Group Title: Immokalee ARC research report
Title: Use of mineral oil sprays to reduce the spread of tomato yellows virus disease in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00094213/00001
 Material Information
Title: Use of mineral oil sprays to reduce the spread of tomato yellows virus disease in Florida
Series Title: Immokalee ARC research report - University of Florida ; SF79-1
Physical Description: 4, 3 leaves : ill. ; 28 cm.
Language: English
Creator: Zitter, T. A. ( Thomas Andrew ), 1941-
Everett, P. H. ( Paul Harrison ), 1927-
Florida Agricultural Research Center (Immokalee, Fla.)
Donor: unknown ( endowment )
Publisher: Agricultural Research Center, IFAS, University of Florida
Place of Publication: Immokalee, Fla.
Publication Date: August, 1979
Copyright Date: 1979
 Subjects
Subject: Tomatoes -- Diseases and pests -- Control -- Florida   ( lcsh )
Mineral oils   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Thomas A. Zitter and Paul H. Everett.
Bibliography: Includes bibliographical references (leaf 4).
General Note: Caption title.
General Note: "August, 1979."
 Record Information
Bibliographic ID: UF00094213
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: oclc - 406473346

Full Text





AGRICULTURAL RESEARCH CENTER
IFAS, University of Flori HU
Immokalee, Florida FEI


USE OF MINERAL OIL SPRAYS TO REDUCE MD/,-
\ OF TOMATO YELLOWS VIRUS DISEASE IN iTR .Or/da /

Thomas A. Zitter and Paul H. Everett1

Immokalee ARC Research Report SF79-1 August, 1979


This report summarizes efforts at controlling the spread of tomato yellows
virus (TYV), a newly recognized aphid transmitted virus affecting tomatoes grown in
Florida. The field experiment was conducted during the period January 23 and May 3,
1979, at the Agricultural Research Center at Immokalee. In addition to following
the movement of TYV in plots sprayed with oil and in plots not sprayed with oil
(control), yield data were taken from tomato plants grouped according to the time of
initial symptom expression and from noninfected plants. This study thus was related
to an experiment conducted during the fall season (Aug.-Dec.) 1978, when the effects
of TYV on tomato yields were first studied (2).


EXPERIMENTAL METHODS

S Tomato seedlings (Lycopersicon esculentum cv. Walter), which were to later
serve as virus source plants in the field plots, were started in the greenhouse at
AREC-Belle Glade on December 8, 1978. These seedlings were inoculated on January 3,
1979, with TYV using aphids which had previously fed on TYV infected plants. Seedlings,
from this inoculation, which failed to develop typical TYV symptoms were reinoculated
using the same procedure on January 17. The isolate of TYV used for both inocula-
tions was the same as that used in the fall experiment (2). All noninoculated tomato
seedlings were grown at ARC-Immokalee. These were seeded December 4, 1978, and a
backup seeding was made January 5, 1979. On January 23 both inoculated (virus source
plants) and noninoculated (virus free) seedlings were transplanted to field plots.
A small number of inoculated seedlings in the initial planting died. These were
replaced with virus inoculated seedlings on February 6 and 12. Noninoculated seed-
lings in the initial planting which died were replaced on February 22 with virus free
seedlings from the backup plants which had been seeded on January 5.

The experimental design consisted of two five-bed plants with each bed contain-
ing 152 plants. The two plots were located 600 feet apart. One plot received
weekly sprays of JMS Stylet-OilR (oil plot), the other received no oil sprays and
served as a control plot. Alternate plants set in the center bed (bed 3) of each
five-bed plot had been inoculated with TYV and acted as a source of the virus. This
arrangement resulted in a total of 76 TYV inoculated plants in each five-bed plot.
Spread of TYV from the source plants was dependent on natural movement of aphids
within the plots.


' 1Associate Plant Pathologist, formerly at Agricultural Research and Education Center,
Belle Glade, 33430 and now Department of Plant Pathology, Cornell University,
Ithaca, NY 14853 and Soil Chemist, Agricultural Research Center, Immokalee, FL 33934.









JMS Stylet-OilR was applied as weekly sprays to the oil plots at a rate equiva-
lent to 3 qt/100 gal water. The oil was applied as a separate spray using a boom
equipped with TX-5 nozzles and 400 psi pressure. A total of 11 oil sprays was
applied beginning February 6. Insecticide and fungicide sprays were applied as
needed but always 1 or 2 days after the oil spray. For this operation the sprayer
boom was equipped with conventional nozzles.

Virus readings were taken periodically during the experiment which lasted 14
weeks from transplanting of virus source plants td harvest. Tomato plants were
tagged when TYV symptoms were first noted, so that a record could be kept on virus
spread and what effect early, medium or late infection would have on fruit yield.
All plots were harvested on May 2 and 3. Fruits from the individually tagged plants
were grouped according to date of initial infection. Fruits from noninfected plants
were also grouped separately. Yield data include "puffy" fruit, which would have to
be subtracted from the total to obtain marketable yields.


