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Group Title: Bulletin. New series
Title: Onion production in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
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STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00014981/00001
 Material Information
Title: Onion production in Florida
Series Title: Bulletin. New series
Physical Description: 18 p. : ill. ; 23 cm.
Language: English
Creator: Stoutamire, Ralph
Florida -- Dept. of Agriculture
Publisher: State of Florida, Dept. of Agriculture
Place of Publication: Tallahassee Fla
Publication Date: 1930
 Subjects
Subject: Onions -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Ralph Stoutamire.
General Note: "September 1930"
General Note: Cover title.
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Bibliographic ID: UF00014981
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA7375
ltuf - AKD9404
oclc - 28534347
alephbibnum - 001962727

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Full Text




September, 1930


ONION

PRODUCTION

In Florida


By
RALPH STOUTAMIRE













State of Florida
Department of Agriculture
NATHAN MAYO, Commissioner
Tallahassee


T. J. APPLEYARD, INC., TALLAHASSEE, FLORIDA

LIBRARY
FLORIDA X

Bulletin No. 39


New Series


























DEPARTMENT OF AGRICULTURE

Nathan Mayo, Commissioner of Agriculture.................Tallahassee
T. J. Brooks, Assistant Commissioner................................Tallahassee
Phil S. Taylor, Supervising Inspector ................................Tallahassee










CONTENTS
PAGE
P lan t C h a ra cteristics ...................................................................................................... 5
R o o t s ........................................................................................................................... 5
P o llin a tio n ....................................................... ............................................... 5
Clim ate and Soil Requirem ents ................................................................ 6
C u ltu r e ... .............................................................. . ............... ............................................. 7
S e e d in g .......................................................... ............................................. 7
Germ nation .............................. 8
Cultivation and W eeding ............. ...................................... 8
Irrigation and Drainage ............. 9
T h in n in g ................................................................................................................. 9
R ip en in g ............... ............. ....................................................................... 9
H a r v e stin g ............................................................................................................ 9
Fertilizers and Cover Crops ............................... 10
Com m ercial Fertilizers .............................................................. 10
The Use of Lim e ......................................................... .............................. 10
M anure ....................... .......................................................... .... 10
Cover Crops ............................................ ................................. ..... 11
Transplanted Onions ......................................................... ................................ 11
M marketing ................... .................................................................... ...... 11
Grading ......................... .................................... .. ............ 12
C o n ta in ers ............................................ ..................................... ......... 1 2
V a r ie t ie s ................................................................................................................ ....... 1 2
Seed Selection ........................ ..................... ...... ... ........... 14
Diseases .............. ................................................................. ...... ..... 15
M ildew .................................................................................................... 15
Onion Smudge ........................................................... ............................... 15
N e c k -R o t ................................................................................................................. 1 6
W hite-Rot ............................................... ............................... ....... 16
I n s e c t s .......................................................................................................................................... 1 7
Thrips ................................. ......................... ..... .. ......... 17
Onion M aggot ........................................ ................................... ......... 17.
A cknowledgm ents ....................................... ....................................................... 18


2-Onion.














