Agriculture Reference
In-Depth Information
(Neem oil is an oil extracted from a tree in India.) Most often,
though, reactive measures will involve the use of fungicides
and/or natural or synthetic pesticides. Because these reactive
measures use substances with greater potential to harm people
or the environment, I don't recommend their application
unless the farmer is certain that a likelihood exists that failure
to apply them will result in an unacceptable level of crop loss.
Another tip to make active measures most effective is to take
a cue from doctors treating HIV and tuberculosis: Never treat
an insect or disease problem with only one active agent at a
time. Using only one active agent increases the odds of
survivors living to convey immunity to that agent in the next
generation. When you mix two or more active agents, you
increase the odds of success while decreasing the odds of
creating resistant organisms. So, for example, I routinely
apply neem oil mixed with a microbial insecticide or garlic
and hot pepper repellents mixed together.
When Disease Prevention Fails
Plant diseases fall into four broad categories: bacterial, viral,
protozoan, and fungal. Usually, these are impossible to
distinguish by the naked eye except through experience with
their symptoms. (See also the Rodale topic recommended
earlier in this chapter.) All such diseases present the problem
that once a plant is infected, it becomes a storehouse of
infective particles that can be spread to other plants via
insects, wind, or handling. The longer an affected plant
remains in the garden, the greater the odds that it will infect
other plants. Diseases caused by viruses, bacteria, and
protozoans are seldom treatable, but sometimes you can save
a plant by pruning out the affected portions. Many fungal
