Environmental spots (Weather Fleck)

Weather fleck, a leaf disorder in flue-cured tobacco, is caused by air Pollutants, primarily ozone (O₃), a secondary pollutant in the atmosphere. Ozone damages leaf tissue, resulting in small, irregularly shaped spots that begin as black, turn brown, typically less than 4 mm (1/8 inch) in diameter. The most serious losses occur just before or during the early stages of harvest, about 4-6 weeks after transplanting, when the lower leaves are maturing, though symptoms can appear at any growth stage. This disorder often follows prolonged rainy periods and during the active growth phase of tobacco when tissues are particularly succulent.

Figures 1 and 2 severe weather flecks symptoms resulting from ozone (O₃) exposure.

Management

Current control measures for Weather Fleck in tobacco involve cultural practices and selecting tolerant varieties. Cultural practices like proper plant spacing, appropriate irrigation, well-balanced fertilization, early topping, and sucker removal help produce leaves that are less susceptible to Weather Fleck.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The Canadian Tobacco Research Foundation (CTRF) is seeking a Plant Breeding and Biology technical assistant who will assist in the successful implementation of greenhouse, field, harvest, and post-harvest activities associated with the CTRF’s plant Protection, Agronomy and Breeding programs.

Please follow this link for the job description and more information related to the position.

If you are if you are interested in applying for this position, please outline your experience and qualifications in a cover letter and resume, be prepared to provide references, and submit this information to one of the following: 

Mail :

P.O. Box 322.

Tillsonburg, ON, N4G 4H5.

Email:

maythem.alamery@ctrf1.com

In person :

Unit 3, 500 Highway 3.

Tillsonburg, ON, N4G 4H5.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The Canadian Tobacco Research Foundation (CTRF) is currently seeking to fill a full-time position in its technical research department. This role involves overseeing all aspects of existing applied and basic research programs for flue-cured tobacco production located in Southwestern Ontario.

Please follow this link or the job description and more information related to the position.

If you are interested in applying for this position, please outline your experience and qualifications in a cover letter and resume, be prepared to provide references, and submit this information to one of the following:

Mail :

P.O. Box 322.

Tillsonburg, ON, N4G 4H5.

Email: maythem.alamery@ctrf1.com

In person :

Unit 3, 500 Highway 3.

Tillsonburg, ON, N4G 4H5.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The Canadian Tobacco Research Foundation (CTRF) is seeking a Technical
Research Assistant who will assist in the successful implementation of
greenhouse, field, harvest, and post-harvest activities associated with the
CTRF’s plant Protection, Agronomy and Breeding programs.

Please follow this link for the job description and more information related to the position.

If you are if you are interested in applying for this position, please outline your experience and qualifications in a cover letter and resume, be prepared to provide references, and submit this information to one of the following: 

Mail :

P.O. Box 322.

Tillsonburg, ON, N4G 4H5.

Email: maythem.alamery@ctrf1.com

In person :

Unit 3, 500 Highway 3.

Tillsonburg, ON, N4G 4H5.

 

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The CTRF is committed to supplying growers with information for the 2024 growing season. If you need assistance with identification of a greenhouse issue or general information related to tobacco production, please contact the CTRF. Please read through this crop news update to become familiar with pests, disorders and management methods that you may encounter this greenhouse season.

The 2024 greenhouse season will be starting soon. As the seed germinates and seedlings grow, pests, fertility and contamination due to drifting of pesticides may arise and affect the crop.  Algae, Black Root Rot, Pythium Damping-off Rhizoctonia Damping-off and Bacterial Soft Rot, are common occurrences in greenhouses.  These pests are highly controlled when trays have been cleaned and steam sterilized at 80ºC (176ºF) for 60 minutes, and when muck beds are adequately steamed at 82ºC (180ºF) for 30 minutes at a 15 cm depth.  For some pests such as Algae, Black Root Rot, Bacterial Soft Rot, and Pythium Damping-off in float trays, chemical control is not available, therefore, steam treatment is essential.

