Bissonnette, Howard L.

University of Minnesota Digital Conservancy

MINNESOTA EXTENSION SERVICE 
UNIVERSITY OF MINNESOTA 
AG-FS-1160 
Plant Pathology 
Howard L. Bissonnette 
Revised 1983 
Verticillium Wilt of Potatoes 
Verticillium wilt of potatoes, sometimes called 
11 early maturi ty 11 or 11 wi 1t, 11 is appearing more often 
in the Red River Valley. The disease was reported 
from an isolated field in the area in 1957. During 
the 1963 growing season, Verticillium albo-atrum, 
the causal agent, was isolated from specimens sent 
to the University of Minnesota pl_ant disease di ag-
nostic laboratory from 25 fields in the Red River 
Valley. 
Verticillium wilt is a major potato disease in 
the Pacific Northwest and the Northeast Atlantic 
states. This disease is now spread throughout all 
areas of our potato growing area. It is a poten-
tially serious disease and causes extensive crop 
losses. Growers of Kennebec and Irish Cobbler 
varieties should be especially concerned ahout wilt 
because affected tubers are poor chippers. 
Potato growers should learn the disease symp-
toms and control the disease while only a small per-
centage of the crop is involved. 
Symptoms 
Lower leaves begin to yellow and wilt in 
mid-August. These symptoms progress upward on the 
plant . Defoliation may be so severe that the stem 
retains only the wilted upper apical whorl of 
leaves. 
External stem streaking has been associated 
with Verticillium wilt in varieties such as Irish 
Cobbler and Sebago. It usually appears with exten-
sive fungus infection under conditions of high soil 
moisture and fertility. Inside of the stem the 
disease may cause the xylem (vascular ring) to turn 
reddish brown and may kill the vines prematurely. 
If the fungus reaches the tubers, the first quarter 
inch of the vascular ring at the stem-end usually 
turns brown (Figure 1). All tubers do not show 
vascular discoloration. However, stem-end browning 
may also be caused by freezing, chemical spray 
injury, or viruses. 
Some varieties may turn pink around the eyes or 
show pinkish brown blotches (Figure 2) on other 
parts of the tuber . The fungus usually does not 
cause a tuber rot. 
Late in the season (mid-September) mature vines 
may show some light brown discoloration of the 
xylem . This is a physiologic condition that is not 
the result of a fungus pathogen. 
If you suspect Verticillium wilt, call your 
county extension agent, area potato agent, the Plant 
Pathology Department of North Dakota State 
University, Fargo, North Dakota, or the University 
of Minnesota, St. Paul. 
Figure 1. Vascula discoloration in tuber infected by the Verticillium 
spp. fungus. 
Disease Cycle 
The importance of tuber transmission is 
generally known and accepted. The seed piece may 
carry the fungus on the surface or in the vascular 
tissue. The wilt fungus grows from diseased seed 
pieces into a new plant or through the stolons into 
the young tubers. 
The fungus may overwinter in the field in 
infected plant parts, for example in stems as 
pseudosclerotia. The fungus may also colonize other 
organic non-potato crop residue in the soil. 
Therefore, infected plant dehris is an important 
source for carryover of the fungus. 
The pathogen riay remain in the soil for as long 
as 3 to 7 years without a host crop or longer if 
weed hosts are present. At least 140 species of 
plants are susceptible to the fungus including such 
weeds as nightshade, lambsquarters, pigweed, and 
horse nettle. 
The occurrence and severity of Verticillium 
wilt is related closely to temperatures during the 
early part of the growing season. When June tef'll-
peratures are medium to high, wilt may be expected 
earlier with greater severity. Wilt may be more 
severe in soil with high pH levels (pH 6.5) and in 
soil of low fertility. 
Stem streaking usually is the first symptom 
observed. It may occur within 30 days after plant 
emergence. Leaves begin to wilt about 60 days after 
emergence. When the soil is extremely moist and 
fertile, the stem streaking symptoms are most pro-
nounced. With high soil moisture and low fertility, 
the wilting symptoms will be most prominent. 
The fungus grows and spreads faster when soil 
moisture is high, but wilt severity increases when 
soil moisture levels are lowered. At harvest the 
pinkeye symptoms appear on the infected tubers. 
Research workers are not cetain if pinkeye is caused 
by the Verticillium fungus or a bacterial infection . 
Verticillium fungus has been isolated from tubers 
with pinkeye. 
Reduction in yield will result from a reaction 
in tuber size. If the wilt is severe, a stand 
reduction may account for some yield loss. Tuber 
quality is usually affected, especially in pro-
cessing potatoes by the presence of the brown 
colored vascular ring. It has been found that 
nematodes, in particular the lesion nematode, may 
increase the disease severity. It appears that 
these nematodes increase in numbers on corn in the 
corn/potato rotation. 
Control 
Control of this potentially serious disease 
involves prevention. Don't introduce this disease 
into new or uninfested areas with diseased potato 
seed. Use disease-free seed. 
Don't plant potatoes in fields known to have a 
wilt problem. Repeated plantings of potatoes will 
increase the incidence of the disease. Machinery 
used in infested fields may spread the disease to 
other fields. Even where wilt is not a problem, a 
3-year rotation should be used with potatoes. 
Certified seed growers should seriously con-
sider burning the vines because this will reduce the 
amount of fungus returned to the soil. This can be 
done by raking the vines into windrows and burning 
them when they are dry. 
At this time, soil fumigation is the on1y 
control for Verticillium wilt. Soil fumigation is 
not always successful plus it is difficult to do and 
is expensive. There are several chemicals 
(fumigants) that may be used.1 
1see Extension Folder AG-F0-1879 for information on 
soil fumigants. 
Figure 2 . Discoloration of tuber, infected with the Verticillium spp. 
fungus. 
Issued in furtherance of cooperative extension work in agriculture and home 
economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. 
Department of Agriculture. Patrick J. Borich, Dean and Director of Minnesota 
Extension Service, University of Minnesota, St. Paul , Minnesota 55108. The 
University of Minnesota, including the Minnesota Extension Service, is commit· 
ted to the policy that all persons shall have equal access to its programs, facilit-
ies, and employment without regard to race, religion, color, sex, national origin, 
handicap, age, veteran status, or sexual orientation. 


Verticillium Wilt of Potatoes

http://conservancy.umn.edu/bitstream/11299/219504/1/Ext_Verticillium.pdf

Verticillium Wilt of Potatoes

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