Progress Report Series No, 47 May 1951
AGRICULTURAL EXPERIMENT STATION
of The Alabama Polytechnic Institute, Auburn, Ala.
S . E. V. SMITH, Director. 
. . .
CONTROL of DISEASES and INSECTS of TOMATOES in ALABAMA
R. Lo SELF, Associate Plant Pathologist
W, Go EDEN, Associate Entomologist
Disease and insects are often limiting factors in production of tomatoes
in Alabama, Tomato growers in the State have suffered severe losses from
diseases and insects for at least the past 
2 years.
This report is a presentation and an analysis of results from experiments
involving the use of newer chemical compounds in control of tomato diseases
and insects,
TOMATO BLIGHTS
Early, late,- and Septoria blights are the main fungus diseases of the
tomato in Alabama. Late blight has been the most destructive of the three
during the past h years in northern Alabama. Early blight has caused most
of the damage in central and southern Alabama;, Septoria blight has caused
damage only to occasional fields.
Description
Late blight, a cool wet weather disease of both potato and tomato, is
caused by Phytophthora infestans,. It overwinters in potato tubers--not in
the seed of tomatoes andprobably not in the soil or crop refuse. It is
spread by wind-blown spores and by infected plants obtained from other areas,
Symptoms of the disease are purplish-black, rapidly.. enlarging areas on
leaves and stems Under humid conditions a downy white growth is present on
the lower leaf surface.. Infected fruits have grayish-green, water-soaked
spots, which turn brown and have a firm, rough surface, These spots increase
in size, Plants may become infected at any stage of growth,
Early blight is caused by Alternaria solani, which may overwinter on the
seed ?suface, in the soil, and old crop refuse, It develops most rapidly un-
der warm, humid conditions and spreads by wind-blown spores. Most damage
occurs on the older leaves, beginning soon after fruit start to set, Symp-
toms on fruit, leaves, and stems consist of irregular, brown, concentrically-
marked dead spots, which enlarge up to one-half inch in diameter, The phase
that sometimes occurs on the younger stems is known as stem canker and causes
breaking over or stunting of young plants, Another species of Alternaria
causes nailhead disease, Symptoms of this disease on the leaves and stems
are similar to those of early blight, but the fruit lesions are sunken and
are about the size of a nailhead-
Septoria blight is caused by Septoria lycopersici which produces spores
that are spread by splashing rain. The organism overwinters on infected
crop refuse of tomato, Jimson weed, horse nettle, and ground cherry plants.
It is favored by wet seasons and moderate temperatures. Symptoms consist of
numerous small water-soaked spots on the leaves. The spots are roughly cir-
cular and have gray centers with dark margins. Later the centers show tiny
dark specks in which spores are produced. Initial infections occur on the
lower leaves of young plants, Under favorable conditions all the leaves may
soon be killed,
Tomato-Disease-Control Experiments in
Central and Southern Alabama
Experiments were conducted with spring tomatoes at the Gulf Coast Substa-
tion, Fairhope, in 1948 and 1949, at the Plant Breeding Unit, Tallassee, in
1949, and at the Chilton Area Horticultural Substation, Clanton, in 1950. All
dusts were applied with hand dusters at rates to give good coverage of the
plants, ranging from about 10 pounds per acre when the plants were small to
about 40 pounds near the end of the season. Sprays were applied with knap-
sack sprayers at Fairhope and Tallassee, and with a power sprayer at Clanton.
The sprays were applied to give complete coverage of both the upper and lower
leaf surfaces. Rates varied from about 40 to 125 gallons per acre, depending
upon stage of growth,
One per cent rotenone was used for the control of both aphids and fruit
worms in 1948 and 1949 In 1950 two materials were used. Aphids were con-
trolled with nicotine sulfate applied as a 3-per cent dust or as a spray of
1 pint of 40 per cent concentrate per 100 gallons of water. Fifty per cent
cryolite dust or 6 pounds of 90 per cent cryolite per 100 gallons of water
was used for fruitworm control.
Substantial yield increases followed the application of all fungicidal
dusts except Phygon XL, Tables 1 and 2, In 1948 and 1949, 6.5 per cent zineb
(zinc ethylene bisdithiocarbamate) dust resulted in yield increases of 24 and
43 bushels respectively, over those from the 6 per cent metallic copper treat-
ment. On the other hand, the 6 per cent metallic copper treatment resulted
in 43.3 bushels more than the 6.5 per cent zineb in one experiment in 1949.
Since the lowest yield increases in 1949 were realized from the use of 3.9 per
cent zineb, 5 and 7 per cent zineb dusts were tested in 1950. The copper dust
was also increased to 7 per cent metallic copper.
