Citation
Soybean cyst nematode in Florida

Material Information

Title:
Soybean cyst nematode in Florida
Series Title:
Florida Cooperative Extension Service Circular 324
Creator:
Mullin, Robert Spencer
Whitty, Elmo B.
Affiliation:
University of Florida -- Florida Cooperative Extension Service -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Agricultural Extension Service, Institute of Food and Agricultural Sciences, University of Florida,
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Agriculture ( LCSH )
Farm life ( LCSH )
Farming ( LCSH )
University of Florida. ( LCSH )
Agriculture -- Florida ( LCSH )
Farm life -- Florida ( LCSH )
Roundworms ( jstor )
Cysts ( jstor )
Crops ( jstor )
Spatial Coverage:
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

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:
61109100 ( OCLC )

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Full Text
CIRCULAR 324
JANUARY 1968


R. S. MULLIN AND E. B. WHITTY





FLORIDA AGRICULTURAL EXTENSION SERVICE
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA, GAINESVILLE




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Sympt~oms ';l

.ut.it in satupted and yeflowt p~nat~ts iniol~.d
area. of a field:. Fi'~ewer breans are produced mm
these diseoase4f plantsthman o nearby heatftby
o nes. If nest Id areas increase in size as the ae~asnia
prrgeursestnd U ibl i moved-L;-~rd byr. fans'l~~di
monti; an uia:~oft watuser. ~If soybea~nsare '-grow
cwitinuouay, infested areas wa. ap~reslad to in-
eludxe entire f~ield andJ farina.






Roots of diseased plants are usually short and
dark in color. There are few, if any, nitrogen-fix-
ing nodules. Close examination with a magni-
fying glass reveals, to the trained eye, lemon-
shaped bodies attached to the roots. These bodies,
which may be white to dark brown in color, are
female nematodes at various stages of develop-
ment.
When feeding, the nematodes inject chemicals
into the root which digest the cell contents. Most
plant injury by the cyst nematode is caused by
these chemicals which spread beyond the cells
being fed upon.

Life Cycle
Each female nematode may produce several
hundred eggs. Most of these remain inside her
body. When the female dies, the body becomes a
leather-like sack filled with eggs. These dead,
egg-filled bodies are called "cysts," thus the com-
mon name for the pest. Live females have a
pearly-white color; but after death, their color
changes to yellow to gold to brown to almost
black. Some eggs may hatch immediately, but
most will remain in the cyst and hatch at various
periods over the next several years. However, in
Florida a high percentage of the eggs will hatch
within one year. The cyst wall plus the egg shell
protect the unhatched nematodes from unfavor-
able conditions, such as drying and fumigants.
Nematode larvae, which have an eelworm
shape, must find a suitable host plant within a
few weeks after hatching. They locate and enter
host roots and begin to feed. As they feed and
become larger, females lose their eelworm shape
and are unable to move to new locations. The
body becomes lemon-shaped and partly breaks
outside of the developing root, so that only the
head and part of the neck are still inside the
root. Males mate with the females at this time.

Dissemination
Soybean cyst nematodes can move only a few
inches through the soil each year by their own
power. For new fields to become infested, cysts
must be transported by some mechanical means.
Cysts may be spread from an infested area in
soil that clings to tractors, plows and other
equipment. Animals and birds may move soil
granules that contain the cysts. Harvesting such






Roots of diseased plants are usually short and
dark in color. There are few, if any, nitrogen-fix-
ing nodules. Close examination with a magni-
fying glass reveals, to the trained eye, lemon-
shaped bodies attached to the roots. These bodies,
which may be white to dark brown in color, are
female nematodes at various stages of develop-
ment.
When feeding, the nematodes inject chemicals
into the root which digest the cell contents. Most
plant injury by the cyst nematode is caused by
these chemicals which spread beyond the cells
being fed upon.

Life Cycle
Each female nematode may produce several
hundred eggs. Most of these remain inside her
body. When the female dies, the body becomes a
leather-like sack filled with eggs. These dead,
egg-filled bodies are called "cysts," thus the com-
mon name for the pest. Live females have a
pearly-white color; but after death, their color
changes to yellow to gold to brown to almost
black. Some eggs may hatch immediately, but
most will remain in the cyst and hatch at various
periods over the next several years. However, in
Florida a high percentage of the eggs will hatch
within one year. The cyst wall plus the egg shell
protect the unhatched nematodes from unfavor-
able conditions, such as drying and fumigants.
Nematode larvae, which have an eelworm
shape, must find a suitable host plant within a
few weeks after hatching. They locate and enter
host roots and begin to feed. As they feed and
become larger, females lose their eelworm shape
and are unable to move to new locations. The
body becomes lemon-shaped and partly breaks
outside of the developing root, so that only the
head and part of the neck are still inside the
root. Males mate with the females at this time.