Onion Production in Florida
By Ralph Stoutamire
THE onion crop of Florida has never been of great com-
mercial importance, at least as far as out-of-state ship-
ments are concerned. A score of years ago this crop was
grown much more extensively than of late. But during the
last three years there has been a revival of interest in it among
quite a group of growers. As a result considerable informa-
tion has accumulated regarding the production of onions.
This plant is adapted to a wide variety of climate and soil
conditions, so that it is known and grown in most countries of
the world. It is of great antiquity, being mentioned in the first
chapters of the Bible, as when the Israelites complained to
Moses because of the lack of this food while they were in the
wilderness.
It is not known definitely when onions were first introduced
into the United States, but early in the seventeenth century
they were being grown in Massachusetts. At the present time
the bulk of the onion crop in this country is grown in New
York, Texas, Indiana, California, Massachusetts, Ohio and Mich-
igan. The production in each of these states is shown by the
graph in figure 1.
PLANT CHARACTERISTICS
Roots: The root system of the onion is fibrous. According to
Goff a young onion plant with leaves 8 inches long was found
to have developed a root system penetrating to a depth of 16
inches. This, however, seems about as deep as the roots ever
go, even of older plants, and most of them are much shallower
growing. This would, no doubt, depend mainly upon soil and
moisture relationships. The roots spread outward and down-
ward, few of them being very deep. In general they extend
about a foot from the base of the bulb. Forty days after plant-
ing the average total root system, in one case, was estimated at
about 400 linear feet.
Pollination: Where attempts at breeding or crop improve-
ment by selection is attempted, it is very essential to know that
cross pollination is readily accomplished, since quite a variety
of insects visit the blooms. Considerable self-fertilization un-
doubtedly takes place also. In case of variety or strain tests,
these should be planted at least half a mile apart.









6 DEPARTMENT OF AGRICULTURE


N.q. Texas Ind. GCalf flass. Ohio flich.

Fig 1. Showing onion production in thousands of bushels in the 7 lead-
ing states. Texas is listed in the "early crop" column along with Cali-
fornia and Louisiana. The remainder of those given in the above graph
are so-called "late crop" states.

CLIMATE AND SOIL REQUIREMENTS
Most of the onions in this country are grown on muck soils,
although a deep sandy or silty loam is quite satisfactory and is
used a great deal. It is generally understood that the onion
does not tolerate an acid soil. Yet in Florida very good crops








ONION PRODUCTION IN FLORIDA


have been produced on soils quite acid in reaction. Onions
seem to grow well following such crops as grasses, cereals and
legumes.
Onions are grown in every state in this nation, either com-
mercially or in the home garden or both. This, in itself, tells
much regarding its adaptation to a wide range in temperature,
humidity, light and soil conditions.
The young plant will withstand a temperature several de-
grees below freezing. In fact, best root development takes place
at relatively cool soil temperature-say from 55 to 65 degrees,
Fahrenheit.
During early growth it is highly essential that ample soil
moisture be maintained near the surface of the ground. New
roots are not developed in a dry surface soil. Furthermore,
growth must be continuous. If for any reason growth is sus-
pended temporarily, the outer scales seem to mature. Upon
the resumption of growth the inner scales resume growth, re-
sulting in a splitting of the bulb.
It has been shown that onions require a relatively long day
before bulbs are developed. Varieties show considerable varia-
tion in this respect, but days of from 13 to 15 hours of daylight
are required. This, undoubtedly, explains why onions in Flor-
ida do not "bottom" before February or March, irrespective
of the time of planting.
In general it may be said that onions thrive best where great
fluctuations in weather do not occur. Since the early stages
of development require relatively cool weather, and since rela-
tively long days are required for the development of the bulbs,
it would seem that plantings made in January would be less
subject to disturbing influences, such as weeds, unfavorable
moisture and temperature, insect pests and plant diseases. It
would seem worthy of some experimental trials to say the least.
Most varieties require about 130 days from seeding to harvest-
ing, where favorable conditions exist. If seedlings are trans-
planted, a crop may be made in about 100 days from time of
setting the plantlets in the field.

CULTURE
Seeding: The bulk of the crop in Florida is seeded directly
in the field. To do this successfully the soil must be in good
tilth and thoroughly pulverized. Seeding at the rate of 31/2
to 5 pounds per acre and at a depth of 1/ to 1 inch are general
rules. In muck soils the seed are frequently planted 2 inches
deep. A seed drill is quite essential to uniform distribution.
The rows are spaced from 14 to 24 inches apart. To keep the
rows parallel is a great convenience when cultivating.








