By Harry Brook
Seed treatment. Another cost and what’s the benefit? Seed treatment with a mix of fungicides and possibly insecticides, is a lot like an insurance policy. Under ideal conditions at seeding you put your seed into the ground at just the perfect depth, moisture and temperature and quickly, up it comes!. Under soil temperatures at 10˚C and adequate moisture, the crop rapidly germinates, emerges and begins the journey to a productive crop.
However, do you ever remember such an ideal spring? Usually, our springs have a habit of coming and going with winter showing up periodically up until May. This is where a seed treatment can pay. It’s a jungle out there, in the soil, with many competing fungi and organisms just looking for the right crop or seed to feed on. A lack of variety in your cropping mix only increases the risks. Seed treatments are one way to prevent diseases and insects from taking out your crop seedling. Don’t expect seed treatments to perform miracles, however. If you used diseased seed, poor germination or poor seedling vigour, seed treatment will not be a miracle product and the crop will still do poorly.
Seed treatments are very good at combating seedling diseases, like smuts, that have spores on the seed coat. Some systemic fungicides are useful at preventing disease from entering and spreading through the new seedling. Others provide a zone of protection around the seed by killing off fungicide. Seed treatments are usually good at protecting the seedling for about two weeks. Then the effects wear off. In peas, this can lead to later root diseases like Fusarium and Aphanomyces root rots, even if they were treated.
One of the worst early season pests for canola is the flea beetle. In some areas, an insecticide in the seed treatment is required just to ensure the crop makes it to the first true leaves. In Alberta, we have two main types of flea beetles that attack canola, the two stripe and the crucifer flea beetle. The insecticide portion of the seed treatment is not equally effective on both species and the two stripe flea beetles are less affected by the insecticide than the crucifer flea beetles. Over time, there has been a shift to primarily two stripe flea beetles. You can’t rely just on the seed treatment to protect your seedlings. Post seedling insecticides might be called for.
Here are a few pointers to consider if you wonder if you should use a seed treatment. You should definitely use a seed treatment if you seed early, before the topsoil is above 5˚C. If you have a tight rotation of two crops, you can easily build up pest levels in the soil, which can kill off a large number of unprotected plants. If you try to economize on seeding rates, you really can’t afford to lose many plants and a seed treatment is needed to preserve plant numbers.
When using seed treatments, it is a very good idea to alternate seed treatment groups. Just as in herbicide, too frequent a use of one particular active ingredient in a seed treatment can lead to resistance and a loss of efficacy of that fungicide. You lose one chemical in a group, consider the whole group as no longer effective. To keep these tools useful, change it up, once in a while, both with crop rotation and seed treatment groups.
Good yields in the fall depend upon a healthy start from the seed in the spring. Use seed treatments judiciously when needed and use good, agronomic practices to ensure your crops get a good start in the spring.