Tomato Technical Bulletin
Syngenta’s Crop Management Strategies Help Protect Your
Superior Vegetables a Reality
Syngenta/ROGERS® Brand is committed to providing
growers with the highest-quality vegetable seed genetics for a
wide range of greenhouse growing systems and environments.
Towards this end, we invest considerable
resources in our seed production process, from breeding all the
way through to delivery. Syngenta/ROGERS’ greenhouse vegetable
breeding efforts are founded on global synergies in Holland,
France, Spain, Morocco, and the United States, and we have a
full staff of scientists and researchers as well as an unmatched
germplasm base. Once a tomato variety has been developed, our
optimized seed production and quality assurance protocols (which
are supported by state-of-the-art seed physiology laboratories)
help ensure that only the best-germinating, highest vigor, and
disease-free seed goes into a ROGERS package.
We believe our commitment to quality positions
ROGERS to be your preferred greenhouse vegetable seed supplier.
Working together, we can make superior vegetables a reality.
Tomato Disease Prevention and Detection Program
Greenhouse tomato production creates an
environment that is especially conducive to some seed-borne
diseases. Therefore, it is important that seed suppliers take
measures to help ensure that the seed purchased by their
customers does not contain any of these diseases.
Bacterial Canker in Mexico Greenhouse Tomato
Several diseases in particular can be
troublesome, even devastating, to tomato crops that grow for
seven months or longer in greenhouses. These diseases include
bacterial canker caused by Clavibacter michiganensis
subsp. michiganensis, tobacco mosaic caused by tobacco
mosaic virus (TMV), tomato mosaic caused by tomato
mosaic virus (ToMV), and pepino mosaic caused by pepino
mosaic virus (PepMV). The causal organisms of
these diseases, once established, can spread very quickly and
extensively on tools and hands during the daily vine pruning,
training, and other handling that occurs with tomato plants.
In greenhouse tomato productions in Mexico,
bacterial canker seems to be the most prevalent of the four
diseases cited above. It is caused by a bacterium that can be
moved easily from plant to plant during handling, and can even
be taken up into the plant through the roots. Once inside the
plant, the bacterium will begin to increase in population, and
will eventually move into the vascular tissue. Over time it will
likely spread up the stem and into the outer foliage. It can
move into or otherwise infect the flower, causing possible fruit
abortion, and reduced yield and fruit quality. The optimal
temperature for growth of the bacterium is about 27 ºC (81 ºF).
Detecting Bacterial Canker
Early detection and diagnosis are the keys to
controlling bacterial canker. The bacterium goes through a
fairly lengthy process of increasing in population before
entering the vascular tissue, so initial symptoms may take weeks
to develop. As a result, infected seedlings may not show
symptoms until several weeks after having been transplanted.
Symptoms from new infections on older plants may not appear for
weeks after infection, depending on temperatures, the amount of
inoculum, and the location of the introduction of the inoculum.
Leaf symptoms may begin as a yellow-green color
with browning along the margins, which most likely will be
accompanied by wilting and distortion of the growth. The veins
commonly have a yellow to brown discoloration if the outer
epidermis is removed. A milky white cloud of bacteria often
exudes out from the cut end if the leaf petiole is placed in
water. The bird’s eye white spotting fruit symptom that is
characteristic of fruit infection in the open field may not
develop on greenhouse tomatoes unless there is splashing or free
water on the fruit surface. As the infection progresses, a
distinct canker can develop on the stem and severely infected
plants may be killed.
Diagnosing Bacterial Canker
Rapid diagnostic tests such as Immunostrips and
ELISA kits can be used to help confirm the identity of the
disease. Additionally, samples for diagnosis can be sent to a
lab where the bacterium can be isolated from the tissue, and
characterized by such tests as PCR, immunofluorescence, and
pathogenicity. Laboratories in the U.S., however, must now have
an APHIS PPQ 526 permit in order to receive diseased samples
from international sources.
