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 Disease and nematode control on...














Title: Field day.
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Title: Field day.
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Publisher: Potato Investigations Laboratory,
Publication Date: 1971
Copyright Date: 1969
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Table of Contents
    Front Cover
        Front Cover
    Table of Contents
        Table of Contents
    Cabbage harvester and fertilizer studies
        Page 1
        Page 2
        Page 3
    Insect control tests
        Page 4
    Variety trials and chemical weed control tests
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Disease and nematode control on cabbage and potatoes
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
Full Text




HASTImS, FLORIDA
APRIL 1, 1971


AGRICULTURAL RESEARCH
21ST FIELD DAY


CENTER


HUME LIBRARY
JUN 15 1971

I.F.A.S. Univ: of Florida


IN COOPERATION WITH FLORIDA
AGRICULTURAL EXTENSION SERVICE


] 0 z0
F= (3 (6 3rL
Po L
1q71










AGRICULTURAL RESEARCH CENTER

Hastings, Florida

TWENTY FIRST FIELD DAY PROGRAM

April 1, 1971
1:30 p.m.



Paul Dinkins, St. Johns County Extension Director, Presiding

Page

Introduction, Paul Dinkins



Cabbage Harvester & Fertilizer Studies of Potatoes 1
and Cabbage
Dr. D. R. Hensel, Center Director

Insect Control Tests
Dr. R. B. Workman, Associate Entomologist 4

Variety Trials and Chemical Weed Control Tests
Dr. J. R. Shumaker, Assistant Horticulturist 5

Disease and Nematode Control on Cabbage and Potatoes
Dr. D. P. Weingartner, Assistant Plant Pathologist 11




Refreshments are provided courtesy of Asgrow Kilgore Company
and Wilson Toomer Company


MIMEO REPORT POL 71-7











CABBAGE HARVESTER & FERTILIZER STUDIES


D. R. Hensel

CABBAGE HARVESTER OUTLOOK:

Several years of research have been devoted to the development of
a cabbage harvester in Florida. Presently, Middleton Harvesters, Inc.,
of Elkton, Florida, have agreed to manufacture and develop this
machine.

Much greater success with a once-over cabbage harvester can be
attained when proper cultural and planting practices are followed.
The major limiting factors for mechanical harvesting are growing
cabbage with uniform cutting height and uniform maturity. Variation
of these factors can be reduced by precise bed preparation, weed
control, direct seeding and other cultural practices. Extremes in
weather also reduce uniformity.

Recommendation is to manage an overall program which mechanical
harvesting is the final stage. Without well prepared land, good weed
control, and use of other cultural practices which increase uniformity,
maximum efficiency of the harvester cannot be obtained.

Whether one wants to accept it or not, mechanical harvesting is
over the horizon and will become a reality in the very near future.
We need to then start thinking in terms of what packing modifications
are needed. In order to efficiently utilize the harvester, it must
be kept busy. If this is done, possibly a central packing shed will
be the next step. When all the cabbage is harvested at one time, a
lot more volume of material will be handled. Best method of grading,
sizing, etc., will have to be developed. Presently, IFAS personnel are
working on this.











FERTILIZATION OF DIRECT SEEDED CABBAGE:


Very little knowledge has been gathered concerning the fertilization
of direct seeded cabbage on sandy soils of Florida. Since interest
in this field has increased an experiment was initiated to find some of
the answers.

Three levels of 6-8-8 fertilizer were broadcast, banded, and sidedressed
which made a total of 27 combinations. The treatments were for both
1969 and 1970:

Fertilizer Treatments for Direct Seeded Cabbage


Lbs. 6-8-8 applied

Broadcast 400 1000 1600

Banded 600 1500 2400

Sidedressed 400 1000 1600


In 1969, there was some toxic effect on the small seedlings due to
high rates of broadcasting. This was observed at 3 weeks by the number
of missing plants. However, the remaining plants gave a significant
response to broadcast by increased vigor. The banding treatments had
little or no effect on the seedlings at 3 weeks. Both the high rates
of broadcasting and banding gave significant increases in yields.
Sidedressing had no effect on yield. As all three factors were increased,
the average head weight increased.