8 DEPARTMENT OF AGRICULTURE

Germination: Onion seed germinate best when the soil tem-
perature is from about 60 to 65 degrees, Fahrenheit. This is
additional evidence against planting too early in fall.
Cultivation and Weeding: It is evident from a study of the
root systems of the onion that it will not tolerate deep culti-
vation. If the ground has been carefully and thoroughly pre-
pared prior to planting, a minimum of cultivation will be
required. It would pay well to grow some tillable crop for a
year or two, where horse cultivation can be employed, in order
to kill out the weed seed in the land. This requires diligence
under Florida conditions, but much expensive hand labor can
be saved in making the onion crop where weed seed have been
reduced in this way.
Hand tools are used almost exclusively in the production of
the onion crop. This is due, no doubt, to the fact that the
plants at seeding stage are delicate and easily damaged. Then,
too, shallow cultivation is more readily practiced with hand
implements. There is another advantage in the use of hand
tools; this is in the closer spacing of the rows. Onion production
thus becomes a very intensified type of vegetable production.
The wire weeder is almost indispensable in growing a crop of
onions. It consists of numerous long, fine steel fingers fastened
to a cross bar of convenient length. Where flat cultivation is
the rule this may be about 4 feet long. For ridge culture it
would have to be modified to suit such conditions. The cross
bar is attached to the wheel hoe. In case of a heavy rain which
packs the soil prior to germination, this weeder is almost the
only tool that can be used to break the crust without seriously
damaging the seed. Even after the crop is up, the weeder
renders very efficient service in keeping down the first crop of
weeds.
Just as soon as it is possible to distinguish the rows, a wheel
cultivator is used. There are several kinds which may be bought
to suit the fancy of the individual. There is a single-wheel
type where the shovels and plows are off-set to prevent the
wheel from running on the plants. Then there is the double-
wheel type which straddles the row. In any case the so-called
"double knife" attachment, which cuts a swath just beneath
the soil surface on both sides of the row, is used. This kills
small weeds and stirs the surface of the ground without covering
the young plants. This operation is usually repeated every
week or ten days, depending upon the rapidity with which
weeds grow, rainfall and other conditions.
For the last cultivation some growers substitute a triple set
of shovels. The shovels turn a small amount of soil against
the rows, affording some protection to exposed bulbs, giving
them a better color. If the shovels are run deep enough, many








ONION PRODUCTION IN FLORIDA 9

roots may be severed, thus hastening maturity. This may be
an important factor in Florida under certain climatic or market
conditions.
Irrigation and Drainage: With the erratic precipitation pre-
vailing in Florida the control of soil moisture is a prime neces-
sity in onion culture. Sub-irrigation or overhead systems are
quite satisfactory. Tiling of the land may serve a dual pur-
pose-drainage and irrigation-if properly done. While there
are no records available in Florida, irrigation plants elsewhere
have frequently more than doubled the yield. A small area
properly handled may be much more productive, proportion-
ately, than larger areas carelessly managed. *














Fig. 2. White Bermuda onions grown in muck soil on the practice farm of
the University of Florida.

Thinning: This operation in Florida can frequently be done
economically by using the onions pulled out as bunch onions
for the local markets. Thinning is necessary in order to pre-
vent crowding. Thin to not closer than 4 or 5 inches in the
row.
Ripening: When the plants develop normally, ripening is
evidenced by a drying of the leaves in the region just above the
bulb, which causes the top to fall over while the leaves are still
green. On the other hand, if the tops dry from the tips down-
ward while standing erect, the neck is not properly closed, with
the result that the bulbs do not keep well in storage. The
latter condition is one frequently seen in Florida, especially
with the Bermuda variety. Early plantings also tend toward
seeding, which is undesirable.
Harvesting: It is essential that harvesting be done in dry
weather, if possible. One of the greatest drawbacks to suc-
cessful onion culture in Florida is the lack of proper curing.
Unless the bulbs are properly cured they will not stand storage.








