Growing EDGE

enews enews at
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.

Customized Control

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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