RESULTS

Effect of oil sprays on spread of tomato yellows virus. The desired amount
of TYV inoculum required to study the spread of this disease in the oil and control
plots was unknown at the beginning of the experiment. It was arbitrarily decided
that alternating diseased and healthy plants in the center bed of each five-bed
plot would ensure sufficient inoculum to test the effectiveness of oil sprays. The
desired number of source plants in both the oil and control plots (76 plants) was
* not reached in either plot because of low efficiency of transmission experienced in
transferring the virus from stock plants. It is not uncommon for the efficiency of
aphids transmitting other yellowing-type virus diseases to be drastically reduced
during low light intensity winter months. Thus, instead of starting with 50% virus
infected plants in bed 3 for the oil and control plots, initial percentages were
actually 20 and 25%, respectively. These percentages of infected plants, however,
were sufficient to allow virus spread in spite of apparently low migrant aphid
populations.

The final percent infection and distribution by bed of TYV in both plots is
shown in Figure 1. The overall spread of virus in the oil plot averaged 9% compared
with 21% in the control plot. The total number of infected plants was greater in
beds 4 and 5 which were located downwind from the central inoculum source than in
beds 1 and 2, and there was considerable down-the-row movement of virus in bed 3.
The weekly movement of virus in bed 3, excluding the source plants,and in the other
four beds is shown in Figure 2. Oil provided a 10% reduction in spread in bed 3
and a 12% reduction when the other beds were combined. For the purpose of noting
the influence of time of infection on subsequent yield, the infection period was
divided into 3 phases: early, mid and late season.

It was shown that the weekly applied oil sprays were effective in reducing the
spread of TYV and that additional trials using varying rates of inoculum would be
warranted.

Effect of time of virus infection on tomato yield. The influence of time of
*infection with TYV upon the yield of 'Walter' tomato is shown in Table 1. The
effect on yield is expressed in kg and lb/plant and the number of 30 Ib boxes per
acre. Reduction in marketable yields was in direct response to the length of time
of infection following the natural spread of TYV. This same response had been
achieved in the fall experiment (2), but in the previous experiment the plants were
inoculated with TYV at fixed weekly intervals. The plants located in the field






-3-


receiving Stylet-OilR grew off better than plants located in the control, which is
S reflected in the overall better yields from the oil plot. This was probably a
location effect and not to the oil per se. However, the percent reduction in yields
due to virus infection in both plots was similar. In this experiment, as in the
fall experiment, infection occurring as late as 5 weeks before harvest resulted in
a substantial yield reduction (15-25% in the present experiment).

The effect of time of tomato yellows infection on tomato fruit size appears in
Table 2. The percent by weight of large and extra large fruit harvested from the
oil plots was consistently higher, presumably because of better growth in that field.
On the other hand, more mini, small and medium size fruit occurred in the control
plots. Early, medium and late virus infection did not seem to influence the separa-
tion of fruit into the various size categories, perhaps because infection was spread
over a longer period.

Influence of virus infection on fruit quality. The quality of fruit harvested
from infected plants from both the oil and control plots was adversely affected by
the length of time that plants were exposed to TYV. A substantial amount of "puffy"
fruit appeared for all virus expression periods, with most occurring in fruit from
plants infected during early or mid-season (Table 3). The amount of spoilage noted
among the "puffy" fruit was minimal over a 10-day observation period.


DISCUSSION

The use of mineral oil sprays to control the spread of many aphid transmitted
virus diseases has previously been reported in Florida (1) and elsewhere. The
virus diseases previously found to be controlled include such common tomato and pepper
viruses as tobacco etch virus and potato virus Y. These organisms belong to a group
of viruses which are transmitted by aphids in a stylet-borne, nonpersistent manner.
These terms imply that virus particles can be acquired and transmitted by aphids in
a matter of seconds, because the particles occur just below the leaf surface and
are carried close to the tip of the aphids' mouthparts. However, the virus is soon
lost by the aphid either through feeding or inactivation. The role that oils play
in preventing transmission remains unclear.

The tomato yellows virus has different properties than tobacco etch or potato
Y viruses. TYV particles occur much deeper in the plant tissue (phloem) and the aphid
must probe deeper to acquire the virus which takes a longer time (matter of hours).
TYV particles, once obtained, can be retained by the aphid for many days, thus
allowing a single aphid to infect numerous plants without the necessity of becoming
"recharged."

Although oil sprays have proven effective in controlling nonpersistent and
semipersistently transmitted virus diseases, control of circulative virus diseases
like potato leafroll virus have been unsuccessful.

