Farm visits and calls conducted by CTRF indicate that nitrogen deficiency is not uncommon in tobacco this season, which is not surprising considering the excessive rainfall experienced so far. For example, weather data from Environment Canada shows in the Tillsonburg area June brought in a total of 159.4 mm (compared to 88.8 mm normal) and July had 150.2 mm compared to 96.2 mm normal).  Moreover, in some cases the rainfall was experienced daily during these two months.  Under such conditions, nitrogen losses can occur through soil erosion or leaching below the root zone and soil type impacts the extent of these losses.

Nitrogen (N) is a critical nutrient for producing good yield and leaf quality of flue-cured tobacco. Stunted growth is the first signal for nitrogen deficiency, and is followed by phenotypic symptoms, including pale, green coloration of the lower leaves.  Since nitrogen is a mobile element and the plant responds to a deficiency by moving the nutrient away from older leaves to younger leaves, the plant symptoms begin on the older lower leaves and progress up the plant if the deficiency continued. The color will change to a light yellow and will become progressively whiter (Figure.1 &2).

Adding N as a corrective measure is the proper solution considering the plant stage, but soil type and previous crop management must be considered when you are making the decision to apply additional nitrogen to your crop since excessive amounts of nitrogen may show no yield benefit and can reduce cured leaf quality and produce cured leaf with unbalanced chemistry. Other negative consequences may be increasing soil acidity, delayed maturity, and increased weed and sucker problems.

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The majority of the crop was planted in May, with some crops being planted in early June. Currently, most crops appear to be off to a good start, and cultivation is now occurring. Not many problems have been reported in fields yet, however, there have been a few reports of nematode, chill injury, and a case where one of the fertilizer bands at planting was too close to the plants and caused an injury. 

 There have been reports of Blue Mold occurrence on tobacco from the United States, where the disease has been recently reported in Pennsylvania. 

 There are no reports of Blue Mold occurrence here in Ontario, where the disease has not occurred since 2009. However, growers should routinely scout fields and any leftover plants in the greenhouse for signs of Blue Mold (please see photos below for some of the Blue mold symptoms). More detailed information about the identification of Blue Mold and its control can be found in the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Blue Mold” posted in the Plant Protection , as well as in OMAFRA publications 842 and 843.

 Yellow necrotic lesions on the upper surface of leaves at the bottom of the plant  are an early symptom of Blue Mold.

Bluish-grey fuzz (Peronospora tabacina) spores on the underside of the leaf are another symptom of Blue Mold.

There have been a few growers asking about tray sanitation now that transplanting has finished. It is important to mention that unless Styrofoam trays are properly sterilized following use each year, it is not uncommon for fungi to build up in the trays and infect the plants. The CTRF has encountered Black Root Rot in Styrofoam trays over the past several years when steam has not been used to disinfect them. As of today, sterilization of Styrofoam trays with steam is the only practice that will control Black Root Rot. For more information on Black Root Rot and its control, please refer to the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Black Root Rot” posted in the Plant Protection  area of this website. Steam sterilization is also recommended for control of Pythium and Rhizoctonia Damping-off, please refer to the technical bulletin entitled “Tobacco Pests and Disorders in the Greenhouse – Damping off” for more information.

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The 2021 greenhouse season is progressing well, despite the cool and cloudy start. Overall, percent seed germination and uniformity of seedling stands in most greenhouses appear to be quite good. 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. In some greenhouses, clipping is started already. Only a few isolated problems have been reported to date with algae and chilling injury being the issues observed the most.

1-Algae

Blue-green algae are the most common algae that colonizes mostly float trays, however in a couple of cases, red-orange algae were also found to be present.  Algae formations depend upon what types were in the substrate used to fill the trays or which types were present on trays from previous seasons or and in greenhouses. Blue-green algae are the most common algae in tobacco greenhouses and produce an oily-looking, blackish-green slimy layer on the tray surface. Red-orange algae are less frequent in tobacco greenhouses, however they can also be found colonizing water systems and seeding soil substrates, such as soilless medium or muck soil beds.

