EVALUATION OF GROWTH ENHANCEMENT ASSOCIATED
WITH USE OF ADMIRE IN WATERMELON
Alton N. Sparks, Jr.1 and Forrest J. Connelly 2
University of Georgia
Cooperative Extension Service
1
Dept. of Entomology
P.O. Box 1209
Tifton, GA 31793
2
Berrien County Extension
516A County Farm Rd.
Nashville, GA 31639
Introduction
Admire was the first of the neonicotinoid insecticides registered for use in
vegetables. It is widely used for control of insects, with most uses targeted at control of
whiteflies and aphids. Benefits of Admire use also include control of flea beetles,
cucumber beetles and impacts on thrips feeding and transmission of tomato spotted wilt
virus. Occasionally, increases in plant growth are noted with use of Admire in the
apparent absence of pests. This test was conducted to evaluate this potential growth
enhancement in a commercial watermelon field.
Materials and Methods
A small plot trial was conducted in a commercial watermelon field (variety Triax
313) in Berrien County, Georgia. The test was established in a field with drip irrigation
and narrow plastic. Rows in the field were on 6 foot centers, with 7 rows between drive
rows. The 7 rows were alternated between seedless and seeded (pollinator) melons with 4
rows of seedless. The test was established in the seedless melons in a single 7-row
section of the field, with the 4 seedless rows as replications (blocks) and insecticide
treatments applied down the rows. The experimental design was a randomized complete
block with 4 replications of 5 treatments. The field was transplanted on 26 March, 2004.
Plots were established three days after transplanting, with the earliest treatments applied
at 4 days after transplanting. The test area was managed by the grower and with the
exception of the experimental treatments was treated identically to the rest of the field.
Experimental plots were one row wide and 30 plants long (with a 27 inch in-row
plant spacing). Actual length of plots varied because of skips and plant mortality.
Treatments evaluated included Admire at 16 oz/ac applied at 4 days after transplanting
(referred to as at-planting), Admire at 12 and 16 oz/ac applied at 10 days after
transplanting, Platinum at 8 oz/ac applied at 10 days after transplanting, and a non-treated
check. Rates were calculated based on 3630 plants per acre (6 ft x 2 ft spacing). Actual
plant spacing was 27 inch within the row (thus actual rates were 88.88% of indicated
rates).
Treatments were applied with a CO2 pressurized backpack sprayer (20 PSI) in 3
oz of water per plant. A single hollow cone nozzle with the insert removed was used to
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make applications. With the insert removed the nozzle sprayed a straight stream of water
which was targeted at the base of the plant. The base of individual plants were treated
with the entire 3 oz of spray for that plant (treatments were applied at the base of the
plant with no treatment outside of this area). Applications were made on 30 March (4
days after transplanting) and 5 April (10 days after transplanting), 2004.
Plant growth was monitored periodically through the season. Vine lengths were
measured once early in the season (20 April) and visual ratings of canopy coverage were
conducted twice (3 and 12 May). These data are not presented as no obvious differences
were detected. Yields were collected from each plot by harvesting mature fruit on four
dates. For the first three harvests, commercial harvest crews selected the melons for
harvest. Melons from each plot were counted and weighed (generally weighed
individually for the first harvest and two at a time thereafter). Yields were evaluated
based on the number of fruit harvested per plot, the total weight of fruit harvested per
plot, and the average weight of fruit (total weight/total number). All data were analyzed
with the PROC GLM procedure of PC-SAS. Where significant differences were detected
(P<0.05), means were separated with LSD (P=0.05).
Results and Discussion
No statistical differences occurred among treatments in the number or total weight
of fruit harvested per plot on any single date, nor in cumulative yields across dates
(Tables 1 and 2). Some differences in average fruit weight occurred in the third harvest
(and a trend for differences in the fourth), but these differences were minor and did not
consistently align with treatments (different admire treatments have the highest and
lowest fruit weights in the third harvest, and the treatment with the highest weight in the
third harvest has one of the lowest weights in the fourth harvest).
Insecticide treatments in this test had minimal, if any, impact on plant growth and
yields. A number of factors may have contributed to this including the slightly reduced
rates as compared to the intended rates. Several other factors may also influence the
potential growth response including application timing and methodology (plant drench
concentrated at base of plant versus application through the drip system distributed along
the row), amount applied per plant (equal per acre rates are higher per plant rates with a
less dense stand), environment (moisture, heat, etc.), and plant species. While the growth
response can be dramatic, it is inconsistent at best. Until the growth response, and factors
influencing this response, are better understood, producers should be cautious about
using Admire for reasons other than insect control.
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Table 1. Number of watermelons harvested per plot, Admire growth enhancement
test, Berrien County, Georgia, 2004.
Treatment
Average number of fruit harvested per plot
1st
harvest
2nd
harvest
Cum.
(1+2)
3rd
harvest
Cum.
(1+2+3)
4th
harvest
Total
Check
13.00
30.25
43.25
11.50
54.75
6.25
61.00
Platinum
11.75
29.50
41.25
10.50
51.75
8.50
60.25
Admire atplanting
13.50
31.00
44.50
8.75
53.25
6.75
60.00
Admire 12 oz.
10.25
34.25
44.50
12.50
57.00
8.00
65.00
Admire 16 oz.
11.25
32.75
44.00
9.00
53.00
8.75
61.75
No significant differences occurred among treatments for any of the data in this table.
Table 2. Weight of watermelons harvested per plot, Admire growth enhancement
test, Berrien County, Georgia, 2004.
Treatment
Average pounds of fruit harvested per plot
1st
harvest
2nd
harvest
3rd
harvest
Check
247.5
501.1
Platinum
228.1
Admire atplanting
Admire 12 oz.
4th
harvest
(1+2+3)
Total
748.6
165.9
914.4
86.3
1000.8
466.4
694.5
163.4
857.9
111.5
969.4
271.6
527.7
799.2
141.7
940.3
90.6
1030.8
193.7
581.8
775.5
176.9
952.4
119.1
1071.5
Cum.
(1+2)
Cum.
Admire 16 oz.
218.5
547.7
766.1
132.7
898.8
120.0
1018.8
No significant differences occurred among treatments for any of the data in this table.
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Table 3. Average weight of watermelons harvested, Admire growth enhancement
test, Berrien County, Georgia, 2004.
Treatment
Average Fruit Weight (lbs/fruit)
1st harvest
2nd harvest
3rd harvest
4th harvest
Check
19.26 a
16.28 a
14.83 bc
14.50 a
Platinum
19.60 a
15.93 a
15.77 ab
12.79 a
Admire at-planting
19.87 a
16.73 a
16.35 a
13.21 a
Admire 12 oz.
19.12 a
16.83 a
14.24 c
14.19 a
Admire 16 oz.
19.53 a
16.75 a
15.15 abc
15.04 a
Numbers within columns followed by the same letter are not significantly different (LSD,
P=0.05).
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