Title: Results of 1970 tests for chemical control of potato seed piece decay at Hastings, Florida
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 Material Information
Title: Results of 1970 tests for chemical control of potato seed piece decay at Hastings, Florida
Physical Description: Book
Creator: Weingartner, David Peter,
Publisher: Potato Investigations Laboratory,
Copyright Date: 1970
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Bibliographic ID: UF00076333
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: 144497730 - OCLC

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O POTATO INVESTIGATIONS LABORATORY
Hastings, Florida

Mimeo Report POL 71-4 AP/p december 190

RESULTS OF 1970 TESTS FOR CHEMICAL C RO OF
POTATO SEED PIECE DECAY AT HASTINGS, I (j_ .
D. P. Weingartner, Asst. Plant Pathologis' Of-/0.

INTRODUCTION:

Seed piece decay of Irish potatoes continues to be a major problem in the
Hastings area. Stands in various fields were reduced 20-75% following heavy
rains and low temperatures in January, 1970. Most decay observed during the
1970 season was due to soft rot bacteria (Erwinia carotovora). However, the
black leg pathogen (E. atroseptica) and fungi such as Fusarium spp. and
Phythium spp. have also been associated with seed piece decay in the Hastings
area. The relative importance of the different bacteria and fungi as causes
of seed piece decay in the Hastings area is unknown. During the 1970 season,
experiments were performed to determine whether seed piece decay could be
reduced by treating freshly cut seed pieces with fungicides or with com-
binations of fungicides and streptomycin sulfate (an antibiotic).

METHODS:

Test 1.-/ As part of a large experiment, yields and emergence from Polyram
treated and nontreated cut bud-end seed pieces were compared. Methods used
in this test were similar to those reported under Test 2 except that in Test
1 cut seed pieces were stored for 3 days under ideal conditions for wound
periderm formation before planting. Treated and nontreated seed pieces were
planted January 29 in subplots of a split plot design with the 10 replications
arranged in a Latin Square Design. Each plot was planted with fifteen 2.0 oz
seed pieces. Potatoes were harvested May 28. Rainfall on February 3
totalling 5.07 inches was followed by freezing temperatures on February 4 and 5
which provided ideal conditions for seed piece decay.

Test 2. Potatoes (Sebago cv.) were cut by hand into approximately 3f oz
seed pieces. All treatments were applied as dusts except Semesan Bel, Agrimycin
17, and Agri-Strep which were applied as dips. Dusts were applied by shaking
freshly cut tubers and the desired amount of fungicide (1.0 lb formulation/
100 lbs cut seed) in paper bags. Seed pieces were dipped for 5 minutes in
Semesan Bel (1.0 lb/7.5 gallons water) and for 30 minutes in Agrimycin 17
and Agri-Strep (both at 100 ppm). Fungicide dusts + Agrimycin 17 combinations
were applied by first dipping cut tubers in Agrimycin 17 and then dusting
seed pieces with fungicide. Semesan Bel + Agrimycin 17 was applied by dipping
potatoes first in Semesan Bel and then in Agrimycin 17. Treated seed pieces
were planted February 27 in a randomized block design with 6 replications.



1/ This test was part of an experiment performed in cooperation with Dr. J. R.
Shumaker, Asst. Horticulturist.


12-30-70
250 copies











Plots were single rows containing 13 hill units spaced 12 inches apart.
Cut seed dusted with talcum (magnesium silicate was used as a diluent for
fungicide dusts, where indicated), nontreated freshly cut seed pieces, and
seed pieces cut 3 weeks before planting served as controls. Following treat-
ment, potatoes were grown following standard procedures practiced in the
Hastings, Florida area and were mechanically harvested June 1, 1970.

RESULTS:

Test 1. Potatoes in this test were exposed to severe weather conditions
during the first week following planting, and seed piece decay was severe.
As shown in Table 1, highly significant differences in stand, yield, and
vigor were observed among treatments on seed obtained from 10 different
sources. The effects of Polyram treatment were greatest on those potato
seed stocks having the poorest stands and yields in control plots. The
effects of seed treatment on USDA foundation seed (not available to growers)
were nonsignificant. Yield increases were highly correlated with increases
in final stand.

