• TABLE OF CONTENTS
HIDE
 Title Page
 Description
 History
 Types of covers
 Specifications
 Installation
 Timing
 Costs
 Weed and pest control
 Specific crop responses
 An integrated system
 Future research
 Reference
 Back Cover






Group Title: Florida Cooperative Extension Service circular 728
Title: Row covers for commercial vegetable culture in Florida
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00014514/00001
 Material Information
Title: Row covers for commercial vegetable culture in Florida
Series Title: Circular
Physical Description: 7 p. : ill. ; 28 cm.
Language: English
Creator: Hochmuth, George J ( George Joseph )
Kostewicz, S. R
Stall, W. M ( William Martin ), 1944-
Publisher: University of Florida, Institute of Food and Agricultural Sciences, Florida Cooperative Extension Service
Place of Publication: Gainesville Fla
Publication Date: [1987]
 Subjects
Subject: Vegetables -- Frost protection -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 6-7).
Statement of Responsibility: George J. Hochmuth, Steve Kostewicz, and William Stall.
General Note: Title from cover.
General Note: "May 1987."
Funding: Circular (Florida Cooperative Extension Service) ;
 Record Information
Bibliographic ID: UF00014514
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: aleph - 001833172
oclc - 29019446
notis - AJQ7282

Table of Contents
    Title Page
        Title Page
    Description
        Page 1
    History
        Page 1
    Types of covers
        Page 1
    Specifications
        Page 2
    Installation
        Page 2
        Page 3
    Timing
        Page 4
    Costs
        Page 4
    Weed and pest control
        Page 4
    Specific crop responses
        Page 4
    An integrated system
        Page 5
    Future research
        Page 5
    Reference
        Page 6
        Page 7
    Back Cover
        Back Cover
Full Text

1987 CIRCULAR 728
7a2"MAY 1987 CIRCULAR 728


ROW COVERS..for
Commercial Vegetable
Culture in Florida
George J. Hochmuth, Steve Kostewicz, and William Stall


/ Florida Cooperative Extension Service


John T. Woeste, Dean


University of Florida


Institute of Food and Agricultural Sciences







Row Covers for Commercial Vegetable Culture in Florida
George J. Hochmuth, Steve Kostewicz, and William Stall*


Cool temperatures play a large role in the uncer-
tainty of vegetable production in Florida. Untimely
frosts in several recent years have shortened
marketing periods for many vegetable crops.
Likewise, production of warm season crops in many
areas of Florida is severely restricted by cool
temperatures during parts of the growing season.
Plant protection by row covers can prevent losses
from untimely frosts and provide a means to
favorably modify the environment around the plant
resulting in more rapid growth, earlier maturity,
and possibly increased yields. An example of the
usefulness of crop covers occurred during the
January 1985 freeze, when wax paper, nursery con-
tainers, and strawberry boxes were used by several
growers in Manatee County to protect young
tomato plants (Fig. 1).


Fig. 1.


regarding row covers in the U.S., and to provide ex-
amples of potential applications of that technology
to Florida vegetable production.

History
Present-day row cover technology dates back to
research during the 1930s by Ware in Arkansas, and
the 1950s in Kentucky by E. M. Emmert, and to C.
A. Shadbolt, O. D. McCoy, and B. J. Hall in Califor-
nia (3,14). The first successful commercial-scale use
of polyethylene row covers was made in San Diego
County, California in 1958. However, widespread use
of row covers did not occur until recently, following
research in New England by O. S. Wells and J. B.
Loy. Their research showed that row covers can be
used economically on many vegetables, particularly
cucurbit crops. Traditionally, row covers have been
used in spring to increase earliness, but recent
research has shown benefits from frost protection as
well.
Types of Covers
There are presently two major types of row cover
materials for commercial use: polyethylene and po-
rous, floating nonwoven materials. Many variations
of each type exist, and new materials are being de-
veloped.
Polyethylene (poly) covers can consist of clear or
pigmented polyethylene installed over wire support
hoops (Fig. 2). Clear poly covers allow slightly


Tomato plants protected by strawberry boxes
and nursery containers in Manatee County.


Description
Row covers are flexible, transparent, or
semitransparent materials used to enclose single or
multiple rows of plants with the objective of enhanc-
ing crop growth and yield by increasing soil and air
temperature and reducing wind damage. The use of
row covers to promote early maturity and increase
yields of vegetables is becoming an established prac-
tice in many cooler production areas in the U.S.
(2,5,6,7,8,12,16,17,18). The purpose of ths publica-
tion is to describe the present state of technology


Fig. 2. Polyethylene row covers installed over wire
support hoops.


*Assistant Professor, Associate Professor, and Professor, respectively, Vegetable Crops Department, Institute of
Food and Agricultural Sciences, University of Florida, Gainesville.
1







Row Covers for Commercial Vegetable Culture in Florida
George J. Hochmuth, Steve Kostewicz, and William Stall*


Cool temperatures play a large role in the uncer-
tainty of vegetable production in Florida. Untimely
frosts in several recent years have shortened
marketing periods for many vegetable crops.
Likewise, production of warm season crops in many
areas of Florida is severely restricted by cool
temperatures during parts of the growing season.
Plant protection by row covers can prevent losses
from untimely frosts and provide a means to
favorably modify the environment around the plant
resulting in more rapid growth, earlier maturity,
and possibly increased yields. An example of the
usefulness of crop covers occurred during the
January 1985 freeze, when wax paper, nursery con-
tainers, and strawberry boxes were used by several
growers in Manatee County to protect young
tomato plants (Fig. 1).


