Organic Research Database

Beginning in 1999 and concluding in 2004, we conducted a study on the control of root rot (Phytopthora fragariae var. rubi) in raspberry fields.  The study had two primary objectives:  to analyze and compare the performance of organic methods of control, and to explore the effects of manure on the suppression of the root rot pathogen.  Also studied was the impact on raspberry plant health and fruit yield.  Results tended not to be statistically significant, but the trends observed were consistent during the 3-year study.  Treating raspberry plants with poultry manure can increase berry yields 38-71% over untreated plants. All of the treatments showed consistently larger yields than plots treated with fertilizer plus Ridomil, which was only 5-17% higher than untreated plots.  This study indicates that organic and biological treatments can be successful in improving raspberry yields and decreasing the occurrence of raspberry root rot.  Poultry manure, dairy manure plus Ridomil, BioVita, and Gliocladium (G-41) tend to be especially successful in increasing yield and cane number.  These can provide greater yield increases than the commonly used chemical fungicide, Ridomil.  Dairy manure and poultry manure plus Ridomil were especially successful in decreasing root rot, and all treatments were more effective than Ridomil alone. 

The studies were carried out on a commercial field of ‘Meeker’ established at the WSU Vancouver station in 1997 on raised beds with drip irrigation.  The site was naturally infested with the root rot pathogen, at medium to high levels of disease incidence.  In Study 1, beginning in 1999, two biological pesticides, Trichoderma (T-22) and Gliocladium (G-41), were compared with the conventional chemical fungicide Ridomil.  The study was a randomized complete block design with 4 replications and 7 treatments:  1) T-22; 2)G-41; 3)gypsum; 4) dairy manure; 5) dairy manure inoculated with T-22; 6) Ridomil; and 7)untreated control.  The planting was managed organically in all other aspects.  In 2000 and 2001, yield was measured in 5 feet of row by hand harvest; in 2002 yield was measured in 25 feet of row by mechanical harvest.  In this study the effects of treatments were overshadowed by a location effect of root rot in the field.  By fall 2002 plants were in severe decline and the study was terminated.

     In Study 2, established in early 2002, dairy manure, poultry manure and Ridomil treatments were applied in 2002, 2003 and 2004.  The study aim was to evaluate if the type of manure affected the control of root rot, and if there was interaction between manure and the chemical control, Ridomil.  In early 2003, G-41 and BioVita, a bioactive soil amendment, were added as separate treatments.  This study was a randomized complete block design with 4 replications and 8 treatments:  1) G-41; 2) BioVita; 3) poultry manure; 4) dairy manure; 5) Ridomil; 6) poultry manure + Ridomil;  7) dairy manure + Ridomil; and 8) untreated control.  Yield of all plots was measured in 2002 for a baseline value, and in 2003 and 2004 weekly sub-samples of 50 berries each were collected from the mechanical harvest samples.  In 2004 hand-picked 50-berry samples were also collected.  In 2003 and 2004 soil samples from each plot were collected every 2 weeks, from manure application to final harvest.  Soil and berry samples were sent for pathogen analysis. 

Project report  http://vegetables.wsu.edu/RaspberryReport2004.pdf

Information on strategies for successful root rot suppression