In the present experiment, oil sprays do appear to reduce the spread of TYV
when applied weekly and using the application techniques which proved so successful
in controlling the spread of nonpersistent virus. Although the exact identity of
*tomato yellows virus is unknown, its transmission properties are those of a circu-
lative virus. The success in controlling virus spread may be attributed to the use
of improved oil formulations, method of application, the apparent involvement of
migrant aphid flights as the major method of spread, or a combination of any or all
of these factors.






-4-


SUMMARY

Weekly application of JMS Stylet-OilR proved so effective in reducing the spread
of tomato yellows virus that additional trials are warranted. This control was
achieved with a 5-6% level of inoculum within each of the two five-bed plots. The
results confirm that infection with TYV significantly reduces tomato yield especially
if the crop is infected early to midway through its development. As previously
reported (2), quality was affected, with TYV infection contributing to an increase
in "puffy" fruit.

In addition to continued evaluation of oil sprays for controlling the spread
of TYV, experiments using oils in conjunction with both soil and foliar applied
insecticides would be appropriate in light of the apparent circulative nature of the
virus.


REFERENCES

1. Zitter, T. A. and H. Y. Ozaki. 1978. Aphid-borne vegetable viruses controlled
with oil sprays. Proc. Fla. State Hort. Soc. 91:287-289.

2. Zitter, T. A. and P. H. Everett. 1979. Effect of an aphid-transmitted, yellow-
ing virus on yield and quality of staked 'Walter' tomatoes. Belle Glade AREC
Res. Rep. EV-1979-3.


Table 1.


Effect of time of tomato yellows virus symptom expression on yield of
'Walter' tomato with and without weekly applications of JMS Stylet-OilR


% reduction
Symptom Yield (includes "puffy" fruit) from plants
Treatment expression kg/plant lb/plant 30# box/A w/o symptoms

Oil spray Early 1.6 3.6 437 68
Medium 3.1 6.8 820 41
Late 4.2 9.7 1170 15
No virus 5.2 11.4 1379 0

No oil Early 1.4 3.2 385 58
Medium 2.4 5.3 641 31
Late 2.6 5.7 691 25
No virus 3.5 7.7 923 0


SEarly 0 to 6 weeks after transplanting.
Medium 6 to 9 weeks after transplanting.
Late 9 to 12 weeks after transplanting.









Table 2. Effect of time of tomato yellows virus symptom expression
on tomato fruit size, with and without JMS Stylet-OilR.


Symptom 1 Oil Fruit size
expression spray Mini Small Medium Large X-Large

- - - - % by weight - - - - -

Early + 1.0 0.6 19.9 50.8 27.5
-0.8 2.0 25.0 45.4 26.8
Medium + 0.6 2.4 18.3 42.4 36.0
-2.3 3.6 32.0 43.4 18.5
Late + 0.9 1.6 17.5 43.3 36.6
-1.7 2.6 27.2 40.4 28.1
No virus + 1.3 2.9 22.2 37.9 35.8
-0.3 2.4 31.6 40.5 25.2


1Early 0 to 6 weeks after transplanting.
Medium 6 to 9 weeks after transplanting.
Late 9 to 12 weeks after transplanting.












Table 3. Effect of time of tomato yellows virus symptoms expression on
"puffy" fruit in oil sprayed and control plots.


Symptom 1 Oil spray No oil
expression (weekly) spray Mean

- - - - % puffy fruit - - - -

Early 56 46 51
Medium 47 40 44
Late 29 19 24
No virus 10 8 9

Mean 36 28


1Early 0 to 6 weeks after transplanting.
Medium 6 to 9 weeks after transplanting.
Late 9 to 12 weeks after transplanting.







FIG. 1. EFFECT OF JMS STYLET-OILR
TOMATO YELLOWS VIRUS OVER


ON THE SPREAD OF
A 12-WEEK PERIOD


NO OIL


I-- OIL SPRAY -


70-

60-

50-

40-

30-

20-

10-

0


VIRUS SOURCE PLANTS
//


17mI


Hr


1 2 3 4 5
BED NUMBER


7
/
/
/


1 2 3


BED NUMBER


V


n


4 5


F r---i 1-1


- I


I-













FIG. 2. WEEKLY SPREAD OF TOMATO YELLOWS VIRUS DOWN THE BED AND
FROM BED TO BED WITH AND WITHOUT JMS STYLET-OIL


I___ EARLY __ __ MID .|- LATE
INFECTION INFECTION INFECTION





46
X5



S---- 6




x

----- -
~0


NO OIL
(BED 3 EXCLUDING SOURCE)


OIL
(BED 3 EXCLUDING SOURCE)


)NO OIL
(AVG BEDS


, OIL
(AVG


1,2,4 & 5)


BEDS 1,2,4 & 5)


1/23 2/13 3/8


DATE EVALUATED





0


3/27


4/2


4/17




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