COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
STATE OF FLORIDA
COLLEGE OF AGRICULTURE. AGRICULTURAL EXTENSION SERVICE
UNIVERSITY OF FLORIDA. AND Vegetable Crop Specialists COUNTY AGrET AND
UNITED STATES DEPARTMENT OF HOME DEMONSTRATION WORK
AGRICULTURE COOPERATING VG E T A R IA N GAINESVILLE FLORIDA
TO: COUNTY AGENTS # 61
(912 IN THIS ISSUE
/ 1. Electrostatic Dusting of Vegetables
> 2. Dimethoate (Cygon) on Tomatoes
\A 3. Guthion Interval Shortened on Some Crops
4. Bud Nematodes in Strawberries
5. PEBC (Tilliam) "Pulled" From Tomatoes
6. Bacterial Leafspot of Cabbage
7. Use of Phosphorus
ELECTROSTATIC DUSTING OF VEGETABLES
Electrostatic dusters are being sold and used in Florida by
vegetable growers. The claim is that efficiency of pesticidal dust
treatment is increased and therefore, less material can be used.
Casselman, Thayer and Genung tested electrostatic on beans at
Belle Glade. They found that electrostatic dusting was significantly
better in the control of bean rust than non-charged dusting. Except
for leafhoppers, electrostatic dusting was not significantly better
than the standard method of application for insect control. Deposi-
tion of negatively charged particles was greater than positively
DIMEHOATE (CYGON) ON TOMATOES
This material was approved for use as a foliar spray on tomatoes
last year and proved to be quite effective for leafminer control.
It is approved for use up to 1 pint of the 4 pound emulsion formula-
tions 21 days before harvest.
Baranoiski has found that drenching the soil at 1 pint per acre
gives control of leafminers for about 3 weeks at Homestead. Drenching
is not approved for use as yet. We rll let you know as soon as it is
GUTHION INTERVAL SHORTENED ON SCME CROPS
Limitation requirements for Guthion on potatoes have been reduced
from 14 to 7 days between last application and harvest. On tomatoes
the time interval was cut from 3 days to no time limitations (NTL).
These changes are for rates of 0.75 actual per acre.
BUD NEMATODES IN STRAWBERRIES
Stunted, heavily-bronzed, crinkled strawberry plants may be in-
fested with bud nematodes. Locascio and Perry have found light
infestations in central Florida and same heavy infestation in north
Florida in nursery stock.
Control methods are being worked on now. No solid recommendations
as yet, but if you suspect nematodes, send a plant sample for identi-
fication and we will try to suggest a control.
PEBC (TILLImI) "PULLED" FRCM TOMATOES
This material gave variable results last year according to the
manufacturer. As a consequence, they are pulling it fran the market
on direct-seeded tomatoes until further notice. It can be bought by
signing a release to the company.
NOTE: Make this change in your "Vegetable Weed Control Guide".
BACTERIAL LEAFSPOT OF CABBAGE
A bacterium has finally been identified as causing the small brown
spot on cabbage causing serious loss to this crop in sane seasons. It
is usually found on the wrapper leaves but sometimes affects the inner
leaves as well. Cross sections of the stem usually show darkened vas-
cular bundles, indicating that the disease may be systemic.
Wehlburg identified the bacterium as Pseudcmonas cichorii. He and
Thayer report that this organism attacks ornamental chrysanthemums,
celery, escarole as well as cabbage. Growers suspecting this disease
on cabbage may try the controls suggested for bacterial blight of
USE OF PHOSPHORUS
Proper use of phosphorus in the fertilization programs for vege-
tables is not so simple as often believed. It has been our observation
that this part of the fertilization program is often mismanaged to the
detriment of the whole program. Considerable basic knowledge has been
accumulated on the behavior of phosphorus in soil. It is extremely im-
portant for anyone recommending or managing a fertilization program for
vegetables to understand and apply these basic facts to insure the de-
First, let's review some of the recent research conducted on
phosphorus here in Florida. Secondly, let's list the-basic facts known
about behavior of phosphorus in soil in simple terms so that they may
be easily remembered and applied to modify a fertilization program as
- 3 -
A. Research Reviews
(1) Fixation By Different Soil Types.