Control measures, such as increased sanitation
and perhaps even the exclusion or eradication of infected
plants, should be implemented immediately if the presence of
bacterial canker is confirmed. It should also be noted that the
bacterium can survive for months in infected plant debris and
soil, and for weeks on surfaces in the greenhouse. Therefore,
these need to be thoroughly sanitized or cleaned before the
introduction of a new tomato crop.
Syngenta/ROGERS – Protocols for Ensuring Healthy
Syngenta/ROGERS takes the responsibility of
providing customers with healthy seed very seriously. Beginning
at the earliest stages of production, we implement a series of
protocols that help ensure the quality of our greenhouse tomato
seed. Various elements of our program are outlined below.
Produce crops in the greenhouse to allow for
better control of the environment. As compared to open field
production, greenhouse production also reduces the
likelihood of introducing diseases.
Produce crops under strict sanitation and
pest control conditions that include:
General disinfection of the greenhouse,
including spraying with a disinfectant.
Soil disinfection with fumigation.
Continuous disinfection of shoes and
hands upon entering, including disinfection mats and
buckets with bleach.
Sanitation of tools during the pruning
and staking of plants. This can include using bleach,
milk, quaternary ammonia, or other compounds.
Using clean trays for transplants.
Using clean media for transplant trays.
Applying pest and disease control sprays,
and other measures, as needed.
Provide personnel trained in pest and disease
identification to inspect each seed crop a minimum of three
to four times during the growing cycle. The advantages of
our inspection process include:
It allows for a complete evaluation of
Plant health in general is monitored, and
adjustments can be made to the fertility program and
plant architecture as needed.
It provides for control of diseases that
are not seed transmitted, but could affect plant health
and the resulting seed quality.
It is pro-active for detection of
possible new diseases.
Extract the seed, soak it in disinfectants,
and rinse and dry it under controlled conditions.
Sample the seed for disease testing using a
method to get a representative sample.
Test each lot of greenhouse tomato seed for
the following diseases:
Bacterial Canker – 50,000 seeds
Bacterial Speck – 30,000 seeds
Bacterial Spot – 30,000 seeds
PepMV – 3,000 seeds
TMV – 3,000 seeds
ToMV – 3,000 seeds
By Wayne Wiebe, Ph.D., Seed Technology Leader
common physiological disorders
affecting tomatoes grown under passive greenhouse conditions in
Over the past decade, tomato growers throughout
Mexico have increasingly adopted methods for cultivating
tomatoes in a protective growing environment. This is because it
allows them to overcome unfavorable climatic conditions, protect
their crops from vectors spreading diseases and viruses, and
helps reduce the incidence of physiological fruit disorders. In
a recent report presented in Mexico, the Asociacion Mexicana de
Productores de Hortalizas en Invernaderos, A.C. (AMPHI)
estimated that by the end of 2005 there would be close to 3,000
hectares of vegetable crops in Mexico growing under some type of
A majority of the total greenhouse acreage
planted in Mexico is devoted to tomatoes, including beefsteak,
saladettes, and cocktail types. In part, this is because
greenhouse-grown tomatoes are often considered to be more
profitable than field-grown tomatoes or other conventional
Just as with open field tomato production,
however, there are common physiological disorders that can
affect the harvest quality of tomato crops. A well-planned
greenhouse management program can often minimize the negative
impact of these disorders, especially when compared to a tomato
crop produced under open field conditions.
Several of the most common disorders affecting
greenhouse tomato crops are provided below, along with a review
of the most commonly accepted best practice crop
management techniques for their prevention (this is not an
exhaustive list of techniques).
the initial challenges of growing tomatoes in the warmer
climates of northwestern Mexico are the extreme variances in
day and nighttime temperatures experienced during the
transplanting and early flowering periods. It is common for
daytime temperatures inside a passive greenhouse to exceed
40 ºC (104 ºF) High temperatures such as these can inhibit
pollination and fertilization, leading to blossom drop and
the subsequent abortion of flowers. Other factors that
commonly contribute to early flower drop are excessive
nitrogen fertilization and high relative humidity.
