Seed pelletizing in tobacco provides improved seed handling for seeding.  The amount of pelletized seed remaining after seeding can be quite substantial in certain cases, requiring proper storage if the seed is to be seeded the subsequent year.  To minimize the deterioration of leftover seeds it is crucial to store the seeds under optimum conditions.  The objective of this study was to determine the best storage environments that would maintain the viability of pelleted seed.

Two seedlots of tobacco (2011 grown CT157 and 2014 grown CT652) both pelletized in the U.S. in early 2015 were stored for periods of 1 and 2 years in 1.) a freezer (-18.0^oC), 2.) a refrigerator (4.0^oC), 3.) a seed room (18^oC),  4.) an office (21-23^oC) in a filing cabinet (office location 1), and 5.) in the same office as in treatment 4 (21-23^oC) but on a book shelf (office location 2).  Each seedlot was stored in small plastic containers with lids and sealed with one exception.  The seeds stored on top of the book shelf were in sealed Petri dishes.  The seedlots were examined for germination before being stored and after each storage period.

The pre-storage germination at 10 days after incubation was 84.5 to 92% with a mean of 88.3% for the two seedlots.

After one year of storage, seeds stored in the office showed the slowest germination, monitored at 7 days after incubation, with this tendency being more apparent in one seedlot than the other, but no statistical differences were found among storage methods in the final germination percentages at 10 days after incubation.  The germination rate index (GRI) (higher value indicates more seed vigour) for seeds stored by the different methods ranged from 5.9 (office location 2) to 6.2 (freezer and refrigerator) compared to the average pre-storage GRI value of 7.2.

After 2 years of storage, statistical differences were found among storage methods at all germination counting dates.  The germination percentage from the first counting at 7 days after incubation was the highest with the freezer (82.2%) and refrigerator (80.8%) storages and considerably lower for the seed room (54.8%), office location 1 (52.0%) and office location 2 (34.0%).   The superior germination observed at the first germination counting date for seed stored in the freezer and refrigerator generally resulted in numerically higher final germination percentages and higher germination rate indices.

Seeds stored in the freezer and the refrigerator for 2 years showed 88.8% and 86.5% germination respectively, at 10 days after incubation, which were just as much as the pre-storage seed germination at 10 days after incubation (88.3%).  Storage with the other methods showed 71.2% (office location 2) to 84.0% (seed room) germination at 10 days after incubation after the 2 years of storage.  The GRI for all the storage methods ranged from 6.3 (freezer) to 4.5 (office location 2).

Temperatures in the different storage environments seem to account for the differences in the germination percentages observed.  Overall, storing pelletized seed in a freezer or refrigerator appears to be the best option to maintain as much seed germination and seed vigour as possible.  The seed must be stored in sealed waterproof containers to keep out moisture, a major cause of rapid deterioration in seed viability and vigour.  Ordinary room temperature storage may be associated with slower germination, and this can result in non-uniform plants and adversely impact the amount of usable transplants.

The full report on this study can be found in the Plant Breeding section of this website.

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An issue being reported on some farms this week is “leaf drop”.  This is where the midrib of the leaf breaks about 2.5 cm (1 in) from the stalk.  Leaf drop is often seen in the lower stalk positions, i.e. sands, seconds or thirds. Some varieties are more prone to this condition than others.  In addition, stage of growth and environmental conditions are contributing factors.  Leaf drop tends to be greatest shortly after a rain or irrigation when the plant is close to the topping stage and conditions are hot and humid.  High winds during the stage when the plant is vulnerable to leaf drop can increase leaf breakage.

Leaf breaks off close to stalk in lower part of the plant is known as leaf drop.  Some varieties are more prone to this problem than others.

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Infection from Potato Virus Y (PVY) is being reported in tobacco fields.  The first PVY infected tobacco plants were observed in late June.  Since then, the virus has been found in several more tobacco fields.  PVY can cause considerable damage to infected plants, especially the necrotic strain which can cause plants to die.

Tobacco plant showing symptoms of the necrotic strain of Potato Virus Y (PVY).

When an aphid feeds on a plant infected with PVY, particles of the virus attach to the aphid’s mouthparts and when the aphid moves to a healthy plant, the virus is transmitted soon after feeding starts.  The virus can infect solanaceous crops such as tobacco, potato, tomato and peppers.  Certain weeds, such as nightshade, ground cherry and lamb’s quarters, can be infected as well.  Aphids can spread the virus between these various crops and weeds.