10 DEPARTMENT OF AGRICULTURE

As a general rule the months of April and May are relatively
dry, thus providing the best season and opportunity for suc-
cessful harvesting. But as these months may be excessively wet
or as the onions may not be ripe, some more dependable way
of curing, other than solar heat, should be available. Kiln
drying has been tried by a few growers with very promising
results. Tobacco curing houses, in one instance, were utilized
in this connection to good advantage. This is another problem
that should receive some consideration experimentally.
FERTILIZERS AND COVER CROPS
Commercial Fertilizers: Muck soils are ordinarily well sup-
plied with nitrogen, but they require liberal amounts of phos-
phate and potash. There is a tendency on the part of many
growers to use little or no fertilizer on muck soils. Experi-
ments on these soils in New York showed that best onion yields
were obtained by using about a ton to the acre of a mixture
containing 3 percent nitrogen, 5 percent phosphoric acid
and 10 or 15 percent potash.
Onion growers who use the sandy loams in Florida have
found it profitable to use from 2,000 to 3,000 pounds of fer-
tilizer per acre, and the tendency has been toward a 10 to 12
percent potash mixture with relatively small amounts of nitro-
gen. Until more is learned experimentally, it would seem safe
to recommend from about 2,000 to 2,500 pounds per acre of a
4-6-12 mixture. At least two and possibly three applications
should be made. When early fall plantings are made, more
fertilizer is required to produce a crop than when the crop is
planted later and is then forced to mature in a shorter time.
A considerable percentage of the nitrogen should be supplied
from organic sources.
The Use of Lime: Almost all experiments where acid soils
have been corrected by applications of lime, increased yields of
onions have resulted. There is in Florida a decided bias against
lime for most crops, probably arising from some unfortunate
trials where very heavy applications were made. By using the
hydrated form in moderate amounts (from 200 to 500 pounds
per acre), it is probable that satisfactory results would follow.
Manure: Since organic matter is so essential to the growth
of most economic crops, especially in the sandy soils of Florida,
barnyard manure, chicken manure and most litter should be
conserved and made into compost. Onions show plainly their
preference for large quantities of organic matter, since they
thrive so well in muck soils. Organic matter not only provides
plant food but improves the physical conditions of the soil,
giving it greater water-holding capacity. In many muck areas








.ONION PRODUCTION IN FLORIDA


where onions are grown extensively, it is not an unusual prac-
tice for the growers to give the land a liberal application of
barnyard manure. They claim that the beneficial action of the
bacteria is worth the cost. Usually it is a good practice to
apply the manure to the crop grown ahead of onions, unless it
is well composted. Weed seed and a tendency to keep the
ground too open are the chief objections to applying manure
to onions.
Cover Crops: Barnyard manure is not as abundant since the
advent of the motorized farm, so cover crops must be relied
upon more and more as a source of organic matter in the soil.
Crotalaria, a leguminous, rank-growing annual that is resist-
ant to nematode infection, is the most promising cover crop
for Florida truckers. Other good legumes are velvet beans, cow-
peas and beggarweed. However, any kind of grass that will
grow on the land will add humus and should be encouraged.
This is not to be construed as a recommendation of such grasses
as nut grass. Bermuda is not as objectionable as nut grass,
but it is so difficult to remove from the land it should not be
allowed to gain foothold, except where it is desired to establish
pasture.
TRANSPLANTED ONIONS
It seems that there are certain advantages secured where
onions are started in a seedbed and later transplanted to the
field. These advantages are: 1. Better controlled growing
conditions; 2. more uniform bulbs; 3. more bushels per acre.
Seed should be sown in drills in a well-prepared seedbed.
About 2 pounds of seed should be planted for each acre of
field to be set. Both top and root pruning are practiced in
order to make strong stocky plants for transplanting. The"
leaves are cut back to about 4 inches. The plants should be
about the thickness of a lead pencil when removed from the
seedbed. Space from 4 to 6 inches in rows from 18 to 24 inches
apart where level cultivation is possible. In other states nar-
rower rows are the rule.
The same cultural practices are followed as when the crop
is grown directly from seed. Only carefully planned tests would
show which of the two methods might prove most satisfactory
for Florida farmers;
MARKETING
Market demands, year after year, for cured onions are quite
constant. Prices of many fruits and vegetables regulate their
consumption. But not so with onions. The average American
home does not consume large quantities of this crop, but it does
use a few every week of the year.








