response (KDR).
It is a contact poison so it must touch the target species.
There is little residual activity, so care must be taken to spray
underneath leaves. Pyrethrum is synergized by piperonyl butoxide
(PBO). Synergism makes a product more effective. In mixtures,
the synergist is ten times more concentrated than the
insecticide. As of yet synergists are not approved for organic
certification, so be careful in purchasing this product. In
marketing pyrethrins, most companies sell a mix. One advantage
is that these products have a low mammalian toxicity. However,
all pyrethrins are very toxic to fish. They should not be used
around streams, ponds, etc. They should also not be sprayed if
there is a danger of runoff.

NOTE: This is different from pyrethroids, which are
synthetic analogs. They are similar, but the pyrethroids are
more persistent and much more toxic. They are not used by
organic growers.

* Rotenone -- Rotenone is derived from the roots of several
tropical legumes (the cuberoot). It is a muscle poison, which
must be ingested to work. After ingesting the poison, the target
insect species stops feeding activity quickly. It was used for
years with the Colorado potato beetle, but they have developed a
resistance to it. It is synergized by PBO, but is marketed
unmixed. Rotenone is toxic to humans (and fish), so precautions
should be taken when using it. It is used for control of some
leaf feeders. Rotenone has a longer residual life than most
botanicals and is effective for about a week.

* Sabadilla -- Sabadilla is made from the seeds of a
tropical lily plant and is available by mail order. It is a
contact nerve poison, which acts very quickly and breaks down
quickly in the environment. It readily degrades in UV light. In
some cases it may act as a stomach poison as well. Sabadilla is
extremely toxic in higher concentrations, so most commercial
products are very dilute, usually 1-2% active ingredient. It
should be used cautiously. Sabadilla is synergized with PBO, but
is sold unmixed. If applying sabadilla, beware that the product
irritates skin and mucus membranes. Sabadilla is effective
against true bugs (e.g. stink bugs, etc.) NOTE: Several true
bugs are among the predaceous beneficial insets. They feed on
insect pests. Keep this in mind, if considering using Sabadilla.
It is non-selective among these species.

*Ryania -- Ryania is derived from the woody stems of
Ryana speciosa, a South American shrub. Ryania is a slow acting
stomach poison. It too is synergized with PBO but is sold
unmixed. The insecticide is moderately toxic to humans and has
low residual activity. Ryania is used to treat pests affecting
corn, apples and pears.

*Nicotine -- Nicotine is considered a botanical but its
use is strongly discouraged. Currently, federal regulations
allow its use as a pesticide in organic growing but it is
extremely toxic to mammals. It is also non-selective, killing
most anything it contacts. It is a fast acting nerve poison. It
is frequently used in greenhouses for control of some soft-bodied
insects. It does degrade rapidly. There are usually much better
alternatives available.

*Neem -- Neem is developed from the seed of the tropical
neem tree Azadrachta indica. Its active compound is azadirachtin
and it has been used for thousands of years in India. Neem has
several modes of action: it is a feeding deterrent and some
believe an ovipositional deterrent as well. It also acts as an
insect growth regulator, disturbing the internal hormone system
thereby preventing insects from molting in their usual
procession. It is effective against the beet armyworm,
diamondback moth, cabbage lopper, and greenhouse whiteflies.
"Align" is a commercial form of neem, which is new on the market.
It has full food crop label. "Bioneem," the more familiar brand
is only approved for ornamentals.

*Limonene and Limanool -- These are citrus peel extracts
which cause insect paralysis. Both insecticides are synergized
by PBO and have the EPAs GRAS (Generally Regarded as Safe)
classification. They evaporate fairly quickly in the environment
and are used to control aphids, mites and fleas.

REFERENCES AND RESOURCES

Ellis, Barbara W. and Fern Marshall Bradley,eds. The Organic
Gardener's Handbook of Natural Insect and Disease Control.
Emmaus, PA: Rodale Press, 1992.

Henn, Tess and Rick Weinzierl, Botanical Insecticides and
Insecticidal Soaps (Circular 1296) Alternatives in Pest
Management. Urbana: University of Illinois at Urbana-
Champaign, College of Agriculture, Cooperative Extension
Service, 1989.

Ware, George W. Complete Guide to Pest Control (with and without
chemicals) 2nd ed. Fresno, CA: Thomson Publications, 1988. (
P.O. Box 9335 Fresno, CA 93791)

Weinzierl, Rick and Tess Henn. Microbial Insecticides (Circular
1295). Alternatives in Pest Management. Urbana: University of
Illinois at Urbana-Champaign, College of Agriculture,
Cooperative Extension Service, 1989.

Williams, Greg and Pat, "Safe and Simple Bug Controls"
BackHome 4 ( Summer 91): 24-25. (Mountain Home, NC 28758)