Fig. 1.


regarding row covers in the U.S., and to provide ex-
amples of potential applications of that technology
to Florida vegetable production.

History
Present-day row cover technology dates back to
research during the 1930s by Ware in Arkansas, and
the 1950s in Kentucky by E. M. Emmert, and to C.
A. Shadbolt, O. D. McCoy, and B. J. Hall in Califor-
nia (3,14). The first successful commercial-scale use
of polyethylene row covers was made in San Diego
County, California in 1958. However, widespread use
of row covers did not occur until recently, following
research in New England by O. S. Wells and J. B.
Loy. Their research showed that row covers can be
used economically on many vegetables, particularly
cucurbit crops. Traditionally, row covers have been
used in spring to increase earliness, but recent
research has shown benefits from frost protection as
well.
Types of Covers
There are presently two major types of row cover
materials for commercial use: polyethylene and po-
rous, floating nonwoven materials. Many variations
of each type exist, and new materials are being de-
veloped.
Polyethylene (poly) covers can consist of clear or
pigmented polyethylene installed over wire support
hoops (Fig. 2). Clear poly covers allow slightly


Tomato plants protected by strawberry boxes
and nursery containers in Manatee County.


Description
Row covers are flexible, transparent, or
semitransparent materials used to enclose single or
multiple rows of plants with the objective of enhanc-
ing crop growth and yield by increasing soil and air
temperature and reducing wind damage. The use of
row covers to promote early maturity and increase
yields of vegetables is becoming an established prac-
tice in many cooler production areas in the U.S.
(2,5,6,7,8,12,16,17,18). The purpose of ths publica-
tion is to describe the present state of technology


Fig. 2. Polyethylene row covers installed over wire
support hoops.


*Assistant Professor, Associate Professor, and Professor, respectively, Vegetable Crops Department, Institute of
Food and Agricultural Sciences, University of Florida, Gainesville.
1







Row Covers for Commercial Vegetable Culture in Florida
George J. Hochmuth, Steve Kostewicz, and William Stall*


Cool temperatures play a large role in the uncer-
tainty of vegetable production in Florida. Untimely
frosts in several recent years have shortened
marketing periods for many vegetable crops.
Likewise, production of warm season crops in many
areas of Florida is severely restricted by cool
temperatures during parts of the growing season.
Plant protection by row covers can prevent losses
from untimely frosts and provide a means to
favorably modify the environment around the plant
resulting in more rapid growth, earlier maturity,
and possibly increased yields. An example of the
usefulness of crop covers occurred during the
January 1985 freeze, when wax paper, nursery con-
tainers, and strawberry boxes were used by several
growers in Manatee County to protect young
tomato plants (Fig. 1).


Fig. 1.


regarding row covers in the U.S., and to provide ex-
amples of potential applications of that technology
to Florida vegetable production.

History
Present-day row cover technology dates back to
research during the 1930s by Ware in Arkansas, and
the 1950s in Kentucky by E. M. Emmert, and to C.
A. Shadbolt, O. D. McCoy, and B. J. Hall in Califor-
nia (3,14). The first successful commercial-scale use
of polyethylene row covers was made in San Diego
County, California in 1958. However, widespread use
of row covers did not occur until recently, following
research in New England by O. S. Wells and J. B.
Loy. Their research showed that row covers can be
used economically on many vegetables, particularly
cucurbit crops. Traditionally, row covers have been
used in spring to increase earliness, but recent
research has shown benefits from frost protection as
well.
Types of Covers
There are presently two major types of row cover
materials for commercial use: polyethylene and po-
rous, floating nonwoven materials. Many variations
of each type exist, and new materials are being de-
veloped.
Polyethylene (poly) covers can consist of clear or
pigmented polyethylene installed over wire support
hoops (Fig. 2). Clear poly covers allow slightly


Tomato plants protected by strawberry boxes
and nursery containers in Manatee County.


Description
Row covers are flexible, transparent, or
semitransparent materials used to enclose single or
multiple rows of plants with the objective of enhanc-
ing crop growth and yield by increasing soil and air
temperature and reducing wind damage. The use of
row covers to promote early maturity and increase
yields of vegetables is becoming an established prac-
tice in many cooler production areas in the U.S.
(2,5,6,7,8,12,16,17,18). The purpose of ths publica-
tion is to describe the present state of technology


Fig. 2. Polyethylene row covers installed over wire
support hoops.


*Assistant Professor, Associate Professor, and Professor, respectively, Vegetable Crops Department, Institute of
Food and Agricultural Sciences, University of Florida, Gainesville.
1







earlier planting resulting in 2 to 3 weeks earliness
and in some cases increased total yields compared
with unprotected crops. The poly can be vented or
unvented. The unvented covers require manual
opening to control heat build-up on warm, sunny
days. Vented poly covers have pre-installed slits or
circular perforations for automatic venting (Fig. 3).
Heat build-up also can be reduced by the use of
pigmented plastics. White poly covers might be
especially useful in Florida in the spring.


Fig. 3. Pre-installed vents in polyethylene row cover.

The floating row covers are manufactured from
various fabric-like materials such as polyester or
polypropylene and have been used in several ways in
the textile industry and in the South as tobacco
plant-bed covers. Field performance of floating row
covers has been similar in several ways to the
polyethylene covers, but, because of their loose,
lightweight fabric nature, these covers have several
advantages over polyethylene covers (6). They can
be laid directly on the plants (floating row covers)
without the use of supporting hoops usually re-
quired by poly covers (Fig. 4). However, hoops
should be used if covers are used during windy peri-
ods. The materials are porous and thus self-ventilat-
ing. Only minor reductions in light levels (10-20%)
have been reported for these covers and this has not
been enough to affect early crop growth. Overhead
irrigation water can be applied while the cover is in
place.


