Cutworms, aphids and hornworms are insect pests that can attack tobacco plants after transplanting.  High population density of these insects can cause significant losses.  Thus, the need for field scouting to ensure that these insects are kept under damaging levels, or below economic thresholds.  This is when the population density at which the costs associated with pest management may be offset by the value of potential yield loss associated with the pest feeding or damage.

Scouting for cutworms, aphids and hornworms requires adequate selection of field sites for a good estimate of each insect’s distribution in the field.  Plants selected for observation should be pre-selected at random before starting scouting to avoid biasing counts by selectively stopping at damaged plants.  The number of sites selected in a field depends on its size.  The more selected and checked sites, the higher the scouting accuracy.  For instance, for fields 2-4 ha (5-10 acres) in size, 5-10 randomly selected sites throughout the field are required.  For fields larger than 4 ha (10 acres) the number of sites checked is increased by 1 site for every hectare (2.5 acres).

Scouting for Cutworms

Cutworms are post-transplant soil insects that damage tobacco during the first four to five weeks after transplanting.  The darksided cutworm is the most commonly seen cutworm on tobacco.  It can damage a tobacco plant by creating holes in leaves, feeding extensively on the growing point (heart) or cutting off the stem at the soil surface.  Studies indicate that a low to moderate population level of cutworms can result in 20-40% damaged plants and a 14-25% loss of yield.

Damage to a tobacco transplant from cutworm feeding

Scout fields for cutworms weekly, from transplanting through to early July.  Cutworms are most active at night; therefore, evenings and early mornings are the best time to scout for these insects.  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 points, or stems 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.

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.

Scouting for Aphids

Aphids, mostly the green peach aphids are often seen on tobacco anywhere from about four weeks after transplanting through to topping.  Aphids can be black, orange or green in colour and winged or wingless.  Adults and nymphs damage tobacco by piercing the leaves and drawing large quantities of plant sap.  Studies indicate that a heavy infestation of aphids reduce the price of cured tobacco leaves 5-50% and also have an effect on chemical constituents of the leaves and yield.  Aphids are also vectors (carriers) of important tobacco viruses such as Potato Virus Y (PVY), Cucumber Mosaic Virus (CMV); Tobacco Etch Virus (TEV) and Tobacco Vein Mottling Virus (TVMV).

Wingless aphids – adult and nymphs; and, aphids feeding on upper leaves of tobacco

Scout fields for aphids from June through to topping.  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 field edges, since most aphids migrating from other crops land in these areas of tobacco fields.  Treat the field when 10% of the plants have 50 or more aphids on the upper leaves.  An exception would be when aphids are detected in tobacco fields near potato, tomato and pepper fields.  These fields should be treated as soon as possible to reduce the possible risk of a virus 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.

Scouting for Hornworms

Hornworms, mostly the tomato and tobacco hornworms, are caterpillars that attack tobacco plants about five to six weeks after transplanting.  The two species of hornworms are biologically similar and are distinguished mainly by the number and shape of the white stripes on each side of their bodies and the colour of the horn on their back end.  The tobacco hornworm has seven diagonal white stripes with black margins and its horn is usually red. The tomato hornworm has eight V-shaped stripes with green margins and a bluish black horn.  Hornworms are voracious feeders.  Young hornworms feeding on tobacco cause small holes in the leaves, while mature hornworms can strip the top and mid leaves of plants leaving only the midribs and main leaf vein.  Studies on hornworm damage and crop loss, indicate 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.

Tomato hornworm and leaf damage caused by a hornworm

Scout fields for hornworms from July to August.  Because of their green colour and preference for the underside of the leaf, hornworms are difficult to find until the damage has occurred.  The presence of distinctively barrel-shaped insect droppings, a sign of hornworm infestation, can help locate the insects in the field.  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 parasitized by other insects such as the Cotesia wasp.  Parasitized hornworms should not be included in the scouting counts.

Hornworm parasitized by Cotesia wasps

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.

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

Telephone: 519-842-8997

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The majority of the crop was planted in May under hot and dry conditions. Plant quality appears to have been quite good this year and most crops appear uniform and are off to a good start.  Cultivation is now underway.  Windy conditions in recent days has caused some damage to tobacco on the sandier knolls in some fields.  There were not many problems observed in greenhouses this year and, so far, only a few problems have been reported in the field.

Progress of tobacco in one of CTRF’s plant protection trials on June 14, 2016.

One problem encountered in some cases again this year has been injury from Black Root Rot, caused by the fungus Thielaviopsis basicola. Typical symptoms are uneven plant growth (in the greenhouse or field) with the slower growing plants having black lesions on the roots.  In the cases so far, the infected plants in the field originated from Styrofoam plug trays in the greenhouse.  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.  Disinfection of Styrofoam plug 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.

Root of greenhouse seedling infected with Black Root Rot.

