By Kaeley Kindrachuk, B.App.Sc., AT, Regional Crops Specialist, Outlook
The last few years have presented numerous challenges for producers and there have been many adjustments made to farming practices in terms of disease management. There are multiple tools that, when used together, will help manage diseases in a crop. These tools include variety and crop rotations, seed quality and treatments, scouting and fungicide use.
When choosing what variety to grow, look for the variety with the highest level of resistance, or choose multiple varieties. It is important to remember that while some of the older varieties still have good ratings, their rating was set in the year the variety was registered. The cereal varieties currently available today range from resistant (R), moderately resistant (MR), intermediate resistance (I), moderately susceptible (MS), and susceptible (S). These varieties and the ratings can be found in the SaskSeed Guide. There are canola varieties available with protection against some diseases. There is ongoing research on improving all crops’ disease tolerance, but there is nothing available to combat disease through variety alone.
The past few years have been abnormally wet, and with shorter crop rotations and increased disease inoculum in the soil, the risk for disease at any point throughout the growing season is great. Extending a crop rotation to at least three years, will help spread out some of the risk. Diseases like pulse root rots have been on the rise across the province. Increasing the number of years between susceptible pulse crops can help improve the health of the crop.
Figure 1. Seed test decision chart
Getting seed tested before planting can help in knowing whether or not that seed should be used and/or if a seed treatment should be used as well. Look for seed that has a high rate of germination and vigor, is free from weed seeds, has high genetic purity and is free or has low levels of seed-borne disease. There are recommendations that can help make the decision as to whether or not wheat or durum seed should be used (Figure 1). When using a seed treatment, look for one with multiple modes of action. Seed treatments will help protect the seed and seedling for up to 21 days, but root rots can infect the plants at any time throughout its lifecycle.
Some disease strains evolve over time and resistant varieties can eventually lose their ability to protect the plant from the disease strains present in a field. Regular scouting and record keeping can help determine if this is the case. For example, scout late in the season for Blackleg by cutting stems near the ground, checking for black lesions and rating each one on a scale of 1-5 for the disease. A rating of 1.5 or higher is a good sign that Blackleg resistance in that variety is no longer effective on races in that field. Unfortunately, this does not help in the current crop year, but will be helpful for the next time canola is grown in that field. Diseases such as Fusarium head blight and Sclerotinia have only one infection cycle per year (monocyclic). When you see the disease symptoms, it is too late for a fungicide application. For these diseases, scout for the conditions that favor the disease. For other diseases like Anthracnose in lentils or Pasmo in flax, scout for early symptoms before applying a fungicide, as they have more than one infection cycle per year (polycyclic) . Some of the things to be considered before spraying a fungicide are field history, environmental conditions and economics. It is also important to remember that fungicide does not cure a diseased crop but helps prevent the disease from spreading.
Disease cannot be managed by one of these practices alone. All of these practices work with each other to help decrease the risk of disease incidence and severity and increase yield and quality. Done in conjunction with each other, over multiple years, the risks will continue to decrease over time.
For more information on diseases or any of these risk management tools:
Visit www.saskatchewan.ca, or
Contact your nearest Regional Crops Specialist