Fig. 4. Floating row cover applied without support
hoops.
Specifications
Plastic row covers are made from polyethylene ap-
proximately 0.75 to 1.1 mils in thickness and are
available in various widths on rolls of various
length. The floating materials are several mils thick
and are available in various widths and lengths.
Manufacturers offer floating materials of various
weights, with the most popular presently being a
weight of about 0.6 oz per yd'.
Future variations in row covers undoubtedly will
appear as research indicates the need. Possibilities
that will be important for Florida include variable
pigmentation to control heat build-up, various
weights of floating material for use in different
seasons, various chemical protective coatings to
allow multiple season use, and widths great enough
to allow row cover use over the twin row, full bed
mulch cropping system for vegetables such as pep-
pers or for multiple row covers for strawberries. One
of the greatest needs is for a porous cover that is
light in weight to be used for growth enhancement
yet has capability for moderate freeze protection.

Installation
Installation of row covers varies considerably
depending on type of crop and grower preference.
Following are guidelines to installation of several
row cover systems.
The California system for cucumbers employs two
sheets of 36-in wide, 1.5-mil perforated, clear







earlier planting resulting in 2 to 3 weeks earliness
and in some cases increased total yields compared
with unprotected crops. The poly can be vented or
unvented. The unvented covers require manual
opening to control heat build-up on warm, sunny
days. Vented poly covers have pre-installed slits or
circular perforations for automatic venting (Fig. 3).
Heat build-up also can be reduced by the use of
pigmented plastics. White poly covers might be
especially useful in Florida in the spring.


Fig. 3. Pre-installed vents in polyethylene row cover.

The floating row covers are manufactured from
various fabric-like materials such as polyester or
polypropylene and have been used in several ways in
the textile industry and in the South as tobacco
plant-bed covers. Field performance of floating row
covers has been similar in several ways to the
polyethylene covers, but, because of their loose,
lightweight fabric nature, these covers have several
advantages over polyethylene covers (6). They can
be laid directly on the plants (floating row covers)
without the use of supporting hoops usually re-
quired by poly covers (Fig. 4). However, hoops
should be used if covers are used during windy peri-
ods. The materials are porous and thus self-ventilat-
ing. Only minor reductions in light levels (10-20%)
have been reported for these covers and this has not
been enough to affect early crop growth. Overhead
irrigation water can be applied while the cover is in
place.


Fig. 4. Floating row cover applied without support
hoops.
Specifications
Plastic row covers are made from polyethylene ap-
proximately 0.75 to 1.1 mils in thickness and are
available in various widths on rolls of various
length. The floating materials are several mils thick
and are available in various widths and lengths.
Manufacturers offer floating materials of various
weights, with the most popular presently being a
weight of about 0.6 oz per yd'.
Future variations in row covers undoubtedly will
appear as research indicates the need. Possibilities
that will be important for Florida include variable
pigmentation to control heat build-up, various
weights of floating material for use in different
seasons, various chemical protective coatings to
allow multiple season use, and widths great enough
to allow row cover use over the twin row, full bed
mulch cropping system for vegetables such as pep-
pers or for multiple row covers for strawberries. One
of the greatest needs is for a porous cover that is
light in weight to be used for growth enhancement
yet has capability for moderate freeze protection.

Installation
Installation of row covers varies considerably
depending on type of crop and grower preference.
Following are guidelines to installation of several
row cover systems.
The California system for cucumbers employs two
sheets of 36-in wide, 1.5-mil perforated, clear







polyethylene supported by 9-gauge wire hoops
(Fig. 5). The wire (70 in length) is formed in an oval
shape so that an approximate 30-in bed width is
enclosed by the row cover. These hoops are placed 5
to 7 ft apart and deep enough in the soil to make a
cover that is 15 to 16 in tall at the center. Wooden
stakes, 1 by 1 in by about 30 in are driven into the
ground at 10- to 25-ft intervals. Wire (16 gauge) is
stapled to the top of the stakes and the two sheets of
poly are clipped together at the wire with
clothespins. The second edge of each poly sheet is
buried in soil at the base of the hoops.


Fig. 5. California two-sheet row cover closed.

A similar system is used for tomatoes, except
longer stakes are employed. With the two-sheet
system, manual venting is employed by rolling the
plastic back as needed and clipping it to the hoops
(Fig. 6). The covers are manually closed during night
and cool periods.
Because of labor cost involved in venting the two-
sheet system, a search was begun for a single-sheet,
self-ventilating cover. Research in New Hampshire
showed that slitted, 1.1- or 1.5-mil, clear,
polyethylene ground mulch could be used as a row
cover. The original use for slitted ground mulch was
for direct-seeded vegetable production in New
Jersey (11). The commonly used 3-ft wide, clear,
polyethylene ground mulch was widened to 5 ft for
use as a cover (Fig 2).


Fig. 6. California two-sheet row cover open.

