Leaf spot disease

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Leaf spot disease is a plant disease caused by fungi of the genus Helminthosporium that occurs on maize .

damage

Damage images

  • H. carbonum: oval spots, 2 to 25 mm long; initially paper-like with a reddish halo and often concentric zones, later brown to russet in color.
  • H. turcicum: irregularly long oval spots 0.5 to 10 cm long; initially watery gray-green, later gray-brown with a narrow dark-brown border. Inside partly blackish.
  • H. maydis: elliptical spots, 2 to 25 mm long; initially yellow-brown, later gray-brown with a narrow red-brown border. Necrotic stripes on wilting seedlings. Due to diverse breed formation, the severity of the infestation and severity of symptoms are very different depending on the variety. Small spots can hardly be distinguished and can also be confused with Phyllosticta or Kabatiella .

meaning

The fungi are widespread and can lead to a loss of assimilation surface. Helminthosporioses have so far only appeared sporadically on inbred lines in an economically damaging manner, but H. carbonum seems to be gaining in importance.

biology

Host plant: maize

Life cycle

The fungi can be introduced with the seeds, but overwinter with mycelium and spores on straw residues . In spring, the spores usually first reach the lower leaves with rain splashes. Starting from these first spots, wind-borne infections occur through conidiospores .

ecology

An increased occurrence is favored by persistently humid thunderstorm periods as well as by heavy rust attack , which enables double infections. The existence of different races makes it difficult to predict.

Combat

  • Indirect: crop rotation and plowing in the crop residues can reduce early infestation. The choice of variety must be given more attention.
  • Direct: The seed dressing brings only partial success.

literature

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