Five per cent zineb gave the highest yields of the dusts tested at Clan-
ton in. 1950. Both 7 per cent metallic copper and 7 per cent zineb appeared to
be somewhat toxic to the plants.
At Fairhope, Dithan D-1 spray reduced yields by 
45.0 and 118.3 bushels
per acre, respectively, in 19h8 and 1949, It increased the yield 206 bushels
at Tallassee in 1949. Since early-blight control was excellent at both loca-
tions, the poor performance appeared to be due to toxicity of the material to
the plants. This toxicity was very pronounced at Fairhope, where it caused
plant stunting and leaf malformations similar to that of 2,4-D injury, A
yield reduction of 19.6 bushels (26 per cent) was also recorded at Clanton
for liquid Parzate, a compound similar 
to Dithane D-14%
Table 1. The Effect of Three Fungicidal Dusts and of Dithane D-14 Spray
on the Yield of Marketable Tomatoes, Fairhope and Tallassee,
1948 and 1949
Yield per 
acre 1/
Treatment 
Fairhope 
Tallassee
1948 1/ 1949 3/ : 
1949
4 replicates replicates 
: replicates
Bushels Bushels : Bushels
No treatment ..................... 
:6 00
Copper dust, 6 pct. ............ 477.3 379.6 269.0
Zineb dust, 3.9 pot. .... ......... 322.6 280.0
Zineb dust, 6.5 pct, .. ........... 
501.6 336.3 312.3
Dithane D-14 Spray
(2 qts. plus 1 lb, 
ZnSO
/ 1/2 lb, lime) ..... .......... 361,6 184.6 
: 270.3
1/ One bushel contains 60 pounds.
7/ Fungicides were applied 7 times
To June 12.
3/ Fungicides were applied 8 times
To June 18.
L/ Fungicides were applied 11 time
to August 16, Five of the applicat:
were reapplied.
at 7- to 10-day intervals from April 17
at 7- to 10-day intervals from April 9
s at 4- to 10-day intervals from June 1
ions were washed off within 24 hours and
Table 2. Effects of Fungicidal Sprays and Dusts on the Yields of
Marketable Tomatoes, 1950
Average yield per acre,
Treatments 
replications
Clantonl/ Cullman2/ Etowah3/
Bushels Bushels Bushels
Phygon XL dust ........... , ,. 4 61 6
Zineb dust, 7 pct., (Z-78 formulation) .... 87,0 72.0
Zineb dust, 5 pct., (Z-78 formulation) .... . 9640 76v3
Copper, 7 pct., (Tribasic) ....... 883 53*0
Zineb, 7 pot., alternating 
iwith copper,
7 pct., (Tribasic) ....... . .
..... 62.6
Liquid Parzate (2 qt. / 1 lb.
ZnSO
4 
$ 1/2 lb. lime/100 
gal) ........
, h6 
9246 170a9
Dithane D-14 (2 qt. / 1 lb,
ZnSO0 / 1/2 lb. lime/100 gal
4
,)... ..... 89.0 215.6
Z-78 Concentrate (2 lb,/100 gal.) , 
. . 73.3 2119
Parzate Concentrate (2 lb./100 gal.) .,,.4,,, 170.3
Tribasic Copper Spray (h lb./l10 gal.)...1. 174.6
Copper A Spray (4 lb,/100 gal.) .. ........ 174,.6
Phygon Spray (3/4 lb., Phygon XL/100 gal.) 184*.3
No treatment . 44444444444.440t*4 74.3 39,3 11046
1/ Seven applications between May 9 and June 16. The last two applications
were washed off within 24 hours., Early blight was severe, but early termi-
nation of the experiment prevented proper evaluation of effectiveness of the
various treatments
4
2/ Nine applications between August 9 and September 27. No application be-
Tween August 22 and September 7, Early infections of mosaic and late blight.
3/ Three early aerial applications of copper dust 
plus nicotine sulfate to
The entire plot, followed by eight applications between August 8 and Octo-
ber 4. August 17, 24, and September 4 applications were washed off within
24 hours.
Tomato-Disease-Control Experiments in Northern Alabama
An experiment was conducted with fungicidal dusts and sprays on fall
tomatoes in 1950 at the North Alabama Horticultural Substation, Cullman. A
spray plot was run simultaneously in Etowah County. Sprays were applied to
the Etowah plot with a power sprayer All other materials were applied with
hand equipment.
Although late blight was severe, data from 
the Cullman plot were some-
what unreliable because of early infection of all plants with tomato 
mosaic.
All materials in the Cullman plot gave good control of late blight, The high-
est yields were obtained from Liquid Parzate and Dithane D-14 sprays, The
highest yielding dust treatment was 5 per cent zineb, The 7 per cent zineb
dust was toxic to the plants, resulting in dead and puckered leaf areas,
Noticeable stunting resulted from use of 7 per 
cent metallic copper.