The single sheet was slitted using two rows of
slits down the length of the cover. The slits were 5 in
long and 0.75 in apart. Different slit sizes and ar-
rangements have become available in recent years.
In addition to slitted polyethylene, the covers can be
made from perforated polyethylene. Perforations of
suitable number and size are required to allow ade-
quate heat escape.
Although, polyethylene covers can be applied as a
floating row cover, they are more commonly in-
stalled over wire hoop supports. The hoops are made
of 9-gauge wire cut in 63-in lengths and formed in an
oval to cover an approximate 30-in bed width.
Longer hoops will be required for Florida's full bed
mulch system in order to clear the bed and plants.
Hoops are placed at 4- to 5-ft intervals after the crop
has been seeded or transplanted. The cover is ap-
plied over hoops with edges of the cover buried at
the base of the hoops. The height of the row cover
depends on the crop grown and clearance
capabilities of installation equipment.
On small acreages, covers can be applied by hand.
A long rod is placed in the roll of poly; two workers
unroll the cover over the hoops and two additional
laborers shovel soil on the edges as the cover is ap-
plied. The single-sheet system can easily be installed
with a mulch laying machine that has been modified
to support the roll of cover above pre-installed
hoops. Machines are available that will install hoops
mechanically and apply the cover simultaneously.







Floating covers can be applied without hoops
because of their light weight. They can be applied by
hand or with a mulch laying machine with minor
alterations to ensure that the cover is laid loosely
over the row. This usually involves the addition of a
wheel, or shaft, in the center of the machine over
which the cover flows as it is being applied. The
wheel, or shaft, raises the center of the cover
material while the edges are being buried causing
the material to be laid with some slack, instead of
tautly. In general, the cover is not affected by light
wind, and usually no rubbing damage occurs to
established plants, except for possibly the leafy
vegetables. Young seedlings, however, can be
damaged by covers during high winds. Windbreaks
should be used in Florida to minimize abrasion
caused by wind action.

Timing
One of the most critical factors in successful use
of row covers is the timing of application and
removal. Both types of covers may provide frost
protection and this protection is generally greater
with the floating materials and greater in fall when
additional warmth can be obtained from the soil.
Slitted row covers have been reported to give 1 to
2 F protection (10,15) while the floating covers can
provide up to 3*F protection (17). Research in
Florida with strawberries showed that frost protec-
tion with floating row covers might be greater than
3F. Heavy weight floating row covers (1.5 oz per
yd2) protect strawberries exposed to temperatures
below 20F (4). These types of covers are applied
only when temperatures fall below 320F. Frost pro-
tection with polyethylene covers is greatest where
moisture condenses on the inner surface of the cover
during the night (13). Frost damage can occur to
leaves in contact with floating row covers or poly
covers. Frost protection, however, is only one of the
benefits of row covers. The major benefit realized
from row covers is their overall growth enhancing
character when used in cool weather.
Tb achieve maximum benefit from covers, precise
timing in application and removal is critical. Gener-
ally, planting need not be done more than 1 to 2
weeks ahead of the normal time because of the
growth enhancing capability of covers. Particular
attention must be given to cover removal because
some crops, such as tomato and pepper, cannot tol-
erate extremely high temperatures that might de-
velop under covers (especially polyethylene) if left in
place too long. Research in Gainesville showed that
polyethylene tunnels and some floating row covers
reduced tomato and pepper yield if not removed on
time.


Improper timing of application and removal is
probably a large factor in some of the conflicting
reports on yield advantages from row covers. With
the advent of new row cover materials, such as "new
generation" floating types and pigmented plastics,
growers will be better able to tailor row cover
material to the crop, time of season, and specific
prevailing environmental conditions. Research is
greatly needed to better define proper cover removal
time for many vegetable crops. Care must be taken
to ensure that covers (especially the floating fabric)
used on bee-pollinated crops are removed when
blossoming begins.
Costs
Costs incurred through use of row covers will de-
pend on the crop and row spacing used, as well as
the type of cover material. Recent research in Il-
linois on muskmelons compared costs of black
polyethylene ground mulch culture to black
polyethylene plus clear slitted polyethylene row
covers (1). In 1982, the cost for black poly mulch ap-
plication was $230 per acre. The mulch plus slitted
cover system costs slightly over $900 per acre to in-
stall as does black poly mulch plus floating cover.
Although the mulch plus cover system costs more
than mulch alone, the increased earliness achieved
with row covers justifies the use.
Fabric covers might be used for more than one
season, and with protective chemical coatings and
ultraviolet inhibitors, this might be extended. The
material should be fumigated prior to re-use.

Weed and Pest Control
Very little research has been done on pesticide use
with installed row covers. In general, insect and
disease control has not been a problem because the
covers are removed about the time spraying com-
mences. Weed control, however, has been a problem
when the covers are used without black
polyethylene ground mulch. The covers not only
enhance crop development, but also hasten weed
growth. In a muskmelon test, chemicals presently
labeled for weed control failed to restrict weed
growth under plastic covers. Application and
phytotoxicity from volatile chemicals are areas that
should be explored. Presently, the use of black poly
ground mulch in conjunction with row covers is the
best option in terms of crop growth enhancement
and weed control.
Specific Crop Responses
The cucurbit crops (muskmelon, cucumber,
squash, and watermelon) have responded best to
both types of row covers. Tomatoes and peppers







Floating covers can be applied without hoops
because of their light weight. They can be applied by
hand or with a mulch laying machine with minor
alterations to ensure that the cover is laid loosely
over the row. This usually involves the addition of a
wheel, or shaft, in the center of the machine over
which the cover flows as it is being applied. The
wheel, or shaft, raises the center of the cover
material while the edges are being buried causing
the material to be laid with some slack, instead of
tautly. In general, the cover is not affected by light
wind, and usually no rubbing damage occurs to
established plants, except for possibly the leafy
vegetables. Young seedlings, however, can be
damaged by covers during high winds. Windbreaks
should be used in Florida to minimize abrasion
caused by wind action.

