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gq. Aliette 80WP and Bacterial Disease Control III. Phytotoxicity
A. R. Chase'
University of Florida, IFAS
Central Florida Research and Education Center Apopka
CFREC-Apopka Research Report, RH-89-9
Aliette 80WP is used in the ornamentals industry for control of diseases
caused by species of both Phytophthora and Pythium. During the past two
years, this fungicide has also been found to control some bacterial diseases
of ornamentals, primarily limited to those caused by Xanthomonads (1,2,3,4).
In addition, reports of phytotoxicity have become more common when Aliette and
other bactericides such as Kocide 101 77WP are used as a tank mix or simply
with too close an application interval. The following study was performed to
determine a safe use pattern for Aliette 80WP and Kocide 101 77WP on three
The plants employed were Aglaonema commutatum 'Maria', Dieffenbachia
maculata 'Camille' and Syngonium podophyllum 'White Butterfly'. Plants were
grown for 3 to 4 weeks to allow adequate time for potential pesticide residues
to wash off as well as development of new leaves. Twelve plants were included
for each of the treatments. Treatments were designed to test the number of
days which should elapse between applications of Kocide 101 77WP and Aliette
80WP. A water treated control as well as each compound singly and as a tank
mix of the two compounds were included. Other treatments included application
of Aliette first with Kocide applied approximately 20 minutes later the same
day, and 1, 2, or 4 days afterward. Treatments with Kocide applied first were
followed by Aliette 1, 2, 4, 7, or 14 days later. The compounds were applied
at labeled rates of 5 lb/100 gal for Aliette 80WP and 1 lb/100 gal for Kocide
101 77WP. Damage was evaluated three days after the final treatment and was
rated as follows: 1 (no damage), 2 (slight damage), 3 (moderate damage), and 4
(severe damage). Damage on these plants consisted of necrotic and chlorotic
spots on any leaf surface and was sometimes more severe along leaf margins.
Each of the three plant species was damaged when an Aliette Kocide tank
mix was applied with phytotoxicity ratings the highest for this treatment
(Table 1). Aglaonema 'Maria' were moderately damaged with both Dieffenbachia
'Camille' and Syngonium 'White Butterfly' slightly damaged. When Aliette and
Kocide were applied alone neither caused any phytotoxicity on these plants.
However, when Aliette is applied first, at least 4 days should elapse before
Kocide is applied to 'Maria' and 2 days for 'Camille' and 'White Butterfly'
(Table 1). When Kocide is applied first, at least 4 days should elapse prior
to applications of Aliette on any of the plants tested.
These results tell us something about the length of time the two compounds
remain active on the leaf surface. Both compounds are safe when used alone
and problems only develop when they are applied closely enough for the acidic
nature of Aliette to affect the copper release from Kocide. When the water pH
IProfessor of Plant Pathology, Central Florida Research and Education Center -
Apopka, 2807 Binion Rd., Apopka, FL 32703.
is about 7.4, the pH of an Aliette solution is about 4.1. A solution of
Kocide in this water has a pH about the same as water alone. However, when
the two compounds are mixed, the pH of the solution is only 4.5 which is low
enough to make too much copper available for the plants to tolerate. Altering
the pH of a Kocide solution to this level with any other acid can cause
symptoms of copper toxicity. Apparently, both Aliette and Kocide remain
in sufficient concentrations on the leaf surface for about 4 days to allow
this reaction to occur regardless of which is applied to the leaf surface
first. This test was performed under greenhouse conditions with plants
watered by hand. Under overhead irrigation, one can expect one or both of
these compounds to wash away more rapidly than the 4 days noted here. In any
event, caution must be exercised when employing Aliette, or any other acidic
material such as vinegar, to the same plants receiving a copper containing
1. Chase, A. R. 1987. Effect of fosetyl aluminum on severity of two
Xanthomonas leaf spot diseases. Proc. of Symposium on Aliette. Pages
2. Chase, A. R. 1987. Update on controlling three bacterial diseases of
foliage plants. Foliage Digest 9(8):1-2.
3. Chase, A. R. 1989. Aliette 80WP and bacterial disease control I.
Xanthomonas. CFREC-Apopka Research Report, RH-89-7.
4. Chase, A. R. 1989. Aliette 80WP and bacterial disease control II.
Pseudomonas and Erwinia. CFREC-Apopka Research Report, RH-89-8.
Table 1. Phytotoxicity of copper on Aglaonema, Dieffenbachia and
Syngonium as affected by timing applications of Aliette 80WP and
Treatmenta Day Aglaonema Dieffenbachia Syngonium
Water -- 1.0 ac 1.1 ab 1.0 a
Aliette 1 1.0 a 1.0 a 1.0 a
Kocide 1 1.0 a 1.0 a 1.1 abc
Kocide 1d 3.0 e 2.2 e 2.0 c
Kocide 1 1.5 c 1.3 bc 1.4 b
Kocide 2 1.3 abc 1.4 c 1.5 b
Kocide 3 1.4 bc 1.1 ab 1.1 ab
Kocide 5 1.2 ab 1.1 ab 1.0 a
Aliette 2 2.1 d 2.2 e 2.3 c
Aliette 3 1.9 d 1.8 d 2.1 c
Aliette 5 1.2 abc 1.1 ab 1.1 ab
Aliette 8 1.0 a 1.0 a 1.0 a
Aliette 15 1.0 a 1.0 a 1.0 a
"Aliette and Kocide were applied on different schedules at
recommended rates of use.
bPhytotoxicity was rated from 1 (no damage) to 4 (severe damage)
three days after the final chemical application.
cNumbers in the same column followed by the same letter were not
statistically different (DNMRT, P=0.05).
Aliette and Kocide were applied as a tank mix for this treatment.