Group Title: ARC-A research report - Agricultural Research Center-Apopka ; RH-81-6
Title: Why should you test pesticides on your plants?
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 Material Information
Title: Why should you test pesticides on your plants?
Series Title: ARC-A research report
Physical Description: 4 p. : ; 28 cm.
Language: English
Creator: Chase, A. R ( Ann Renee )
Armstrong, T. J
Osborne, L. S
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center-Apopka
Place of Publication: Apopka Fla
Publication Date: 1981
Subject: Plants -- Effect of pesticides on -- Florida   ( lcsh )
Pesticides -- Testing -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: A.R. Chase, T.J. Armstrong, and L.S. Osborne.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065948
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70921776

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Copyright 2005, Board of Trustees, University
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i.-i/ -Why should you test pesticides on your plants?- .
A. R. Chase, T. J. Armstrong, and L. S. Osborne
University of Florida, IFAS i i
Agricultural Research Center Apopka
ARC-A Research Report RH-81-6 -

Pesticides are routinely used by most nurserymen and are generally- --.

efficaceous and nonphytotoxic. However, when new pesticides become avail-

able or new plants are grown it is wise to test the new combination of

pesticide and plant. Even pesticides with broad spectrum labels for all

ornamentals should be tested since some plants can be damaged under certain

growing conditions. Thus, testing the specific pesticide-plant-growing

condition combination is very important in producing high quality plants.

Growers are advised to anticipate potential pest problems and test

recommended pesticides prior to broad scale usage. The following test

illustrates this potential problem.

Red marantas were grown in steam sterilized potting medium for two

months. They were then treated with a soil drench of Pesticide A at the

labeled rate and retreated at the recommended interval. Another set of

plants was treated with water only. Four months after initial treatment

plants were rated for chlorosis which was apparent on most pesticide

treated plants, while plants which received water only were a healthy green

color. Plants were rated on a 1 (severe chlorosis) through 4 (no chlorosis

or healthy) scale. The average rating for plants receiving water was 3.3

while that for pesticide treated plants was 2.2. There was no obvious

reduction in growth and the leaves did not show any other symptoms of phyto-

toxicity. It is probable that had the entire planting been treated with

Assistant Professor of Plant Pathology, Agricultural Technician II, and

Assistant Professor of Entomology, Agricultural Research Center Apopka.

pesticide, the chlorotic state of the plants would have been attributed to

other causes. Previous to this test we had seen no evidence that this
pesticide caused chlorosis on red maranta and would not have expected this to

occur. Damage such as this can occur if a phytotoxicity test does not pre-

cede broad scale use of a new or previously untried pesticide. An example

of the procedure used to perform a phytotoxicity test is included below.
The initial test need only consist of two treatments. The first is a

set of control plants which will be sprayed with water only and serve as a

comparison for pesticide treated plants. The second set of plants will be

sprayed with the pesticide at the rate recommended on the label. Each set

of plants should include at least ten healthy, representative plants from the
group you wish to treat with the pesticide. If you want to use the pesticide

on ten different foliage plants you should include ten of each species in the

phytotoxicity test. When the plants are sprayed be sure to handle both sets

of plants the same. If the pesticide is accompanied by a spreader-sticker
then the control water treatment also should include the spreader-sticker.

Apply the pesticide to the plants according to labeled instructions and re-
peat the treatment on the interval suggested. Some pesticides are safely

used at the labeled frequencies while they are phytotoxic when usedmore

frequently. At the research center we apply pesticides at least four times
before concluding the experiment. However, since time and the pressure to

treat may be important you may choose to shorten the experiment. There are

many ways that phytotoxicity can appear on your plants including leaf tip or

marginal burn, stunting, chlorosis, complete collapse of leaves, leaf drop,
and distortion. Any abnormalities found only in pesticide treated plants

indicates a potential hazard and the pesticide should be handled accordingly.

The following points should be mentioned with respect to conducting pesticide


1. Stressed plants (those plants which are wilted or have received

excessive amounts of either fertilizer, water or light), are

more susceptible to phytotoxicity damage than healthy plants.

2. All treatments should be made during the time of day which best

fits the normal production operation. Plants are more susceptible

to damage when chemicals are applied to them during the heat of the

day and these periods should be avoided. During winter, wait until

the water and air warm before spraying plants.

3. Do not confuse fertilizer burn or a disease with phytotoxicity

caused by pesticides. If a symptom is found on the pesticide

treated plants as well as on the control plants, then you can

assume that the symptom is indicative of another problem.

4. If abnormalities are seen on your treated plants which are absent

on your control plants you should conduct the test a second time

or refrain from large scale use until the abnormalities can be


5. It is important to realize that the results obtained are only

true for the conditions existing during the experiment. It is

usually impossible to determine the safety of a pesticide used

under varying conditions in a single test. Be sure to design

your phytotoxicity test to conform to the actual spraying environ-



plants are infected or infested to try a new combination and don't perform


phytotoxicity tests by spraying entire plantings. The financial risks run

by eliminating a small preliminary test are very great and should be avoided

whenever possible. Creating a working procedure for conducting phytotoxicity

tests in your nursery can save you time and money.

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