Extension Circular 1812. This circular is about maintaining alfalfa stands. It explains the infection, and symptoms of bacterial wilt

Weihing, John L.

English

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University of Nebraska - Lincoln
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Historical Materials from University of Nebraska-
Lincoln Extension Extension
1950
EC1812 Alfalfa Wilt and the Maintenance of
Alfalfa Stands
John L. Weihing
Follow this and additional works at: http://digitalcommons.unl.edu/extensionhist
This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for
inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University of
Nebraska - Lincoln.
Weihing, John L., "EC1812 Alfalfa Wilt and the Maintenance of Alfalfa Stands" (1950). Historical Materials from University of Nebraska-
Lincoln Extension. 2740.
http://digitalcommons.unl.edu/extensionhist/2740
MAINTENANCE OF 
A clear example of a wilt-susceptible next to a wil 
E.C.l812 
StP > 1950 
occ ~_.,.. "- N l s 
RCOM 
CODPEIATIVE EIITEDSIOII IUOIII In AfOIIICIIlTUIIE ~AD;;;D-;miiii£ruiitlllllm:----_j 
UniUEIISITV OF DEIIIASIIA COLLEIOE OF AfORICIII.TURE, ADD THE UDITED 
STATES DEPAITIIIEDT OF AfORICULTUIIE COOPERATIRt; , W. U. LAmBERT. 
o.ctll. liiKIIUI . 
ALFALFA WIL':2:/ AND THE MAINTENANCE OF ALFALFA STANDS 
By John L. Weihi~/ 
INTRODUCTION 
According to widespread reports alfalfa stands 
throughout the state were severely damaged during the 
past winter. Many relatively young meadows showed such 
extreme losses of plants that the fields have been or 
soon will be plowed up. While there are several factors 
which may have contributed to these winter losses, pre-
liminary surveys indicate that the primary cause is 
bacterial wilt, a serious disease of alfalfa. A recent 
inspection of alfalfa in the Platte Valley showed most 
pl_ants in 3-year old stands to be severely affected by 
this disease, whereas many 4-year old plantings had de-
teriorated to a point that they will not give profit a-
ble returns. Other f actors which may have hastened de-
terioration of the diseased plants are cutting 
practices and the growing of non-winter-hardy vari e -
ties. 
Bacterial wilt is not new to Nebraska. The diseas e 
has been a problem along the Platte, Republican and 
Missouri Rivers, and on upland irrigated soils for more 
than 20 years. 
SOURCE OF THE WILT ORGANISM 
The wilt organism is not seed borne. It is soil 
borne and should be considered as always present in 
Nebraska soils. Therefore, control measures for this 
disease should never be relaxed. 
Intensification of the disease in a field is im-
mensely aided by irrigation which not only distributes 
1 Coryuebactaium iusidiosum . 
' Extension Plant Pa thologist. 
-2-
the wilt organism over the field but also creates an 
excellent environment for its activity. 
INFECTION AND SYMPTOMS OF BACTERIAL WILT 
Infection occurs during spring and early sLUIIII1er. 
Entrance of the organism is gained through wounds re-
sulting from winter injury and mechanical damage, and 
also from diseased stems to healthy stems by the sickle 
bar during cutting. 
Usually the first symptom to be noticed is a 
dwarfing and yellowing of the entire plant. The stems 
are short, the leaves are small and pale, and the 
growth is slow. 
When the roots of these dwarfed plants are cut a-
cr oss, a. yellow to brownish colored ring is found just 
under the bark. In the early stages of the disease in 
t~e r oot, the yellow color may be in narrow streaks 
which soon merge into a continuous yellowish to 
br ownish ring. 
Death is not sudden, but usually takes place 
during l at e sLUIIII1er of the second year after infection. 
MAINTENANCE OF ALFALFA STANDS 
Satisfactory maintenance of alfalfa stands over 
l ong periods involves the use of winter-hardy, wilt-re-
sistant varieties and proper cutting practice. 
Variety 
The varieties Ranger and Hardistan are both 
winter-hardy and resistant to bacterial wilt, whereas 
Cossack and Ladack are winter-hardy but wilt-suscepti-
ble . The latter two varieties show some tolerance to 
bacterial wilt, hence they ma.y withstand the disease a 
year or two longer than the extremely susceptible va -
rieties Grimm, Nebraska Common, and Dakota 12. Varie-
tie s that are both winter- and wilt-susceptible and 
-3-
which should never be grown in Nebraska are the Argen-
tine, Chilean and Southwestern Common sorts. 
Seed Source 
Alfalfa seed sown in Nebraska should have been 
produced in a region that has winter conditions compa-
rable to, or more severe than, those of Nebraska. This 
will give maximum assurance that it is of a variety 
which possesses sufficient winter-resistance to with-
stand the rigorous conditions of Nebraska. 
Cutting Practices 
Cutting practices should be so designed as to af-
ford both high yield of good quality hay and sufficient 
replenishment of food reserves in the roots to maintain 
plant vigor. Repeated experiments have shown that these 
can be accomplished by delaying cuttings until the 
plant reaches the 1/10 to 1/2 bloom stage. Little is 
gained by permitting the plant to go beyond 1/2 bloom. 
Immediately following cutting, the food reserves 
decline until the plant reaches a height of 8 to 10 
inches. This low point of food reserves should be con-
sidered at all times but especially during the fall. To 
cut plants in this stage, late in the summer, results 
in insufficient stored food for the plant to survive 
the winter in a vigorous condition. 
Cultural Operations 
Any operation that causes wounds to the crowns and 
roots opens an avenue for invasion by the wilt organ-
ism. Nothing is gained by spring-toothing or inter-
tilling broadcast stands of alfalfa. 


