Managing the complex biological system of an organic small grain farm can be a challenge, particularly in terms of disease and insect management. Because synthetic fungicides and insecticides are generally not allowed in an organic system, prevention is the main strategy for avoiding pest problems.
Successful prevention usually involves many different strategies in combination, rather than relying on a single one. The foundation of any organic pest-management strategy is crop rotation, sanitation, and cultural practices such as variety selection.
The second tier in the hierarchy is mechanical and physical methods that may include introduction of natural predators, natural traps, and repellents, and development of habitat for natural enemies.
The third tier of the hierarchy is the use of biological or allowed synthetic substances for the control of pests. These methods are allowed only (and are most effective) when the foundational practices in the first and second tiers are in place.
These third-tier measures (see figure) are for use once a disease or pest is present, after the first levels of prevention strategies have failed. Understanding foundational biological principles, rather than simply substituting organic inputs for conventional ones, is a key to good organic management.
Disease Management
Climate and Location
Two important determining factors for disease development are climate and location. Areas with low humidity generally have much less disease pressure than areas with high humidity, since it usually takes six to 12 hours of continual leaf wetness for a fungal leaf disease to develop.
This probably explains why the Great Plains states are the top organic-grain producing states in the US. If you live in a region of the United States with high humidity and heavy disease pressure, you need to consider carefully whether organic small-grain production is right for you.
Cultural Practices
There are several cultural practices to help prevent diseases, including variety selection, delayed planting, and irrigation timing.
Resistant Varieties
The first step in disease management is selecting a variety with disease resistance. Choose varieties that are specific to your area and that have been bred with resistance to local diseases. For example, stem rust is a common grain disease that can be managed by good variety selection.
State Extension stations conduct annual variety trials that list the resistance levels of different varieties. Check their annual reports for recommendations. While resistant varieties provide the first line of defense, there is no one variety of grain that is resistant to every disease. Prioritise your selection of resistant varieties by the diseases most common in your area.
Seed Quality
Find the plumpest, highest-germinating seed possible, and plant in high density to account for any loss of stand due to damping off. When possible, select Certified seed from a reputable dealer. Make sure the seed is a pure variety, and that you know what you are buying.
In general, Certified seed should be purchased every third year. Regular use of Certified seed will help manage seed-borne diseases such as smut and bunt.
The term “Certified seed” does not refer to certified organic. Rather, it denotes seed that is produced under conditions that assure its purity and vigour.
Certified seed is produced from foundation, registered, certified, or other approved seed stocks. This seed is two generations from foundation seed. Certified seed cannot be used to produce
Certified seed again without the approval of the state certification agency, which can approve production only under extreme conditions. Double-certified seed is seed that is considered both Certified (from Foundation seed) and certified organic.
Currently, the chance of locating double-certified seed is very slim. However, the Organic Seed Alliance continues to work toward increasing the quality and amount of organic seed used in field crop production. Their website is www.seedalliance.org
Rotation
Rotation is another tool for disease management. Fungal diseases such as tan spot and Septoria survive on stalk residue.
Fusarium head blight is also carried in the residue of wheat, barley, and corn. Moving to a legume or oilseed in rotation will help break this disease cycle.
Delayed Planting
Planting when soil temperatures are warmer can help manage soil-borne fungi such as Pythium and Rhizoctonia. Typically, these fungi are more of a problem in larger-seeded crops such as garbanzo beans and corn.
However, if you have had problems with these diseases in the past, try delaying your spring planting until soil temperatures are warm enough to allow optimal seed germination and plant establishment.
Irrigation Timing
If you are growing grains using irrigation, do not irrigate during the flowering stage. Flowering is the susceptible period for Fusarium head blight and ergot. If you are able to control timing of water application, do not water during this period.
Crop Scouting
Crop scouting is an essential part of disease management. The earlier you can detect diseases in the field, the more time you have to respond. Hone your skills in disease diagnosis. Local Extension agents often have identification guides available in print and online versions.
Likewise, most land-grant universities have Extension pathologists on staff and diagnostic labs where growers can send any questionable plants for diagnosis.
If you discover a disease in your fields, there are several options. If the disease is not a serious problem for further infestation, or harmful for human or animal consumption, you may choose simply to live with the reduced yield.
Another alternative is application of biological or allowed synthetic substances. Check the ATTRA Biorationals: Ecological Pest Management Database (www.attra.ncat.org/attra-pub/biorationals/) for allowed organic substances for specific diseases. Extreme cases may require terminating the affected portion of the crop before the disease gets out of hand.
Storage Environment
Finally, manage for storage diseases in addition to in-crop diseases. Storage mold can be managed by constantly checking grain moisture during harvest. Hand-held grain moisture meters are available to purchase. Discontinue harvest when the grain moisture content exceeds 12%.
If there is concern about the grain’s moisture content, use aeration in the bin to dry the grain. High moisture levels and elevated bin temperatures lead to mold, grain deterioration, and insect infestation.
Specific Grain Diseases
Special thanks to Dr Mary Burrows and Dr Bill Grey of Montana State University for providing information on specific grain diseases and their management. In addition to general cultural practices, there are some specific diseases of which organic small grain growers should be aware.
Some are relatively harmless and will only slightly decrease yields. Others are more serious and can lead to crop failure or be detrimental to livestock and human health. Proper identification of these serious diseases is important in order to decide the best management strategy.
What to do with the crop will depend on weather conditions, the pathogen level, and the amount of susceptible host material. In most cases, the presence of disease will simply reduce the crop yield. In extreme cases, the diseased portion of the crop should be terminated to reduce potential infection of other areas.
It is difficult to make specific threshold and management recommendations for each disease within the scope of this publication. Land-grant universities often have plant pathology labs that will diagnose a disease and provide specific management recommendations.
Source: https://attra.ncat.org
