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Copyright 2005, Board of Trustees, University
JAN J .1978
SFt. Pierce ARC Research Report RL 1977-5 I.F.A.S. Univ. of Florida October 1977
Flat fan vs. hollow cone spray patterns against fungus diseases of three
R. M. Sonoda and N, C. Hayslip
A 4-5 day spray schedule using nozzles producing a flat fan spray pattern gave
better, but not significantly so, control of powdery mildew on squash and a complex
of foliage diseases on Morgan melon than did nozzles producing a hollow cone pattern,
The two systems provided almost identical protection against a light infection of
gray leaf spot (Stemphvlium solani) on Homestead 24 tomatoes.
Most foliar fungicide sprays on vegetables are applied using nozzles producing
a hollow cone pattern of spray droplets. The test reported here is part of a con-
tinuing effort to determine if a triple flat fan pattern is superior to the standard
hollow cone pattern for some diseases on some crops. Previous work (1) indicated
that the flat fan pattern was more effective than the hollow cone pattern in reduc-
ing the incidence of powdery mildew on Morgan melons.
Materials and Methods
Seeds of 'Poinsett' cucumber, 'yellow straight neck' squash, and 'Morgan' melon
were sown by plug-mix planting in the field on March 15-16 '77 in hills 2 ft apart
on 3.5 ft wide elevated beds. 'Homestead 24' tomatoes were transplanted at the same
time at the same spacing. The centers of the beds were 12 ft apart and there were
20 ft buffer areas between replicates. The treatments were arranged in a randomized
complete block design with four replicates. Each replicate consisted of 15 ft long
subplots containing seven or eight hills of a single crop. There were 5 ft between
subplots. The crops were randomly distributed within each replicate. The plots
were fertilized with 700 lb/A of 4-16-4 when bedded and with 600 lb/A 8-12-20 on
Apr 6 '77 when beds were enlarged.
For the flat fan pattern, a cluster of three Spraying Systems Tee-Jet SS 8002
flat fan nozzles was arranged so that one nozzle faced forward -450 below horizontal,
another -90 below horizontal and a third faced backwards at -45 below horizontal.
The spray patterns from these nozzles were in a plane perpendicular to a vertical
plane in the direction of tractor movement. As plants grew the flat fan clusters
were increased from one set of three nozzles to three sets of three nozzles each.
Hollow cone nozzles, Spraying Systems D-4-23 were arranged in a plane perpen-
dicular to the direction of tractor movement to cover the same swath width as the
flat fan pattern. As plants grew the hollow cone nozzles were increased from three
to seven. Finished spray per treated acre ranged from 50 to 140 gallons through
the growing season. Tractor speed was adjusted to apply the same amount of Dithane
M-45 at 1.5 lb/100 gal with both nozzle types. The sprays were applied at 4-5 day
intervals, Cygon, Diazinon, and Lannate, singly or in combination were sprayed
separately with another spray machine at weekly intervals.
Associate Plant Pathologist and Horticulturist (Center Director),
University of Florida, IFAS, Agricultural Research Center, Fort Pierce
Results and Discussion
Diseases were not noticed in the planting until May 15. At this time light
incidence of powdery mildew on squash, powdery mildew and a light incidence of
gummy stem blight on Morgan melon, and a light incidence of Stemphylium solani on
Homestead-24 tomato were noticed. Ratings of disease incidence were made on
June 7 '77.
Powdery mildew incidence on squash was rated by estimating the surface area
covered by the fungus on the sixth from the youngest leaf on six plants per repli-
cate. A disease severity index was calculated by determining the mean incidence
per treatment from the mean incidence per replicate. As Table 1 shows, the flat
fan treatment had the lowest index, however, the difference was not statistically
significant. No differences were obtained in yield of squash fruit between treat-
ments or treatments and control.
Gray leaf spot incidence on Homestead 24 tomato was very light, A disease
severity reading was made by counting the number of lesions on the terminal three
leaflets on the third from youngest fully expanded leaf on five plants per replicate.
A disease severity index was calculated by determining the mean incidence per treat-
ment from the mean incidence per replicate. Both flat fan and hollow cone nozzle
treatments had nearly the same index (Table 1). Both treatments were better than
control. No fruit yield comparisons were made since disease incidence was so light.
Morgan melon was affected by both powdery mildew and gummy stem blight. A per-
cent defoliation estimate was made for each replicate and a disease severity index
was computed by determining mean defoliation per treatment. The flat fan treatment
had a lower defoliation rating (Table 1) than the hollow cone, but not significantly
so. A once-over harvest of melons on June 16 '77 did not show any significant
differences in yield, although the flat fan treated plots had the highest yield.
(Flat fan, 53; Hollow cone, 47; and control, 38 Ib/plot).
No diseases were noticed on Poinsett cucumber.
Although the differences in disease control between flat fan and hollow cone
spray patterns were not significant, the results indicate that further tests should
be conducted, especially under more severe disease pressures.
- 3 -
Table 1. Disease severity indices for powdery mildew on yellow straight neck squash,
gray leaf spot on Homestead-24 tomato, and powdery mildew and gummy stem
blight on Morgan melon following a 4-5 day spray schedule with flat fan
and hollow cone nozzles using 1.5 lb/100 Dithane M-45.
Disease Severity Index
powdery mildew grey leaf spot defoliation
Nozzle (squash) (tomato) (melon)
flat fan 4.17 5.9 a- 0.9% a
hollow cone 13.7 5.0 a 8.5 ab
control 12.6 16.3 b 24.2 b
1/ Means in a column followed by the same letter are not significantly different
at the 5% level (Duncan's multiple range test).
1. Sonoda, R. M. and N. C. Hayslip. 1977. Comparison of two spray nozzle
arrangements for control of "Morgan" melon diseases. Fungicide and
Nematocide Tests. 32:87.