Sorghum Diseases

Sorghum Diseases

Sorgum Disease

Sorghum diseases

  1. Covered kernel smut
  • Covered kernel smut disease (Sporisorium sorghi) affects the panicle damaging developing sorghum grains.
  • It manifests with cone-shaped capsules developed within the panicles.
  • They may cover some parts or the whole panicle with capsules containing spores that once broken spread to contaminate other sorghum plants causing further infection.

Control

  • Use of sorghum disease-free seed which is dressed with thiram or any other effective chemical.
  • Cutting off the infected panicle and bury in the soil to prevent further spread of the disease.
  • Plough down to burry and destroy disease-carrying crop residues.
  • Crop rotation with non-host crops especially legumes.
  • Use of resistant varieties.
  • Integrated disease management where a combination of the above strategies to reduce crop damage is adopted.
  1. Ergot
  • Ergot disease, caused by Sphacelia sorghi, also known as sugary disease affects the panicle producing mycelium in the affected grain.
  • The affected spikelet produces honeydew which is a concentrated suspension of conidia.
  • The disease affects sorghum at flowering and severe during rainy and humid conditions.
  • The disease is spread through infected seed with sclerotinia germinating and releasing spores that infect the sorghum spikelet ovary.
  • Insects and rain splash also spread the disease.

Control

  • Adjusting planting dates to have sorghum flower at the time when there is low rainfall and low relative humidity.
  • Plant clean seed dressed with thiram or any effective chemical
  • Burn crop residue; deep plough soil at planting.
  • Crop rotation; and where possible spray fungicides such as mancozeb 80 Wp (2kg/Ha) or Cabendazim (500gm/Ha) at panicle emergence.
  • Repeat the spraying after a week, especially if rain occurs.
  1. Anthracnose
  • Anthracnose disease caused by Colletotrichum graminicola, that commonly attacks sorghum leaves, stems, and panicle.
  • Symptoms include brick red coloration in a lengthwise split stem.
  • Small circular leaf lesions develop into mature lesions with straw-colored centers that are reddish and blackish purple and later coalesce into larger necrotic tissue.

Control

  • Practicing crop rotation with leguminous crops to break the disease lifecycle.
  • Field sanitation where sorghum residues should be collected and destroyed before the onset of the rains to reduce disease spread.
  • Use of resistant or tolerant varieties.
  • Integrated disease management reduces damage due to anthracnose disease.
  1. Northern leaf blight
  • Symptoms of Northern corn leaf blight disease include long elliptical shaped lesions with grey centers and tan to red boarders.
  • Control measures include; burning crop residues; deep ploughing at planting and crop rotation.
  1. Sorghum rust
  • Rust disease, caused by Puccinia purpurea, manifests as brown blister-like pustules formed on the upper and lower side of the leaf.
  • The pustules rapture and release the powdery mass of reddish brown spores which are commonly dispersed by wind and animal contact.
  • Other hosts include: Citronella grass, Creeping wood sorrel, Columbus grass, Johnson grass and Sudan grass.

Control

  • Practicing crop rotation with leguminous crops to break the disease lifecycle.
  • Field sanitation where sorghum residues should be collected and destroyed before the onset of the rains to remove the primary source of the disease.
  • Use of resistant or tolerant varieties.
  1. Striga (witchweed)
  • Striga, commonly known as witchweed, is a parasitic weed the affecting many cereals including sorghum. It causes 20-80% grain yield loss under severe infestation.
  • The common striga in Uganda is Striga hermontheca.
  • Symptoms of striga damage to sorghum include stunted growth, yellowing and sometimes failure to bear panicles under severe infestation.
  • The damage occurs when striga parasitizes the sorghum plant by colonizing roots, taking up the water, mineral nutrients, and photosynthetic assimilates thereby retarding growth and development of the host.
  • Striga plants produce thousands of small seeds in a season which remain viable in soils for up to 15-20 years and a few can grow in a season where host plants exist.

Control

  • Striga weed is mainly managed and controlled Inter-planting sorghum with a “chaser” Celosia argentea.
  • Practicing crop rotation with trap crops such as cotton.
  • Use of resistant/tolerant sorghum varieties and regular weeding before the weed flowers.
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