In 1970, the same experiment was repeated. Since the weather was
quite different than 1969, the response of cabbage to the treatments
also differed. In 1970, dry weather prevailed throughout the early
part of the growing season. This created a toxic effect on the
seedlings wherever the broadcast and banding rates were high. The
crop was also subjected to numerous freezes. This reduced quality,
uniformity, and overall yields, however, a reduction in yield was noted
wherever the fertilizer was broadcast and banded at high rates.
Increased sidedressings were beneficial when combined with lowest
rates of broadcast and banded fertilizer and reduced yields when higher
rates of them were applied.











STRIP MULCHING OF CABBAGE:


Strip mulching of vegetable crops on Florida sandy soils has been
tried by Norman Hayslip at the Agricultural Research Center, Fort Pierce.
A small strip of plastic placed directly over the fertilizer band prevents
leaching of the fertilizer and helps to insure crop growth without
re-fertilizing.

This year for the first time, the Agricultural Research Center,
Hastings, has tried this approach. For variables these are:

Single Row Conventional Method

Double Row Plastic Double and Triple Cabbage
Foil "
Unmulched "

Fertilizer Lbs. 6-8-8/A
Starter 0 300 600
Under Mulch 1000 2000 3000


EFFECT OF VARIOUS CROPPING PRACTICES ON POTATO PRODUCTION:

The overall objectives of this test is to (1) determine what is
happening in the micro-structure of soil as it is cropped and (2) what
combinations of cropping practices will improve production. In this
test virgin soil (un-cropped), relatively new land, and old potato
soils are being compared. In cooperation with Dr. G. M. Volk of the
Soils Department at the University of Florida, changes in micro structure
have been detected as the soil becomes older with cropping.

Variables in this test in addition to age of land are: subsoiling
maturity of cover crop (immature and mature), kind of cover crop (soybeans,
hybrid sorghum, cocklebur, and volunteer), and 5 nitrogen fertilization
variables.

In 1969, subsoiling increased yields. Mature hybrid sorghum
and volunteer growth gave higher yields. Mature hybrid sorghum and
volunteer cover when plowed down in old land gave higher yields whereas
they gave highest yields on new land when they were plowed down immature.

In 1970, heavy rains caused considerable damage to test plots.
Some plots replanted; however, variation in potato yields was too great
to determine any significant trends.

Mrs. A. J. Overman, Research and Education Center, Bradenton,
has been following these plots to determine if any significant changes
in nematode populations have occurred.







Itt





INSECT CONTROL TESTS

R. B. Workman

CRUCIFEROUS CROPS: Pesticides are being tested against cabbage worms
and aphids on 2 varieties of cabbage, collards, brussels sprouts,
and rutabaga. Bacterial (Bacillus thuringiensis) treatments include
Biotrol XK, Dipel, and Thuricide HPC. Chemical tests include Azodrin,
AC 72841, AC 84484, Cygon, Fundal, Lannate, MC 4044, Monitor, Phosvel,
and Orthene. Not being tested because of poor results the past few years
on cabbage loopers are Dibrom, Parathion, Phosdrin, and Toxaphene.

POTATOES: Insecticide tests for aphids and worms include Azodrin,
Bacillus, Cygon, Furadan, Meta-Systox-R, Orthene, Parathion, Phosvel,
Systox, and Zolone.

PESTICIDE OUTLOOK: The outlook for registration of new pesticides on
cabbage and potatoes has been poor. In the past 6 years, 6 pesticides
on cabbage and 5 on potatoes have been discontinued from use through
resistance or regulation. Two effective compounds are available for
grower use on cabbage loopers and 2 for green peach aphids. Insect
control costs have risen 5-6 times in just a short time. The difference
between good and poor insect control with pesticides depends on time
of application, coverage (nozzle number and placement, pressure,
gallonage, spreaders, etc), and weather. Safety precautions must
be followed closely. Read the label. Pesticide container disposal
remains a problem.

CABBAGE VARIETAL RESISTANCE TO CABBAGE LOOPER: Different cabbage
varieties planted in the field for several seasons and not protected
against cabbage loopers have shown some resistance to attack. All
varieties were unmarketable, however. Market Topper and Market Prize
have shown the most resistance followed by Abbott and Cobb No. 5, Autumn
Marvel, and Little Rock. Greenback, Harvester Queen, Headstart, King Cole,
Marion Market, Roundup, and Superette have been injured the most.