Unlike blue-green algae, the red algae lack motility structures, this probably being the main reason for the algae to be less spread in float trays or muck soil beds, in which we have seen and found these algae often imbibed in the vermiculite layers on the muck bed. In float trays, the red algae tended to be attached to the sides of the Styrofoam tray cell, often staining them red-orange (Fig. 1).

Fig. 1.- Blue-green algae (arrow) and red-orange algae (circle).

Note the red/orange-stained Styrofoam surfaces under the red algae.

This because algae cause oxygen levels in the media to fall, and or promote formation of nitrites in the tray media which inhibits root growth as well as competing with the plants for fertilizer.

Fig. 2. a) Tray cells and seed covered with blue green algae and b) poorly established seedling due to algae.

  More information on algae can be found here.

2-Chilling Injury

Chilling injury was also of concern especially with some of the recent weather conditions.  The initial symptoms of chilling injury are often a bright yellow color in the growing point of the seedling and upward cupping of the leaves, as shown in the image below (Fig. 3).

Fig. 3. Chilling injury

As the seedlings become larger and the leaves grow out, some leaves will be 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.

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. Also, some varieties are more susceptible than others to chilling injury. However, cold injury is not usually severe enough to be fatal to the seedlings, but it can delay growth and allow other problems, such as algae on trays, to be more damaging than they would otherwise be.

Clipping is underway in tray greenhouses. Bacterial Soft Rot (also known as Blackleg) is a common issue during this crop phase in the greenhouse.Bacterial Soft Rot is caused by several bacteria with Pectobacterium carotovorum (previously Erwinia carotovora) being the most important. As seedlings are clipped, leaf debris from the clipper fall back onto the seedlings foliage as shown in Figure 4, and when conditions are favorable, for example, high nitrogen levels, warmtemperatures, high humidity, long periods of leaf wetness, and plant injury (by stress or wounding), outbreaks of Bacterial Soft Rot will occur. Bacterial spread to healthy seedlings continues as more clipping is carried out, particularly when clipping is done on wet foliage.

Fig. 4. Leaf debris from clipper that has fallen back on to the seedlings.

Bacterial Soft Rot can become a serious seedling problem during extended periods of warm, wet, overcast weather conditions during the greenhouse season.  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

Fig. 5. Seedlings in a tray infected with Bacterial Soft Rot

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.

Click here for more information on Bacterial Soft Rot

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

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Two new flue-cured tobacco strains (CTH251 and CT92) have been recommended for registration by the Ontario Recommending Committee for Flue-Cured Tobacco (ORCFCT). The decision was made during the ORCFCT ‘s annual meeting held on February 23, 2021. The new varieties are being entered in the registered cultivar trial in 2021, along with the popular registered cultivars in Ontario. A brief description of the new strains is given below.  

CTH251

CTH251 is a male sterile hybrid. Information on the parents used to develop hybrids is not released. CTH251 is similar to CTH14 for several traits including days to topping, plant height, leaf number, leaf spacing, and area of the eighth leaf. Grade index, yield, and company rating are similar between CTH251 and CTH14, and percent “O” grades are similar. Percent off-grades for CTH251 do not appear to be different from CTH14.    

CT92

CT92 (tested as 16DA9-2) is a conventional variety derived from crosses involving the cultivar CT681 and a breeding line 20KA15-2, and the cultivar CT572. CT92 has improved Black Root Rot tolerance, a trait that will make it a useful option where soil-borne disease is a problem. In comparison to CTH14, CT92 is higher yielding, similar in grade index and earlier topping. 

The leaf width of the eighth leaf and tip leaves is slightly wider than CTH14 though the lengths are similar for CT92 and CTH14. CT92 has about 3 cm higher plant height with wider spaced leaves, and the number of leaves per plant is approximately one less than CTH14. CT92 has a greater potential for producing improved returns.

Total “O”, “L”, and “F” grades are similar between CT92 and CTH14 and “CR” grades seem to be slightly lower than CTH14. The company rating for CT92 is comparable to CTH14. 

Percent lamina is higher than for CTH14. 