The following are some problems that may occur in the greenhouse during the growing season:

1-Uneven emergence

Uneven emergence (Fig. 1) may be related to seed quality, improper environmental conditions during storage of the seed, unknown genetic factors, exposure of the seed or the greenhouse environment to chemicals (i.e. un-rinsed bleach on trays), excessive algal growth on trays and other factors.  It is a good idea to keep a count of the number of seedlings through time in several trays across the greenhouse to get an idea of how emergence is progressing.

2-Algae

Thick mats of algae may develop on the surface of either float or dry trays, especially under cool and dim conditions (Fig. 2).  A number of different types of algae may form on trays depending upon which types were in the substrate used to fill the trays or which types were present upon the trays from previous seasons.  Blue-Green Algae are the most common algae in greenhouses and produce an oily-looking, blackish-green slimy layer on the tray surface.  Algae will cause oxygen levels in the media to fall and inhibit root growth, as well as compete with the plants for fertilizer.  In some cases Blue-Green Algae seem to be toxic to the seedlings, possibly through compounds they release or by promoting the formation of nitrites in the tray media.

There are no chemical treatments for algae control in tobacco greenhouses.  Algae are best managed by providing conditions as favourable as possible for seed germination and early seedling growth, so that the seedlings will establish quickly and outpace the formation of the algae on the media surface.  Following good tray fertilization practices is also essential because fertilization encourages algae growth.  Therefore, fertilizer should not be added to float tray water until the plants have reached the two-leaf stage.  For dry trays, fertilizer applications should not start until three weeks after seeding.

3-Rhizoctonia Damping-off and Target Spot

Rhizoctonia Damping-off is caused by the soil borne fungus Rhizoctonia solani, the same fungus that causes the tobacco diseases Target Spot both in the greenhouse and field and Sore Shin in the field.  R. solani also infects a large number of other cultivated crops.

With Damping-off (Fig. 3A), the fungus infects the stem at the soil line and rots the base of the plant causing plants to dry up or topple over.  With Target Spot (Fig. 3B), the fungus releases spores from the soil surface that drift up onto the leaves and causes infection that appears as water-soaked, rotting lesions.  Damping-off and Target Spot infected root fragments and leaves can attach to the Styrofoam and if the trays are not cleaned and steam sterilized before reusing them, these plant pieces carrying the fungus will allow it to establish in the trays and multiply, thus becoming a significant source of inoculum.  In muck beds, the infected plant parts fall onto the ground and in the presence of considerable moisture, the fungus grows and spreads contaminating more areas of the seedbed, which is often visible by patches of wilted and dead seedlings.  Steam sterilization of muck beds is an effective control for the disease.

If infection is found to be present in the greenhouse on seedlings, the disease can be controlled through applications of the registered fungicide Senator 50 SC (a.i. thiophanate-methyl 500 g/L).

4-Pythium Damping-off

Pythium Damping-off in greenhouses is caused by Pythium spp.  Some Pythium species produce swimming spores (zoospores) that can swim in water films on leaf surfaces, hydroponic media, float water and surface water (streams or ponds).  While doing so, they can also adhere to surfaces such as roots, seeds, soil particles or tray surfaces where they can then grow and spread.

Pythium spp. infection affects the vigour of seedlings and can result in poor quality transplants.  Infected seedlings show yellowing of lower leaves, stunting and wilting.  The roots of infected seedlings present a light brown discolouration in the early stages of infection and later they become dark brown with a slime looking appearance.  Infected roots fall off the trays leaving seedlings without a root system.

Pythium Damping-off is best controlled with steam sterilization of the Styrofoam trays.  Similarly, steam sterilization also controls Pythium Damping-off in muck bed greenhouses. Pythium Damping-off can be prevented from infecting seedlings and spreading in greenhouses by not using surface water sources (e.g. ponds, creeks, etc.) to fill float beds or to irrigate seedlings, ventilating greenhouses as much as possible, keeping the trays or seedbed surface as dry as possible by the evening, promoting good drainage of the muck bed, using recommended seedling rates and avoiding high plant populations, and removing infected plants or trays from greenhouses.  The fungicide Ridomil Gold 480 SL (a.i. metalaxyl 480 g/L) is the only fungicide registered for Pythium Damping-off control, however, the fungicide cannot be used in float tray greenhouses. Ridomil Gold 480 SL must be applied within 72 hours (3 days) prior to seeding.