VARIETY TRIALS AND CHEMICAL WEED CONTROL TESTS


J. R. Shumaker

VARIETY TRIALS:

Cabbage: Varieties are primarily being evaluated for their fresh market
adaptability to this area. Measurements are also being taken to
evaluate varietal uniformity. A high degree of uniformity is essen-
tial to the success of a once-over harvesting operation. Hybrid
varieties continue to show higher degrees of uniformity for market
maturity, plant type, head shape, and size than open-pollinated
ones.

Replicated and observational trials are currently being conducted.
Varieties being tested in replication are shown in the following
table:


Variety


Head Start


Variety


Green Boy


Princess No. 39

Hybrid No. 31

Harvester Queen

Pack Rite No. 42

Market Prize

Market Topper

Roundup

Superette


King Cole

Little Rock

Kleen Cut


Jet Pak


Hybrid No. 72


Atlas No. 70

Saf-Gard No. 18

Tokyo Pride No. 21

Sentinel No. 19

Red Head Hybrid

Titan


Great Dane

Rio Verde

A & C No. 5


__








VARIETY TRIALS:


Potatoes: Sebago, standard chipping variety in the area, continued to
perform extremely well in 1969 and 1970 trials. Wauseon (B5036-40)
a recently named variety shows promise as a white table stock
variety. While generally considered undesirable for chipping
trade, Red LaSoda was the highest yielding variety during both
years. Yield, specific gravity values, and chip color evaluations
of Pungo, recommended variety for fields with corky ring spot
infested soils, were essentially equal to those of Sebago during
both years.


1969


USIA Chipl/
Variety Cwt/A Color


Specific
Gravity


1970
US1A Chip'/ Specific
Cwt/A Color Gravity


White
Sebago

Wauseon

Pungo

Norchip

Pa-6HS-9

Anoka

Peconic

Superior

LaChipper

Red
Red LaSoda

Chieftain

LaRouge


243

238

248

207

209

208

237

209


3.3 1.073

2.8 1.068

4.3 1.072

3.5 1.076

5.0 1.077

4.3 1.070

3.4 1.068

4.5 1.075

2.4 1.066


5.1 1.068

4.3 1.064

8,1 1.070


333

279

314

295

303

271

257


301


345

289

308


3.8 1.066

4.8 1.064

4.2 1.071

3.2 1.074

3.4 1.070

6.5 i.067

5.0 1.068


3.4 1.068


5.4 1.059

4.2 1.060

6.4 1.058


1 = extremely light color; 10 = dark.


1/ Chip Color:








SEBAGO SEED STOCK:


Imperative to successful and profitable potato production is obtaining
a good vigorous stand by the prevention of seed piece decay and black
leg disease. The need for and use of sound, healthy seed stocks is
apparent and widely accepted. This is accomplished, primarily, by use
of certified seed. Florida growers have recently utilized a State
Seed Inspection Service to implement their needs for high-quality
planting stocks. However, even with the use of certified seed,
coupled with local inspection and recommended management practices,
north Florida growers have observed differences in response among
Sebago seed stocks. As a result, additional information was needed
on the variability among grower-available Sebago seed stocks. Com-
parison also was made between fungicide treated seed (Polyrai;u)(% W)
and nontreated seed, and between stem-end and bud-end seed pieces.

Effect of Sebago seed stock and seed piece treatment on the yield and
the specific gravity of potato tubers 1970.

Seed Piece Seed
Specific Treated Nontreated Stock
Seed Stock Gravity Bud-end Bud-end Stem-end Mean
US1A Cwt/A
USDA Maintenance 1.0589 270 274 283 275 aI-
Maine 1.0583 257 226 225 236 ab
New Brunswick 1.0598 257 221 212 230 ab
New York 1.0583 215 233 231 227 b
PEI 5878 1.0571 239 220 215 225 b
PEI 2778 1.0578 219 183 204 201 bc
Michigan 1.0579 205 a 153 b 147 b 168 cd
PEI 2920 1.0572 173 a 120 b 110 b 134 de
PEI 4286 1.0564 169 a 111 b 70 b 117 e
Rejected 1.0564 152 a 98 b 72 b 107 e

Seed piece mean

Yield 215 a 184 b 177 b

Specific Gravity 1.0586 a 1.0581 a 1.0569 b


1/ Any two means in any seed stock, seed piece, or seed piece by
seed stock group with the same letter are not significantly
different at the 5% level. Absence of letters in a grouping
denotes nonsignificance.













