CLEMSON – Experts from the Clemson University Cooperative Extension Service and Cornell University taught participants in a workshop this week techniques for sampling and identifying key cucurbit diseases and their symptoms and insect pests and their natural enemies.

Cucurbits are plants from the gourd family, such as cucumbers, melons, pumpkins and squash.

Tony Keinath, a researcher at the Clemson Extension Coastal Research and Education Center in Charleston, talks about preventing downy mildew in cucurbit plants during a recent workshop.

Tony Keinath, a researcher at the Clemson Extension Coastal Research and Education Center in Charleston, talks about preventing downy mildew in cucurbit plants during a recent workshop.
Image Credit: Denise Attaway/Clemson

United States Department of Agriculture National Agricultural Statistics Service Census data show that in 2012, 1,846 acres of cucumbers and about 7,350 acres of melons were harvested in South Carolina, respectively. The census data also shows 153 acres of pumpkins and 1,013 acres of squash were harvested.

Downy mildew is a major disease that affects most cucurbits. Tony Keinath, a researcher at the Clemson Coastal Research and Education Center in Charleston,  said prevention is the best way to handle this disease.

“If you do detect it on your plants, it is important you act quickly to control it,” Keinath said. “If not properly managed, this disease can cause a decrease in yield and quality.”

Symptoms of downy mildew include pale green to yellow spots that turn brown on cucumbers and cantaloupes. On squash and pumpkins, the spots are small, bright yellow flecks across the leaf surface. Brownish-purple spores are found on the undersides of infected leaves in the early morning. Management steps growers can take include using cultural practices such as:

  • Plant cucurbits as early as possible.
  • Choose cultivars that are resistant to downy mildew.
  • Use trellises for cucumber vines.
  • Summer squash, zucchini and acorn squash tolerate some downy mildew. They still produce marketable fruit when diseased.
Laura Dahl of Easley captures insects from the Clemson Student Organic Farm so that she can examine them in a lab of the Clemson Biosystems Research Complex.

Laura Dahl of Easley captures insects from the Clemson Student Organic Farm so that she can examine them in a lab of the Clemson Biosystems Research Complex.
Image Credit: Denise Attaway/Clemson

Other management tools include spraying with fungicides. Fixed copper fungicides can be used to help prevent downy mildew if applied before plants have become infected with the disease.

Growers can register with the  Cucurbit Downy Mildew Alert System to get email alerts and/or text messages when downy mildew outbreaks are reported. Growers should start spraying as soon as an outbreak is reported in their state, said Keinath, who is a coordinator for the alert system.

Gummy stem blight was another disease Keinath mentioned, saying he hasn’t heard many complaints about the disease this year because it’s been a dry year. Other diseases addressed during the workshop included anthracnose and powdery mildew.

In addition to protecting cucurbit crops from diseases, it’s also important to stave off insects that may attack the crops. Powell Smith, a Clemson Extension vegetable entomologist from Lexington County, said growers should remain vigilant and “…take action to prevent the economic injury level from being reached.”

David Richmond of Laurens uses a microscope to examine an insect captured a the Clemson Student Organic Farm.

David Richmond of Laurens uses a microscope to examine an insect captured a the Clemson Student Organic Farm.
Image Credit: Denise Attaway/Clemson

The workshop was divided into two parts. The first part took place at the Clemson Student Organic Farm. The farm is a fully operational six-acre demonstration farm located on the Clemson University campus. It serves as a resource for training and education in sustainable and organic agriculture. The farm was certified organic in 2005 and follows the National Organic Program rules which prohibit the application of synthetic fertilizers and pesticides. It also has achieved USDA Good Agricultural Practices (GAPs) certification governing food safety in the production and handling of produce. In addition, the farm also produces a wide variety of seasonal fruits and vegetables for its community supported agriculture program.

Shawn Jadrnicek, farm manager, said research conducted at the farm helps growers all over the United States.

“The Student Organic Farm bridges the gap between the classroom and hands-on research and education,” Jadrnicek said. “With the support of Clemson University and dedicated students, the farm has developed innovations in season extension, cover-cropping and other sustainable practices helping farmers across the country.”

The second part of the workshop took place in at the Clemson Biosystems Research Complex headhouse, a support facility for the greenhouses at Clemson University. It consists of two reach-in growth chambers, four controlled environment rooms and seven 100-square-foot, walk-in growth rooms. While at the headhouse facility, participants used microscopes to examine leaves and insects they took from the farm.

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