Timing
One of the most critical factors in successful use
of row covers is the timing of application and
removal. Both types of covers may provide frost
protection and this protection is generally greater
with the floating materials and greater in fall when
additional warmth can be obtained from the soil.
Slitted row covers have been reported to give 1 to
2 F protection (10,15) while the floating covers can
provide up to 3*F protection (17). Research in
Florida with strawberries showed that frost protec-
tion with floating row covers might be greater than
3F. Heavy weight floating row covers (1.5 oz per
yd2) protect strawberries exposed to temperatures
below 20F (4). These types of covers are applied
only when temperatures fall below 320F. Frost pro-
tection with polyethylene covers is greatest where
moisture condenses on the inner surface of the cover
during the night (13). Frost damage can occur to
leaves in contact with floating row covers or poly
covers. Frost protection, however, is only one of the
benefits of row covers. The major benefit realized
from row covers is their overall growth enhancing
character when used in cool weather.
Tb achieve maximum benefit from covers, precise
timing in application and removal is critical. Gener-
ally, planting need not be done more than 1 to 2
weeks ahead of the normal time because of the
growth enhancing capability of covers. Particular
attention must be given to cover removal because
some crops, such as tomato and pepper, cannot tol-
erate extremely high temperatures that might de-
velop under covers (especially polyethylene) if left in
place too long. Research in Gainesville showed that
polyethylene tunnels and some floating row covers
reduced tomato and pepper yield if not removed on
time.


Improper timing of application and removal is
probably a large factor in some of the conflicting
reports on yield advantages from row covers. With
the advent of new row cover materials, such as "new
generation" floating types and pigmented plastics,
growers will be better able to tailor row cover
material to the crop, time of season, and specific
prevailing environmental conditions. Research is
greatly needed to better define proper cover removal
time for many vegetable crops. Care must be taken
to ensure that covers (especially the floating fabric)
used on bee-pollinated crops are removed when
blossoming begins.
Costs
Costs incurred through use of row covers will de-
pend on the crop and row spacing used, as well as
the type of cover material. Recent research in Il-
linois on muskmelons compared costs of black
polyethylene ground mulch culture to black
polyethylene plus clear slitted polyethylene row
covers (1). In 1982, the cost for black poly mulch ap-
plication was $230 per acre. The mulch plus slitted
cover system costs slightly over $900 per acre to in-
stall as does black poly mulch plus floating cover.
Although the mulch plus cover system costs more
than mulch alone, the increased earliness achieved
with row covers justifies the use.
Fabric covers might be used for more than one
season, and with protective chemical coatings and
ultraviolet inhibitors, this might be extended. The
material should be fumigated prior to re-use.

Weed and Pest Control
Very little research has been done on pesticide use
with installed row covers. In general, insect and
disease control has not been a problem because the
covers are removed about the time spraying com-
mences. Weed control, however, has been a problem
when the covers are used without black
polyethylene ground mulch. The covers not only
enhance crop development, but also hasten weed
growth. In a muskmelon test, chemicals presently
labeled for weed control failed to restrict weed
growth under plastic covers. Application and
phytotoxicity from volatile chemicals are areas that
should be explored. Presently, the use of black poly
ground mulch in conjunction with row covers is the
best option in terms of crop growth enhancement
and weed control.
Specific Crop Responses
The cucurbit crops (muskmelon, cucumber,
squash, and watermelon) have responded best to
both types of row covers. Tomatoes and peppers







Floating covers can be applied without hoops
because of their light weight. They can be applied by
hand or with a mulch laying machine with minor
alterations to ensure that the cover is laid loosely
over the row. This usually involves the addition of a
wheel, or shaft, in the center of the machine over
which the cover flows as it is being applied. The
wheel, or shaft, raises the center of the cover
material while the edges are being buried causing
the material to be laid with some slack, instead of
tautly. In general, the cover is not affected by light
wind, and usually no rubbing damage occurs to
established plants, except for possibly the leafy
vegetables. Young seedlings, however, can be
damaged by covers during high winds. Windbreaks
should be used in Florida to minimize abrasion
caused by wind action.

Timing
One of the most critical factors in successful use
of row covers is the timing of application and
removal. Both types of covers may provide frost
protection and this protection is generally greater
with the floating materials and greater in fall when
additional warmth can be obtained from the soil.
Slitted row covers have been reported to give 1 to
2 F protection (10,15) while the floating covers can
provide up to 3*F protection (17). Research in
Florida with strawberries showed that frost protec-
tion with floating row covers might be greater than
3F. Heavy weight floating row covers (1.5 oz per
yd2) protect strawberries exposed to temperatures
below 20F (4). These types of covers are applied
only when temperatures fall below 320F. Frost pro-
tection with polyethylene covers is greatest where
moisture condenses on the inner surface of the cover
during the night (13). Frost damage can occur to
leaves in contact with floating row covers or poly
covers. Frost protection, however, is only one of the
benefits of row covers. The major benefit realized
from row covers is their overall growth enhancing
character when used in cool weather.
Tb achieve maximum benefit from covers, precise
timing in application and removal is critical. Gener-
ally, planting need not be done more than 1 to 2
weeks ahead of the normal time because of the
growth enhancing capability of covers. Particular
attention must be given to cover removal because
some crops, such as tomato and pepper, cannot tol-
erate extremely high temperatures that might de-
velop under covers (especially polyethylene) if left in
place too long. Research in Gainesville showed that
polyethylene tunnels and some floating row covers
reduced tomato and pepper yield if not removed on
time.