SEBAGO SEED STOCK: (continued)


Seed piece decay and black leg disease, as causative effects on
1970 stand, accounted for 96% of the variation in yields of potatoes.
As stands decreased, there was a decrease in yields. Results show
great variation among grower-available Sebago seed stocks for both
stand and yield. As seed stock emerging stands decreased due to seed
piece decay, fungicide treated seed increased stands over nontreated
seed. The use of locally inspected, high quality, certified seed is
recommended. While fungicide treated seed of the better performing
stocks did not increase yields, economical benefits were obtained
by treating the poorer performing stocks. On this basis, the
relatively low cost of seed treatment would provide insurance when
inferior seed stock is planted.









CHEMICAL WEED CONTROL:


Herbicides and rates listed herein do not constitute recommendations.
Growers are urged to proceed with caution when applying herbicides.
Always check the container label for recent changes regarding crop,
rate, time schedule, and soil type approved for use.

Cabbage: Transplanted cabbage 1970-71. Variety, Head Start. Transplanted,
November 30, 1970. Replicated, 4 times. Plots, 4-rows by 25 feet.
Treatments applied after cultivation December 21, 1970 over-the-
top via 4-row sprayer -- 40 gpa, 2 flat-tip nozzles per row and at
30 psi. Watered at approximate rate of 1000 gal/A directed in the
row after last treatment applied.


Broadcast
Rate
Treatment Lb. AI/A


Lasso 4E
Dacthal 75W
Dacthal 75W
Lasso 4E + Vegadex 4E3-
Dacthal 75W + Lasso 4E44/
Lasso 4E
Dacthal 75W + Tok 50W4/
Tok 50W
Planavin 4E
Planavin 4E
Vegadex 4E
Randox 4E + Vegadex 4 3/
Control


3.0
6.0
10.5
1.5 + 3.0
6.0 + 1.5
1.5
6.0 + 4.0
4.0
1.0
0.5
6.0
3.0 + 3.0


Weed Control Ratings-
3-3-71 Prim-/
rose
and
Other
Chick- Broad-
Dock Weed leaf


9.4
9.4
9.3
9.3
9.3
8.6
8.6
8.5
8.4
7.5
5.5
4.5
1.0


8.5
8.9
8.9
8.5
9.0
6.9
8.1
3.3
8.9
7.4
9.0
8.5
1.0


9.5
7.5
7.8
9.3
8.6
9.3
8.9
8.4
8.1
8.3
9.8
9.1
1.0


1/ Weed control ratings are on the basis of 1 = no control, 10 =
complete control. Primrose (Oenothera lacinata), Dock (Rumex
spp.), and Chickweed (Stellaria media)
2/ Primrose constituted approximately 95%. Other broadleaf weeds
were Cudweed (Gnaphalium spp.) 2%, Watercresses (Rorippa spp.) 2%
and Misc. weeds 1%.
3/ Tank mix.
4/ Compound superimposed.


Cwt/A
Once-
over
Harvest
3-1-71


172
190
195
187
178
199
177
193
197
176
168
170
167







CHEI TCAL WEED CONTROL:


Potatoes: Variety, (Maine) Sebago. Planted January 29, 1971. Treatment
applied from February 22, 1971 to February 25, 1971, preemergence to
crop and weeds via 4-row sprayer at 30 psi and 40 gpa. Eptam bedder
incorporated and approximated an in-the-row band rate of twice the
broadcast rate. Crop bedded March 4, 1971 for frost protection and
uncovered the following day. Frost injury the morning of March 9.