DEPARTMENT OF AGRICULTURE


Then there is the "green" or "bunch" onion market.
Recently there has been a strong tendency in certain Florida
trucking areas to cater to the demand for mixed cars of
vegetables. Some green onions are shipped in response to this
demand. Some also is sold on the home market which, during
winter, demands considerable quantities of attractively bunched,
good quality stuff of this type. The bunches should be tied
neatly and washed thoroughly, and the tops should be clipped
evenly. The flavor should be mild. Variety and rapidity of
growth usually have the greatest influences upon flavor at this
early stage, although soil types may also be a factor. Where
the demand for green onions is strong, it may be desirable to
plant sets, in order to get size more quickly. On the other hand,
if the green onions are merely a by-product of the main crop,
it is doubtful whether sets can be planted because of the greater
costs involved.
Grading: The usual method of grading is to pass the bulbs
over a slatted table. The slats are spaced far enough apart to
permit dirt and the smaller bulbs (those under 11/2 inches in
diameter) to fall through. United States Grade No. 1 calls
for onions of similar varietal characteristics: Firm, mature,
well-shaped; free from doubles, splits, bottle-necks, scallions,
dirt, tops or other foreign matter, damage caused by sprouting,
freezing, disease, insects, mechanical or other injury. A toler-
ance of 5 percent is allowed below the requirements of this
grade, but a tolerance of only 4 percent is allowed for decay.
Grade No. 2 includes the bulbs which do not meet the require-
ments of Grade No. 1. These are further graded into sizes as
follows: Boilers, from 3/4 to 11/. inches in diameter; small,
from 11,. to 13/4 inches; large, over 21/4 inches; very large, over
3 inches. Not more than 5 percent by weight may be below
the specified size and not more than 10 percent by weight may
be above the specified maximum size.
Containers: Most of the northern-grown crop is marketed
in so-called "grass sacks" of 100-pound capacity. They have
a coarse mesh which provides ventilation and easy inspection.
Southern or Bermuda onions are handled in slatted crates. The
latter move directly to market, mostly from April to June.
Dry onions supply the markets from then until March, winter
shipments coming mostly from storage. Fewest cars move dur-
ing June.
Considerable quantities of onions are imported, especially
during years of small production in the United States.
VARIETIES
Onions are commonly grouped into three classes as follows:
1. Those propagated by divisions-Potato onions, Multipliers.








ONION PRODUCTION IN FLORIDA 13

2. Those propagated by bulblets or top sets-Egyptian or
Winter onions.
3. Those propagated by seed-Yellow Globe Danvers, Ebe-
nezer, Prizetaker, Red Bermuda and other common varieties.















Fig. 3. Two varieties grown side by side. "White" Bermudas on the reader's
right, and to his left are "Red" Bermudas.

A very small proportion of the onions produced in the United
States fall in the first two classes. The leading varieties of the
third class are listed by Morse (1923) as follows:
1. Australian Brown.
2. Extra Early Red Flat.
3. Ohio Yellow Globe.
4. Prizetaker.
5. Red Wethersfield.
6. Southport Red Globe.
7. Southport White Globe.
8. Southport Yellow Globe.
9. White Portugal.
10. Yellow Danvers.
11. Yellow Globe Danvers.
12. Yellow Strasburg.
13. Bermudas.
Spanish varieties, such as Sweet Spanish, Denia, and Valen-
cia, are increasing in favor. This is also true of Ebenezer.
Little has been accomplished in determining the better, or
best, varieties for Florida. Recent studies have shown that
such varieties as Prizetaker and Yellow Globe Danvers are not
adapted to the short days in the tropics and sub-tropics. In
this respect the Bermudas seem most desirable. But the Ber-









DEPARTMENT OF AGRICULTURE


mudas are all very poor keepers, and they seem more or less
susceptible to splitting under Florida conditions.
Australian Brown has many desirable qualities. It is a very
good keeper. It does require a longer time to mature, however,
than many other varieties and this is objectionable in Florida,
not only because of markets but also because of the difficulty
of curing during June.
White Portugal is grown as an early-market onion and for
sets. They do not keep as well as most of the yellow varieties,
such as the Yellow Globe Danvers.



















