Plant Pathology Infobytes 

April 5, 1996
Give Blackberry Rosette A Knockout Punch
                                          
 Blackberries have always been a southern favorite. Unfortunately,
 this crop is susceptible to rosette, a fungus disease which can
 seriously reduce fruit yield.
 
 Blackberry rosette is easily recognized by the bunchy type of
 growth which appears on infected canes in the spring. These
 bunches, or rosettes, produce diseased flower buds which tend to be
 longer and larger than normal buds. Flowers which form on rosettes
 also have more pink coloration and usually are sterile. As a
 result, few if any berries are formed on rosette growth.
 
 Popular varieties of blackberries are all susceptible to this
 disease. Control of rosette requires the application of fungicides
 at intervals through the season. The new growth must be protected
 from fungus infection with a full-season application program.
 
 Spray No. Time of Application           Fungicide Recommended    
      
   1       Late April or early May            Benlate 50 WP
           when primocanes are about
           2 feet tall
 
   2       Three weeks later                  Benlate 50 WP
 
   3       Two to three weeks later           Kocide 101 
           during harvest                      
 
   4       One to two weeks later             Kocide 101
 
   5       One week after close of            Benlate 50 WP       
           harvest        
 
   6       Two to three weeks following       Benlate 50 WP
           spray number 5 
 
   Note: Applications no. 5 and 6 are especially critical if rosette 
   blooms are still present
                                                                   
 
 Application Rates: 
   Benlate 50 WP - .75 lb/acre or 3 teaspoonful per 2.5 gals of    
   water.
   Kocide 101 - 4 lbs/acre or 10 tablespoonfuls per 2.5 gals of    
   water; Kocide DF may also be applied at the indicated application 
   times and at the rates listed for Kocide 101.
 Application Restrictions:
   Do not apply more than five sprays of Benlate 50 WP per season.
 
 Harvest Restrictions: Number of days required from day of last    
   application until harvest, Benlate WP - 3 and Kocide 101 - 0. 
   
 All fungicides should be applied in sufficient volume of water to
 obtain coverage and to the point of run-off.


Written by the late Dr. Frank Killebrew

A black line that separates the body text from footer information