All treatments except Phygon gave excellent 
control of late blight on
the fruit and foliage in the Etowah plot. Phygon resulted in poor late
blight control even though a high yield of marketable greenwrap fruits re-
sulted.
During the period when late blight was most severe, 28 and 64 per cent
of the culls from the Phygon and no-treatment plots, respectively, had late
blight. At the same time only a trace of the culls from 
all of the other
treatments were infected with late blight. The high yield of the Phygon
treatments was attributed to the better fruit worm control from the use 
of
DDT rather than cryolite, as suggested by the manufacturer of Phygon.
All sprays in the Etowah plot resulted in yield increases of 60 to 105
bushels per acre, The compounds fell into the following four classes.rated
from greatest to least yield increases of marketable green-wrap fruit:
1,. Dithane D-14 (105 bushels) and Dithane Z-78 (101.3 
bushels)
2. Phygon spray (73.7 bushels)
3. Tribasic copper and Copper A (64 bushels 
each)
4. Liquid Parzate (60,3 bushels) 
and Parzate concentrate (59.7 bush-
els).
INSECTS of TOMATOES
Tomato Fruitworm
The tomato fruitworm, Heliothis armigera, also known as the corn ear-
worm and cotton bollworm, does severe damage each year to the fall tomato
crop in Alabama,
The adult of the tomato fruitworm is a moth with a wing expanse of
about l inches. Color of the moth varies. In general, the front wings
are light grayish brown, marked with dark gray irregular iines and with a
dark area near the tip of the wing, The rear wings are white with some dark
markings,
The worms vary greatly in color from a light green or pink to brown or
nearly black with lighter under parts. They are marked with alternating
light and dark stripes running lengthwise of the body. The stripes are not
always the same on different worms, but there is usually a double dark line
lengthwise of the body in the middle of the back, The head is yellow and
unspotted, and the legs are dark or nearly black. The moth lays her eggs
singly on leaves of the tomato plant, As the larvae hatch, they feed spar-
ingly while crawling over the leaves of the plant. They finally find their
way to the fruits, into which they cut holes and burrow, usually at the
stem end. A worm may feed on a single tomato until fully grown, or it may
move from one tomato to another, injuring several before it completes its
growth. The mature worm leaves the fruit and enters the soil, where it
changes to the pupal or resting stage. There may be several generations in
one season,
Potato Aphid
The most important aphid, or plant louse, of the tomato is the potato
aphid, Macrosiphum solanifolii,
The potato aphid when full grown is nearly one-eighth of an inch long,
It is.- a clear green or pink glistening .color. The insect overwinters as
the egg, which is deposited chiefly on roses. The insects may be found
regularly on the succulent parts of rose bushes in the spring. During the
summer winged forms fly to potato and tomato fields. A generation may be
developed every 2 or 3 weeks. Each unmated female may give birth to 50 or
more active nymphs in a 2-week-period, The tomato vine will become covered
rapidly with aphids.
The aphids suck the juices from the leaves and tender portions of the
plant
. 
The: most noticeable injury is the devitalizing of the blossom
clusters so that the blossoms fall and no tomatoes are set. The aphid may
also cause serious injury by infecting.tomato plants with virus diseases,.
Tobacco mosaic can be carried from one plant to another by this insect,
Severe stunting of plants may result from early infection with mosaic, and
the yield may be drastically reduced, In the fall the aphids move back to
roses or other favored overwintering plants. On these plants wingless,
egg-laying females develop, After mating occurs, the winter eggs are laid
on the -leaves and stems of the rose,
Tomato-Insect-Control Experiments
Two experiments were conducted in 1990 on control of tomato insects
on fall tomatoes
0 
A test at the North Alabama Horticulture Substation,
Cullman, included controls for both the aphid and fruitwormo An experi-
ment conducted on an Etowah County farm included only controls for the
tomato fruitworm,
6
Both experiments involved the use of insecticidal dusts. The dusts
were applied by hand-operated rotary dust guns. Eight applications of
dusts were made at weekly intervals during August and September. The
dusts were applied to give complete coverage of the plants. The rate var-
ied from 10 pounds per acre when the plants were small to 40 pounds per
acre near the end of the season. The dusts included 6 per cent zineb
(Z-78 formulation) for blight control The plots consisted of five rows
of tomatoes 50 feet long. The treatments were replicated four times and
were randomized, The yield data were obtained by harvesting worm-free
tomatoes from the three inside rows of each plot. The results of the
experiments are presented in Tables 3 and 4h
Table 3. Yield of Marketable Tomatoes Following Application of
Insecticidal Dusts for Fruitworm and Aphid Control, North Ala-
bama Horticulture Substation, Cullman, 
195G
Yield Increase over
Treatment
per acre no treatment
Bushels Bushels
No fruitworm insecticide;
aphicide only ......................... 96
Cryolite (50 per cent sodium
fluoaluminate) ................ ....... 119 23
Cryolite (50 per cent sodium
fluoaluminate); aphicide ............... 121 25
Methoxychlor, 5 per cent; aphicide .... ,. 182 86
DDD, 5 per cent; aphicide .............. 219 123
DDT, 5 per cent; aphicide ............ ,. 161 65
LSD, 5 per cent level 21
1/ All plots received dust containing 6 per cent zineb (Z-78 formulation)
for blight control. Treatments indicated as receiving aphicide were
dusted twice with 3 per cent nicotine sulphate for aphid control.
