Pest Of The Month: Powdery Mildew Of Tomato

Powdery Mildew of Tomato

Identification

Symptoms of the disease occur only on the foliage. Symptoms initially appear as light green to yellow blotches or spots that range from 1/8 to 1/2 inch in diameter on the upper surface of the leaf. These spots eventually turn brown as the leaf tissue dies. Eventually, the entire leaf will turn brown and shrivel, but remains attached to the stem. The white, powdery growth of fungal mycelium is typically present on the lower surfaces of affected leaves.

The plant is not killed by the disease, but is weakened and productivity is greatly decreased.

Survival And Spread

In Florida, powdery mildew is caused by Oidium neolycopersici. In western regions of the U.S. and other parts of the world, powdery mildew also may be caused by the fungus Leveillula taurica.

The powdery mildew fungi are obligate parasites; they can only survive on a living host. The removal of nutrients from host cells causes the yellowing and eventual necrosis of tomato tissue.

The fungus reproduces by producing spores or conidia. These spores are transported long distances by wind, air currents, or workers. When the conidia land on tomato leaves, they germinate and enter the leaf through stomates.

The pathogen has a wide host range and survives on weeds and crops in the solanaceous family like pepper as well as other hosts or volunteer tomato plants from one season to the next.

The fungus grows at moderate to cool temperatures. Unlike other fungi, which require free water and high humidity for optimal development, epidemics have been noted during relatively dry conditions. High relative humidity favors disease development while free water from overhead irrigation may discourage disease. Mild temperatures favor infection while higher temperatures hasten the death of infected leaves.

Management Methods

An integrated approach should be used to control powdery mildew in the greenhouse. Maintenance of high relative humidity can help reduce disease incidence. Removal of infected foliage and severely infected plants will reduce the spread of inoculum. Greenhouses should be sanitized between crops. Registered fungicides should be applied to plants as soon as symptoms are observed.

In the field, control measures would include scouting, rouging of infected plants, use of resistant varieties, and spraying preventative chemicals such as the strobilurin fungicides. Applications of sulfur will help control new infections but sulfur should be used with caution at temperatures above 85°F.

Leave a Reply

Featured Stories

CitrusIt’s Time For Young Farming Leaders To Engage [Opinion]
October 21, 2014
Florida Grower editor Frank Giles says there are capable and talented youths in the ag field ready to step up and take the reins. Read More
Farm ManagementResearchers Finding Biofuel Fits For Florida
October 21, 2014
Alternative crops identified that are suited for the state's climate and can easily be processed for power. Read More
CitrusBayer CropScience Launches New Award To Recognize Produce Industry Innovators
October 21, 2014
Award recognizes innovation that enhances the role of produce in creating better lives. Read More
FruitsCalifornia Department Of Food And Agriculture Awards $3.6 Million To Assist Farmers With Drought
October 21, 2014
State Water Efficiency And Enhancement Program highlights projects implement irrigation systems that reduce water and energy use. Read More
FruitsWashington State University Researchers See How Plants Optimize Repair Of Sun Damage
October 21, 2014
Results could lead to development of crops that recover from sun damage more easily. Read More
CitrusReport: Major Food And Agriculture Employers Can’t Fill Vital Jobs
October 21, 2014
Current shortage of young farming professionals means ample employment opportunity for the next generation. Read More
More Vegetables6 Savory Tomato And Pepper Varieties For Florida Growers
October 20, 2014
Leading vegetable seed companies highlight a half dozen high-performance selections for producers in the Sunshine State. Read More
CitrusGrowers Need To Take The Ball And Run — Now! [Opinion]
October 18, 2014
Help yourself, your farm, and fellow colleagues by becoming more involved in your industry. Read More
CitrusLegendary Florida Citrus Grower And Advocate Passes
October 17, 2014
Joe L. Davis Sr. will be remembered for his straight talk and sage advice. Read More

The Latest

CitrusIt’s Time For Young Farming Leaders To Engage [Op…
October 21, 2014
Florida Grower editor Frank Giles says there are capable and talented youths in the ag field ready to step up and take the reins. Read More
Farm ManagementResearchers Finding Biofuel Fits For Florida
October 21, 2014
Alternative crops identified that are suited for the state's climate and can easily be processed for power. Read More
CitrusBayer CropScience Launches New Award To Recognize Produ…
October 21, 2014
Award recognizes innovation that enhances the role of produce in creating better lives. Read More
FruitsCalifornia Department Of Food And Agriculture Awards $3…
October 21, 2014
State Water Efficiency And Enhancement Program highlights projects implement irrigation systems that reduce water and energy use. Read More
FruitsWashington State University Researchers See How Plants …
October 21, 2014
Results could lead to development of crops that recover from sun damage more easily. Read More
CitrusReport: Major Food And Agriculture Employers Can’t Fi…
October 21, 2014
Current shortage of young farming professionals means ample employment opportunity for the next generation. Read More
Apples & PearsInvasive Pest Found First Time In U.S. At Border Crossi…
October 20, 2014
Moth known to feed on apples, apple buds, leaves, and shoots, is found in a container full of pump valves originating in China. Read More
More Vegetables6 Savory Tomato And Pepper Varieties For Florida Grower…
October 20, 2014
Leading vegetable seed companies highlight a half dozen high-performance selections for producers in the Sunshine State. Read More
CitrusGrowers Need To Take The Ball And Run — Now! [Opi…
October 18, 2014
Help yourself, your farm, and fellow colleagues by becoming more involved in your industry. Read More
CitrusLegendary Florida Citrus Grower And Advocate Passes
October 17, 2014
Joe L. Davis Sr. will be remembered for his straight talk and sage advice. Read More
GrapesNew American Viticultural Area In Northern California E…
October 17, 2014
“Eagle Peak Mendocino County” lies entirely within the North Coast viticultural area. Read More
GrapesMapping Grape Crown Gall Tumor Disease
October 17, 2014
Scientists are close to cracking the disease’s genetic code, a major boon to vineyard protection. Read More
NutsAlmond Growers To Promote Bee Health
October 16, 2014
Almond Board of California announces comprehensive Best Management Practices. Read More
Cucurbits6 Juicy Watermelon Selections For The Sunshine State
October 16, 2014
Leading vegetable seed companies highlight a half dozen high-performance varieties for Florida producers. Read More
CitrusDiversification Is King For Small Farm’s Success
October 16, 2014
Being flexible and adapting to the times critical for Central Florida's Vo-LaSalle Farms. Read More
CitrusAsian Citrus Psyllid Moves Into Northern California
October 15, 2014
First detections made of damaging insect in Santa Clara and San Joaquin counties. Read More
Farm ManagementVidalia Onion Committee Reaches Younger Audience with D…
October 15, 2014
“V is for Vidalia” campaign focused on social and digital media outreach. Read More
VegetablesSakata Seed America To Debut “Tasty 10 By Sakata Coll…
October 15, 2014
The collection includes a new variety and will be launched at the PMA Fresh Summit Oct 17-19. Read More