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Copyright 2005, Board of Trustees, University
/6 CONSIDERATIONS TOWARD SAFE AND SUCCESSFUL CHEMICAL USE1
H-UMTh L !Y A. R. Chase
IFAS, University of Florida
S': '3 A ricultural Research Center-Apopka
ARC-A Research Report RH-81-18
.F.A.S. Un of Frda
Disease control can be accomplished best by using a combination of
methods available to growers. Each method involves one of three areas,
including the host, the environment, and the pathogen. The most
commonly employed approach to disease control has been chemical spraying
which is based generally upon therapeutic applications of pesticides
following the recognition of a serious disease outbreak. Pesticides are
not as easy to use as they first appear. There are several important
steps which must be taken to insure the safe and successful use of
The first and most important step to pesticide use is diagnosis of
the problem. In the absence of accurate diagnosis, an inappropriate
chemical may be selected and disease control fails. Prior to any
application of costly chemicals the problem must be diagnosed either
through previous grower experience with the problem or preferably through
consulting personnel trained to diagnose plant disease. In many cases
the problem is not a disease and could be worsened if pesticides were
applied by phytotoxicity damage to the crop. In others, two similar
appearing diseases can be caused by widely differing organisms. Root rot
of foliage plant seedlings may be caused by Rhizoctonia, Pythium, or
Phytophthora spp. Benomyl controls Rhizoctonia but has no discernable
effect on the other two fungi. Similarly, ethazol or metalaxyl aid in
Presented at the Gold Coast Short Course, Oct. 29, 1981, Boca Raton, Fla.
control of Pythium and Phytophthora spp. but show no activity
against Rhizoctonia spp. If an accurate diagnosis is not made,
this disease may not be controlled due to selection of the wrong
The second step toward disease control involves the selection
of the most efficacious chemical, This can be accomplished by using
pesticide labels or the recommendations published through the state
extension service for pest control which are listed at the end of this
article. Once the disease is known, the proper chemical used on each
crop can be chosen.
It is at this point that a grower should determine whether or not
a pesticide will be safe for use on his crop. If the pesticide is
newly registered or has not been used by the grower previously, a
phytotoxicity test should precede broadscale use. Procedures for
performing a phytotoxicity test have been covered in a previous report
and will not be discussed in depth here. Some important points are
1. Choose the right chemical.
2. Read the label.
3. Wear protective clothing.
4. Avoid high temperatures.
5. Apply the accurate rate of the pesticide.
6. Apply several times at labeled intervals,
7. Test under the conditions you would normally apply the pesticide.
8. Test each type of plant you would like to treat with the pesticide,
9. Test the chemicals prior to a serious disease outbreak.
The last point is especially important since once a problem has become
serious it is unlikely that a grower will have time to perform a
Prior to use of the chemical on your crop a reexamination of the
label will confirm the rate of use of the pesticide, the interval
of use and the method of application. It is very important to know
whether or not the pesticide should be applied to the foliage of the
plant or to the soil, and therefore, the plant roots. Diseases such
as Cylindrocladium root rot of Spathiphyllum sp, cannot be controlled
through foliar sprays of benomyl. Although this pesticide is systemic,
the concentration of benomyl in the roots will not be sufficient to
control the disease. Only application of a soil drench will result in
enough pesticide to affect the development of this root rot disease.
Similarly, application of fungicides to the roots of a plant will have
little effect on a leafspot. In general, root rot diseases must be
treated through soil drenching and leafspot diseases through foliar
sprays. In cases in which the pathogen lives in the soil and then
progresses into the leaves of the plant, a combination of the two
methods will be necessary, An example of this type of disease is
Rhizoctonia aerial blight of many foliage plants.
Finally, the most important method of disease control is avoiding
disease. Use a combination of control methods designed toward
maintaining healthy plants and be prepared to use chemicals wisely and
safely if a problem occurs, This involves planning ahead and testing
new chemicals on your crops before serious problem arises. It is
costly to apply pesticides and especially undesirable if their
application does not result in control, Therefore, it will save you
money if you are prepared and follow these basic steps.
1. Avoid outbreaks of pests.
2. Develop contingency plans for potential problems,
3. Get an accurate diagnosis of the problem,
4. Choose the most efficacious chemical for that problem.
5. Perform a phytotoxicity test prior to broadscale use
(preferably prior to an outbreak).
6. Follow the label for rate and interval of application.
7. Apply the pesticide to the correct area of the plant.
8. Follow safety precautions to protect yourself and your
workers from poisoning.
Chase, A. R., T. J. Armstrong, and L. S. Osborne. 1981. Why should
you test pesticides on your plants? ARC-Apopka Research Report
Dunn, R. A., R. W. Henley, and D. G. Burch. 1981. Nematode control of
Florida commercial foliage crops 1981. Foliage Digest 4(5):12-14,16.
Henley, R. W., L. S. Osborne, and A. R. Chase. 1981. How safe are the
pesticides you use? Foliage Digest 4:3-4.
Short, D. E., and R. W. Henley. 1980. Insect, mite, and related pest
control on commercial foliage crops 1980. Foliage Digest 3(3):10-14.
Simone, G. W. 1980. Disease control pesticides for foliage production -
1980. Foliage Digest 3(10):3-12.