5-Black Root Rot

Black Root Rot is caused by the fungus Thielaviopsis basicola, which infects tobacco and many vegetable crops, ornamentals, and field crops.  Most of the Black Root Rot occurrences in tobacco reported over the years have originated in the greenhouse, particularly when trays older than five years are used.

Black Root Rot infection occurs in trays when infected roots penetrate the Styrofoam crevices and remain behind when seedlings are pulled from the trays (Fig. 4A).  Also, infected root fragments can be left behind on tray surfaces.  If the trays are not cleaned and steam sterilized, the fungus thrives and builds in inoculum potential from year to year and may eventually contaminate most of the trays in a greenhouse.  Black Root Rot infected seedlings (Fig. 4B) have very few healthy roots and perform poorly in the field after being transplanted.  These plants usually show pale green leaves and yellow discolouration of lower leaves and will be stunted and/or wilted.  Fields with Black Root Rot infected seedlings tend to be uneven throughout most of the growing season. Black Root Rot can also occur in muck bed greenhouses.  There are no fungicides registered to control Black Root Rot in the greenhouse or in the field.  Steam sterilization is the most reliable method to control the disease.

6-Bacterial Soft Rot

Bacterial Soft Rot is caused by several bacteria with Pectobacterium carotovorum (previously Erwinia carotovora) being the most important. The disease is favorably influenced by several factors including high nitrogen levels, extended periods of warm, wet, overcast weather conditions, high humidity, long periods of leaf wetness and plant injury (by stress or wounding).

The disease infects tobacco seedlings in both dry and float trays and has the potential to destroy large numbers of plants in a relatively short period of time. Initially, the bacteria colonize wounded tissues, organic matter, and debris in trays.  Leaves touching the surface of a tray can become infected and the rot can spread through the petioles into the stem.  Debris and leaves infected by P. carotovorum appear necrotic and slimy (Fig. 5). Systemic infections, which arise when the bacteria move from previously infected plant parts, debris, or wounded tissues into healthy plant parts, results in the darkening of stems. This stem discoloration tends to primarily move up one side of seedlings (Fig. 6), hence the disease name “Blackleg”.

There are no control agents registered for the control of Bacterial Soft Rot in tobacco greenhouses. Removal of trays with the diseased seedlings from the greenhouse and replacing them with blank trays is the best control in this situation.  Some control practices include, not over-fertilizing, keeping the foliage of the seedlings as dry as possible, and ventilating the greenhouse adequately to keep the humidity level down. When clipping begins, keep leaf debris from the clipper out of the beds and avoid clipping when the leaves are wet.

7-Tobacco Mosaic Virus

Tobacco Mosaic Virus (TMV) is most serious when infection starts in the greenhouse because the disease is rapidly spread when clipping the plants.  Transmission of the virus in this manner can lead to an entire crop being affected.  Unfortunately, TMV almost never produces any visible symptoms while the seedlings are in the greenhouse, instead first being noticed after the plants have already been put out into the field.  Trays from any greenhouse suspected of being contaminated with TMV should be disposed of and anything which may have come in contact with the infected plants must be disinfected with a strong bleach solution (i.e. diluted 1:1 with water).  Particular attention must be paid to the disinfection of clippers. 

8-Pavement ants

Pavement ants (also called Harvester ants) can occasionally be a problem in muck bed greenhouses.  These ants collect seed and seedlings from the bed and may be quite damaging by thinning down the plant stand (Fig. 7).  There are no insecticides registered for Pavement ants control in muck bed greenhouses.  Laying out a bait of corn meal for the ants has shown some promise as they prefer it as a food source compared to tobacco seed.