Fig. 4. Onions marketed in this manner find favor on many tables. They
must be used at an early stage or they will become too 'hot."

SEED SELECTION
Carefully conducted strain and variety tests should be used
as a basis for selection and breeding, so as to secure an onion
well adapted to Florida's climate. At the present time some of
the Spanish varieties give promise in this connection.
Good seed is the first and most important factor in successful
onion production. Onion seed deteriorates rapidly in this
climate. The following comparisons show how onion seed in
Connecticut lost their vitality with age. The seed were Califor-
nia grown:
Number Percentage
of That
Samples Germinated.
Seed less than 1 year old ............................ 400 88.18
Seed between 1 and 2 years old ..........-. 220 77.46
Seed between 2 and 3 years old .............. 2,023 57.34
Seed between 3 and 4 years old ................ 1 10.00








ONION PRODUCTION IN FLORIDA 15

Seedmen in Florida claim that in a single year onion seed loses
practically all its ability to germinate.
Uniformity in size, shape, color and time of maturity of bulbs
is essential. Methods usually employed in growing onion seed
for the trade are not all that could be desired. As a conse-
quence there are usually wide variations in a field grown from
such seed from.a single source. For instance, the Ohio Experi-
ment Station in an onion variety test found one strain, sup-
posedly a Globe variety, which had but 65.8 percent Globes.
It showed 2 percent scallion, 9 percent flat, 7 percent off
color and 26.1 percent bottle-neck. This was not the poorest
lot tested. Off-color is a serious trouble, since a red or yellow
onion in a pile of white ones is very conspicuous. Only 8 of the
66 strains tested passed a perfect record as to color.
DISEASES
Mildew: This is one of the most destructive diseases in
Florida. It may be recognized by the furry, violet-colored
growth upon the leaves. It is especially conspicuous when the
leaves are wet with dew. Within a few days large areas become
pale green and then yellow. The seed stalk as well as the leaves
may be affected. They collapse and die.
The disease is caused by a fungus called "Pernospora.
schleideniana" which works very rapidly in high temperatures
in the presence of dews, rains, cloudy and foggy weather. It
is often most destructive to a seed crop.
Control: Good aeration of the field will do much toward
controlling mildew. This may be facilitated by running the
rows in the same direction as of prevailing winds and by avoid-
ing wind breaks or other obstructions to the wind. If the rows
are planted somewhat wider apart, better aeration is possible.
Onions should not be planted on the same piece of land
oftener than once in three or four years. The resting spores of
the fungus are carried on diseased leaves. It is imperative that
these be kept away from disease-free fields.
Spraying has been employed to some extent. A 4-4-50 bor-
deaux mixture, with 3 pounds of resin fish-oil soap to each 50
gallons, is quite effective. Several applications may be re-
quired to protect the young foliage.
Onion Smudge: This disease is widespread and affects white
varieties mostly. Small dark green to black spots form on the
outer scales, often in the shape of concentric circles. The fun-
gus causes little damage but lowers the market value on account
of the smudge appearance. Where bulbs are stored without
proper curing or drying, the disease may cause considerable
loss.









DEPARTMENT OF AGRICULTURE


Control: The fungus that causes this trouble lives in the
soil, hence crop rotation is one of the most effective means of
control. Diseased bulbs or other refuse from the storage house
should not be carried into disease-free fields. Dry bulbs
thoroughly and quickly prior to storing. See that adequate
ventilation is provided in the storage bin.



















Fig. 5. The tendency of the Bermuda onion to split may be noticed among
those in these containers.