Improper timing of application and removal is
probably a large factor in some of the conflicting
reports on yield advantages from row covers. With
the advent of new row cover materials, such as "new
generation" floating types and pigmented plastics,
growers will be better able to tailor row cover
material to the crop, time of season, and specific
prevailing environmental conditions. Research is
greatly needed to better define proper cover removal
time for many vegetable crops. Care must be taken
to ensure that covers (especially the floating fabric)
used on bee-pollinated crops are removed when
blossoming begins.
Costs
Costs incurred through use of row covers will de-
pend on the crop and row spacing used, as well as
the type of cover material. Recent research in Il-
linois on muskmelons compared costs of black
polyethylene ground mulch culture to black
polyethylene plus clear slitted polyethylene row
covers (1). In 1982, the cost for black poly mulch ap-
plication was $230 per acre. The mulch plus slitted
cover system costs slightly over $900 per acre to in-
stall as does black poly mulch plus floating cover.
Although the mulch plus cover system costs more
than mulch alone, the increased earliness achieved
with row covers justifies the use.
Fabric covers might be used for more than one
season, and with protective chemical coatings and
ultraviolet inhibitors, this might be extended. The
material should be fumigated prior to re-use.

Weed and Pest Control
Very little research has been done on pesticide use
with installed row covers. In general, insect and
disease control has not been a problem because the
covers are removed about the time spraying com-
mences. Weed control, however, has been a problem
when the covers are used without black
polyethylene ground mulch. The covers not only
enhance crop development, but also hasten weed
growth. In a muskmelon test, chemicals presently
labeled for weed control failed to restrict weed
growth under plastic covers. Application and
phytotoxicity from volatile chemicals are areas that
should be explored. Presently, the use of black poly
ground mulch in conjunction with row covers is the
best option in terms of crop growth enhancement
and weed control.
Specific Crop Responses
The cucurbit crops (muskmelon, cucumber,
squash, and watermelon) have responded best to
both types of row covers. Tomatoes and peppers







Floating covers can be applied without hoops
because of their light weight. They can be applied by
hand or with a mulch laying machine with minor
alterations to ensure that the cover is laid loosely
over the row. This usually involves the addition of a
wheel, or shaft, in the center of the machine over
which the cover flows as it is being applied. The
wheel, or shaft, raises the center of the cover
material while the edges are being buried causing
the material to be laid with some slack, instead of
tautly. In general, the cover is not affected by light
wind, and usually no rubbing damage occurs to
established plants, except for possibly the leafy
vegetables. Young seedlings, however, can be
damaged by covers during high winds. Windbreaks
should be used in Florida to minimize abrasion
caused by wind action.

Timing
One of the most critical factors in successful use
of row covers is the timing of application and
removal. Both types of covers may provide frost
protection and this protection is generally greater
with the floating materials and greater in fall when
additional warmth can be obtained from the soil.
Slitted row covers have been reported to give 1 to
2 F protection (10,15) while the floating covers can
provide up to 3*F protection (17). Research in
Florida with strawberries showed that frost protec-
tion with floating row covers might be greater than
3F. Heavy weight floating row covers (1.5 oz per
yd2) protect strawberries exposed to temperatures
below 20F (4). These types of covers are applied
only when temperatures fall below 320F. Frost pro-
tection with polyethylene covers is greatest where
moisture condenses on the inner surface of the cover
during the night (13). Frost damage can occur to
leaves in contact with floating row covers or poly
covers. Frost protection, however, is only one of the
benefits of row covers. The major benefit realized
from row covers is their overall growth enhancing
character when used in cool weather.
Tb achieve maximum benefit from covers, precise
timing in application and removal is critical. Gener-
ally, planting need not be done more than 1 to 2
weeks ahead of the normal time because of the
growth enhancing capability of covers. Particular
attention must be given to cover removal because
some crops, such as tomato and pepper, cannot tol-
erate extremely high temperatures that might de-
velop under covers (especially polyethylene) if left in
place too long. Research in Gainesville showed that
polyethylene tunnels and some floating row covers
reduced tomato and pepper yield if not removed on
time.


Improper timing of application and removal is
probably a large factor in some of the conflicting
reports on yield advantages from row covers. With
the advent of new row cover materials, such as "new
generation" floating types and pigmented plastics,
growers will be better able to tailor row cover
material to the crop, time of season, and specific
prevailing environmental conditions. Research is
greatly needed to better define proper cover removal
time for many vegetable crops. Care must be taken
to ensure that covers (especially the floating fabric)
used on bee-pollinated crops are removed when
blossoming begins.
Costs
Costs incurred through use of row covers will de-
pend on the crop and row spacing used, as well as
the type of cover material. Recent research in Il-
linois on muskmelons compared costs of black
polyethylene ground mulch culture to black
polyethylene plus clear slitted polyethylene row
covers (1). In 1982, the cost for black poly mulch ap-
plication was $230 per acre. The mulch plus slitted
cover system costs slightly over $900 per acre to in-
stall as does black poly mulch plus floating cover.
Although the mulch plus cover system costs more
than mulch alone, the increased earliness achieved
with row covers justifies the use.
Fabric covers might be used for more than one
season, and with protective chemical coatings and
ultraviolet inhibitors, this might be extended. The
material should be fumigated prior to re-use.