Broadcast Rate
(Lb. AI/A)

3.0 (6.0)


Treatment

Eptam 6E

Eptam 6E

Lasso 4E


2.0 (4.0)

3.0


Lasso 4E

Maloran 50W

Maloran 50W

Lorox 50W

Lorox 50W

Premerge 3E

Patoran 50W

Patoran 50W

Eptam 6E + Lorox 50W'/

Eptam 6E + Patoran 50wi/
2/
Lorox 50W + Lasso 4E2-

Patoran 50W + Lasso 4E2

Bay 94337 70W

Bay 94337 70W


2.0

2.0


2.0

1.0


2.0


2.0 (4.0) + 1.0

2.0 (4.0) + 2.0

1.0 + 2.0

2.0 + 2.0

1.5

0.75


18 Noncultivated


1/ Compound superimposed.
2/ Tank mix.


Treatment
Number










DISEASE AND NEMATODE CONTROL ON CABBAGE AND POTATOES


D. P. Weingartner

CABBAGE

Nematicide Tests

Objectives: Several soil fumigants and granular nematicides were
evaluated in 1970-71 for nematode control on cabbage. The
test had 2 objectives: (1) determine whether nematodes decrease
yields of cabbage harvested near midseason in the Hastings area,
and (2) study efficacy of various nematicides under Hastings'
area cultural practices.

Methods: The sorghum cover crop was knocked down during the first
week in September and chopped with a stalk chopper. The land
was rotivated September 16. All soil fumigants (except Fumazone
86 (0.8 GPA) which was applied October 21) were applied with
gravity flow equipment October 2. Granular materials were
applied October 13 with a Knoble applicator. Granules were
applied in 14-16 inch wide bands on flattened rows and were then
incorporated into the upper 2 inches of soil using a single
cultivation unit from a rolling cultivator. Beds were shaped
October 21 and direct seeded with Head Start cv. cabbage
October 22. Plants were harvested February 15, 1971.

Results: Data from this test are shown in Table 1. Soil fumigants
significantly reduced populations of parisitic nematodes and
significantly increased yields of cabbages over nontreated
controls. Telone (7.0 GPA), D-D (10.0 GPA), and Vorlex (7.0 GPA)
provided good nematode control. Furadan 10G, which is not
currently registered for use on cabbage, also significantly
increased yields.

Conclusions: 1. Parasitic nematodes do affect production of early-
midseason cabbage in the Hastings area.
2. In fields where soil samples indicate nematodes are a problem,
row application of soil fumigants can control nematodes and
increase yields of cabbage.









Table 1. Results of 1970-71 cabbage nematode test.


Treatment and Ratel-


Mean
Head
Weight
(Lbs.)


Yield
(Ton/Acre)


Nematodesl/
in 100cc
Soil


Increase3/
in Crop
Value
($/Acre)


Cost of3-/' /
Chemical
($/Acre)


Added/, 4/
Cost to
Market
($/Acre)


Soil fumigants
Telone 5 GPA
Telone 7 GPA
D-D 10 GPA
Vorlex 7 GPA
Fumazone 86 0.8 GPA-./
Fumazone 86 2.5 GPA

Granular nematicides
Furadan 10G 30 lb.
Dasanit 15G 20 lb.
Nemacur 156 20 lb.
Tirpate 10G 12 lb.
Control
Control


1.73
1.91
2.08
2.20
1.83
1.78


2.01
1.98
1.86
1.89
1.80
1.63


8.8
11.3
10.7
10.8
9.9
9.8


11.9
9.4
8.9
8.5
9.11 x
7.8)P.5


22.4
5.2
8.2
1.8
25.8
23.4


25.8
31.0
31.6
31.2
52.4
62.4


18
168
132
180
84
78


204
54
24
0


11.00
15.40
17.00
50.40
9.76
30.50


13.50
10.20
NR
NR


10.37
96.77
76.13
79.49
48.38
44.93


117.50
31.10
NR
NR


-3.37
56.83
38.88
60.11
27.86
3.57


73.00
17.70
NR
NR


F values of all data are significant at 1%.

