Explore effective strategies and common pitfalls in managing onion diseases in horticulture. Assess your understanding of symptoms, prevention, and treatment techniques.
You notice pale green spots and a fluffy purple-gray growth on your onion plants early in the morning. What is the most likely cause?
Explanation: Downy Mildew in onions presents as pale spots with a purplish, downy growth, particularly visible in humid conditions. White Rot mainly shows as a white, woolly fungus at the base; Pink Root causes pink to red discoloration of roots; Black Mold involves black spores usually on harvested bulbs.
Why is practicing crop rotation important for onion disease management?
Explanation: Crop rotation limits the buildup of pathogens like Fusarium or Sclerotium in soil, reducing disease incidence. Sunscald is managed by other means; fertilizer absorption and bulb maturity are influenced by different agronomic practices rather than rotation.
Which irrigation method best helps prevent foliar diseases like Botrytis leaf blight in onions?
Explanation: Drip irrigation keeps foliage dry, which reduces the risk of foliar diseases. Overhead sprinklers and flood methods can wet leaves, promoting disease, while furrow irrigation does not protect foliage as effectively in comparison to drip.
At what stage is it most effective to apply fungicides for onion disease control?
Explanation: Applying fungicides early at disease onset is effective in preventing spread. Post-harvest or during storage applications are less useful for live plant protection; bulb curing addresses different issues unrelated to foliar diseases.
If onion bulbs develop water-soaked spots during storage that later turn black and powdery, which disease is most likely responsible?
Explanation: Black Mold is characterized by black, powdery fungal growth on stored bulbs. Downy Mildew affects foliage, Neck Rot causes soft, gray mold near the neck, and White Rot usually presents white growth at bases rather than black mold on stored bulbs.