Historically, the main nematode pest of Ontario tobacco has been the root lesion nematode, Pratylenchus penetrans. However, in 2017, another species, the tobacco cyst nematode (TCN) was observed in Ontario tobacco fields. TCN forms an almost impermeable cyst and can persist in the soil without a host for several years, making it difficult to control.  Symptoms include stunting of plants and a reduced root system. Yellow to dark brown female nematodes and cysts are often visible with the naked eye on affected roots, 6-8 weeks after planting.

To reduce populations of this pest, fumigants should always be used in conjunction with the following cultural practices.

Early root and stalk destruction

This practice is a critical step toward reliable and acceptable nematode control in the future by limiting nematode reproduction cycles. Destroy root and stalk debris soon after harvest to expose the eggs and juveniles to drying, which should limit further increases in nematode populations after the crop is harvested.

To do this:

  1. Cut stalks into small pieces with a bush-hog or similar equipment immediately after final harvest.
  2. 2. Disc stubble the same day that stalks are cut, exposing roots at the soil surface.
  3. Re-disc the field 2 weeks after the first operation.
  4. Plant a cover crop when the root systems are completely dried-out and dead.

Sanitation

Effective sanitation can prevent the spread of TCN to non-infested fields. This involves use of nematode-free transplants, avoiding sources of transplant and irrigation water that are near infested fields, removing all soil from equipment and shoes after working in infested fields and controlling weeds such as jimsonweed and nightshades since these are also hosts of tobacco cyst nematode.

Crop rotation

Rotation of tobacco with non-host plants such as small grains (e.g., rye, wheat), millet, sorghum, corn and soybean, can suppress TCN populations. Longer rotations (more than 2 years) are desirable. Avoid rotating with solanaceous crops such as tomato, pepper and eggplants if TCN is present, as these are potential hosts.

Resistant varieties

The use of resistant varieties is important for the successful management of TCN. As of December 2022, there are not registered Canadian cultivars with resistance to TCN.