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Questions and Answers
What is the primary organism responsible for powdery mildew of cucurbits?
Which of the following best describes the visible symptoms of powdery mildew on plants?
What type of reproduction does the powdery mildew fungus predominantly employ?
What environmental conditions are favorable for the development of powdery mildew?
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What is the role of the haustoria produced by the powdery mildew fungus?
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How does the powdery mildew fungus primarily disperse its spores to cause secondary infection?
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Which of the following statements is true about the cleistothecia of the powdery mildew fungus?
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What control measures are effective in combating powdery mildew of cucurbits?
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Study Notes
Powdery Mildew of Cucurbits
- A widespread disease, affecting cucurbits worldwide, including India
- Caused by Sphaerotheca fuliginea or Sphaerotheca humuli var. fuliginea
- Primarily affects plants in the Cucurbitaceae family, particularly Lagenaria vulgaris (Bottle gourd)
Symptoms
- Initially, small white spots appear on leaves and stems, becoming powdery as they expand
- The powdery substance covers the entire host surface
- Later, black, pinhead-sized structures called cleistothecia develop on the powdery mass
- Infected leaves fall off, and the fruits remain small
Host-parasite Relationship
- The fungus is an obligate ectoparasite, growing on the host's surface and sending haustoria (pear-shaped structures) into epidermal cells
- Haustoria absorb nutrients from the host
- Reproduction occurs through chains of white, unicellular conidia produced on conidiophores
- Conidia are dispersed by wind, causing secondary infections
- Sexual reproduction leads to the formation of cleistothecia, containing a single ascus with eight ascospores
Environmental Relationship
- Dry conditions favor the development of powdery mildew
- Spores have a high moisture content and germinate without external water
- Primary infection requires moisture
- Ideal temperature for growth: 11°C to 28°C
Disease Cycle
- The fungus has a wide host range, persisting on collateral hosts throughout the year
- Primary infection occurs through germination of conidia from collateral hosts
- Cleistothecia are rarely formed, making them less significant in disease recurrence
Control
- Colloidal sulfur and thiram dust are effective in managing powdery mildew
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Description
This quiz explores the widespread disease of powdery mildew that affects cucurbits, particularly in India. You will learn about its causes, symptoms, and the host-parasite relationships involved in its lifecycle. Discover the characteristics of the fungi responsible for this disease and their impact on cucurbit plants.
