Seedling, root, stem and cob rot

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Seedling, root, stem and cob rot is a plant disease caused by various types of fungus ( Fusarium sp., Helminthosporium sp., Nigriospora sp.).

damage

Damage

Diffuse to streaky brown discolouration on roots and stem base (Fusarium sp.) Even on seedlings . Occasionally blackish stem base, coupled with signs of yellowing ( Pythium sp.) Or with elongated, watery spots on leaves ( Helminthosporium sp.). From milk stage of the leaves die off from bottom to top. Depending on the variety and pathogen, the medullary tissue in the lowest internodes is predominantly decomposed and overgrown by white to pinkish- red mycelium ( Fusarium sp.), Or the nodes are browned and rubbery-like, with the top ones weakening initially (especially Fusarium graminearum ). The cobs can hang slack and show prematurely withered lizards. After periods of wetness, individual grains or entire zones are attacked by whitish to pink mycelium, which grows through the lizards and can be externally visible ( Fusarium culmorum , Fusarium graminearum , Fusarium moniliforme, etc.). Occasionally black cob rot ( Helminthosporium sp., Nigriospora sp.) Also occurs.

meaning

The pathogens occur everywhere, but become more important in warmer areas. Thanks to the treatment of seeds , damage only occurs when cultivated with care. A moderate to severe stem rot attack hinders the water and nutrient supply and leads to inadequate grain filling and emergency ripening . If it is mainly the base of the stalk that becomes diseased, the stalks break when exposed to the least amount of stress, which ultimately means that the harvest is difficult and lost. The average loss of earnings is assumed to be around ten percent, but can amount to up to 35 percent.

biology

Host plants: All cereals and maize, presumably also grasses and some plants from other families.

Life cycle

The fungi overwinter on the seeds and on infested plant remains in the soil. Fusarium culmorum can also survive saprophytically on non-host plants. The infections occur mainly through the roots , but occasionally also through wounds at the base of the stem and leaf attachment points. Mycelium that has penetrated the stem decomposes the medullary tissue between the vascular bundles and can progressively grow from bottom to top into all nodes and into the cobs. Conidiospores can be spread from exposed mycelial pads (stem injuries, cobs) with the wind or with splashes of rain.

ecology

Cool and damp germination conditions occasionally promote unspecific root rot due to slowed growth. B. Phytium sp. In contrast, the dreaded Fusarium stem rot occurs for the first time in dry and warm spring weather. For later infections and the further development of the disease, the willingness of the plant to become sick is to a large extent decisive. Stressful situations such as lack of water, excessive N / K ratio , severe infestation of leaf diseases and too high stand densities promote infestation . The development of the disease is significantly accelerated as soon as the sugar present in the stem is shifted into the grain, so that precocious varieties are more at risk. Soil contamination increases with the proportion of maize and grain in the crop rotation , while beet years and probably also artificial meadow years have a reducing effect.

Combat

Indirectly

A crop rotation that is as varied as possible , in particular avoiding maize-maize consequences, as well as all measures that are beneficial for straw rotting, reduce soil contamination. Adequate potash fertilization, not too deep and not too early sowing and irrigation until flowering can reduce the sensitivity of the plants. When choosing the variety, it is important to ensure that there is little susceptibility, especially in early-ripening varieties and in crop rotations with a strong grain.

Directly

The seed dressing reduces early infestation with non-specific pathogens, but does detect Fusarium sp. not or only insufficiently.

literature

  • F. Häni among others: Integrated plant protection in arable farming. Zollikofen 1987, ISBN 3-906679-03-9 .