Protected right from the beginning The importance of quality in seed treatment The use of high-quality, <strong>healthy</strong> seed is one of the most important factors contributing to efficient agriculture. The cereal grower depends on it to ensure the good early establishment of a <strong>healthy</strong> crop, and ultimately, financial success. 28 COURIER 2/06
Fusarium ear blight Snow mould in winter barley In order to support this, treated seed must satisfy a number of requirements. It must have an adequate thousand-seed weight, good germinability, varietal purity and last but not least, it must be free of infection. Given the major importance of seed to the farmer, legal requirements designed to guarantee seed quality were established at an early stage. One example is the set of requirements laid down in the seed-quality regulations that determine the maximum allowable levels of infection of seed crops by various pathogens. Seed lots that satisfy these criteria are considered to be acceptable – but no information is available about exact levels of infection below these thresholds. The major problems here are those fungal diseases that are transmitted exclusively via the seed, and which can therefore only be controlled effectively through seed-treatment. These pathogens tend to have very short generation times, so they are often able to build up their populations quickly and cause extensive damage, even if infection in the original seed crop was within the thresholds set in the seed quality regulations. This is why severe infections occur regularly if seed-treatment is omitted, even if high-quality seed has been used: this results in serious losses in yield and quality, and ultimately, economic penalties. The only reliable method for avoiding this problem remains the systematic use of seed-treatments based on effective crop protection compounds. Modern active substances have a broad spectrum-of-action Following the ban, more than 25 years ago, on the marketing of mercury-based crop protectants, a whole range of new active substances and products were developed for use as seed-treatments. Some of these new compounds were the first systemic active substances; they were able to control pathogens that had previously been uncontrollable, or which were controllable only through dosages so heavy that they jeopardized the vitality and germinability of the seed. Today, a large number of different systemic seed-treatments are available on the market, which can differ greatly in their properties, as well as in price. Nor has product development stopped in this area, as is demonstrated by the ongoing adoption of active substances from the strobil- urin class into new seed-treatment products. Seed-treatments designed to control seed-borne pathogens, including the various smuts, the snow mould pathogen (Microdochium nivale), and Fusarium culmorum, must meet certain minimum standards in terms of percent control. Product efficacy against seed-borne pathogens is tested for during the biological trials that are required under the regulatory procedure. However, many systemic active substances, especially those in the triazole class, show spectra-of-action that go well beyond the official requirements, controlling a range of significant leaf-diseases too. These include the pathogens that cause mildews, net-blotch of barley, common root rot of barley and rye, Rhynchosporium, both species of Septoria, rusts, Fusaria and others. One specialist area in the use of seed-treatments is the control of take-all of cereals. This disease is not actually seed-borne, but as a „disease of rotations“, it can nevertheless only be controlled directly using the appropriate seedtreatments. There is now a choice of seed-treatment products on the market that are registered for the control of these pathogens. Some of these have certain incidental effects that can positively influence the emergence and early development of the cereal plant, i.e. beyond the active substance’s direct fungicidal effect. Although for some diseases (e.g. smuts), there is a direct correlation between the number of infected ears and the extent of harvest losses, the yield benefit associated with the use of broad-spectrum seed-treatments is not always attributable to the control of a specific pathogen. As well as differing in their spectra-ofaction, seed-treatments differ in their potency, particularly under “worst-case” conditions. Strong infection potential tends to highlight a product’s reserves, or con- Stinking smut of wheat Loose smut of barley 2/06 COURIER 29
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