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The CTRF is committed to supplying growers with information for the 2021 growing season. If you need assistance with identification of a greenhouse issue or general information related to tobacco production, please contact the CTRF. The office facilities are currently open to be a resource for tobacco growers, however, a previous appointment is required due to COVID-19 endemic circumstances. Please read through this crop news update to become familiar with common diseases and control methods that you may encounter this greenhouse season.

The 2021 greenhouse season is ongoing.  At this time, it appears that most greenhouses have been seeded or will be seeded in the next few days.  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 and Rhizoctonia Damping-off, 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 muckbeds are adequately steamed at 82ºC (180ºF) for 30 minutes at a 15 cm depth.  For some pests such as Algae, Black Root 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 plant 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 dry or float trays, especially under cool and dim conditions (Fig. 2).  A number of different types of algae may form on trays depending upon what types were in the substrate used to fill the trays or which type 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 soilborne 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 muckbeds, 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 muckbeds 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 and recommended fungicide Senator 70WP or Senator 50 SC (a.i. thiophanate-methyl 70% or 50 %).

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 muckbed 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 muckbed, 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 and recommended for Pythium Damping-off control, however, the fungicide cannot be used in float tray greenhouses. Ridomil Gold 480 SL must be applied within 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 muckbed 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-Chilling injury
Chilling injury shows up as a cupping of the cotyledons and leaves (Fig. 5).  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.

7- Heat injury
Heat injury occurs when warm and sunny conditions occur during germination of tobacco seedlings. Temperatures above 37°C (100° 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. 6). 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).

8-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.

9-Pavement ants
Pavement ants (also called Harvester ants) can occasionally be problems 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 muckbed 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.

10-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.

11-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 disinfected with a strong bleach solution (i.e. diluted 1:1 with water).  Particular attention must be paid to the disinfection of clippers.  If in doubt, throw them out.

Always read the label before applying a pest control product!

More detailed information about Algae, Black Root Rot, Rhizoctonia and Pythium Damping-off 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

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CTRF is pleased to announce the hiring of Dr. Maythem AL-Amery as the Team Leader of the CTRF. Maythem completed his graduate work at the University of Kentucky within the Department of Plant and Soil Sciences. Maythem is excited to join the CTRF and looks forward to working with tobacco growers and industry. Maythem is replacing Dr. Mitchell Richmond, who has accepted another position.

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

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The agronomic performance data for the registered varieties grown in 2020 can now 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 for 2020. A two-year (2019 + 2020) and three-year (2018 + 2019 +2020) average of these varieties are also presented. If you have questions about this handout, please contact the CTRF.

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

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The Canadian Tobacco Research Foundation is seeking a Team Leader who will oversee all aspects of an established applied research program for flue-cured tobacco production situated in Southwestern Ontario. 

The Team Leader provides scientific leadership to a research team that has a successful track record of developing new varieties for Canadian production, effective control methods for diseases and insects, and improved management practices and new technologies in the areas of agronomy, curing and storage.

A description of the responsibilities and qualifications for this position and how to apply are provided in the job advertisement.

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

Telephone: 519-842-8997

Web Address: http://ctrf1.com

Harvest on many farms has abruptly stopped due to the frost that occurred on September 19, 2020. This is considered one of the worst wide-spread frost events to hit the tobacco producing areas of Ontario since August 28, 1982.

To provide an update on the CTRF activities for 2020, the Plant Breeding, Plant Protection and Agronomy 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.

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

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The 2020 version of OMAFRA’s Flue-Cured Tobacco Crop Protection Guide, Publication 843 is now available.  Growers who have not received a copy, can contact the CTRF to request one by following this link.

Publication 843 contains recommendations on registered pest control products for flue-cured tobacco in Ontario.  There is a list of control products in the publication’s tables with a column that identifies whether a product is “TREC Approved”.  TREC stands for Tobacco Review and Evaluation Committee, which tests the acceptability of a product for use in flue-cured tobacco production.  Certain tobacco contractors require that control products used by their growers are TREC approved.  Check with your contractor as to their requirements.

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