9-Chilling injury

Chilling injury shows up as a cupping of the cotyledons and leaves (Fig. 8).  Although not usually severe enough to be fatal to the seedlings, it can set them back and allow other problems, such as algae on trays, to be more damaging than they would otherwise be.  To minimize chilling injury, keep an eye on greenhouse temperatures, especially in areas where cold drafts can occur.  It is important to note that chilling injury can also occur after a large shift in cooler temperatures in addition to the absolute minimum temperature.

10-Heat injury

Heat injury occurs when warm and sunny conditions occur during germination of tobacco seedlings. Temperatures above 37°C (98.6° F) in the greenhouse can severely injure or even kill transplants.  This type of injury is more often seen on dry trays and dryness of the soil media exacerbates the injury. When heat injury occurs, typically the older leaves of the seedlings collapse and turn brown (Fig. 9). If the growing point of the seedlings is not damaged and is still active, seedlings may recover normally. If the growing point is damaged, plants may not recover or if so, they can produce excessive suckers.  To avoid heat injury, make sure to lower greenhouse vents/curtains once temperatures begin to approach the upper 20’s (20-25° C) (70-80°F).

11-Phosphorus deficiency
Phosphorus deficiency is common in rapidly growing float plants where a low phosphate fertilizer has been used.  Symptoms look very similar to early Target Spot and appear as small, dark green water-soaked spots on the leaf surface.  Control is achieved by applying fertilizer with a higher phosphorus analysis.

12-Spray drift from field operations
Tobacco seedling injury in greenhouses from drifting sprays in the field is becoming more common.  Being aware of what is going on in the vicinity of the greenhouse and taking the appropriate measures with vents and fans to minimize the entry of outside air when spraying operations are occurring in fields nearby, will help minimize damage caused by spray drifts.

Always read the label before applying a pest control product!

More detailed information about Algae, Black Root Rot, Rhizoctonia and Pythium Damping-off , Bacterial Soft Rot and Tobacco Mosaic Virus can be found in this section of the CTRF website.

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Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The CTRF is holding an “Open House” on Thursday, December 14, 2023, between the hours of 8:30 a.m. and 12:00 noon.  Please stop by and look at the cured leaf samples of registered and promising varieties that will be on display.  Handouts on the performance of the registered varieties will be available.  The CTRF’s plant pathology will have a display in CTRF’s lab that highlights some of the research that was conducted this year.  Click here for the program and directions.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The agronomic performance data for the new registered variety CTH274, in addition to a summary of the main registered varieties, can be viewed on the CTRF Plant Breeding website.

The CTRF established plots of the most commonly grown flue-cured tobacco varieties in Ontario to compare performance. If you have questions, please contact the CTRF.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

To provide an update on the CTRF activities for 2023, the Plant Breeding, and Plant Protection programs have prepared research updates which can be found in the research portion of the CTRF website. By following the links, you can take a look at some of the research that the CTRF is conducting and some of the results from the experiments.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) launched the  Ontario Crop Protection Hub, an official online Crop Protection resource for all agricultural commodities produced in Ontario, tobacco included. With this online resource, OMAFRA will no longer publish printed versions of Protection Guides for all crops. For tobacco, the previous Crop Protection Guide was Publication 843 Flue-Cured Tobacco Crop Protection Guide.  

The hub (online resource) for tobacco has two components: One component that contains supporting information for flue-cured tobacco, can be accessed using the link :

https:// cropprotectionhub.omafra.gov.on.ca/supporting-information/flue-cured-tobacco-supporting-information

The second component refers to flue-cured tobacco pest management and crop protection options available for flue-cured tobacco. This information can be accessed using the link. 

https:// cropprotectionhub.omafra.gov.on.ca

The OMAFRA Crop Protection Hub for tobacco includes all products registered for use on tobacco in Canada. Contractors may have specific requirements regarding certain control products used on tobacco. Therefore, growers should check with their contractor as to their requirements.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com

Progress of Seedlings in Greenhouses

The 2023 greenhouse season is progressing, and it has been characterized by few warm days and many cool and cloudy days. Nevertheless, most greenhouses have good seed germination and seedling uniformity. Based on the greenhouses that the CTRF has visited, seedlings between farms do vary in size depending on the type of production method being used and when seeding was started.

