Oakes Irrigation Research
Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701)
742-2700, email: rgreenla@ndsuext.nodak.edu
EFFECT OF PREHARVEST
SPRAYING OF BENOMYL
AND FERTILITY ON STORAGE LIFE OF CARROTS.
Robert W. Stack, NDSU Plant Pathology Department
Chiwon Lee, NDSU Plant Sciences Department
Richard Greenland, Oakes Irrigation Research Site
Larry Cihacek, NDSU Soil Science Department
Yield and quality of ND grown carrots are excellent, but one impediment to
wider marketing of carrots from ND is the need to store the crop for an extended
winter period. In 1996, growers reported substantial losses in carrots stored
for 3-5 months. Losses were due to decay, mainly caused by white mold
(Sclerotinia sclerotiorum). In 1997 we established trials at the
Oakes Irrigation Research Site to test the effect of certain treatments on
storage of carrots. In 1997 and again in 1998, we compared storage life of
carrots which received a preharvest benomyl foliar spray and those that did
not. In the 1997 crop, evaluated in February 1998, benomyl almost doubled
the proportion of carrots still sound after 16 weeks. In the 1998 crop, evaluated
after 20 weeks, there was only a trace of white mold and no treatment effects
were seen.
In 1999, there were three studies to be evaluated for storage. In a repeat of the fungicide treatment trial, carrots (cvs 'Navajo' and 'Bolero') were grown in beds 30" wide (spaced on 57" centers) by 20 ft long as for commercial production. Six pairs of beds were chosen for this experiment. Of each pair, one bed was sprayed with benomyl fungicide 10 days before harvest. In the second trial, a late summer treatment of calcium nitrate was applied to six beds of carrots. Four comparable check beds did not receive this treatment. In a third trial several levels of calcium fertility were applied as described in Larry Cihacek's report.
Carrots from all three experiments were harvested in mid-to-late October, 1999. Prior to lifting, carrots were mechanically topped. Only commercially harvestable carrots were retained. Carrots were washed by hand and sorted. After washing, sound carrots were packed into doubled heavy plastic bags - two bags per rep and treatment. Bags held approximately 11 to 13 lbs of carrots each. Bags were then placed in crates in a cold storage room at 37 F. Bags of carrots will be examined in February 2000, and proportion of sound carrots determined for all treatments and checks. To assure development of some level of white mold storage rot, crowns of carrots in one of each of the two bags per treatment and replicate were inoculated with a droplet of ascospore suspension of S. sclerotiorum prior to storage.
Go to top of Benomyl and fertility on carrots study
Go to Oakes Irrigation Research Site 1999 annual report
Go to Oakes Irrigation Research Site disease studies