Dissemination
Soybean cyst nematodes can move only a few
inches through the soil each year by their own
power. For new fields to become infested, cysts
must be transported by some mechanical means.
Cysts may be spread from an infested area in
soil that clings to tractors, plows and other
equipment. Animals and birds may move soil
granules that contain the cysts. Harvesting such





::crops as peanuts, potatoes or gladiolus corms from
:infested fields can result in the spread of the
t'iiematode. Wind and water erosion can move the
".cysts over considerable distances. Granules of
soil are often picked up during harvest of soy-
'?eans from infested fields. Granules about the
same size as seeds may not be removed by the
cleaning process. Thus the nematodes may be
s ead to new fields when the contaminated seed
are planted. This may be the method by which
nematodes were introduced to Florida.

Hosts
SThe soybean cyst nematode will reproduce on
iany plants other than soybeans. Crop plants
4.at support the nematode include hairy vetch,
Itte lespedezas, snap beans and lupine. Weed
a~asts include beard-tongue, chick-weed, common
.mullen, sesbania and low hop clover. Undoubted-
..ly, there are other host plants in Florida that have
rot been determined.

Control
Three general methods-sanitation, crop rota-
tion, and resistant varieties-can be used to keep
losses on infested fields at a minimum and to pre-
vent spread of the nematode.
Sanitation will prevent movement of cysts from
one field to another in granules of soil that cling
to shoes, machinery, animals or harvested por-
tions of crops. Shoes, machinery and equipment
should be thoroughly cleaned before moving from
infested fields. Soil should be removed from crops
such as peanuts, potatoes or gladiolus corns. Care
should be exercised when animals grazing on in-
fested fields are moved to new pastures.
To prevent the spread of the pest through con-
taminated seed, soybean growers should obtain
their seed from a source known to be free of the
nematode. Much of the seed planted in Florida is
produced in states that are infested with the cyst
nematode. Farmers can be sure of nematode-free
seed if they produce their own seed or purchase
them from nematode-free areas of Florida.
Rotations will help p r e v e n t the nematode
population from becoming high enough to cause
damage. Non-susceptible crops should be included
in rotations, even if the cyst nematode is not
known to be present on the farm. If weed hosts
are not controlled, the rotation will be of limited





::crops as peanuts, potatoes or gladiolus corms from
:infested fields can result in the spread of the
t'iiematode. Wind and water erosion can move the
".cysts over considerable distances. Granules of
soil are often picked up during harvest of soy-
'?eans from infested fields. Granules about the
same size as seeds may not be removed by the
cleaning process. Thus the nematodes may be
s ead to new fields when the contaminated seed
are planted. This may be the method by which
nematodes were introduced to Florida.

Hosts
SThe soybean cyst nematode will reproduce on
iany plants other than soybeans. Crop plants
4.at support the nematode include hairy vetch,
Itte lespedezas, snap beans and lupine. Weed
a~asts include beard-tongue, chick-weed, common
.mullen, sesbania and low hop clover. Undoubted-
..ly, there are other host plants in Florida that have
rot been determined.

Control
Three general methods-sanitation, crop rota-
tion, and resistant varieties-can be used to keep
losses on infested fields at a minimum and to pre-
vent spread of the nematode.
Sanitation will prevent movement of cysts from
one field to another in granules of soil that cling
to shoes, machinery, animals or harvested por-
tions of crops. Shoes, machinery and equipment
should be thoroughly cleaned before moving from
infested fields. Soil should be removed from crops
such as peanuts, potatoes or gladiolus corns. Care
should be exercised when animals grazing on in-
fested fields are moved to new pastures.
To prevent the spread of the pest through con-
taminated seed, soybean growers should obtain
their seed from a source known to be free of the
nematode. Much of the seed planted in Florida is
produced in states that are infested with the cyst
nematode. Farmers can be sure of nematode-free
seed if they produce their own seed or purchase
them from nematode-free areas of Florida.
Rotations will help p r e v e n t the nematode
population from becoming high enough to cause
damage. Non-susceptible crops should be included
in rotations, even if the cyst nematode is not
known to be present on the farm. If weed hosts
are not controlled, the rotation will be of limited





value. The length of an effective rotation has not
been determined for Florida, but in other states
a 2- to 3-year rotation with non-host crops on in-
fested fields has been satisfactory for producing
good yields.
If an infested field must be planted to soybeans,
then a resistant variety is recommended. At pre-
sent, Pickett is the only resistant variety known
to be suitable for planting in Florida. The Pickett
variety will yield satisfactorily on infested fields,
but it will not yield as well on non-infested sol
as the better-adapted and recommended varieties
for Florida.
Reasonably good control can be obtained with
the use of chemical nematicides. However, cost
of materials and application may prohibit their
use for soybeans.


This guide was prepared by R. S. Mullin, Plant Patholo-
gist, and E. B. Whitty, Assistant Agronomist.





























































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