Once PVY is in a field of tobacco, further spread can occur via aphid feeding.  Control of aphids in the field may help to reduce the spread of the virus within the field or to other tobacco fields, however, it will not control the virus from being introduced into the field from other sources.

For more detailed information about PVY and aphids, please refer to the technical bulletins posted in the Plant Protection area of this website.

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Soon after transplanting, tobacco seedlings can be damaged by several insect pests. The population of these insects can vary from year to year and field to field during the growing season.  Regular scouting of tobacco fields is the best way to know the pests present and the potential damage level they might be causing to tobacco.  For some insect pests there are specific economic thresholds (ET) established.  ET is the pest population level at which control should be initiated to keep the pest population from reaching economically damaging numbers. Insecticides should be applied only when the established ET for a given pest is reached. Applying insecticides based on ET is economical because it reduces insecticide use and associated costs, protects workers and the environment, and has the potential to reduce pesticide residues by avoiding unnecessary applications.

Field Scouting – Site Selection

Tobacco fields should be scouted for cutworms, aphids, hornworms and Japanese beetles, since these insect pests can attack tobacco after transplanting.  At high population densities these insects can cause significant losses, thus the need for field scouting to ensure that these insects are kept below the ET.

Tobacco field infested with aphids.

To scout tobacco fields, it is recommended to adequately select the field sites for a good estimate of each insect’s distribution in the field.  Plants for observations should be pre-selected at random and before starting scouting to avoid biasing counts by stopping at damaged plants.  The number of sites selected in a field depends on its size and the more selected and checked sites, the higher the scouting accuracy.  For fields 2-4 ha (5-10 acres) in size, it is recommended to select  5 to 10 randomly selected sites throughout the field, and for fields larger than 4 ha (10 acres) the number of sites checked is increased by 1 site for every hectare (2.5 acres).

1-Cutworms

Cutworms, mostly the darksided cutworms, are soil insects that damage tobacco during the first four to five weeks after transplanting.  Cutworms damage tobacco plants by creating holes in leaves, feeding extensively on the growing point (heart) and/or cutting off the stem at the soil surface.  Fields should be scouted for cutworms weekly, from transplanting to early July.  Scouting should be done early morning or evenings because cutworms are most active at night.  When scouting, select and stop at 5-10 sites or more and examine 20 plants per site for signs of cutworm feeding (holes in leaves, missing growing point, or stem severed at soil line).  Treat the field when at least 5% of the plants show signs of cutworm feeding, or when 2 or more cutworms are found per 100 plants.

Tobacco transplants defoliated and cut-off at soil line from cutworm feeding.

Information about cutworms and their control can be found in the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Insect Pests: Cutworms, Wireworms and Seedcorn Maggots” posted in the Plant Protection area of this website and in OMAFRA publications 842 and 843.

2-Aphids

Aphids can begin to infest tobacco shortly after transplanting.  The green peach aphid is the aphid most commonly found on tobacco, and it can be black with wings and green or orange/red without wings.  Aphids damage tobacco by piercing the leaves and drawing large quantities of plant sap and by depositing large amounts of honeydew on the leaves, which makes these leaves non-marketable and/or reduce the price of the cured leaves by 5-50%.  Leaves highly infested with aphids can also affect yield and the chemical constituents of the leaves.  Aphids also damage tobacco by carrying and transmitting viruses such as Potato Virus Y (PVY), Cucumber Mosaic Virus (CMV); Tobacco Etch Virus (TEV) and Tobacco Vein Mottling Virus (TVMV).

Winged and wingless adult aphids (top), green and orange/red nymphs (bottom), and aphids feeding on upper leaves of tobacco (right).

Field scouting for aphids should start in June and continue until topping.  To scout for aphids, stop at 10 or more sites per field and examine 20 plants per site.  Check for aphid adults and nymphs on the underside of the upper tobacco leaves.  Early in the season, special attention should be given to areas near the edges of fields, since most aphids migrating from other crops land in these areas.  Treat the field when 10% of the plants have 50 or more aphids on the upper leaves.  Tobacco fields near potato, tomato and pepper fields should be treated as soon as possible to reduce the possible risk of viruses spreading in the tobacco from the neighbouring crops, particularly PVY.

Information about identification of aphids and their control can be found in the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Insect Pests: Aphids” posted in the Plant Protection area of this website and in OMAFRA publications 842 and 843.

