How to Manage Pests
UC Pest Management Guidelines
Tomato
Bacterial Speck
Pathogen: Pseudomonas syringae pv. tomato
(Reviewed 1/08,
updated 1/08)
In this Guideline:
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Bacterial speck appears as dark brown to black lesions of
various sizes and shapes on leaves, fruit, and stems. Tissue adjacent to the
lesions is initially yellow. Leaf lesions are frequently concentrated near margins,
causing extensive marginal necrosis (tissue death). Lesions
on immature fruit are slightly raised and small, varying in size from tiny flecks to 0.125 inch
(3 mm) in diameter and cause raised
black spots on mature fruit. Fruit lesions are superficial, seldom penetrating more than a
few cells deep.
The bacteria survive in soil, in debris from diseased plants, and on
seeds. Infection is favored by cool, moist weather. The pathogen is spread by
splashing rain or sprinkler irrigation. Disease progress is stopped during hot
weather. In severe cases, infected plants are stunted, which may result in a
delay in fruit maturity and yield reduction.
Cultural controls and
copper spray generally provide adequate control of bacterial speck in early
planting.
Cultural Control
Delay planting in spring to avoid exposing tomatoes to cool, wet
conditions that favor disease development. When the disease appears, change
from overhead to furrow irrigation. Do not plant tomatoes in a field previously
planted to tomatoes that developed the disease; instead rotate with a nonhost
crop such as small grains or corn.
There are two races in
California: Race 0 and Race 1.
Many varieties are resistant against Race 0 but none currently possess
resistance against Race 1 and the occurrence of this race is increasing
throughout the state.
Organically Acceptable
Methods
Cultural control is acceptable for use on organically certified produce.
Monitoring
and Treatment Decisions
Copper-containing bactericides provide partial disease control. Timing
is critical. Apply before rainfall and repeat at 10- to 14-day intervals when
cool and moist conditions prevail. Copper is strictly a protectant and must be
applied before an infection period occurs. One or two treatments are usually
enough to protect tomatoes during the most susceptible stages of growth.
Spraying can stop when temperatures move into the 90° F range.
| Common name |
Amount/Acre** |
R.E.I+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| The following
materials are listed in order of usefulness in an IPM program, taking into
account efficacy. When choosing a pesticide, also consider information
relating to environmental impact.
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| A. |
COPPER HYDROXIDE |
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(50% copper equivalent) |
2 lb |
24 |
0 |
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MODE
OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
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| B. |
COPPER HYDROXIDE |
1.5–2 lb |
24 |
0 |
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MODE
OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
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...PLUS... |
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MANCOZEB |
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(Dithane M-45) 80WP |
2 lb |
24 |
5 |
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(Dithane F-45) 37F |
1.6 qt |
24 |
5 |
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(Penncozeb) 75DF |
1–1.5 lb |
24 |
5 |
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MODE OF ACTION GROUP
NAME (NUMBER1): Multi-site contact (M3)
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COMMENTS: The addition
of mancozeb increases the efficacy of copper. Check with your processor
concerning allowed materials and rates. Be sure to follow label directions on
all products when making a tank mix; the most restrictive label precautions and limitations must be followed. |
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UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Diseases
R. M. Davis, Plant Pathology, UC Davis
G. Miyao, UC Cooperative Extension, Solano/Yolo counties
K. Subbarao, USDA Agricultural Research Station, Salinas
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the disease section:
B. W. Falk, Plant Pathology, UC Davis
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