AGRICULTURAL RESEARCH CENTER
Hastings AREC Research Report HAS1984-1 April 19, 1984
Evaluation of soil fumigants and aldicarb for control of bacterial wilt
and corky ringspot in Atlantic and Sebago cultivar potatoes.
D. P. Weingartner, Assoc. Pat T i9 \i
J. R. Shumaker, Assoc. Horti u i- lu
Introduction Li c
Bacterial wilt and tuber brown rot. As the names suggest, this dis se
is distinguished by wilting plants during the season and decag rs
at harvest. The disease is caused by ia'.,-. o udoi as
solanacerarum. Although affected tubers ofteTT r"de. 7, actual rotting
is due to secondary organisms. The bacterium is soil borne and is known
to persist for long' periods of time in roots of weed hosts. There may
be other mechanisms of survival as well.
Bacterial wilt was a very important disease in northeast Florida during
the 1920's and 30's. Incidence and severity of the disease decreased
dramatically with the introduction and wide use of Sebago cultivar during
the mid 1940's. In Florida, Sebago possesses a high degree of tolerance
to bacterial wilt.
The disease is favored by warm and dry weather during March and April.
* Often first symptoms do not occur in NEF until mid April. Usually, but
not always, BW occurs in intense foci in which nearly all plants are
affected. Often wilt is more prevalent near water furrows, or cross
cuts and at low or high spots in fields. Root injury can lead to increased
incidence of BW. Significant increases can occur, for example, if chisels
used to dispense liquid nitrogen are placed too close to emerged plants.
This disease is also known to be more severe when root knot nematodes
are present. There is a range in the degree of susceptibility of US
potato cultivars to BW. Sebago, Ontario, Katahdin and Green Mountain
are examples of tolerant cultivars in Florida. Kennebec, La Chipper
and BelRus have been less severely affected than Atlantic or Pungo in
one or more ARC experiment (Table 1).
Table 1. Relative susceptibility of potato cultivars to corky
ringspot disease and bacterial wilt in NEF.
Potato cultivar CRS BW
Sebago ++++ ++
Pungo 0 ++++
Atlantic ++++ ++++
Superior 0 ++++
Green Mountain + ++
Red Lasoda ++++ ++++
BelRus +++ +
Hudson 0 ?
Chipbelle ++++ +++
Belchip + +++
Centennial + ++++
Gold Rus ++ +++
Kennebec ++++ ?
Oceana + ++
Late Superior 0 ++++
Ontario ++++ +
La Chipper ++++ +
Russet Burbank ++++ +
Penn 71 ++ ?
Wauseon ++ ?
Katahdin ++++ ++
1/ Susceptibility categories were assigned as follows:
CRS 0 = immune; + = < 10% affected tubers; ++ = 11-25%;
+++ = 26-50%; ++++ = > 50% affected tubers.
BW ? = no data; 0 = 0% affected plants; + = 5 5% affected
plants; ++ = 6-12%; +++ = 13-20%; ++++ = 21-100% infected
plants. Categories were based on the most severe disease
reaction observed in our tests.
Corky ringspot disease Corky ringspot is caused by tobacco rattle virus
which is transmitted to potato tubers by stubby root (trichodorid)
nematodes. The disease was first reported in NEF during 1946. The
symptoms include circular lesions on the surface of tubers and necrosis
within the tuber flesh ranging from diffuse flecks to distinct arcs.
Farms constituting approximately one third of the NEF potato acreage
are affected to varying degrees by CRS.
There is a range of susceptibility among U.S. potato cultivars to CRS
(Table 1). Sebago, Atlantic, La Chipper, and red-skinned cultivars,
are very susceptible to CRS whereas Superior, Late Superior, and Pungo
are highly resistant.
The disease is effectively controlled in NEF through application of
aldicarb. Foliar applications of oxamyl have also been effective, however,
this method of control is more costly than aldicarb. Soil fumigation,
regardless of chemical or dosage tested, has failed to control CRS in
The 1982 season marked the first year since 1946 that Sebago was supplanted
as the principal cultivar grown in NEF. As shown in Fig. 1 Atlantic has
replaced Sebago as the number one potato cultivar produced in NEF. Because
of the suseceptibility of Atlantic to BW, it is highly probable that
significant losses to the disease will result if weather favorable to
development of the disease occur during March and April. Therefore, even
though losses in NEF due to BW have been minimal since the mid 1940's, due
to the increased acreage planted to Atlantic, the disease must be treated
as a threat to potato production in NEF.
In experiments performed during 1975-77 incidence of bacterial wilt was
reduced following in-row applications of soil fumigants such as 1,3D (Telone).
We had no data, however, on the effects of an overall or broadcast fumigation
treatment on the disease. The objectives of the experiment discussed in
this report were to: (i) compare in-row to a similated overall fumigation
treatment for control of nematodes, CRS, and BW; (ii) compare efficacies
of 1,3D, EDB, and EDB + chloropicrin; both when used singly and in combination
with aldicarb. In this report we confine our discussion to BW and CRS
Soil fumigants were applied at standard rates using a single chisel/row.
