COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
STATE OF FLORIDA
COLLEGE OF AGRICULTURE, AGRICULTURAL EXTFN:ON SERVICE
UNIVERSITY OF FLORIDA, AND Vegetable Crop Specialists CouNTY AGENT AN.D
UNITED STATES DEPARTMENT OF HOE DEMONFSTPATION WORh
AGRICULTURE. COOPERATING E G T A R I A N AINESVILLE FLORIDA
NO: 59 April 23, 1963
TO: COUNTY AGENTS
We have been maintaining a close watch all spring on development of
watermelon mosaic virus (WMV) on watermelons in south Florida. It appears
that there is no great cause for alarm at the present time. Incidence of
WMV in the south Florida area is very normal. Unless something unforeseen
happens, we do not expect any large scale, serious outbreaks of WMV on
watermelons this year.
Reasons for last year's serious outbreak of WV on watermelons (worst
on record in Florida) are not completely understood. However, a thorough
study of the problem by County Agents, Extension Specialists and Station
workers revealed a possible correlation between severe summer drought and
heavy incidence of T4MV the following season. The reasoning was as follows:
an extremely dry summer as we had in 1961 would permit volunteer cucurbits
to live over into the fall season. WMV innoculum in quantity could then be
transferred by insects to fall squash and cukes which in turn would cause
winter planted watermelons to be rather heavily infected quite early in the
season. A heavier than usual incidence of WM appeared in central and north
Florida last year, possibly as a result of the heavy WMV infestation in south
Extension Specialists are keeping a close eye on this season's crop to
check on watermelon mosaic virus development. Please report any serious out-
break of WMV on watermelons, cukes or squash to us and if you have any doubts
on identification, send us some good plant specimens.
The use of liquid fertilizers, especially nitrogen and nitrogen and
phosphorus mixtures, has increased appreciably over the past few years.
Liquid fertilizers are being used on pastures, field crops and citrus. Use
of liquid fertilizers in vegetable production is not too widespread as yet,
but it is expanding rapidly.
We lack sufficient research on the use of liquid fertilizers to formu-
late sound recommendations. In the interim and until such time when research
might prove differently, it is felt that liquid fertilizers can be used, with
some reservations, in the production of vegetable crops in Florida. Growers,
using liquid fertilizers, should realize that proper placement is still Im-
portant and that minor elements, sulfur and calcium may have to be supplied
by other methods of application.
A research project recently completed by Dr. B. D. Thompson, Dr. D. D.
Gull and Mr. L. H. Halsey of the University of Florida's Department of
Vegetable Crops sheds new light on factors affecting quality and appearance
in tomatoes. They compared the affect of seasons, area, grower practices,
and storage temperatures on ripening of tomatoes.
They found no real differences between areas in Florida in quality of
mature, green tomatoes ripened at different temperatures after harvest.
Quality varied considerably between seasons and between growers within areas.
Growers, who sprayed for disease control "as needed" as contrasted to the
"regular spray schedule" produced tomatoes that were subject to Alternaria
rot. A good, preventive, disease control program is a must in order to pro-
duce good quality tomatoes in Florida.
Post-harvest temperatures, simulating the transit period, had marked
affect on quality and appearance. Temperatures of 400F. for six days
following harvest (then followed by 70 F. for ripening), accentuated unde-
sirable disorders such as stippling, ghostly appearance, dark seeds, decay,
soft fruit and graywall. The other temperatures studied, 550F. and 700F.,
showed almost none of these undesirable features.
The increase of incidence of graywall is interesting to note. Even
though fruit, selected for this study, were outwardly free of syu ptas,
graywall developed to the extent of 12% in fruits subjected to 40 F. tempera-
tures for a period of six days. These results may help explain why graywall
may or may not show up in susceptible varieties every season or even at any
definite stage of growth or harvest.
NITROGEN NEEDS ON MUCK SOILS
In a three-year study on nitrogen, requirements for vegetable crops
grown on muck soils, Drs. P. J. Westgate and R. B. Forbes of the Central
Florida Station clearly demonstrated that nitrogen needs on muck soils are
dictated by temperature. During the winter months, spinach responded each
of the three years to nitrogen in readily available form. Response to
additional nitrogen was greatest in the coldest winter season and least in
the warmest of the three winters.
Sweet corn responded in a similar way. In a warm spring, application
of nitrogen did not increase yield, but during the previous spring, which was
quite cool, nitrogen increased sweet corn yields significantly.
By keeping a close check on temperatures during the growing season,
muckland growers can determine need for nitrogen for any of his vegetable
crops with a fair degree of accuracy. The major portion of the nitrogen
for muckland application should be in a readily available form.
MISCELLANEJJS NOTES FROM HERE AND THERE
Charleston Gray 133 -
If you should see Charleston Gray 133 going down to Fusarium
wilt, even in late stages of growth, don't be surprised.
Don Lander, Collier County Agricultural Agent, has made this
observation this spring. In fields with both growing side by
side, he noted significantly more Charleston Gray 133 affected
with wilt than in the Charleston Gray variety.
Potato Vine Killer Approved For Use
Mason Marvel reports that it is now legal to use DNBP
as a vine killer for potatoes. It is officially cleared for
use up to ten days before harvest and where there are no ex-
Bacterial Leafspot On Watermelon
As yet unidentified, a bacterial disease caused serious
damage to watermelon foliage in south Florida in February and
early March. It could be quite serious if it becomes a regular
thing. Warm weather in March and April seemed to have helped
immensely in clearing it up in the South Florida area, but the
same disease apparently has been found in Central Florida.
A very uncanmon disease in Florida, cucumber scab, develo-
ped to serious proportions in south Florida in late winter and
early spring. A large amount of cukes in infested fields had to
be culled out due to severe scabbing and deformity. Keep an eye
out for this disease and let us know of any suspected cases.
New Bean Releases Coming
The USDA has announced release to seedsmen of foundation
seeds of two advanced lines of bush green for increase.
These two breeding lines, B 3370 and B 3125-X-5-2 as yet,
have not been named, but it will probably be done within the
year. These two beans have promising potentials for fresh market
Cantaloupe Variety Name Changed
The cantaloupe variety released last year under the name
"Florigold" by the Florida Agricultural Experiment Stations is
undergoing a change of name to eliminate "an infringement on a
private label". In a revision of Circular S-139, due out within
a month or two, this variety is being renamed "Florida # 1'
F. S. amison James Montelaro Macon E. Marvel
Head of Department Associate Vegetable Crops Assistant Vegetable
Specialist Crops Specialist