Repeated soil applications of fungicide reduce activity against cavity spot in carrots
AuthorsJames J. Farrar
J. Joseph Nunez
R. Michael Davis
Authors AffiliationsJ.J. Farrar is Assistant Professor, Plant Sciences Department, California State University, Fresno; J.J. Nunez is Farm Advisor, UC Cooperative Extension (UCCE), Kern County; R.M. Davis is UCCE Specialist, Department of Plant Pathology, UC Davis.
Hilgardia 56(2):76-79. DOI:10.3733/ca.v056n02p76. March 2002.
In recent years, carrot growers in the San Joaquin Valley have suffered economic losses due to cavity spot, a soilborne disease, despite frequent applications of the fungicide mefenoxam. Although the pathogen remained highly sensitive to mefenoxam in laboratory studies, the effective dosage of the fungicide was apparently compromised in certain fields. Compared to its longevity in soils with no history of mefenoxam use, such as fields using organic production methods, the fungicide degraded rapidly in soil from fields with repeated mefenoxam use. Our research reveals that repeated applications of the fungicide to soil can increase the activity of microorganisms that degrade it, potentially reducing its efficacy against cavity spot. This is problematic in California since mefenoxam is the only fungicide available to carrot growers for cavity spot control. It may be prudent to practice long crop rotations and to limit use of mefenoxam, where possible.
Bailey AM, Coffey MD. A sensitive bioassay for quantification of metalaxyl in soils. Phytopath. 1984. 74:66-9.
Bailey AM, Coffey MD. Biodegradation of metalaxyl in avocado soils. Phytopath. 1985. 75:135-7.
Bailey AM, Coffey MD. Characterization of microorganisms involved in accelerated biodegradation of metalaxyl and metalachlor in soils. Can J Microbiol. 1986. 32:562-9.
Davis RM, Nunez JJ, Guerard JP, Vivoda E. If registered, fungicide could reduce cavity spot in carrots. Cal Ag. 1991. 45((2)):29-30.
Droby S, Coffey MD. Biodegradation process and the nature of metabolism of metalaxyl in soil. Ann Appl Biol. 1991. 118:543-53. https://doi.org/10.1111/j.1744-7348.1991.tb05344.x
Farrar JJ, Davis RM. Detection and quantification of metalaxyl using the MIDI Microbial Identification System. Phytopath. 2000. 91:S184-
Schrandt JK, Davis RM, Nunez JJ. Host range and influence of nutrition, temperature and pH on growth of Pythium violae from carrot. Plant Dis. 1994. 78:335-8.
Vivoda E, Davis RM, Nunez JJ, Guerard JP. Factors affecting the development of cavity spot on carrot. Plant Dis. 1991. 75:519-22.
Wicks TJ. Effect of metalaxyl on the control of Phytophthora crown rot of almonds. Aust J Exp Agric. 1988. 28:547-52. https://doi.org/10.1071/EA9880547
Also in this issue:The Use of Computer-Assisted Mapping Techniques to Delineate Potential Areas of Salinity Development in soils: II. Field Verification of the Threshold Model Approach
The Use of Computer-Assisted Mapping Techniques to Delineate Potential Areas of Salinity Development in soils: I. A Conceptual Introduction
ANR helps youth prepare for world of work
Africanized bees discovered in central San Joaquin Valley
New wildlife center cleans oiled birds
4-H “national conversation” garners new ideas for youth development
Survey explores influences on youth workforce preparation
National trends inform workforce research
Career awareness and part-time work examined in lives of high school seniors
California Conservation Corps offers youth career development opportunities
Teen financial literacy evaluated to develop outreach materials
Long-term studies find benefits, challenges in alternative rice straw management