Weed and Pest Control
Very little research has been done on pesticide use
with installed row covers. In general, insect and
disease control has not been a problem because the
covers are removed about the time spraying com-
mences. Weed control, however, has been a problem
when the covers are used without black
polyethylene ground mulch. The covers not only
enhance crop development, but also hasten weed
growth. In a muskmelon test, chemicals presently
labeled for weed control failed to restrict weed
growth under plastic covers. Application and
phytotoxicity from volatile chemicals are areas that
should be explored. Presently, the use of black poly
ground mulch in conjunction with row covers is the
best option in terms of crop growth enhancement
and weed control.
Specific Crop Responses
The cucurbit crops (muskmelon, cucumber,
squash, and watermelon) have responded best to
both types of row covers. Tomatoes and peppers








have responded positively but seem to be more sen-
sitive to high temperature in the covers, making
timely ventilation, or cover removal, critical (16).
Other crops that have responded positively to row
covers include lettuce, radishes, and beets. A por-
tion of the positive response of crops such as
radishes and squash to row covers (particularly
floating) has been the protection from insects while
the cover was in place (9,17).
Research on row covers in Gainesville has shown
increased earliness of muskmelons and strawberries
when row covers were installed during cool early
season periods. Total yield was not increased. With
muskmelon, increase in early yield only occurred
where row covers were used in conjunction with
black polyethylene ground mulch (Table 1). The row
covers should be removed when muskmelons begin
flowering. In Florida, the row covers would have
substantial importance in the northern areas to
speed development of warm season crops such as
muskmelon or watermelon. The higher prices for the
earlier crop might justify the use.
Row covers, particularly if mechanized, might be
useful in Florida for light frost protection of
tomatoes, peppers, and strawberries during winter
production periods. Research in Gainesville showed
that row covers can protect strawberries from freez-
ing temperatures (4). Some row covers gave similar
protection to overhead irrigation when air
temperatures in the plant crown area reached 25 F


(Table 2). This research indicates that certain row
covers might be suitable alternatives to overhead ir-
rigation for freeze protection of crops in areas where
water for farming is in short supply.

An Integrated System
Research in several states has shown that row
covers alone produce positive yield responses.
However, their fullest potential has been realized
where they are used as part of an integrated, growth
intensifying program. Research indicates that this
system should include black polyethylene ground
mulch. Likewise, drip irrigation can be used in the
system to ensure that adequate moisture is present
under covers to support the accelerated growth of
plants. Drip irrigation also facilitates application of
fertilizers to plants while covers are in place.
Research shows that drip irrigation operation dur-
ing a freeze event does not enhance freeze protection
over row cover use alone (4).

Future Research
Although row covers are evolving as part of an
overall growth and yield enhancing system, there is
much research needed to refine the components for
Florida. Additional crops need to be studied for
their adaptivity to the row cover system. One area
needing additional study is frost protection of
vegetables. Floating covers laid directly over the


Table 1. Yield response of muskmelons in Gainesville to various cold protection methods.

Yield (cwtlacre)

Early Total
Protection method Nonmulched Mulched mulched
1984

None 1 17 b1 279
Tunnel slittedd poly) 41 130 a 327
Tunnel (polypropylene) 17 111 a 294
Floating (polypropylene) 8 111 a 325
Hot cap 11 20 b 276

1985

Tunnel slittedd poly) 19 167 a 589
Tunnel (perforated poly) 29 192 a 505
Floating (polypropylene) 7 162 a 601
Floating (polyester) 3 155 a 482
Floating (cross-laminated) 7 148 a 552
No cover 1 55 b 453


1Means in column within single year followed by same letter are not significantly different by Duncan's multiple
range test at 5% level.








have responded positively but seem to be more sen-
sitive to high temperature in the covers, making
timely ventilation, or cover removal, critical (16).
Other crops that have responded positively to row
covers include lettuce, radishes, and beets. A por-
tion of the positive response of crops such as
radishes and squash to row covers (particularly
floating) has been the protection from insects while
the cover was in place (9,17).
Research on row covers in Gainesville has shown
increased earliness of muskmelons and strawberries
when row covers were installed during cool early
season periods. Total yield was not increased. With
muskmelon, increase in early yield only occurred
where row covers were used in conjunction with
black polyethylene ground mulch (Table 1). The row
covers should be removed when muskmelons begin
flowering. In Florida, the row covers would have
substantial importance in the northern areas to
speed development of warm season crops such as
muskmelon or watermelon. The higher prices for the
earlier crop might justify the use.
Row covers, particularly if mechanized, might be
useful in Florida for light frost protection of
tomatoes, peppers, and strawberries during winter
production periods. Research in Gainesville showed
that row covers can protect strawberries from freez-
ing temperatures (4). Some row covers gave similar
protection to overhead irrigation when air
temperatures in the plant crown area reached 25 F


(Table 2). This research indicates that certain row
covers might be suitable alternatives to overhead ir-
rigation for freeze protection of crops in areas where
water for farming is in short supply.

An Integrated System
Research in several states has shown that row
covers alone produce positive yield responses.
However, their fullest potential has been realized
where they are used as part of an integrated, growth
intensifying program. Research indicates that this
system should include black polyethylene ground
mulch. Likewise, drip irrigation can be used in the
system to ensure that adequate moisture is present
under covers to support the accelerated growth of
plants. Drip irrigation also facilitates application of
fertilizers to plants while covers are in place.
Research shows that drip irrigation operation dur-
ing a freeze event does not enhance freeze protection
over row cover use alone (4).

Future Research
Although row covers are evolving as part of an
overall growth and yield enhancing system, there is
much research needed to refine the components for
Florida. Additional crops need to be studied for
their adaptivity to the row cover system. One area
needing additional study is frost protection of
vegetables. Floating covers laid directly over the


Table 1. Yield response of muskmelons in Gainesville to various cold protection methods.

