Soil fumigation for Ontario tobacco

Most Ontario tobacco growers are aware that the Telone products (Telone II and Telone C-17) are no longer available for sale or use in Canada.  As of last fall, the registration for these products was withdrawn.  Hopefully most tobacco growers have tried alternative fumigants or other management strategies (e.g. cover crops) on portions of their fields, and are familiar with the application of these products.  The remaining fumigants recommended for use on flue-cured tobacco fields in Ontarioare the metam sodium-based products Busan 1020, Busan 1236, and Vapam HL, and the chloropicrin product Chloropicrin 100.  See the 2012 version of Appendix A. Products used in producing flue-cured tobacco in Ontario for rates and other details.

The metam sodium products are recommended for nematode control in tobacco fields.  For successful use of these products, it is critical to ensure the soil is thoroughly and deeply loosened in advance (a week before treatment), while keeping the soil moist until time to treat, watering if necessary.  Chloropicrin 100 is recommended for use on tobacco fields where black root rot or black root rot plus nematodes is a problem.  Research done by the Canadian Tobacco Research Foundation at three different locations found no difference in yield, grade or level of nematode control between tobacco treated with Chloropicrin 100 or Telone C17.  However, some early efficacy problems were reported when Chloropicrin 100 was not properly applied.   Problems with Chloropicrin 100 can arise when tractors travel too quickly across the field, as the rate delivered depends on the speed of the tractor – less is delivered if the tractor is travelling at a higher rate of speed.  This is a key difference between Chloropicrin 100 and Telone C17.

Before applying any fumigant, remember that the soil temperature should be at least 10°C (50°F) and ideally closer to 13-15°C (55-60°F) at a 15 cm (6 in.) depth). For safe and effective use of all fumigants, ensure you closely follow the instructions on the product label.

Post fumigation

Remember that tobacco plants can be killed or severely stunted by the presence of residual fumigant in the soil.  To guard against this, a week before transplanting, it’s a good idea to check several areas of the field, including a lower area, for residual fumigant in the soil.  Knock down the top of the fumigant hill and transplant about 10 plants down the centre of the row.  If a four-row applicator was used, transplant into each of the four rows to check the consistency of the fumigant application.  As a comparison, 10 plants should be planted between the fumigant rows where no fumigant was applied.  After a couple of days, check the plants early in the morning to see how they compare to the plants between the fumigant rows.  If only the plants in the fumigant row are laying down and their stems are limp below ground without any signs of insect feeding, fumigant is still present in the soil.  In this case, the hills should be opened with a single chisel or cultivator tooth about 2 to 3 days prior to planting in order to allow the remaining fumigant to escape.

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