Management Tips for Prevention of Blossom
varieties based on growing conditions. The optimum
temperatures for tomato pollination are between 21ºC (70 ºF)
to 28 ºC (82 ºF), with an optimum relative humidity around
70%. Extended periods of relative humidity under 60% may
result in the stigma drying out to that extent that the
pollen cannot stick to it. At relative humidity levels above
80%, the pollen grains stick together and do not disperse
well, thus causing poorly pollinated flowers.
ventilation and crop cooling. Effective ventilation is
critical to helping reduce the air temperature inside the
greenhouse. By moving air through the crop, the plants can
become active and increase their rate of transpiration, thus
helping create a cooling microclimate inside the greenhouse.
The inside temperature of a passive greenhouse will never be
cooler than the outside air temperature, so it is wise to
adopt shade curtains or micro-foggers as a means to reduce
the inside greenhouse temperature.
nutrients. High levels of nitrogen (N) can contribute to
early and excessive vegetative growth and throw plants out
of balance. It is recommended that growers consult with a
crop nutrition specialist to develop a fertilization program
that provides the proper quantity and ratio of the nutrients
required for each specific stage of plant and fruit
development. Levels of boron must also be sufficient and
approved hormones. The use of approved fruit setting
agents and hormones can aid the grower to set early flowers
under extreme heat conditions. These fruit are not usually
of export quality, but the technique is useful as its helps
balance the plant in its early stages of development and can
contribute to an overall better quality crop.
with bees (Bombus terrestis).
Use a minimum of four hives per hectare. Bees will not work
under extreme temperatures, so in extremely hot conditions
mechanical means such as vibrators should be used to
Fruit showing graywall in center pith area*
Gray wall is commonly observed in west Mexico
and the northern coastal Baja tomato growing areas during
periods of low light and morning fog, and during the winter
and spring tomato production windows.
The exact cause of gray wall is elusive. The
fruit defect is associated with a wide variety of
environmental conditions including, but not limited to, high
nitrogen, low potassium and compacted soil conditions or
growing medium. TMV, certain bacteria and fungi are also
thought to be contributing factors to the development of
Also called blotchy ripening, gray wall
symptoms usually appear on immature tomato fruit as blotchy
gray or brownish-gray spots. As the tomato matures to red,
the discolored areas remain gray or turn yellowish,
resulting in fruits that do not ripen evenly. The dark brown
tissue can also be seen in the walls of the tomatoes when
they are cut open, making them less desirable to consumers.
Management Tips for the Prevention of Gray
gray wall tolerant varieties
Syngenta/ROGERS offers tomato growers a wide selection of
new commercial indeterminate tomato varieties that are
widely adaptable and have shown tolerance to gray wall. One
such variety is Silvana (41564).
only varieties that offer TMV resistance
Academic research indicates a greater incidence of gray
wall in non-TMV resistant varieties.
An awareness of predicted cold fronts or rainy conditions
allows the grower to implement early preventative crop
management steps that may help reduce gray wall. Such steps
may include de-leafing above the bottom truss to allow more
light penetration to the crop, increasing K fertilization
levels, and reducing the frequency of irrigations. Growers
can stay apprised of weather conditions by watching local
television reports and viewing such websites as
or MICRO CRACKING (Crazing)
Mexico, russeting in passive greenhouses is common. A close
examination of tomatoes with russeting reveals fruit with
hundreds of minute cracks on the surface, creating a dull
red color and rough texture. In addition to the generally
undesirable appearance, the shelf life of affected tomatoes
is greatly reduced due to water escaping through the minute
surface cracks. Upon losing 5% of their weight from water
loss, tomatoes shrivel, become soft, and break down.
Management Tips for the Prevention of Russeting
conditions that cause condensation on the fruit.