Yield (cwtlacre)

Early Total
Protection method Nonmulched Mulched mulched
1984

None 1 17 b1 279
Tunnel slittedd poly) 41 130 a 327
Tunnel (polypropylene) 17 111 a 294
Floating (polypropylene) 8 111 a 325
Hot cap 11 20 b 276

1985

Tunnel slittedd poly) 19 167 a 589
Tunnel (perforated poly) 29 192 a 505
Floating (polypropylene) 7 162 a 601
Floating (polyester) 3 155 a 482
Floating (cross-laminated) 7 148 a 552
No cover 1 55 b 453


1Means in column within single year followed by same letter are not significantly different by Duncan's multiple
range test at 5% level.








Table 2. Effect of row covers for freeze protection of strawberries.


Freeze damaged Early
flowers and fruit' yield2
Cold protection method (% of total) (flats per acre)

Floating
Polyester 16 18
Polypropylene (0.6 oz/yd) 14 46
Polypropylene (1.5 oz/yd) 12 26
Polypropylene (2.0 oz/yd) 10 42
Extruded fabric 40 9
Polyethylene foam 6 67
Polyethylene tunnel 23 21
Check (no cover) 92 .2
Check (overhead irrigation) 6 53


'Additive damage of first four freeze events of winter of 1985; lowest temperature was 25 F.
2Cumulative yield of first 10 harvests.


plants might be a suitable alternative to large
amounts of overhead irrigation presently used for
frost protection. New row cover materials and varia-
tions of existing ones, which will require field study,
are being developed. Management practices such as
time of application and time of removal have not
been addressed adequately in research to date.
Wide-width row covers need to be evaluated because
they offer increased management efficiency over
single-row covers. Research on weed control and fer-
tility requirements under row covers has only
begun. Many southern vegetable producing states,
such as Florida, are just beginning to evaluate row
cover use. These areas offer great potential for ex-
panding their use.
Row cover production is one of the fastest growth
areas in the agricultural plastics industry. Row
covers hold much potential for increasing vegetable
production and net farm income by permitting
growers to meet specific marketing strategies not
possible without their use. Research in Florida is
not yet complete, but growers interested in row
cover use are encouraged to evaluate them on a trial
basis. Contact the Vegetable Crops Extension Ser-
vice of the Institute of Food and Agricultural
Sciences for advice.



Literature Cited
1. Gerber, J.M., J.E. Brown, and W.E. Splitt-
stoesser. 1983. Economic evaluation of plastic
mulch and row tunnels for use in muskmelon pro-
duction. Proc. Natl. Agric. Plastics Conf. 17:46-50.


2. Gerber, J.M. 1984. Plastic row tunnels for
muskmelon production in Illinois. Ill. Vegetable
Growers Schools Hort. Ser. 50:126-128.
3. Hall, B.J. 1972. Agricultural plastics in Califor-
nia. HortScience 7:373-378.
4. Hochmuth, G.J., S.R. Kostewicz, and S.J.
Locasio. 1986. Row covers for frost protection of
strawberries. Proc. Natl. Agric. Plastics Conf.
19:175-184.
5. Kohm, P.C., and H.C. Wien. 1983. New tunnel
materials for early vegetable production in New
York State. Proc. Natl. Agric. Plastics Conf.
17:31-36.
6. Loy, J.B., and O.S. Wells. 1983. Use of spun-
bonded polyester as a plant row cover over
vegetables. Proc. Natl. Agric. Plastics Conf.
17:54-62.

7. Loy, J.B., and O.S. Wells. 1982. A comparison
of slitted polyethylene and spunbonded polyester
for plant row covers. HortScience 17:405-407.

8. Mansour, N.S. 1984. Floating row covers give
plants TLC. Am. Veg. Grower, Dec:8-10.

9. Natwick, E.T., and A. Durazo, III. 1985.
Polyester covers protect vegetables from white flies
and virus disease. Calif. Agric. July-Aug:21-22.

10. Shadbolt, C.A., O.D. McCoy, and F.C.
Whiting. 1962. The microclimate of plastic shelters
used for vegetable production. Hilgardia
32:251-266.








11. Smith, N.J. 1973. Slit mulch. Am. Veg.
Grower 21:13-14.
12. Taber, H.G. 1983. Effect of plastic soil and
plant covers on Iowa tomato and muskmelon pro-
duction. Proc. Natl. Agric. Plastics Conf. 17:37-45.
13. Waggoner, P.E. 1958. Protecting plants from
the cold. The principles and benefits of plastic
shelters. Conn. Agric. Exp. Sta. Bul. 614.
14. Ware, G.W. 1936. Plant protectors and other
factors influencing earliness and production of can-
taloupes. Arkansas Agric. Exp. Sta. Bull. No. 324.


15. Wells, O.S., J.B. Loy, and T.A. Natti. 1977.
Slit mulch film used as row covers. Proc. Natl.
Agric. Plastics Conf. 13:448-452.
16. Wells, O.S. and J.B. Loy. 1981. Slitted plastic
row covers for vegetable production. Proc. Natl.
Agric. Plastics Conf. 16:124-128.
17. Wells, O.S. and J.B. Loy. 1985. Intensive
vegetable production with row covers. HortScience
20:822-826.
18. Wells, O.S., and J.B. Loy. 1986. The current
status of row cover use in the United States. Proc.
Natl. Agric. Plastics Conf. 19:4-9.


Multiple row polypropylene cover for
freeze protection of strawberries.






















































































COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES. Jo-- Woes:e
Director, in cooperation with the United States Department of Agriculture, publishes this information to further the ~rose o' me May 8 ac JL-e
30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to indivwajas ana r'stc:.os -'a:
function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publicatons (excud g 4-H a.-c yo,
publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies fo' oju-o-s:a:e "'ase-s s
available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesvlie, Fornca 326 '. Bero'e .,cz -,
this publication, editors should contact this address to determine availability. Repnnted 1993.




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