Through good variety selection one can prevent diseases and pests. In the catalogue stem rot (Fusarium spp.) and corn smut (Ustilago maydis) resistance are included. Also, the varieties are evaluated on Helminthosporium tolerance, soil coverage, plant height and earliness of flowering.
Since 2007 maize in the Netherlands is relatively widespread affected by leaf spot diseases. These diseases are caused by the fungus Helminthosporium, of which two species occur in the Netherlands. The first and most important is the Helminthosporium turcicum (Northern leaf blight or Setosphaeria turcica) and the second is the Helminthosporium carbonum (Helminthosporium leaf spot). In the beginning of an attack little dull gray-green spots occur. H. turcicum shows large oblong gray brown spots up to 15 cm long. H.turcicum only attacks the leaves. H. carbonum spots remain restricted to 2-3 cm. Ultimately spots of all species coalesce in large parts of the leaves and even the whole plant can die. Especially in an early attack (July), both the grain yield and the ‘VEM-value’ ( VEM = feeding unit for milk) are negatively affected by a Helminthosporium attack. Corn that is infected by Helminthosporium is susceptible to an attack of Fusarium (stem rot). This causes less yield and crop losses, especially for grain maize. Helminthosporium does not seem to be toxic to livestock. The damage can be minimized by crop measures. The first infection originates from the crop residues from previous years. Rotation can thereby prevent or limit infection. Decomposition of corn stubble reduces the risk of infection. The best practice at this moment is a proper variety selection. Varieties with 100% resistance are not yet available.
After flowering, the corn crop becomes more susceptible to Helminthosporium, because the plant will increasingly focus on the production of the flask and less on maintaining the leaves. Varieties that bloom earlier are therefore slightly more susceptible to Helminthosporium. Therefore it is better to compare varieties of similar maturity (of flowers). Late flowering varieties are generally less susceptible. This should not be exaggerated, because there are very early flowering varieties, which have a good to very good resistance.
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In the tables the varieties of the variety catalogue are noted, plus varieties that have been studied for three years (but are not recommended or not registered) and varieties that have been investigated for two years. After the third year of research the two examined varieties can be placed on the recommendation catalogue. The varieties that have been tested for one year are not included because the results of a one year study are not reliable enough for the Dutch maize grower.
This year, the tolerance of varieties to leaf spot disease (Helminthosporium) are incorporated into the recommendations catalogue.
The results of research of Applied Plant Research are used in the official National and Recommended Catalogue of Varieties of Agricultural Crops.
The variety bulletin is a review of the official research on cultivation and use of fodder maize of Applied Plant Research, part of Wageningen UR, in commission of Plantum NL. Plantum NL is the Dutch association for breeding, tissue culture, production and trade of seeds and young plants. The results of this research provide the basis for the recommending variety catalogue in the Netherlands.
Applied Plant Research tests the varieties according to a protocol, which in consultation with all breeders and representatives of growers is set up and is authorized by the “Commissie Samenstelling Aanbevelende Rassenlijst’ (CSAR) (Commission Assembly Recommended Variety Catalogue).
Through the introduction of new varieties on this variety catalogue the ‘VEM-value’ ( VEM= feeding unit for milk) is increased with 14 % during the last 18 years.
