How To Protect Your Plants From Pests
Use of varieties with genetic resistance to pests and diseases is also a time-honored way to prevent pest problems. When you buy seeds or transplants look at the seed packets and transplant labels for claims about disease and pest resistance. Contrary to what you might think, dis-ease and pest resistance are in most cases not the result of genetic engineering, but of plant breeding methods that have been practiced for hundreds of years.
For insect pests, two other forms of prevention are the
use of floating row covers and the use of transplants
(see getting seeds and plants and transplanting). Floating row covers keep pests
off your crops through a combination of a
physical barrier (the row cover) and the
creation of conditions under the cover that
are unfavorable for insect growth and reproduction. Use of transplants does not
actually keep pests off your crops, but by
leaving plants in your home or a greenhouse until they are large enough to defend themselves at least a little bit, you increase the chance that any pest problems
you do have will not kill your plants. Most
plants have few defenses when they are small, but as
they grow older, their stems get thicker and less tasty
for insects, and they develop the ability to release bitter
or otherwise unpleasant substances in response to insect feeding. Their resistance to disease also increases.
If you have used the various preventative tactics mentioned above and you still have insect pest problems, there are some compounds that are used as organic pesticides. Keep in mind that these compounds are not like some of the conventional insecticides you might have used in the past – if they are o.k. for use in organic production, they are less toxic to your health, or at least break down more quickly in the environment than standard pesticides. Most of these compounds only kill insects when the insects are very small (larvae, or worm-like creatures, rather than adults). Also, most of these compounds are only effective for a day or two after you apply them, after which point they are destroyed by sunlight, rain, or just exposure to the air.
A thorough discussion of organically approved pest controls is beyond the scope of this manual. However, three of the most commonly used compounds are azadirachtin, which is derived from the seeds of an Indian tree called Neem, pyrethrin, which is derived from chrysanthemums (a flower) and Bt toxin, which is derived from a soil-dwelling bacterium called Bacillus thuringiensis. Azadirachtin is marketed in compounds with names like Neemix, Green Light Neem, and Agroneem. Pyrethrin is marketed under various names, of which Pyganic is one of the most widely sold. Bt toxin is marketed under many different names – when you buy it, make sure to get a variety that is supposed to be effective for the kind of pests you have (some varieties affect Colorado potato beetles, for example, while others do not). Azadirachtin and Bt toxin are not harmful to people at all, but pyrethrins definitely can be – all should be used with care. All three compounds work by poisoning insects. There are other insecticidal (insect-killing) compounds that are based on oils and soaps, but these compounds work (at least in some cases) by covering the holes through which insects breathe, which chokes them.
See resources for more information for directions to more
information about pest control (Peaceful Valley Farm Supply
is one business in particular whose web site and catalog provide many products for organic pest control together with information about how and when to use them). In general, before you launch an elaborate program to deal with any kind of
pest or disease, you should talk to an experienced gardener
and/or a local agricultural extensionist (again, see resources
for more information) to make sure that you have both identified your pest or disease accurately and come up with treatment methods that are safe, organic, and potentially useful.