1/ Rates = material applied/row acre (13070 ft).
2/ Populations of sting, stunt, and stubby root nematodes are added together to give a single value. Sample
was taken at midseason. Nematodes separated via sucrose centrifugation method.
3/ Crop value calculated on basis of: $1.50/bag or $0.03/lb. Chemical costs are based on distributor's
prices March 17, 1971. Marketing costs = $.864/50 lb. and are taken from Ag. Econ. Report 15. Costs and
Returns from Vegetable Crops in Florida Season 1969-70 with comparisons. Page 3.
4/ NR = chemical not registered on cabbage and cannot be used at the present time.
5/ Fumazone 86 0.8 GPA applied at planting.


Net3/,4/
Return
($/Acre)









CABBAGE (continued)


Fungicides

Introduction: Downy mildew continues to be a serious disease problem
on seedling cabbage. Last year several fungicides provided
excellent control when applied at 3.0 lbs/acre on a weekly schedule.
These fungicides were evaluated this year at 3 different rates in
order to determine the lowest efficacious dose when applied on a
weekly schedule.

Methods: Cabbage cv. Red Acre, which is highly susceptible to downy
mildew, was the test crop. Seed beds were planted December 17,
1970. Fungicide applications were made December 30, January 7-8,
and January 11-12. Eight drizzling rainfalls, favorable temperal.1ires,
and long periods with relative humidity exceeding 90% during the
test period created miserable conditions for spraying and an ideal
environment for a downy mildew epiphytotic.

Results: A hard freeze on January 21 killed all seedlings which were
stunted or severely affected by downy mildew. Relative control
of downy mildew by the materials tested could therefore be
assessed by rating the surviving stands of plants. Data are
shown in Table 2. The most important observation in this year's
test was that none of the materials used, including Chloranil,
gave satisfactory control of downy mildew. Due to the frequent,
drizzling rains, fungicides apparently washed from the leaves
very quickly. Generally, the high rates of the fungicides were
the most effective. Difolatan 4F was the most effective material
under the weather conditions.

Discussion: In order for a foliar fungicide to be effective, it must
adhere to the leaf surface and be present when fungus spores
land on the host plant. This year, we apparently measured
sticking qualities of the fungicides and surfactants used rather
than efficacy of a given fungicide under optimum conditions.
Observations made during the past 2 seasons indicate that the
most important factor in fungicidal control of downy mildew in
the Hastings area is adherence of fungicides to cabbage leaf
surfaces. In subsequent tests, stickers and various surfactants
will be tested.








Table 2. Results of 1971 tests for fungicidal control of downy mildew.

Stand Rating-a/,b/
Low Rate
Treatment (LR) 1 x LR 2 x LR 3 x LR

Difolatan 4F 1.0 qt. 5.1 ab 5.2 ab 7.9 a

Thynon 75W + Dupont Spreader Sticker 1.0 lb. 3.0 b 3.0 b 5.3 ab

Polyram 80W 1.0 lb. 1.0 b 3.0 b 4.0 ab

Bravo 75W (Daconil 2787) 1.0 lb. 2.8 b 2.0 b 4.5 ab

Manzate D 80W + Dupont Spreader Sticker 1.0 lb. 2.5 b 2.1 b 4.5 ab

Dithane M45 80W + Triton B1956 1.0 lb. 1.7 b 3.6 ab 3.1 b

TC 904 1.0 qt. 1.6 b 3.4 b 4.1 ab


Chloranil 65W + Dupont Spreader Sticker 4.0 lb. 2.9 b -- --

Check 1 1.9 b --

Check 2 2.0 b -- --


a/ Hard freeze on January 21 killed all plants which were stunted or severely
affected by downy mildew. Mildew control was therefore assessed by
rating plots on a 0-10 scale with 0 being all plants dead and 10 perfect
mildew control (perfect stand).

b/ Data are means of 4 replicates. Ratings followed by the same letter do
not differ significantly at 5% according to Duncan's multiple range test.










CABBAGE (continued)

Genetic resistance to downy mildew: Four F2 cabbage selections from
Clemson University are being evaluated for resistance to downy mildew.
The selections are reported by W. C. Barnes, Clemson Horticulturist
to carry resistance in the heading stage to downy mildew. The test
is not complete, however, several observations have been made (Table 1).
All of the selections can be infected by the fungus causing downy
mildew, however, they are more vigorous under severe disease pressure
than cv. Copenhagen. One selection, C-133 B, appears to be less
severely affected by mildew in the Hastings area and is somewhat more
vigorous than the other 3 selections.