3-Hornworms

Tomato and tobacco hornworms attack tobacco plants about five to six weeks after transplanting.  The tomato hornworm is the hornworm most commonly found feeding on tobacco.  Hornworms are voracious feeders.  Young hornworms damage tobacco by creating small holes in the leaves and mature hornworms strip the top and mid leaves of plants leaving only the midribs and main leaf vein.  A damage estimate for hornworms is that 100 hornworms feeding on tobacco leaves can result in 2 kg (72 oz) cured leaf loss, which is an average of 20.4 g (0.72 oz) of cured leaf per hornworm.

Fields should be scouted for hornworms from July to August.  Hornworms are green in colour and prefer the underside of the leaf, which makes them very difficult to detect until damage has occurred.  A sign of hornworm presence and feeding that helps locate the insect is the presence of distinctively barrel-shaped insect droppings around the infected leaves/plants in the field.

To scout for hornworms, stop at 5-10 sites per field and check the underside of leaves of 20 plants at each site, and record the number of hornworms.  Treat when the population averages 1 or more hornworms per 20 plants.  Often, hornworms are seen covered with white cases (cocoons) of the Cotesia wasp that parasitizes them. Parasitized hornworms feed less – the feeding of five parasitized hornworms causes damage equivalent to that of one healthy hornworm.  Therefore, five parasitized hornworms should be considered as one healthy hornworm in the scouting counts.

Tomato hornworm healthy (top) and parasitized by Cotesia wasps (bottom) and tobacco leaf damage due to hornworm feeding (right).

Information about identification of hornworms and their control can be found in the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Insect Pests: Hornworms” posted in the Plant Protection area of this website and in OMAFRA publications 842 and 843.

4-Japanese Beetles

Japanese beetles feeding on tobacco has been occurring in some tobacco fields in recent years and infestations appear to be increasing each growing season, however, damage so far has typically not been economically significant.  The Japanese beetle was first detected in Canada in 1939 and has since become well established in Ontario.  This beetle is known to feed on more than 300 plant species.

Field scouting for Japanese beetles can occur while scouting for aphids and hornworms.  The beetles are easy to detect in the field starting in late June through to August because of their bright metallic green and coppery brown coloured bodies, and by the damage they induce on leaves while feeding.  Their feeding on tobacco creates ragged holes and removes the leaf lamina leaving only the leaf veins giving the leaf a lacy appearance.

There are no economic thresholds established for Japanese beetles on tobacco in Ontario and there are no registered products for their control.

Japanese beetle and leaf damage it can cause.

Information about Japanese beetles can be found in the technical bulletin entitled “Tobacco Pests and Disorders in the Field – Insect Pests: White Grubs” posted in the Plant Protection area of this website.

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There have been further reports of Blue Mold on tobacco in the United States.  The disease has been recently reported in fields in Georgia and South Carolina.  Earlier in the season it was known to be present in Pennsylvania and on tobacco in greenhouses in Georgia.

To date, there have been no reports of Blue Mold in Ontario.  Growers should routinely scout fields for signs of Blue Mold (see photos below for some of the symptoms).  More detailed information about 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 area of this website, as well as in OMAFRA publications 842 and 843.  If you find Blue Mold, please report it immediately.

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

Bluish-grey spores on the underside of the leaf are another symptom of Blue Mold.

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The majority of the crop was planted in May under cooler and wetter conditions, which were not overly stressful to transplants. At this time, most crops appear to be off to a good start, with cultivation now starting to occur on several farms.  Cultivation in combination with daytime temperatures that are expected to rise to the upper 20’s and low 30’s (°C) over the next several days, should help promote root development and good plant establishment.

View across CTRF’s variety trials in the Delhi area on June 8, 2017 just prior to cultivation.

Plant problems observed in greenhouses this spring include high salts in the seedbed, heat damage, nitrogen deficiency, chemical injury, aphids, Damping-Off from the organisms Rhizoctonia and Pythium, Bacterial Rot and Black Root Rot.

Transplants infected with Black Root Rot (caused by the fungus Thielaviopsis basicola) from the greenhouse can result in an uneven crop throughout the growing season.  Black Root Rot infected plants are later to develop resulting in later topping and maturity.

Root of greenhouse seedling infected with Black Root Rot.

Unless styrofoam plug trays are properly sterilized following use each year, it is not uncommon for the fungus to build up in the trays and infect the plants.  Every year for the past several years we have encountered Black Root Rot in styrofoam plug trays when steam has not been used to disinfect them.  Disinfection of styrofoam plug trays with steam is the only practice that will control Black Root Rot.  Some growers who do not follow this practice feel that because they have never had the disease in the past this trend will continue in the future.  Unfortunately, the stats suggest that there is a better chance of getting Black Root Rot in trays if they are not disinfected with steam than winning the lottery!  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.

