Powdery Mildew of Cucurbits Overview

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?

What is the role of the haustoria produced by the powdery mildew fungus?

How does the powdery mildew fungus primarily disperse its spores to cause secondary infection?

Which of the following statements is true about the cleistothecia of the powdery mildew fungus?

What control measures are effective in combating powdery mildew of cucurbits?

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

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.