Broad resistance to downy mildew will not be available in commercially
available seed for several years.
Table 3. Evaluation of downy mildew severity.


Stand./
Selection Rating
or Variety Dec. 21


6.4


C-133 B

C-134 D

C-132 F

C-132 A


Copenhagen (Control)


4.3

3.4

2.8


Vigor
Rating
Dec. 21

7.0

5.4

5.0

4.4


Disease
Stand Severity
Rating Rating
March 9 March 9


7.5

7.0

6.0

4.8

4.2


4.4

4.5

5.1

5.5


a/ Ratings were made as follows:
1. Stand 1-10, with 10 being a perfect stand. Whole plots were
rated.
2. Vigor 1-10, with 10 representing vigor of hypothetical non-
infected plants. Whole plots were rated.
3. Disease severity 1-7. 1 = 1-2% leaf surface affected; 2 = 3-15%;
3 = 16-35%; 4 = 36-70%; 5 = 71-85%; 6 = 86-99%; 7 = 100% affected
or plants dead. Fifteen plants were rated from each test plot.
4. Lesion index 1-10. 1 = 1-100 lesions/plant; 2 = 101-350;
3 = 351-750; 4 = 751-1000; 5 = 1000-1500; 6 = 1501-2000; 7 = 2001-
2500; 8 = 2501-3000; 9 = 3001-3500; and 10 = 3501 + lesions/plant.
Fifteen plants from each plot were rated.

Black rot tests: Antibiotics were evaluated for curative effects on plants
severely infected with black rot bacteria. A hard freeze killed
most of the plants in the test and no data were obtained. Similar
tests will be -onn9ictedI whenever possible.


Lesion
Rating
March 9


5.9

6.3

6.7

6.8









POTATO

Nematode control: 1970 season. Soil fumigants and granular nematicides
were evaluated for nematode control in soil with high populations
of sting and stunt nematodes. The following tests were performed:

1. In-row application of soil fumigants.
2. In-furrow application of granular nematicides (3.0 lb/acre ai).
3. Row application and soil incorporation of granular nematicides
(3.0 and 5.0 lb/acre ai).
4. Row application of soil fumigants 1 week before and at time of
planting.
5. Comparison of a resistant variety (Pungo), susceptible variety
(Sebago), soil fumigant (Telone), and a granular nematicide
(Furadan) for control of corky ring spot disease of potatoes.

Results: Results of 2 of these tests are shown in Table 4. The results
of 1970 nematode control tests can be summarized as follows:

1. Soil fumigants generally controlled nematodes better than g,-.iii,,lr.
nematicides. In-furrow application of granular nematicides
increased yields whereas soil incorporation of the same materials
at the same rates did not. Both row application of soil fumigants
and contact nematicides applied in-furrow significantly increased
crop value over that of controls.
2. Quality of potatoes was improved by nematicide application.
3. Potato chip quality and specific gravity were not affected
significantly by nematicide treatments.
4. Row application of soil fumigants 1 week before and at planting
reduced yields of potatoes.

Control of corky ring spot disease: Corky ring spot disease did not
occur in test plots. Potato cv. Pungo produced significantly greater
yields than did cv. Sebago. There were no practical differences in
potato chipping quality between the 2 varieties, although Pungo
did tend to chip darker than Sebago. Treatment with Telone (9.5 GPA)
and Furadan (1.9 Ib/acre ai) did not significantly affect yields of
either Sebago or Pungo.

Seed piece decay: Two experiments were performed to determine whether
seed piece decay could be controlled with fungicides and/or
antibiotics. Dr. Shumaker will report on one of these tests.