At Gainesville, Breland and Locascio found that Kanapaha soil
"fixed" larger amounts of phosphorus than Ona soil. This means
that phosphorus is less available on Kinapaha than on Ona soil
and should, therefore, receive larger amounts of the element to
supply the needs.
(2) Accumulation of Phosphorus Reserves.
Forbes and Westgate found that phosphorus reserves totaled as
much as 7,000 pounds per acre on the sandy soils at Sanford that
have been fertilized for 50 to 60 years. Over an eight-year period,
a total of 10 crops grown showed no response to addition of phosphorus.
(3) Response of Peppers to Phosphorus.
Ozaki obtained a significant response fran phosphorus on peppers.
Surprisingly, 22 pounds of phosphorus was as good as 44 pounds per acre.
Splitting these amounts into two applications showed no added benefits.
(4) Calcium Phosphorus Relationships.
Hortenstine and Stall working with tomatoes on sandy soil at
Fort Pierce found phosphorus increased vine growth, calcium increased
fruit size. They observed that increasing phosphorus rates decreased
calcium intake. A decreased calcium intake has been reported to in-
duce "nutritional leaf-roll". How this may be brought about is ex-
plained by these workers and Volk as follows:
"Phosphorus reduces soil pH which in turn reduces
nitrification Low nitrification would result in
low nitrate Nitrogen with a concurrent lowering
in calcium intake by the solanaceous crops (tomato,
eggplant, pepper and potato). Nitrate nitrogen
apparently has the effect on mobilizing calcium in-
to the plant".
(5) Phosphorus On Old and New Land.
Hensel reported that potatoes responded to phosphorus in each of
a three-year test at Hastings. On old continuously cropped land, res-
ponse to phosphorus was found when rates up to 200 pounds of P205
were used. On new land, potatoes responded to rates up to 400 pounds
B. The results presented in these short reviews substantiate
some of the basic facts already known about the phosphorus and its'
use. Following are smae "rule of thumb" facts with which a person
should become familiar if he is to nodify a phosphorus fertilization
program as needed.
i(1) Phosphorus does not move appreciably in the soil.
(2) Phosphorus accumulates (from ,continual fertilizer V
"applications) in the upper foot of soil. -
,\ (3- Most of the total supply of phosphorus in a soil
is tied up chemically. X
S'(4) Soil, phosphorus is low in solubility in water or
-" ---the soil solution.
(5) Acid soils contain excess, iron and aluminum, both
readily combine with phosphates to convert them into
sparingly soluble compounds.
(6) Alkalipe or calcareous soils contain calcium n-which
combines with phosphates to form sparingly soluble
(7) In general -- availability of phosphorus is'at a6
maximum between pH 6.5 and 7.0.
(8) As c(solu-le. phosphorus is removed from the soil by
pl .ts-, it is replaced from the fixed forms.
(9) Low soil moisture lowers the solubility of the fixed
forms of phosphorus.
,(10l) Mixing phosphates with the soil increases fixation.
(11) Banding phosphates retards fixation.
(12) Organic matter in general increases availability of
(13) Rapid microbial growth may cause temporary "drop in
(14) Maximum benefits from maintaining high phosphorus
fertility are not realized unless other nutrients are
supplied at proper levels.
(15) Plant in the early stages of growth have an extremely "
high need for phosphorus (as much as 50% of total phos-
phorus uptake occurs when plants have developed only 20%
of total growth.
(16) Plant species vary widely in their ability to extract .
phosphorus from the same soil.
(17) Soils va~r in their ability toL fix phosphorus.
'(18) Water-soluble phosphorus will move about one inch
from the point where it is applied in the soil.
(19) Less than 20% of phosphor-is applied is utilized by
the crop the year of application.
(20) Placement of phosphorus in close proximity to seed
I and young seedling is especially important. Phos-
phorus is necessary for rapid root development.
(21) Many species of plants (especially seedlings) cannot
forage for phosphorus very satisfactorily in cold
soils. Close placement of a water soluble P is very
important during winter months.
F. t Jamison, Head L' James Montelaro
Vegetable Crops Department Associate Vegetable Crops
ason E. Marvel
Associate Vegetable Crops