Powdery Mildew – The Silent Threat Lurking in Your Crops

From pathogens to prevention.

Powdery mildew is one of the most widespread plant diseases worldwide. It infects leaves, stems, and even fruits of numerous angiosperms. As it is a chronic infection, it is a continuous important problem that affects many different crops across the world.

PATHOGEN AND CROPS

Powdery mildews belong to the order of the Erysiphales and the pathogenic ones are spread in different families and genuses. Each species causes powdery mildew on different crops. There have been several revisions to the taxonomy of powdery mildew fungi. Whereas appendages used to serve as a morphological identifier in distinguishing genera, scientists have applied molecular phylogenetic analyses in doing so.

Here are some of the pathogenic species and the crops they infect:

SYMPTOMS

Source: USU Extension - Utah State University

As the name suggests, white superficial mycelium and conidia appear on the leaves and stems, making it easily detected. The spots enlarge and get denser as the disease develops. Other typical symptoms include necrotic blotches, premature leaf fall, a general decline in growth, fruit deformation, and chlorosis. Inflorescence and berries are most susceptible when young and can be fully covered with mildew. Severe infection may hinder the growth of fruits.

LIFE CYCLE

Generic diagram of the life cycle of a powdery mildew. (Source: Courtesy G. L. Schumann from “Plant Diseases: Their Biology and Social Impact", APS Press)

The life cycle of powdery mildews generally starts with a conidia or ascospore landing on the host plant and germinating, although it should be noted that ascospores have not been found in all powdery mildew species. One or two germ tubes are formed and act as a penetration tool. The fungus directly penetrates the host cell wall through enzymatic activity and turgor pressure. After the breakdown, the fungus develops a haustorium to supply it with nutrition.

Powdery mildews reproduce both asexually and sexually. Asexual reproduction starts within a few days of infection. Conidiophores emerge from vegetative hyphae and conidia are produced serially. Conidia are then dispersed through wind over relatively short distances.

When the asexual growing season ends, sexual reproduction occurs via chasmothecia, which are small, round fruiting bodies containing asci, specialized sacs where ascospores are produced. As the nucleus from the male gametangia moves to the female gametangia through plasmogamy, it results in a dikaryotic cell, from which asci develop. The number of ascospores per ascus varies among the species from two to eight. Under favorable conditions, chasmothecia open and release ascospores.

Powdery mildew fungi overwinter in several forms – chasmothecia, bud perennation, and mycelium become active again when favorable conditions return in the spring.

HOW CAN METOS HELP YOU?

Powdery mildew is a persistent threat to many crops, but with METOS solutions, you can track, and prevent outbreaks before they happen. Since powdery mildew fungi are largely affected by environmental conditions, it is important to precisely monitor the condition and disease risk.

UNLOCK THE POWER OF TECHNOLOGY FOR FARMING

METOS has tools to alert the occurrence of various diseases, including powdery mildew, in different crops using different kinds of sensors. Download our in-depth guide and discover:

  • How weather and environmental conditions influence disease risk
  • The right sensors for your specific crops
  • Why smart disease monitoring improves crop protection

Don’t let the diseases take control!

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