There continues to be only one report of Blue Mold in tobacco from the United States. This report came from Georgia in late March where Blue Mold was found in six 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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The 2016 version of OMAFRA’s Flue-Cured Tobacco Crop Protection Guide, Publication 843 is now available.  Growers who have not yet received a copy, can contact CTRF to get one.

Publication 843 contains recommendations on registered pest control products for flue-cured tobacco in Ontario.  In the publication’s tables that list the control products, there is 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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Seed germination and seedling uniformity in most greenhouses appear to be quite good.  In some of the earlier seeded greenhouses, a preventive application of Senator 70WP fungicide has already been made for the control of Rhizoctonia Damping-off.  The application is made when the larger leaves of the seedlings are about 1.5 cm in diameter (dime-sized) or at the first sign of disease.

Chilling Injury

Some growers have expressed concerns over chilling injury to their greenhouse seedlings and whether the injury will affect the growth of these plants in the field.

Some of the initial symptoms of chilling injury are a bright yellow colour in the growing point of the seedling and upward cupping of the leaves.  As the seedlings become larger and the leaves grow out, some leaves will be malformed, cupped and have a distinct yellow/white discolouration.

Seedlings showing cold injury symptoms.

Seedlings will outgrow chilling injury in the greenhouse without any ill-effects on the seedlings when they are transplanted to the field.

Chilling injury is caused by exposure of the seedlings to a large variation in air temperature in the greenhouse.  An example of how this can occur is when a greenhouse is being ventilated on a very cool but sunny day.  If it is windy outside, the temperature drop will be enhanced when a ridge or side vent is open on the windward side.  Also, some varieties can be more susceptible than others to chilling injury.

Effects of Algae

On some farms this year we have seen where algae in trays has affected the emergence and early growth of some of the seedlings.  Slower growing seedlings affected by algae will sometimes only reach the 2 leaf stage and turn brown and die.  Seedlings that do not die tend to remain small and eventually become shaded out by the seedlings that are growing normally.

Tray of seedlings affected by algae.

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.  Not fertilizing for 2 or 3 weeks after seeding can also help to prevent an early buildup of algae in trays.

Disinfecting trays with steam prior to use will help to reduce algae in trays at the time of seed germination and seedling emergence.  Tray steaming also helps to control diseases, such as Black Root Rot, that can be harmful to tobacco.

Further information about algae and measures to reduce its effect on seedlings can be found in a technical bulletin in the plant protection area of this website.

Injury from Heat and Dryness

Abnormally warm and sunny conditions from April 16-18 appears to have been partly responsible for some leaf injury to seedlings in some dry tray greenhouses.  In these cases, the moisture content of the media was also likely on the dry side at some point while conditions were warm and sunny.  The older leaves of the seedlings collapsed and turned brown, however, the growing point appears not to have been injured and is still active.  These seedlings should recover normally.  It should be noted that in the photo below, the seedlings are also in need of additional nitrogen.

Leaf injury from heat and dryness.

Field Soil Fumigation

It’s that time of year again when it will not be too long before soil fumigation occurs.  Appropriate soil moisture is important for the fumigant to be effective.  Conditions that are too dry can result in an unsafe release of the fumigant from the soil and poor control of soil pathogens, such as nematodes.

The product label for the soil fumigant that will be used provides information on soil moisture conditions required at the time of application.  For chloropicrin based products (Chloropicrin 100 and Pic Plus Fumigant), if there is less than 50% available water capacity 20 cm below the surface, the soil moisture must be adjusted.  For metam sodium based products (Busan 1020 and 1236, and Vapam HL), the soil moisture in the top 15 cm must be between 60% to 80% of available water capacity, otherwise the soil moisture must be adjusted.

The product label for the soil fumigant being used will provide information on how to determine soil moisture using the USDA Feel and Appearance Method.  An instrument, such as a tensiometer, can also be used.  Irrigation prior to fumigation or waiting until there is sufficient rainfall will be necessary in situations where a tilled soil is found to be too dry for fumigant application.

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Telephone: 519-842-8997

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Active Blue Mold was found in six tobacco greenhouses in Georgia over the Easter weekend (March 25-27).  The infected greenhouses are now empty.  No occurrences of active Blue Mold have been reported in any tobacco fields in the state. This is the first report of Blue Mold in the tobacco growing areas of the United States in 2016.  To date, there have been no reports of Blue Mold in Ontario.  Growers should routinely scout greenhouses 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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Mailing Address: CTRF, P.O. Box 322, Tillsonburg, ON  N4G 4H5

Telephone: 519-842-8997

Web Address: http://ctrf1.com

The Tobacco Pests and Disorders bulletins, published in the Plant Protection area of this website, have been recently updated. The updates incorporate new information on several pests and plant protection products that have been recently registered and are recommended for use on tobacco.

