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New Developments in Melon Powdery Mildew Management

The Issue

Powdery mildew of melon is a common problem in all California melon production areas and multiple fungicide applications are used to control it. Resistant melon varieties are available, but plant resistance-breaking strains of this pathogen can render them susceptible. In addition, some fungicides are no longer effective due to the development of fungicide-resistant strains of the pathogen.

The most sustainable control strategy integrates the use of varieties with mildew resistance and prudent use of fungicides. In this way, an entire melon producing area is not completely reliant on either approach to control the disease. Also, rotation of fungicides with different modes of action is an important strategy in reducing selective pressure that causes resistance. A search for such fungicides may lead to registration of new materials. This would aid in mildew control and resistance management.

In addition, there is a need to assess powdery mildew susceptibility of modern melon varieties in the low desert production area of California.

What Has ANR Done?

Cooperative Extension Advisors Thomas Turini and Keith Mayberry conducted trials comparing both the susceptibility of muskmelon varieties and the effectiveness of new fungicides. In addition, they tested fungicides in rotation to encourage techniques to reduce the likelihood of resistance being developed by the mildew. This information has been made available to California farmers and pest control professionals at field days and in farmers’ trade journals and meetings.

The Payoff

Farmers have new tools to fight powdery mildew

As a result of these UC experiments, new materials are available for use against powdery mildew. Data were submitted to the EPA to help support registration of new fungicides that will aid in preventing development of resistance. One of these materials, Procure, was approved for use in California in January, 2003.

Also, melon growers know more about the use of fungicides and resistant varieties to manage the disease. Many farmers are now using fungicide rotation programs. Pest control professionals use information from these trials to select varieties and to choose fungicides. Agricultural professionals from many production regions in California have contacted us regarding these studies.


Supporting Unit: Imperial County

Thomas Turini, Advisor, Plant Pathology
Cooperative Extension, 1050 E. Holton Road
Holtville, CA 92250, 760-352-9474 taturini@ucdavis.edu