EC1812  Alfalfa Wilt and the Maintenance of Alfalfa Stands

DigitalCommons@University of Nebraska

University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnHistorical Materials from University of Nebraska-Lincoln Extension Extension1950EC1812 Alfalfa Wilt and the Maintenance ofAlfalfa StandsJohn L. WeihingFollow this and additional works at: http://digitalcommons.unl.edu/extensionhistThis Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted forinclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University ofNebraska - Lincoln.Weihing, John L., "EC1812 Alfalfa Wilt and the Maintenance of Alfalfa Stands" (1950). Historical Materials from University of Nebraska-Lincoln Extension. 2740.http://digitalcommons.unl.edu/extensionhist/2740MAINTENANCE OF A clear example of a wilt-susceptible next to a wil E.C.l812 StP > 1950 occ ~_.,.. "- N l s RCOM CODPEIATIVE EIITEDSIOII IUOIII In AfOIIICIIlTUIIE ~AD;;;D-;miiii£ruiitlllllm:----_j UniUEIISITV OF DEIIIASIIA COLLEIOE OF AfORICIII.TURE, ADD THE UDITED STATES DEPAITIIIEDT OF AfORICULTUIIE COOPERATIRt; , W. U. LAmBERT. o.ctll. liiKIIUI . ALFALFA WIL':2:/ AND THE MAINTENANCE OF ALFALFA STANDS By John L. Weihi~/ INTRODUCTION According to widespread reports alfalfa stands throughout the state were severely damaged during the past winter. Many relatively young meadows showed such extreme losses of plants that the fields have been or soon will be plowed up. While there are several factors which may have contributed to these winter losses, pre-liminary surveys indicate that the primary cause is bacterial wilt, a serious disease of alfalfa. A recent inspection of alfalfa in the Platte Valley showed most pl_ants in 3-year old stands to be severely affected by this disease, whereas many 4-year old plantings had de-teriorated to a point that they will not give profit a-ble returns. Other f actors which may have hastened de-terioration of the diseased plants are cutting practices and the growing of non-winter-hardy vari e -ties. Bacterial wilt is not new to Nebraska. The diseas e has been a problem along the Platte, Republican and Missouri Rivers, and on upland irrigated soils for more than 20 years. SOURCE OF THE WILT ORGANISM The wilt organism is not seed borne. It is soil borne and should be considered as always present in Nebraska soils. Therefore, control measures for this disease should never be relaxed. Intensification of the disease in a field is im-mensely aided by irrigation which not only distributes 1 Coryuebactaium iusidiosum . ' Extension Plant Pa thologist. -2-the wilt organism over the field but also creates an excellent environment for its activity. INFECTION AND SYMPTOMS OF BACTERIAL WILT Infection occurs during spring and early sLUIIII1er. Entrance of the organism is gained through wounds re-sulting from winter injury and mechanical damage, and also from diseased stems to healthy stems by the sickle bar during cutting. Usually the first symptom to be noticed is a dwarfing and yellowing of the entire plant. The stems are short, the leaves are small and pale, and the growth is slow. When the roots of these dwarfed plants are cut a-cr oss, a. yellow to brownish colored ring is found just under the bark. In the early stages of the disease in t~e r oot, the yellow color may be in narrow streaks which soon merge into a continuous yellowish to br ownish ring. Death is not sudden, but usually takes place during l at e sLUIIII1er of the second year after infection. MAINTENANCE OF ALFALFA STANDS Satisfactory maintenance of alfalfa stands over l ong periods involves the use of winter-hardy, wilt-re-sistant varieties and proper cutting practice. Variety The varieties Ranger and Hardistan are both winter-hardy and resistant to bacterial wilt, whereas Cossack and Ladack are winter-hardy but wilt-suscepti-ble . The latter two varieties show some tolerance to bacterial wilt, hence they ma.y withstand the disease a year or two longer than the extremely susceptible va -rieties Grimm, Nebraska Common, and Dakota 12. Varie-tie s that are both winter- and wilt-susceptible and -3-which should never be grown in Nebraska are the Argen-tine, Chilean and Southwestern Common sorts. Seed Source Alfalfa seed sown in Nebraska should have been produced in a region that has winter conditions compa-rable to, or more severe than, those of Nebraska. This will give maximum assurance that it is of a variety which possesses sufficient winter-resistance to with-stand the rigorous conditions of Nebraska. Cutting Practices Cutting practices should be so designed as to af-ford both high yield of good quality hay and sufficient replenishment of food reserves in the roots to maintain plant vigor. Repeated experiments have shown that these can be accomplished by delaying cuttings until the plant reaches the 1/10 to 1/2 bloom stage. Little is gained by permitting the plant to go beyond 1/2 bloom. Immediately following cutting, the food reserves decline until the plant reaches a height of 8 to 10 inches. This low point of food reserves should be con-sidered at all times but especially during the fall. To cut plants in this stage, late in the summer, results in insufficient stored food for the plant to survive the winter in a vigorous condition. Cultural Operations Any operation that causes wounds to the crowns and roots opens an avenue for invasion by the wilt organ-ism. Nothing is gained by spring-toothing or inter-tilling broadcast stands of alfalfa. 

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EC1812 Alfalfa Wilt and the Maintenance of Alfalfa Stands

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