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Copyright 2005, Board of Trustees, University
SAGRICULTURAL RESEARCH AND EDUCATION CENTER
/ Sanford, Florida .
Research Report 75-6 J 19
June 30, 1975
An Evaluation of Selected Insecticides for the Control of
Leafminers on Celery in Central F o ---- _
William H. Denton
Assistant Entomologist' JAN : 1978
INTRODUCTION .F.A.SUn. of Florida
Damage to celery plants by leaf mining dipterons Liriomyza spp., has
increased recently in Florida. The apparent reduced effectiveness of chemicals
currently used for control of these leafminers has caused considerable concern
within the celery industry. Therefore, in cooperation with the Florida Celery
Exchange, AREC-Belle. Glade, and the chemical industry, a few promising
materials were selected for testing. The selection of these materials was based
on performance in earlier tests and the probability-of registration of these
compounds for use on celery by the E PA.
The results shown in this report are not intended as insect control
METHODS AND MATERIALS
These tests were conducted on muck (Everglade mucky peat) at the branch
farm near Zellwood, Florida. Plants of varieties 6-83 and 14-10 were obtained
through AREC-Belle Glade, and transplanted on October 18, 1974. Each
treatment was replicated three times in a completely random design. Each plot
consisted of three 20-ft. rows with 36-in. row spacing. The plots were separated
by a guard row.
Four compounds were used in this test (Table 1), oxamyl (Vydate L),
rnethomyl (Lannate L), dimethoate (Cygon), and methamidophos (Monitor). Only
methamidophos was applied to both varieties. The other compounds were tested
,n variety 6-83 alone.
Dyrene was applied throughout the trial period to control Cercospora apii.
Symptoms of this disease would mask the damage caused by the leafminers.
l11 material was applied at a rate of 100 gallons per acre with tractor-mounted
spray equipment with two overhead nozzles per row at 250 psi. This equipment
s equivalent to commercially available applicators.
Damage was assessed in the field three times prior to harvest. The
November 6 sample was prior to initiating application of chemicals. The fourth
Assessment was of plants removed from the field at harvest. The number of
nined leaflets per plant was counted on each sampling date. The sample from
each plot consisted of ten plants from the center of the middle row. At harvest,
en plants were removed from the same area of each middle row of each plot.
Harvest data consisted of (1) total number of mined leaflets before the
bunches were trimmed and topped to a uniform 15-in. length, (2) total number
of mined leaflets after trimming and topping, (3) weight of bunches after
trimming and topping, and (4) average size of bunches according to the number
of dozens per crate when prepared for fresh market.
Supplemental data consisted of recording cutworm damage to internal
petioles, on January 29, and at harvest on February 11. This damage was
characterized by feeding scars and grooves in the cupped portion of the mature
petioles. This cutworm damage occurred at later growth stages.
Analyses of variance were performed on the individual groups of data to
compare efficacy among all treatments. Duncan's new multiple range test
was used for comparisons among treatment means.
Table 1.- Insecticide treatments applied to celery from November 6, 1974,
through February 4, 1975,
Rate Timing of
Treatment Variety Chemical lb. ai/100 G/A application
1 6-83 Vydate 2E 0.25 twice weekly
2 Vydate 2E 0.50 once weekly
3 Vydate 2E + 0. 50 + "
Lannate L 0.50 "
4 Cygon 2.67E 0.25 "
5 Monitor 4E 1.00 "
5 14-10 1.00 "
6 6-83 Untreated ---
7 14-10 "
RESULTS AND DISCUSSION
Based on the data collected prior to harvest (Table 2), superior control of
leafminer was achieved with twice weekly applications of oxamyl at 0. 25 lb. ai/A
and weekly applications of the oxamyl plus methomyl combination. Comparable
control was achieved with the weekly application of oxamyl at 0. 50 lb. ai/A.
The initial application of methamidophos was delayed, therefore, only the
harvest data provides a fair comparison of this compound with the other treatments.
At harvest, all compounds provided equivalent control, except dimethoate.
The average number of mined leaflets in the dimethoate plots was not
significantly different from the untreated plots.
Of significant interest is the damage ratings of the bunches after trimming
3nd topping to the 15-in. length (Table 3). Based on the average number of
nined leaflets on the remaining foliage, all treatments were equivalent, being
significantly different only from the untreated. The most drastic change in
damage ratings was in the dimethoate treatments.
Table 2.- Comparison- of average number of mined leaflets per plant at four
stages of growth (n=30).
Treatment Sampling date
Treatment 2/ 2/ 2/ 2/1-3/
number Variety 11/6-2 11/25- 12/112/ 2/11-
1 6-83 2.2a 3.5ab 8.9a 4.7a
2 2.7a 5.7abc 11.4ab 7.9a
3 3.2a 3.2a 1.9a 8.7a
4 5.2a 5.9abc 19.6 bc 31.8ab
5 2.7a 12.6 bc 21.8 c 4. Oa
5 14-10 2.4a 27.2 d 34.4 d 3.6a
6 6-83 3.0a 10.6abc 27.1 cd 55.6 b
7 2.3a 13.5 c 36.6 d 40.5 b
7 14-10 3.3a 29.2 d 59.1 e 49.5 b
- Values within each column followed
by the same letter are not significantly
2/Damage is cumulative no distinction made between new and old damage.
3/Data taken after removal from field plots, therefore, early damage is not
reflected in these figures.
It should be noted that the pest population during this test could not be
classed as severe or heavy. Significant differences among the treatments may
have been expressed under a severe infestation.
Least cutworm damage (Table 3) occurred in the plots treated with the
oxamyl-methomyl combination and with methamidophos. Adequate performance
of methomyl and methamidophos against lepidopterous pests has been shown in
previous tests. Oxamyl was not expected to perform well against cutworms.
As shown by the untreated plots, the cutworm infestation was light.
Table 3.- Efficacy- of treatments based on data at harvest.
Number of mined leaflets
Average 2/ Average si'e Before4, After 5/ Cutworm6
Treatment weight (lb.)- of bunch-' topping- topping- damage-
1- 6-83 2.60 bcd 2.15 bcde 4.7a 1. Oa 1.3ab
2- 2.66 bcd 1.98abc 7.9a 1.8a 1. 7ab
3- 2.76 bc 1. 97abc 8. 7a 2. 5a 0. 3a
4- 3. 32a 1.60a 31.8ab 2.5a 1. 7ab
5- 2.21 de 2.03 bcd 4. Oa 3.7a 0.7a
5-14-10 2.40 bcde 1.82 cde 3.6a 0.3a 0.Oa
6- 6-83 2.89ab 2.45abc 55.6 b 22.8 b 6.3 d
7- 2.33 cde 2.32 de 40.5 b 16.5 b 4.7 cd
7-14-10 2.06 e 2.62 e 49.5 b 17.0 b 3.0 bc
1/Values followed by same letter are not significantly different.
2 Average weight after trimming and topping to a uniform 15-in, length.
3/Sized according to number of dozens per crate if packed for fresh market.
4/Data taken after removal from field plots, but before bunches were trimmed,
5/ Data taken after removal from field plots, but after bunches were trimmed,
6/number of damaged petioles per plant.
Average number of damaged petioles per plant.