Test 2. Unfavorable conditions for seed piece decay existed during this
test and incidence of seed piece decay was negligible. Seed pieces treated
with Agrimycin 17, Polyram, Manzate 200, Benlate, Thynon, Daconil 2787,
Captan, and Dithane M-45 tended to emerge earlier than controls (Table 2).
These effects of the treatments were most striking 27 days after emergence.
In addition, seed pieces treated with these materials attained maximum
observed stand 5-8 days earlier than did the freshly cut control. The
increases in earliness of emergence are especially interesting because
similar observations were made in Test 1.

Demosan, Mertect, and Busan 72 tended to delay emergence and reduce yields
when compared to the freshly cut control.

Vigor ratings taken 38 days after planting also reflect effects of treat-
ments on emergence. That is, the greatest vigor ratings indicate earliest
emergence.

Small delays in time to emerge associated with addition of Agrimycin 17 to
fungicides were nonsignificant. There were no detectable interaction effects
of Agrimycin 17 x fungicides on final stand, days to attain maximum, vigor,
yield, or specific gravity.

Storing of cut seed for 3 weeks (temperature and relative humidity were
not monitored) before planting significantly reduced stands and yields.
Dusting of freshly cut seed pieces with talcum also reduced yields when
coimpuard .to noniasted freshly cut seed.


POL 71-4 Page 2










DISCUSSION:


Treatment of cut seed pieces with Polyram in Test 1 significantly increased
stands and yields of potatoes when weather conditions predisposed seed to
decay. It was not possible to systematically sample decayed seed pieces in
this test, however, only bacteria were observed when 12 tubers were examined
during various stages of decay. Polyram is not known to have bactercidal or
bacterostatic activity. The role of Polyram in reducing bacterial seed piece
decay in this test is not understood. A possible explanation of the effects
of Polyram is that treatment reduced populations of root rotting fungi in
rhizosphere soil, thereby allowing treated tubers to more quickly establish
a functional root system. Increases in rates of emergence in Test 2 could
be similarly explained.

Seed pieces cut 3 weeks before planting were carefully selected and showed
no visible signs of decay. Penicillium and Aspergillus spp. were the only
fungi found on cut surfaces. Reduced stands and yields resulting from use
of this seed emphasize the need for storing cut seed under optimum conditions
(45-500 at 90-95% relative humidity) for wound periderm formation.

Based on results of these tests, treatment of cut potato seed pieces with a
registered fungicide is recommended for the Hastings area. Fungicides can
be applied either by dusting or dipping freshly cut seed pieces in the
material. Streptomycin sulfate formulations can be tried on a small scale.
Streptomycin sulfate, however, interferes with wound periderm formation and
should always be used in conjunction with an effective fungicide. Follow
all label restrictions and directions when treating cut seed.



Table 1. Results of 1969-70 potato seed piece treatments. Test 1.-2

% Stand at Various Intervals Vigor- Yield/ Specific3
Treatment (days) after Planting Rating Cwt/A Gravity

33 37 40 45
Polyram 82.1 84.4 85.3 85-3 7.1 270.4 1.0586

Nontreated 66.7 71.1 72.8 72.3 5.9 232.9 1.0581

1/ All differences between treated and nontreated seed pieces are significant
at 1% level. No practical significance is attributed to differences in
specific gravity values.
2/ Vigor ratings based on 1 10 with 1 being least vigorous.
/ Yield and specific gravity data are based on average of 5 replications
whereas emergences and vigor are based on 10 replications.


POL 71-4 Page 3






Table 2. Results of 1969-70 potato seed piece treatments. Test


%o Stand /
Attained Days to 3 Total/

2/ 20 27 Stand Attain Vigor- Specific Yield
Treatment-/ Days Days 35 Days Stand Rating Gravity Cwt/A


Check (freshly cut, nontreated)
Check (freshly cut, dusted
with talcum)
Check (cut 3 weeks before
planting)

