Southeastern U.S. Vegetable Crop Handbook - 2023 - 56

PLANTING AND LAND PREPARATION
Beds that are slightly raised are advantageous because they allow
for good drainage. Beds should be firmed and not freshly
tilled before planting and soil should be firmed over the seed at
planting. A basket or roller attachment is often used to firm the
soil over the seed as they are planted. Light irrigation will be
required frequently during warm, dry periods for adequate germination.
Windbreaks
are almost essential in areas with primarily
sandy soils. Sand particles moved by wind can severely damage
young carrot plants, reducing stands. Small grain strips planted
between beds or at least planted between every few beds can
help reduce this sandblasting injury.
Begin by deep turning soils to bury any litter and debris and
breaking soils to a depth of 12-14 inches. Compacted soils or
those with tillage pans should be subsoiled to break the compacted
areas. If uncorrected, compact soil or tillage pans can result
in restriction of root expansion. It is best to apply lime after deep
turning to prevent turning up acid soil after lime application.
Prepare a good seedbed using bed-shaping equipment. Do not
use disks or rototiller to avoid soil compaction. Carrots should
be planted on a slightly raised bed (2-3 inches) to improve drainage.
After beds are tilled and prepared for seeding, it is best to
allow the beds to settle slightly before planting. Avoid other
tillage practices that can increase soil compaction. Following in
the same tracks for all field operations will help reduce compaction
in planting areas.
SPECIAL NOTES FOR PEST MANAGEMENT
DISEASE MANAGEMENT
Root-Knot Nematode: By far, the most destructive problem in
carrots is root-knot nematodes. Root-knot nematodes are small
eel-like worms that live in the soil and feed on plant roots. Since
the root of the carrot is the harvested portion of the plant, no
root-knot damage can be allowed. Root-knot causes poor growth
and distorted or deformed root systems which results in a non
marketable root. Root-knot damage also allows entry for other
diseases such as Fusarium, Pythium, and Erwinia.
If any root-knot nematodes are found in a soil assay, treatment
is recommended. Good success has been obtained using
field soil fumigation to eradicate root-knot nematodes in the
root zone of carrots. Use nematicides or fumigants listed in the
" Nematode Control in Vegetate Crops " tables in the Disease
Control section.
SOIL-BORNE ROOT DISEASES
Depending on the cropping history of the field, Pythium, Southern
Blight, and Sclerotinia may cause problems. It is advisable
to avoid fields where these diseases have been identified in the
previous crop. Deep turning is also necessary to help prevent
root diseases.
Pythium Blight: is usually characterized by flagging of the foliage
indicating some root damage is occurring. Under wet conditions,
Pythium may cause serious problems to the root causing a
white mycelium mat to grow on the infected area which rapidly
56
turns to a watery soft rot. Forking of the root system is also a
common symptom associated with Pythium infection. Rotation
is considered a major factor in reducing Pythium along with the
use of fungicides.
Southern Blight: Southern blight causes serious damage to carrots.
This disease is usually associated with carrots remaining
in the field after the soil begins to warm in the spring. This disease
causes a yellow top to develop with a cottony white fungal
growth associated with the upper part of the carrot root. The top
of the root and the surrounding soil may be covered with a white
mycelium with tan sclerotia developing as the disease progresses.
Southern Blight is best controlled by using rotation and deep
turning.
Sclerotinia Blight: Sclerotinia blight causes serious damage to
the roots of carrots. This disease is usually worse under wet soil
conditions. White mycelium forms around the infected area and
later, dark sclerotia develop on the white mycelium which is a
good indicator of Sclerotinia rot. This disease causes a progressive
watery soft rot of the carrot root tissue and is considered a
potential problem in the production of carrots. Rotation and deep
turning of the soil are recommended to reduce losses to this disease.
Rhizoctonia:
Rhizoctonia rot causes brown to black lesions
to develop on the sides of the carrot root. The disease is much
worse under cool, wet conditions. Saturated soil conditions often
enhance all soil-borne diseases which are potential problems
in carrot production. Rhizoctonia damage can be minimized by
using rotation and good cultural practices. Soil fumigation will
prevent damage with any of the soil inhabiting fungi.
FOLIAR DISEASES
Bacterial Blight: Bacterial blight causes irregular brown spots
on the leaves and dark brown streaks on the petioles and stems.
The lesions on the foliage begin as small yellow areas with the
centers becoming dry and brittle, with an irregular halo. The
bacterium affects the leaflets, stems and petioles as the disease
progresses. Some of these lesions may crack open and ooze the
bacteria. These bacteria may be washed down to the crown of
the plant causing brown lesions on the top of the root. The earlier
the infection occurs the greater the damage to the root. The
bacterium is spread by splashing water and takes about 10-12
days before symptoms appear after inoculation. Disease development
progresses rapidly between 77˚ and 86˚ F. Crop rotation
is a major factor in controlling Bacterial blight.
Alternaria Blight: Alternaria blight causes small dark brown to
black spots with yellow edges forming mostly on the leaf margins.
The spot increases as the disease progresses and in some
cases entire leaflets may be killed. In moist weather, the disease
can move so rapidly it resembles frost injury. Such conditions
can reduce the efficiency of mechanical harvesters which require
strong healthy tops to remove the carrot from the soil. Alternaria
may also cause damping off of seedlings and a black decay of
roots. The spores and mycelium are spread by splashing rains,
2023 Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2023

Table of Contents for the Digital Edition of Southeastern U.S. Vegetable Crop Handbook - 2023