Consider improving poorly ventilated greenhouses.
significant temperature and humidity fluctuations. In
the morning, after the suns rises, increase the greenhouse
temperature slowly to avoid a rapid decrease in ambient
humidity and a rapid increase in inside temperature. Use
thermal curtains or shade cloths if available.
a favorable microclimate. Increase the total head
population of the crop up to 5% by leaving an extra shoot
during a cropping period conducive to russeting. This can
help create a favorable microclimate inside the greenhouse.
irrigation schedules. Better manage your crop irrigation
schedule by using tensiometers. Consider revising your
optimum K levels. Maintain K levels at the optimum
levels for the appropriate stage of your crop’s development.
BLOSSOM END ROT
Fruit on plant showing BER on sidewall*
Cross section of fruit showing internal BER*
Fruit showing symptoms of BER: top left
fruit showing mild BER, others showing
Blossom end rot is one of the most common
fruit disorders. Best known to tomato growers worldwide by
its symptoms, tomato BER is not caused by an organism but is
rather the result of an insufficient amount of calcium
reaching the blossom end of the tomato fruit to maintain
cell integrity. It usually appears as a light tan, brown, or
black sunken area on the outside of the blossom end of the
tomato fruit, but sometimes occurs on the inside of the
fruit as well. It is not soft, but firm, and has a leathery
Although adequate calcium may be applied in
the nutrient solution, insufficient water may prevent it
from reaching the fruit. If plants have reached the point of
wilting due to stress caused by high temperature (greater
than 28 ºC), high humidity, rapid plant growth, excessive
salinity, or high nitrogen, it is very difficult for
nutrients to reach the fruit and they may show the symptoms
Management Tips for the prevention of Blossom
varieties with a strong root system.
Syngenta/ROGERS’ Charleston, Silvana, Pascaline, and Tsarine
varieties are good options.
Avoid the use of excess N, especially in the ammonium form,
as it increases the demand for calcium.
using grafted tomato transplants.
Many Mexican greenhouse growers are adopting this crop
management technique as a means to control BER. Rootstocks
can offer the scion variety a greater root mass and greater
root pressure, thereby providing more efficient
translocation of water and nutrients up the tomato plant to
the tomato fruit during stressful growing conditions late in
the growing season.
wide fluctuations in your irrigation program.
Use tensiometers to monitor the need for irrigation.
Consider applying high quality, well balanced foliar
nutrients sprays to complement your fertilization program.
Remove and discard any immature fruit that
show BER symptoms. Once a fruit has blossom end rot, it will
not go away.
Plan for Success
Unlike field-grown tomatoes, the complex cropping
requirements of greenhouse tomatoes require regular management
and attention. There are no simple formulas for successfully
raising greenhouse tomato crops, but there are several important
management steps growers can take to increase the chance of a
strong harvest. Taking the time to create a well thought out and
comprehensive crop management program is one important factor.
It is also important to stay vigilant and anticipate fruit
disorder problems before they occur.
J.B, R.E. Stall, and T.A. Zitter, editors, Compendium of
Tomato Diseases, The American Phytopathological Society,
Douglas, Greenhouse Crops in
North America: A Practical Guide to Stonewool
Estevez, Juan Carlos,
en el sur de Sonora,
Richard, Greenhouse Tomato Handbook, Mississippi State
University Cooperative Extension Service, 1997.
Greenhouse Tomato Proceedings,
American Society for Horticultural Science, 1995.
Brad and Wayne Wiebe, Tomato Diseases: A Practical guide
for Seedsmen, Growers, and Agricultural Advisors, 1997.
Allen and Vicente Zamudio, Field Trial Observations and
Research, Syngenta Seeds, Inc., 2000- 2005.
By Allen Gill, Syngenta Greenhouse Business
*Photo credits: Dr. Stephan M. Olsen, Professor of
Horticultural Science, North Florida Research and Education
Center, Quincy, Florida