Ag-17-

Ag-17 + Talcumj

Agri-Strep

Busan 72 10% W7i
Busan 72 10% W + Ag-171/


Polyram 7% W
Polyram 7% W + Ag-17


Manzate 200
Manzate 200


8% w /
8% w + Ag-171/


Semesan Bel
Semesan Bel + Ag-17


Demosan
Demosan
Demosan
Demosan


34.6
28.2

20.5


17.9

43.6

20.5

23.1
7.7

15.4
11.5

34.6
42.3

14.1
12.8


5% w7J 6.4
5% W+Manzate 200 8% -/ 7/2.6
5% W+Manzate 200 8% W+Ag-17 9.0
5% W + Ag-17I/ 1.3


91.0
85.9

61.5


97.7
97.7

80.8


94.9 100.0


85.9

87.2


93.8

97.7


80.8 88.5
82.1 94.6


97.4
98.7


98.5
100.0


100.0 100.0
100.0 100.0


89.7
82.1

73.1
74.4
68.0
62.8


97.7
96.2

96.2
97.7
97.7
98.5


32.7
32.3

34.0


29.0

27.7

31.0

32.7
31.3

27.0
27.0

24.2
24.3

32.3
34.0

32.7
34.0
34.0
34.0


4.3
3.8

2.5


4.3


3.8
3.9

4.5
4.7

4.8
4.8

4.1
3.6

3.0
3.1
3.3
3.0


1.0597
1.0571

1.0573


1.0579

1.0594

1.0572

1.0579
1.0600

1.0605
1.0594

1.0604
1.0599

1.0580
1.0587

1.0561
1.0565
1.0576
1.0572


251.4 abcd
207.1 bcdef

136.7 g


252.4 abcd

235.3 abcde

242.3 abcde

205.1 cdef
244.3 abcd

268.4 ab
269.4 a

245.3 abcd
260.4 abc

255.4 abcd
229.0 abcde


231.2
198.1
226.2
231.2


abcde
def
abcde
abcde


(continued)


POL 71-4 Page 4


2.-1/





Table 2.1/ (continued)

% Stand c
Attained Days to3' 4/ Total-
20 27 Stand Attain Vigor- Specific Yield
Treatment-/ Days Days 35 Days Stand Rating Gravity Cwt/A
Benlate 10% WI/ 35.9 88.5 92.3 27.8 4.4 1.0588 229.0 abcde
Benlate 10% W + Ag-171/ 25.6 82.1 90.0 27.7 4.3 1.0592 234.1 abcde

Thynon 8% W7-/ 42.3 98.7 100.0 26.0 4.4 1.0572 244.3 abcd
Thynon 8% W + Ag-17-7/ 35.9 92.3 97.1 28.8 4.8 1.0580 264.4 ab

Daconil 2787 8% w-/ 39.7 98.7 98.5 26.3 4.9 1.0582 254.4 abcd
Daconil 2787 8% W + Ag-177 33.3 92.3 93.8 26.5 4.2 1.0585 250.3 abcd

Captan 7.5% W 37.2 93.6 96.2 26.3 4.3 1.0592 250.3 abcd
Captan 7.5% W + Ag-17 37.2 94.9 98.5 26.3 4.7 1.0602 258.4 abc

Dithane M-45 8% NI/ 35.9 97.4 100.0 26.0 4.7 1.0586 255.4 abcd
Dithane M-45 8% W + Ag-177/ 37.1 96.2 98.5 28.3 4.5 1.0584 248.3 abcd

Mertect 10% W 7.7 82.1 96.2 34.0 2.8 1.0625 187.0 f
Mertect 10% w + Ag-17 9.0 69.2 86.9 34.0 2.7 1.0594 172.9 fg
LSD .01 12.8 19.3 12.3 6.4 0.74 NS 44.2
LSD .05 7.8 14.0 9.2 4.8 0.56 NS 33.2


1/ Data based on means of 6 replicates.
2/ Agrimycin 17 and Agri-Strep applied as


100 ppm dips, Semesan Bel as a dip at 1.0 lb/7.5 gallons water


and all other materials as dusts at 1.0 lb formulation/100 lbs cut seed.
Number of days between planting date and date of maximum observed stand.
Based on rating system of 1-5 with 1 being least vigorous. Data taken 38 days after planting.
Yields followed by same letter indicate Duncan's multiple range groupings which do not differ significantly
at 5% level.
Ag-17 = Agrimycin 17.
Materials diluted with talcum used in check.


POL 71-4 Page 5




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