Watermelon Disease Control Demonstration

Lane, Oklahoma

2005

 

 

 

The objective of this project is to demonstrate to the use of fungicides for controlling foliar diseases in watermelon.  The demonstration will include two different fungicide treatments and two different methods to decide when to apply the fungicides.

 

Fungicides: 

  1. A mixture of Dithane 75DF applied at 2 lbs. per acre and Topsin 70 WP applied at ½ lb. per acre.
  2. Bravo Weatherstick applied at 1½ pints per acre.

 

Application Decision Methods:

  1. Apply on a calendar schedule.  Since diseases have already been observed in other fields in the area we chose a weekly schedule.
  2. Apply based on the Mesonet Anthracnose Forecaster Model. 

 

For both methods an initial fungicide application was made when plants began to produce male flowers.  That day was July 24.

 

Activity Record

Date

Field Observations and Activities

Fungicide Application

Calendar

Forecaster

July 24

First Flowers Observed.

 

 

July 26

Apply Fungicides, no diseases observed.  Sprayer used in applying Fungicides.

Yes

Yes
Aug. 4 Apply Fungicide

Yes

  
Aug. 5 Mesonet Anthracnose Forecaster Checked.  An infection hour total of 58 hours since the date of the last fungicide application falls short of the 80 hours recommended for an additional application.  

Not Recommended
Aug. 8 The Mesonet Anthracnose Forecaster reports an infection hour total of 94 hours since the last fungicide application on July 26.  This exceeds the 80 infection hours recommended for an additional application.  Foliage is abundant and has a healthy appearance so far.

Clean Foliage       Crop Canopy

 

Yes
Aug. 10 Weekly Fungicide Application

Yes

  
Aug. 17 Weekly Fungicide Application

Yes

  
Aug. 20 Application based on the Anthracnose Forecaster will be made today.  There is an infection hour total of 109 hours since the last fungicide application.  This exceeds the 80 hours recommended for an additional application.  The forecaster was not working properly for several days so we missed the point when 80 hours was reached.  

Yes
Aug. 25 Lesions have appeared on some leaves during the past week or so.Much of the foliage is free of symptoms.

Some of the leaves have lesions and tissue death at the margins.  This seems to be caused by the fungus that causes gummy stem blight.

Lesions can be found on some leaves.

Some disease can be found in all treatments.  Incidence is light and no treatment effects are obvious at this time.  Weekly applications will be made today.  For the forecaster treatments, infection hours total 37 since the last fungicide application and spraying is not recommended.

Yes

  
Aug. 31 Fungicide treatments were applied for Weekly and Anthracnose Forecaster treatments.  The Forecaster reached just 80 hours.

Yes

Yes
       
       
       

 

 

For questions or comments contact Jim Shrefler by e-mail or by phone at 580-889-7343

 

This information is provided for educational purposes only.  When using pesticides, always read and follow label directions.  Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.