A bulletin on aphids is now available. Identified in this bulletin is a new threshold to trigger treatment for aphids.  The new threshold states that treatment should be applied when at least 10% of the plants in an area have 50 or more aphids on the upper leaves.  Immediate treatment, however, is recommended when aphids are detected in tobacco fields that are near potato, tomato and pepper fields, to help reduce the risk of Potato Virus Y (PVY) transmission by the aphids.

The harvester ant bulletin now specifically refers to pavement ants, which are the most common harvester ants found in muck soil greenhouses.

Included now in the bulletin on Tobacco Mosaic Virus, are specific recommendations on sanitization of greenhouse and field equipment.

Among the new registered products are Fulfill 50WG Insecticide, active ingredient (a.i.) pymetrozine, registered for aphid control in the field, which has been included in the aphid bulletin, and the fumigant Pic Plus, a.i. chloropicrin 85.1%, registered for nematode and Black Root Rot control, which has been included in the Brown Root Rot and Black Root Rot bulletins.  Information on air and soil temperatures, and soil moisture requirements when the active ingredients metam sodium and chloropicrin are used, is now included in the bulletin on Brown Root Rot (caused by Root-Lesion nematode).  The name for the insecticide Ripcord 400 EC, a.i. cypermethrin 407 g/L, has been changed to Mako Insecticide.  Information about this is in the bulletin on cutworms, wireworms and seedcorn maggots.

Despite the fact that the product application rates are provided in these bulletins, always refer to the product label before use.

There were no changes to the recommendations for sterilization of dry and float trays. For Styrofoam trays, steam treatment of 80°C for a minimum of 1 hour needs to be applied to eliminate Black Root Rot from the trays.  For muck soil seedbeds to be sterilized properly, a temperature of 82°C needs to be held for 30 minutes, at a 15 cm depth.

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Agronomic performance data on the registered varieties grown in 2015 can now be viewed in the plant breeding area of the website.

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Telephone: 519-842-8997

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CTRF is holding an “Open House” on Thursday, December 10 between the hours of 8:30 a.m. and 12:00 noon.  Cured leaf samples of registered and promising varieties will be on display.  Handouts on the performance of the registered varieties will be available.  There will also be a plant pathology display in CTRF’s research lab.  Click here for the program and directions.

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

Telephone: 519-842-8997

Web Address: http://ctrf1.com

Fulfill 50WG Insecticide has been granted registration for control of aphids on field tobacco.  The formulation contains the active ingredient (a.i.) pymetrozine.  Fulfill 50WG Insecticide is in the insecticide group 9B.  This group is different from all other insecticides registered and TREC approved for aphid control on flue-cured tobacco, such as Assail 70 WP (a.i. acetamiprid), which is in the insecticide group 4, and Orthene 75 SP (a.i. acephate) and Pro Malathion 50 EC (a.i. malathion), which are both in the insecticide group 1B.

Fulfill 50WG Insecticide translocates both upward and downward within the plant and protects the tobacco plant by interfering with the aphid’s ability to feed.  Affected aphids stop feeding shortly after exposure but may remain on the plant foliage until they die, which usually occurs within two to four days.

Fulfill 50WG Insecticide must be applied on tobacco foliage when aphids first appear and before populations build up to damaging levels.  The application rate is 193 g product/ha and a maximum of two applications (386 g product/ha) per season is permitted.  The use of a non-ionic adjuvant is recommended to improve the performance of Fulfill 50WG Insecticide under drought stress conditions (see product label for particulars).  When applying, use sufficient water to attain good leaf coverage.  A minimum of 100 L of water/ha is recommended.

When two applications of the insecticide occur, allow seven days between applications.  The re-entry interval after application is 12 hours.  The pre-harvest interval (PHI) is 14 days.

The Canadian Tobacco Research Foundation (CTRF) evaluated Fulfill 50WG Insecticide in several field experiments and found the insecticide to be efficacious for controlling aphids on tobacco, and the Tobacco Review and Evaluation Committee (TREC) found the insecticide to be acceptable for flue-cured tobacco production.

Always read the label before applying a pest control product.

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Several growers have already finished harvesting, while those still harvesting should be done by the end of this month.  There are no significant disease or insect problems to report at this time.  Similar to the past several years, there were no reports of Blue Mold in the Ontario tobacco crop.

Final harvesting pass in CTRF’s variety trials located near Delhi, ON on September 22, 2015.

CTRF has now completed harvesting its 2015 variety trials.  These trials are conducted in cooperation with growers.  This year there were a total of 42 promising flue-cured varieties being tested in replicated trials, with some of these varieties being grown at multiple sites.  The main objectives of CTRF’s breeding program are to develop varieties with good quality, high yield and disease resistance.  Several varieties under test have resistance to Black Root Rot, Tobacco Mosaic Virus, Blue Mold and/or Potato Virus Y.  Screening of breeding lines with high tolerance to Root-Lesion Nematodes is also occurring.  Similar to past years, CTRF will be holding an Open House later this year for growers to view cured leaf from various varieties.

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

Telephone: 519-842-8997

Web Address: http://ctrf1.com