Table h Yield of Marketable Tomatoes Following Application of
Insecticidal Dusts. for Control of Tomato 
Fruitworm, Gilliland
farm, Etowah County, 1950
Treatmentl/ Yield Increase over
per acre no treatment
Bushels Bushels
None .. .,..... 
..... , .... 
79
Cryolite (50 pct, sodium
fluoaluminate) .............. ... 105 26
Methoxychlor5, pctP ..... 0.0....0 l.0 108 29
DDD, 5 pct 139 60
DDT, 5 pct. , ....................... o 99 20
LSD, 5 pct, level 29 
-
1/ All plots received two applications of 3 
per cent nicotine sulphate
dust for aphid control. Six per cent zineb (Z-78 formulation) 
was in
cluded in all dusts 
for blight control.
Aphids did not become numerous enough at any time during 
the season
to seriously affect the plants. Two applications 
of 3 per cent nicotine
sulphate dust 
resulted in a 
yield increase 
of only 2 bushels 
of market-
able tomatoes per acre, Table 3. The tomato plants 
in all plots in this
experiment were severely damaged by early infection 
with tobacco mosaic,
It is not known to what extent this disease was spread by the aphids. 
-
DDD was superior to the other insecticides for 
fruitworm controlA
An increase of 123 bushels per acre was obtained following its use 
at
Cullman and -60 bushels per acre on the Etowah County 
farm. These yields
were significantly greater than those resulting 
from use of any other
insecticidea Methoxychlor was the next best insecticide 
at both loca-
tions. There was an increase of 86 bushels per acre following 
its use
at Cullman, but only 29 bushels on the Etowah County 
farm, DDT was
significantly better than cryolite at Cullman where 
all treatments were
significantly better than no treatment, Only DDD and methoxychlor gave
significant control on the Etowah County farm,
SUMARY
Disease Control
1. Both 5 and 6.5 per cent zineb (zinc ethylene bisdithiocarbamate)
dusts gave good control of early and late blight and resulted in high
yield increases.
2. The 3.9 per cent zineb dust was inferior to 6.5 per cent zineb
dust in both disease control and yield, but it was better than no fungi-
cide in both trials 
in 1949,
3, Both 7 per cent zineb and 7 per cent metallic copper controlled
early and late blight, but they were toxic to tomato plants. They re-
sulted in lower tomato yields than did 5 per cent zineb in central and
northern Alabama in 
1950,
4. Six per cent metallic copper gave high yield increases at Fair-
hope through control of early blight when late blight was not present.
5. Phygon XL dust resulted in reduced yields at Clanton and gave
poor control of early blight.
6. Dithane D-14 spray resulted in reduced yields at Fairhope in
1948 and 1949, while controlling early and late blight. Liquid Parzate,
a similar compound, behaved in a similar manner at 
Clanton in 1950.
7. All materials tested in an Etowah County spray plot gave good
yield increases, All gave good late blight control except Phygon XL,
high yield from which was attributed to better fruit-worm control. The
compounds listed according to bushels of yield increase over that oftke
check plot were as follows: Dithane D-14 (105); Dithane Z-78 (1013),
Phygon XL (73.7), Tribasic Copper and Copper A (6)4 each), Liquid Parzate
(60.3), and Parzate Concentrate 
(59.7).
Insect Control
1. Aphids did not do serious damage to the tomatoes and control
procedures resulted in very low yield increases in the one-year test.
2, Significantly higher yields were obtained following the use of
5 per cent DDD than from any other insecticide tested.
3. Five per cent methoxychlor was significantly better than DDT or
cryolite at Cullman. It was not significantly superior to DDT and
cryolite on the Etowah County farm,
h. DDT was significantly better than cryolite at Cullman, but not
on the Etowah experiment,
5. All insecticides were significantly better than no treatment 
at
Cullman, while on the Etowah plots only DDD and methoxychlor were signif-
icantly better.
9