In a large test 11 different fungicides were evaluated alone and in
combination with Agrimycin 17 (streptomycin sulfate, an antibiotic).
Complete '







Table a/4. Results of 1970 potato nematode tests.
Table 4. Results of 1970 potato nematode tests.--


Total Cost to
Marketable Nematodesib/ Crop Cost of Market Net Increase
Potatoes in 100cc Value Chemical Crop in Crop Value
Treatroent and Rate (cwt/acre) Soil ($/acre) ($/acre) ($/acre) ($/acre)

Test 1. In-row application of soil fumigants
D-D 6.0 GPA 139.0 36.3 387.90 10.20 143.87 27.46
D-D 8.0 GPA 136.1 24.1 374.85 13.60 140.86 14.02
Telone 6.0 GPA 146.7 30.3 405.30 13.20 151.83 33.87
Vorlex 4.0 GPA 135.1 6.7 372.60 28.80 139.83 -2.40
w-85 4.0 GPA_/ 29.6 -0-
Control 113.3 221.3 322.50 -- 116.13

LSD .05 25.9

Test 2. In-furrow application of granular nematicides
Nemacur 15G NR 2.0 Ib/acred/ 150.5 195.3 429.45 15.00 155.77 66.34
Dasanit 15G NR 2.0 lb/,a red/ 146.4 205.7 414.30 10.20 151.21 60.55
Mocap NR 3.0 Ib/acre-'A/' 55.7 137.0
Furadan NR 3.0 Ib/acred/ 134.4 198.3 381.60 12.00 135.10 36.66
Control 105.9 304.7 301.95 13.50 109.61

LSD .05 30.3
a/ Crop value based on $3.00/cwt for US14 and $1.50/cwt for US1B at harvest. Cost of chemicals based on
March 1971 prices. Prices of Nemacur and Mocap were estimated. Cost of harvesting and marketing
potatoes based on $1.035/cwt and is taken from Ag. Econ. Report 15. Costs and Returns from Vegetable
Crops in Florida season 1969-1970 with comparisons.
b/ Populations of sting and stunt nematodes are added together to give a single value.
c/ The 4.0 GPA rate of W-85 used in this test exceeded label restrictions by 2.2 GPA and was phytotoxic.
Mocap applied in-furrow was phytotoxic. However, the same rate of Mocap was not phytotoxic when
incorporated into soil in another test.
d/ NR = Material not registered for use on potatoes. Dasanit is registered for use as a control for
wireworms, however, it is not registered at rates used in this test and it is not registered for
in-furrow treatment. At the present time, none of the granular materials used in Test 2 can be used at
the tested rates nor can they be applied in-furrow.










POTATO (continued)

Seed piece decay was negligible in the test. However, cut seed
treated with fungicides tended to emerge earlier than nontreated seed.
Results obtained with 4 fungicides registered for use as seed
treaters are shown in Table 5.

Although seed piece decay did not occur in the test, the increased
rates of emergence could be important during seasons when heavy rains
and cold temperatures favor decay. The reason for the increase in
rate of emergence is not known.

1971 Season

Nematicides: Nine different experiments with nematicides are in progress.
The objectives of these tests are to:

1. Determine optimum rates of soil fumigants to be used on Hastings'
elevated rows.
2. Determine efficacy of several soil fumigants and contact
nematicides for control of corky ring spot disease, root knot
nematode damage, and control of sting and stunt nematodes.
3. Determine whether different nitrogen sources in fertilizer affect
yields in fumigated soil. (This test is being performed jointly
with Dr. D. R. Hensel).
4. Determine whether efficacies of some herbicides and nematicides
are affected when the materials are used on the same land during
the same growing season. (This test is being performed jointly
with Dr. J. R. Shumaker).
5. Study effects on yields of different means of application of
granular nematicides.

Seed piece decay: Ten different fungicides are being evaluated alone and
in combinations with different formulations of streptomycin sulfate
for control of potato seed piece decay.









POTATO (continued)

Table 5. QResilts of 1970 seed piece decay experiment.


Days tob- Total/
Attaineda/ Attain Yield
Treatment Stand (%) Stand (cwt/acre)

Check (freshly cut, nontreated) 97.7 32.7 251.4 a

Check (cut 3 weeks before planting) 80.8 34.0 136.7 b

Polyram 7% W 98.5 27.0 268.4 a

Manzate 200 8% W 100.0 24.2 245.3 a

Dithane M-45 8% W 100.0 26.0 255.4 a

Captan 7% W 96.2 26.3 250.3 a


a/ Attained stand = maximum plants emerged.

b/ Days to attain stand = mean number days from planting to day when
maximum % plants were emerged.

c/ Yields followed by same letter do not differ significantly at 5%.




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