Preventative applications of the fungicide for the control of Rhizoctonia Damping-off in greenhouses has occurred, and clipping is underway.

Some of the problems that have been reported so far include algae on media surface (float trays) and chilling injury.

Effects of  Algae on  Seedlings in Trays

Certain algae present on the surface of tray media can affect seedling emergence and establishment. Two situations are usually seen in these cases, one where the seedlings are not able to emerge through the algae and the other being where the seedlings emerge but cannot establish themselves before succumbing to the algae and dying (as shown below).

Cool and cloudy weather conditions are ideal for algae growth, and there are no chemical treatments for algae in tobacco greenhouses. Conditions that are optimum in the greenhouse for rapid seed germination and early seedling growth help seedlings to outpace the algae so that the seedlings become large enough that the algae can no longer affect them.  As seedlings grow, the canopy will close over and shade the media surface, therefore, reducing the negative effects of algae. At this time, in some greenhouses, the after-effects that algae can have on young seedlings in trays are evident and are characterized by significant stands reduction and uneven seedling growth.

Chilling Injury

Chilling injury is being observed in some greenhouses. Chilling injury is caused by exposure of the seedlings to a large variation in air temperature, such as when ventilation occurs on a very cool but sunny day or at night when the temperature outside is quite cold and the temperature drops significantly in the greenhouse because the heaters do not have enough capacity to maintain the set temperature.

The initial symptoms of chilling injury are often a bright yellow colour in the growing point of the seedling and upward cupping of the leaves, as shown in the image below.

As the seedlings become larger and the leaves grow out, some leaves become malformed, cupped, and have a distinct yellow/white discoloration. Seedlings do outgrow chilling injury without any ill-effects on the seedlings when transplanted to the field. However, when chilling injury affects the seedling growing point, the plant responds by producing lateral growing points, (suckers), which affects the quality of seedlings.

Clipping Tobacco seedlings in Greenhouses

Currently, clipping of seedlings is taking place in most greenhouses. Be on the lookout for the occurrence of Bacterial Soft Rot (also known as Blackleg), a disease that occurs in both float and dry trays greenhouses during clipping. Bacterial Soft Rot starts when leaf debris fall back onto the seedlings from the clipper, becoming a food source for the  bacteria.  Factors such as, warm temperatures, high humidity, extended periods of leaf wetness, high nitrogen levels and plant injury (by stress or wounding) contribute to  Bacterial Soft Rot spread and outbreaks in greenhouses.

Bacterial Soft Rot infects tobacco seedlings in both dry cell and float trays and has the potential to destroy large numbers of plants in a brief period of time. Initially, the bacteria colonize wounded tissues, organic matter, and debris in trays. Leaves touching the surface of a tray can become infected and the rot can spread through the petioles into the stem of the seedlings. 

Infected seedlings transplanted into the field may not become well established and may not survive. There are no control agents registered for control of Bacterial Soft Rot in tobacco greenhouses. Removal of trays with the diseased seedlings from the greenhouse and replacing them with blank trays is the best control in this situation.  Other practices for control include trying to keep leaf debris from the clipper out of the beds, not clipping when the leaves are wet, not over-fertilizing, keeping the foliage of the seedlings as dry as possible, and ventilating the greenhouse adequately to keep the humidity level down in the greenhouse.

Tobacco fields Soil fumigation

Soil fumigation in preparation for the season has started.  It is important to remember that cooler temperatures and rainy conditions that have been occurring lately may impact the performance or efficacy of the soil fumigants.

When applying fumigants, ensure that the soil temperature and soil moisture are in accordance with the label requirements/recommendations for the specific soil fumigant that is being used.  As we get closer to planting season, please note that different soil fumigants may require different time intervals between fumigation and transplanting.

Please follow the label associated with the soil fumigant that was used and refer to the product label for more information.

Post prepared and sent by Canadian Tobacco Research Foundation

Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address:  http://ctrf1.com