CHLORINATION OF VEGETABLE WASH WATER: GUIDELINES FOR SMALL SCALE GROWERS
by Trevor Suslow, Extension Specialist, Department of Vegetable Crops, UC Davis
Washing vegetables with clean, domestic water removes many undesirable surface contaminants. Sanitation by chlorination of wash water is one option for the home user.
Sanitation is an essential process to include any time produce for commercial sale is washed to remove soil, debris, or to reduce decay on surfaces wounded or cut during harvest.
Wash water for the majority of vegetables should be maintained in the range of 75-150 ppm (parts per million) chlorine. Hypochlorite powders (25% active ingredient) or liquids (5.25% a.i.) are inexpensive and readily available.
The tables below give the amounts of hypochlorite to add to clear, clean water for disinfestations.
Effective chlorine concentrations are reduced by temperature, light, and interaction with soil and organic debris.
The wash water should be tested periodically with a monitoring kit, indicator strips, or a swimming pool-type color indicator kit. Concentrations above 200 ppm can injure some vegetables (such as leafy greens and celery) or leave undesirable off-flavors.
More detailed information on this topic is available in Suslow's publication, "Water Disinfection: A Practical Approach for Calculating Dose Values for Preharvest and Postharvest Applications." Publication 7256. The free publication is online at the ANR catalog Web site: http://anrcatalog.ucdavis.edu/specials.ihtml/a>
For more information, contact Trevor Suslow, Cooperative Extension, Mann Lab, Department of Vegetable Crops, UC Davis. 530/754-8313. tvsuslow@ucdavis.edu
| Hypochloride Amounts for Disinfestations |
| Table 1. | Target ppm | ml/l | oz/5 gal. | Approx. |
| | | | Cup/50 Gal. |
| Bleach (5.25%) | 50 | 0.95 | .55 | .5 |
| 75 | 1.43 | .80 | .75 |
| 100 | 1.9 | 1.1 | 1.0 |
| 125 | 2.4 | 1.4 | 1.25 |
| 150 | 2.9 | 1.7 | 1.50 |
| Table 1. | Target ppm | ml/l | oz/5 gal. | Approx. |
| | | | Cup/50 Gal. |
| Powder (25%) | 50 | .2 | .12 | .1 |
| 75 | .3 | .17 | .15 |
| 100 | .4 | .23 | .2 |
| 125 | .5 | .29 | .25 |
| 150 | .6 | .35 | .3 |
| Maintain a neutral solution pH (6.5 to 7.5). | | | |
THE CENTRAL COAST VEGETABLE IPM PROJECT: EXECUTIVE SUMMARY
by Bill Chaney, Farm Advisor, UCCE Monterey County
The Central Coast Vegetable IPM Project, which began in 1997, recently completed its work. The project was a collaboration among growers, Pest Control Advisors (PCA's), industry professionals, and UC Cooperative Extension to determine strategies for managing the pea leafminer. This group, which formed the Management Team, was unique in its high level of cooperation and is solely responsible for the success of this project.
The project focused on implementation of new strategies of pest control, using commercial-scale field demonstrations in head lettuce, romaine, and celery. Fields were side-by-side comparisons of different pesticide regimens. The “Grower Standard” treatments included all registered materials for that crop. The IPM treatments excluded organophosphates, carbamates, and pyrethroids, when an alternative treatment was possible. Insect populations and damage were monitored throughout the crop cycle by project staff and PCA’s, but treatment decisions were made by the PCA. Harvest data, including yield and quality indicators, were collected from each trial. Pesticide costs and yield data were used to determine the cost per carton of the pesticide treatments.
From 1997 to 2000, the project, in cooperation with growers, conducted 46 field demonstrations covering 667 acres. This acreage represented, conservatively, a risked investment of 2 million dollars by the grower cooperators, which does not include the great expense of staff time donated to cooperating in the project. These demonstration fields included 29 head lettuce fields, 10 romaine fields, and 7 celery fields from Watsonville to Oxnard. In these fields, the reduction in the number of applications of OP’s, carbamates, and pyrethroids for the IPM treatments compared to the grower standard was 87%, 88%, and 72% for head lettuce, romaine and celery, respectively. However, the project clearly shows that eliminating these FQPA-targeted materials is not possible at this time. One or more of the excluded pesticides was used on the IPM treatment in 38% of the head lettuce, 29% of the romaine, and 100% of the celery trials.
In these fields, switching to the use of the IPM treatments had little effect on harvest quality or quantity. There were no significant differences in yield for romaine or celery. In head lettuce, 12% of the replicated field trials had significantly higher yield from the IPM treatment. However, many of the "softer" IPM materials are more expensive than older OP’s, carbamates, or pyrethroids. Thus, there was a higher cost for the IPM treatments, up to $0.08 per carton higher.
The project had a significant education and outreach component. Growers and PCA’s participated in field days, workshops, and annual update meetings. Field data and insect identification information were also disseminated through a newsletter. In addition, a picture guide to pest and beneficial insects was published by the project. The project also developed a Web site - http://ccvipmp.ucdavis.edu - which posts project information including newsletters, trial protocols, insect photos, and data from the demonstration plots.
Additional useful Web site: http://www.spiderweb.fmc.com
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