Leek and Onion – Allium Problems

Leek Moth

  • Will not affect ornamental alliums
  • White or brown patches develop where leaves ahve been eaten by caterpillars.
  • Larvae bore into bulbs or stems causing secondary rots.
  • More prevalent near the coast where two generations in May and October can cause problems
  • No effective insecticide for home gardeners
  • Keep plants well watered in summer for strong growth
  • In severe cases grow under fleece

Onion White Rot

  • Affects onions garlic shallots but less severe on leeks.
  • Symptoms include yellow and wilting leaves
  • Roots rot and leave mould and black sclerotia in the soil which can survive to cause problems for 8 years
  • Plants become loose in the soil and start to go soft.
  • Most severe in cool wet summers
  • Transmitted by contaminated soil not airborne
  • Control by destroying affected plants before sclerotia form. There is no chemical control.
  • Avoid spreading contaminated soil on boots.

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