In the field, there have not been many problems reported as of yet. To date, there have been a few reports of fumigant injury, and a case where one of the fertilizer bands at planting was too close to the plants and caused injury.

There continues to be only one report of Blue Mold in tobacco from the United States. This report came from Georgia in March where Blue Mold was found in two flue-cured tobacco greenhouses.  Up until now, there have been no reports of Blue Mold here in Ontario.  Growers should routinely scout fields and any leftover plants in the greenhouse for signs of Blue Mold.  Information about 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 area of this website and in OMAFRA publications 842 and 843. If you find Blue Mold, please report it immediately.

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Percent seed germination and uniformity of seedling stands in most greenhouses appear to be quite good. Clipping is underway in tray greenhouses and fungicide application for prevention of Rhizoctonia damping-off has occurred.

Only a few isolated problems have been reported to date. These include injury from fertilizer salts (float trays), excessively high temperatures (ventilation failure in a float tray greenhouse), algae on media surface (float trays) and bacterial soft rot (float trays).

Figure 1. shows damage to seedlings caused by Bacterial Soft Rot in a float tray greenhouse. Leaf debris falling back onto the seedlings from the clipper, as shown in Figure 2., is a good food source for the bacteria.  This is an ideal starting point for the disease to become established and have the potential to infect healthy seedlings.

Figure 1. Seedlings infected with Bacterial Soft Rot.

Figure 2. Leaf debris from clipper that has fallen back on to the seedlings.

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.

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Blue Mold on flue-cured tobacco was recently reported in Georgia, where the disease occurred in two greenhouses in South Georgia in March, 2017.  Reports indicate that the infestations appear to have been controlled and tobacco in the area is being transplanted into the field.  This is the first report of Blue Mold in the tobacco growing areas of the United States.  To date, there have been no reports of Blue Mold in Ontario.  Growers should routinely scout greenhouses for signs of Blue Mold as the season progresses.  Information about 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 area of this website and in OMAFRA publications 842 and 843.  If you find Blue Mold, please report it immediately.

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The following are some of the highlights from the annual meeting of the Ontario Recommending Committee for Flue-Cured Tobacco held on February 22, 2017.

Variety Situation

Eight tobacco varieties were grown in farmers’ fields in Ontario in 2016, and for the sixth consecutive year, CTH14 was the most popular variety grown, occupying 59.3% of the acreage.  CT572 was the next most popular variety at 25.3% of the acreage and has been in this same position (second place) since 2002.  The rest of the varieties grown were CT157 (7.7%), CC160 (3.0%), NC297 (2.2%), CTH2 (1.6%), CTH8 (0.7%) and CT652 (0.2%).

Registered Variety Trial

The registered variety trial is conducted annually to provide growers with information about the current performance of the registered varieties. The committee reviewed results from the past three years.  The data set showing the physical, agronomic and chemical characteristics of the registered varieties over these years can be found in the plant breeding section of this website.

Ontario Regional Variety Registration Trial  and Small-Scale Variety Release

New elite varieties in the breeding program are evaluated for at least 2 years at 3 locations in this trial before being considered for registration. Based on overall merit, the committee approved a small-scale release for the conventional variety 13AA27-4 to allow up to 12 producers to grow this variety on a limited scale in 2017.  13AA27-4 was among the varieties that were put on display at CTRF’s Open House in December, 2016.  The average yield of 13AA27-4 across locations was 3,824 kg/ha, which was statistically similar to Delgold (3,656 kg/ha) but superior to CT157 (3,214 kg/ha).  The grade index for 13AA27-4 was 81 compared to 73 for Delgold and 65 for CT157.  13AA27-4 was rated an 80 for the company visual evaluation of useability and was higher than Delgold (75) and CT157 (79).  Other entries found to be promising in the trial were CTH144 (TMV resistant) and CTH128 (Black Root Rot resistant).  13AA27-4 and these two other entries have been kept in the trial and will be evaluated in 2017 along with five other promising varieties that have been advanced into this trial from the strain trials.

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Several diseases can affect tobacco seedlings in greenhouses and, if growers have not already done so, now would be a good time to control some of these diseases before seeding.  Information on the control of algae, black root rot, and Rhizoctonia and Pythium damping-off can be found in an article entitled “2017 Growing Season Will Begin Shortly – Importance of Steam Sterilizing Styrofoam Trays and Muck Seedbeds” in the Plant Protection section of this website.

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