An overall treatment was similated by applying the fumigants using three
chisels/row, each delivering the standard dosage. A split plot design "was
used with the two dosage levels (i.e. one chisel vs three chisels)
constituting the main plots and fumigants or fumigants + aldicarb the
subplots. Four row plots were used and data were taken from the center
two rows, one being planted to Atlantic and the other to Sebago. The
fumigants and rates applied were: Soil Brom 90 1.8 gal/acre/chisel
Terr-o-cide 54-45 2.6 gal/acre/chisel, and Telone II 6.0 gal/acre/chisel.
Aldicarb was applied at 3.0 lb ai/acre in-the-row. Rows were spaced 40
Fig. 1. Percentage 1982 NEF potato acreage planted to different potato cultivars.
Table 2. Incidence of bacterial wilt in Atlantic and Sebago potatoes
as affected by soil fumigants and method of application.
Fumigant Application method1/ Fumigant
1 chisel 3 chisels mean
Soil Brom 90 8.2 1.3 4.7
Terr-o-cide 54/45 3.0 1.8 2.4
Telone II 6.1 1.4 3.7
Application method 5.7 1.5
1/ Data are expressed as no. wilted plants/25 feet plot.
Table 3. Incidence of bacterial wilt as affected by potato
cultivar and application method.
Cultivar Application method1/ Cultivar
1 chisel 3 chisels mean
Atlantic 9.4 2.5 5.9
Sebago 2.1 0.4 1.3
Method 5.7 1.5
1/ Data expressed as no. wilted plants/25 feet plot.
Table 4. Incidence of bacterial wilt in Atlantic and Sebago potatoes
as affected by soil fumigation and aldicarb treatment.
Fumigant Temik treatment!/ Fumigant
Soil Brom 90 3.5 6.0 4.7
Terr-o-cide 54/45 2.5 2.2 2.4
Telone II 3.9 3.6 3.7
Aldicarb./ 2.6 3.9
1/ Data are expressed as number of wilted plants/25
2/ Difference between Temik and no Temik was nonsignificant.
Table 5. Percentage tubers with brown rot as affected
by soil fumigant and application methods.
Fumigant Application method Fumigant
1 chisel 3 chisels mean
Soil Brom 90 15 4 10
Terr-o-cide 54/45 5 1 3
Telone II 6 3 5
Application method 9 3 -
Table 6. Percentage tubers with brown rot as affected by
soil fumigants and potato cultivars.
Soil Brom 90 15 4 10
Terr-o-cide 54/45 5 2 3
Telone II 8 2 5
Cultivar mean 9 3
Table 7. Percentage tubers with brown rot as affected by potato
cultivars and application methods.
1 chisel 3 chisels
Atlantic 14 4 9
Sebago 4 1 3
Application 9 3 -
Table 8. Percentage tubers with brown rot as affected
by fumigant and Temik treatment.
Fumigant Temik Treatment Fumigant
Temik No Temik mean
Soil Brom 90 6 13 10
Terr-o-cide 54/45 4 2 3
Telone II 4 5 5
Temik mean 5 7 -
Table 9. Percentage tubers with CRS
methods of application and
Fumigant 1 chisel
as affected by
use of Temik
Soil Brom 90 3 35 3 54 24
Terr-o-cide 54/45 2 41 3 32 20
Telone II 1 41 0 15 14
Means 2 39 2 34
Temik mean 2%
0 Temik mean 37%
1 chisel mean 21%
3 chisel mean 18%
Incidence of BW was significantly affected by both soil fumigants and
method of application (Table 2). Incidence of wilt was least in
Terr-o-cide 54-45 (54% EDB + 45% chloropicrin) treated plots and greatest
in those fumigated with EDB. A significant reduction in wilt was
associated with the triple chisel treatments. There also was a significant
fumigant x chisel interaction wherein differences in BW incidence among
fumigation treatments were reduced when the rate was increased. Incidence
of wilt was less in Sebago than in Atlantic (Table 3). Also, increasing
the rate of fumigant applied reduced wilt more in Sebago than in Atlantic.
Incidence of BW was further reduced following application of aldicarb
Incidence of tuber brown rot followed patterns similar to those of BW
(Tables 5, 6, 7, & 8). However, in contrast to BW which was reduced more
in Sebago than Atlantic following use of three chisels (Table 3), brown
rot was reduced more in Atlantic (Table 7).
As in previous experiments, soil fumigation failed to control CRS (Table
9). Tripling the dosage also failed to reduce the percentage tubers
affected. The percentage tubers affected by CRS was significantly less
following aldicarb application.
Discussion and Conclusions
The 1983 experiment due to fortuitous concommitant occurence of high
levels of both CRS and BW confirmed several observations made previously
and enabled us to learn more concerning use of soil fumigants in NEF.
The experiment confirmed: (i) Sebago is less severely affected by BW
than Atlantic; (ii) soil fumigation, even at increased dosages fails
to control CRS in NEF; (iii) Temik is highly effective in controlling
CRS in NEF; (iv) Incidence of BW and brown rot can be reduced with
fumigants. This was the first time we have observed a significant
difference in BW among soil fumigation treatments. Ironically the most
cost effective treatments used in the experiment (Soil Brom 90 and
Terr-o-cide 54-45) are no longer available due to recent regulatory
A similar experiment is being performed during 1984 in which 1,3D, 1,3D
+ chloropicrin and metam-sodium are being evaluated.