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Disease of the Month - Heat / Drought related Deformities

 
  Hort Snacks - July 2018
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 Crops Affected: range of crops (depending on disorder)

Symptoms / Conditions Favouring Development:

Hollow Heart (potatoes)

  • Common in oversized or rapidly growing, early tubers
  • Very dependent on cultivar
  • Most severe under rapid tuber growth conditions
    • Uneven moisture (dry followed by wet) or fertility
    • Wide plant spacing or missing plants
  • No visible external symptoms
  • Internal symptoms – tan to brown walled cavities that develop from brown areas at or near the centre of tubers
Hollow Stem (broccoli and cauliflower)
  • No visible external symptoms
  • Small cracks occur internally, which coalesce to form a hollow central stem
  • Cause is suggested to be related to plant nutrient balance, as well as growth conditions after head initiation
Forking (carrots)
  • Cause can be a result of disease or pest damage, compacted or heavy soils, excessive plant densities, or other factors that damage the root tips
  • Location of the fork can give an indication of when the damage occurred and may suggest probable cause
Growth Cracks (carrots, rutabaga, turnips, potatoes, cabbage, tomatoes, cherries)
  • Rapid tissue growth leads to vertical cracking, with cracks varying in size
    • Cracks may originate along root or tuber or in neck areas
    • Older cracks may have a layer of rougher wound tissue over the inside of the crack
    • More typical on larger roots
  • Fruit cracking can occur as radial or concentric cracks
    • Can occur as “bursting” when very rapid
  • Is typically the result of fluctuating soil moisture levels, specifically when abundant moisture follows a dry spell
Jelly End Rot (potatoes)
  • Most prevalent in Russet Burbank potatoes
  • Stem end tissues of tubers become glassy, jelly-like and shrivels and dries up
  • Favoured by high soil temperatures and dry conditions followed by excellent moisture
  • Often associated with misshapen tubers
Brown Bead (broccoli)
  • Buds of broccoli florets turn tan or brown and can fall off easily
  • Associated with rapid growth in high temperatures following abundant moisture
Sunscald (various crops)
Bulb crops
  • Soil level tissues shrivel, and the plant withers and dies
  • Young, sensitive plants are damaged by hot, sunny conditions in dry springs
Beans / Fruit crops (e.g. tomatoes)
  • Small, water-soaked spots on plant parts only on exposed sides of the plant, typically in intense, direct sunlight following cloudy, high humidity and high temperature conditions
  • Spots become brown to white and grow together to form large necrotic lesions; may be sunken
Management:
  • Maintain adequate (and uniform, if possible) moisture levels throughout the growing season
    • This may involve the use of irrigation, improving soil moisture hold capacity, etc.
  • Ensure plants are uniformly spaced within the row
  • Avoid excess or inadequate fertilization (particularly nitrogen)
  • For some disorders (e.g. hollow heart / hollow stem), there are varietal differences in susceptibility
  • If possible, adjust planting dates to avoid having susceptible stages present during hot, dry conditions.
  • Avoid irrigation to ripe fruit (susceptible to cracking)
 
 
 
 
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on June 26, 2018.