Neck-Rot: In most areas this disease causes loss in both
field and storage. Small white dots first appear on the leaves.
They rapidly elongate in the same direction as the leaf. Sur-
rounding this point of infection, there develops a water-soaked
area somewhat yellowish in color. The fungus lives over in the
soil or on the bulbs.
Control: White varieties suffer more than red or yellow.
Early maturity of the crop is effective. Provide good field
aeration. Prevent wounding of bulbs. Dry the bulbs thoroughly
before storing. If neck-rot is prevalent, storage in bins, boxes
or bags is not recommended. Pick a storage temperature close
to freezing. Keep diseased bulbs and refuse from being carried
into disease-free fields.
White-Rot: This disease has been reported from a number
of states, notably from Oregon, Kentucky and Virginia. It at-
tacks onions, leek, garlic and shallot. According to Walker, its
first symptom is a yellowing and dying back from tips of leaves.
Roots and leaf bases are attacked. Roots are gradually de-


16








ONION PRODUCTION IN FLORIDA


stroyed and the scales take on a semi-watery decay with much
fluffy mycelium present. Decay may continue in storage.
Control: So far as known no effective control has been found.
The precautions suggested for the control of other diseases will
no doubt be effective in checking white-rot.
INSECTS
Thrips: This is undoubtedly one of the most damaging pests
that attack the onion crop. It attacks the epidermis of green
leaves and sucks their juices, producing a silvery appearance to
the foliage which later dies. A thrip is about 1/25 of an inch
long and is pale yellow in color, tinged with black. Its eggs
are laid just beneath the leaf surface and hatch in about four
days. Most serious damage usually results when precipitation
is highest and when temperatures are above normal.
Control: The spotted and convergent ladybird beetle, the
insidious flower bug and the larva of the syrphus fly prey upon
thrips. Heavy rains often destroy many of them.
Dusts and sprays usually are not effective as control measures
for thrips, and they are expensive. Some success has attended
their use. A soap-nicotine-sulphate spray or a 5 percent nico-
tine sulphate dust have been helpful. Perhaps one of the most
promising substances for spraying with nicotine is "penetrol."
This increases the effectiveness of the nicotine by at least 33
percent.
Rely on preventative measures as much as possible. Clean
cultivation, burning or clearing of fence rows, ditch banks, etc.,
will be found effective. Multiplier onions or onion sets should
not be planted near a field which is intended for onions, since
they serve as breeding places. In Florida it would seem that
plantings made in cool weather are less likely to be seriously
attacked. Keep the plants growing by providing ample mois-
ture and available plant food. An onion crop, if properly han-
dled, may outgrow an attack of thrips.
Onion Maggot: This insect causes great loss in some places.
Plants are attacked at all stages of growth. The bulbs are tun-
neled, and this is usually followed by decay. The maggot is
white to yellowish. It is blunt behind, tapering toward the
head. Adults are greyish brown, hump-backed flies that are
sluggish in their movements.
Control: One of the most effective control measures is a
trap crop. Where every 50th or 100th row is left vacant in
seeding the field and later planted or set to scallions, a good
breeding ground is provided for the maggots. By destroying
the plants at the proper stage, the control is quite effective.








18 DEPARTMENT OF AGRICULTURE -.

A poisoned bait is sometimes used effectively. Lovette recom-
mends sodium arsenite, 1/4 ounce; molasses, 1 pint; water, 1
gallon; chopped onion, 1/2 pound. The bait is placed in the
field in shallow pans, about 24 of them to the acre.: The flies
are attracted to the bait prior to the time of egg laying. There-
fore, the bait must be in the field before this time.

ACKNOWLEDGMENTS
In the preparation of this bulletin much assistance has been re-
ceived from Professors C. E. Abbott and M. R. Ensign of the
Florida College of Agriculture. The former cooperated in
securing photographs, while the latter gave a lot of valuable in-
formation on the subject. He also read and criticised the manu-
script. For this assistance the author is most grateful and de-
sires to express his appreciation.




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