Growers should be scouting their fields for insects and diseases. Hornworms are common in tobacco fields at present. This is somewhat earlier than normal and some growers have already treated. Aphids are also starting to appear in some tobacco crops, however to date they have not caused any significant impacts on plants.
Treatment for hornworms is justified when the population averages 5 or more hornworms per 100 plants, while the treatment threshold for aphids occurs when at least 20 percent of the plants in an area have 5 or more groups of aphids on each upper leaf. Dipel WP, Thuricide, HPC, Orthene 75% SP and Sevin XLR are all recommended for the control of hornworms on tobacco, while Orthene 75% SP, ProMalathion 50EC and Assail 70WP are recommended for the control of aphids. Note that these products have differing pre-harvest intervals and re-entry requirements. Refer to Publication 298, Flue-Cured Tobacco Production Recommendations and consult product labels for more information and full application instructions.
Japanese beetles have also been observed in some tobacco fields. The Japanese beetle was first detected inCanadain 1939 and has since become well established inOntario. Growers of horticultural crops in southernOntarioare becoming increasingly familiar with these large beetles with a bright metallic green and brown colouring.
Adults appear in late June and early July, mating and feeding voraciously on a wide variety (over 300 species and counting) of plants. Japanese beetles tend to reach their peak in late July, and feeding is often most extensive on warm, sunny days and on plant parts exposed directly to the sun. So far, damage to tobacco by Japanese beetles has been minimal. There are no products registered for Japanese beetle control on tobacco in Canada, however insecticides applied for control of other tobacco pests may have some effect on this insect.
There have been isolated reports of Tobacco Mosaic Virus (TMV) and target spot in some fields, however at present there are no widespread disease issues inOntariotobacco. As of July 13, there have been no reports of blue mold from Ontario tobacco, nor are we aware of any new reports from the U.S.since the report from Pennsylvania in June. Ontario growers should be monitoring their fields regularly for this disease. Growers are asked to report any suspected cases to the OMAFRA office in Simcoe at 519-426-4434 or 519-426-3823. More information on this disease can be found in OMAFRA Publication 298 – Flue-Cured Tobacco Production Recommendations or in the CTRF publication “Flue-Cured Tobacco Best Management Practices – Blue Mold” (September, 2004).