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Tue Jul 5 15:33:59 EST 1994
The featured article from the Summer issue of Growing Edge compares
biological controls to chemical controls for plants. Here is an
excerpt from "Biological Controls for Specialty Collections Part II" by
Justina Marie Kelliher.
Many gardeners assume that biological and botanical controls are always
the best choice. Some growers would go so far as to sacrifice an entire
crop or lose a choice ornamental before reaching for a chemical control
method. But when you are working with rare, endangered, long-lived or
especially valuable plants, the choice of control methods becomes more
complex. My greenhouse, filled with rare and/or difficult to grow
succulents, many grown from seed, represents a substantial investment in
time, effort and money. As a result, my goal is to maximize the use of
biological controls and reduce pesticide use without sacrificing the
health of my plants.
The high value of my collection also makes a difference in the effort
and expense IÕm willing to accept to prevent insect damage. The higher
cost of some biological control agents is more than justified in this
situation. Cheaper measures, pulling and destroying diseased plants for
example, might make more sense in a vegetable garden or flower bed.
This bias in favor of biological controls has its practical side.
Resistance by pathogens is a problem encountered in chemical-based
control systems. Substituting or supplementing with biological controls
is a way to help preserve the usefulness of the chemicals we do have and
are willing to use. Biological controls do not select for resistance to
chemicals and if used in an integrated program can slow the development
of resistance in pest species.
As you plan and implement your pest control program, it is important to
remember that successful strategies are usually site-specific. My
greenhouse is located in Western Oregon, for example. What works well
here in terms of specific problems, control measures and timing may not
work in your greenhouse or grow room. Even in the same area, there can
be major differences from one greenhouse environment to another. As a
pest management consultant, IÕve learned to adjust the timing and
methods to the situation at hand. One of my clients grows bamboo and I
often have to time the releases differently because he maintains a much
higher humidity in his greenhouse. Even my own propagation room needs a
different management system than the main greenhouse.
This article will focus on my succulent greenhouse as a working example.
It is always important to look at your plants and identify your own
problems rather than following a rigid set of guidelines. After all, you
know your plants and conditions better than anyone else could. Your
methods and timing will need to be adjusted to your climate and the
system that you already have set up for the health of your plants.
The first step of any project is defining your goals. Integrated pest
management is a step-by-step management system. Research is used as an
input at most steps of the process, but it can only tell you what could
be done. What should be done can only be determined in the context of
your goals. The next step is to identify problems and possible problems,
and look at possible solutions, including the no-treatment option.
Choose a solution that best serves your goals and implement it. The
final step is the most importantÑevaluating your chosen solution. If
something does not work, a change needs to be made, which usually brings
you back to an earlier step.
All of this might seem obvious, but it is surprising how many gardeners
reach in a haphazard way for any solution that comes along during a
crisis and ignore preventative measures when problems subside, all for
the lack of a well-thought-out and consistent plan. The system (outlined
at ????) consists of several loops to account for the constantly
changing nature of natural systems. Use it.
There are several different pests that I expect to appear in the spring.
The monitoring method that I use is a yes/no system. If one pest is
found, I plan the insect releases. It generally takes about two weeks
for the biological control agents to arrive, so timing is crucial.
The pests that I plan for in the spring are mealybugs, scale, whiteflies
and mites. Fungus gnats are a persistent problem all year and I try to
maintain a low population. Slugs, snails and sow bugs are also year-
round problems. I try to limit their population by excluding them from
the greenhouse environment and handpicking (see ÒPest Control for
Greenhouse Growers,Ó Vol.4 #1, page 39 for more on excluding snails and
slugs from the greenhouse).
The spring insect releases consist of the generalist predators, crypts
and lacewings. I also add predatory nematodes and microbes to the soil.
If I find any spider mites, I release predatory mites, although that is
usually not a problem until early summer when things dry out.
So begins this issue's featured article from Growing Edge.
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