Alternatives to MEBR for California Cropping Systems
Location: Water Management Research
Title: Pest Control in Field-Grown Ranunculus Without Methyl Bromide
| Klose, Susanne - UC DAVIS |
| Ajwa, Husein - UC DAVIS |
| Wilen, Cheryl - UCCE |
| Mellano, Mike - MELLANO & COMPANY |
Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: September 1, 2008
Publication Date: November 6, 2008
Citation: Klose, S., Gerik, J., Ajwa, H. A., Wilen, C., and Mellano, M. A. 2008. Pest control in field-grown Ranunculus without methyl bromide. Page 29 in: Proc Annu. Intl. Res. Conf. Methyl Bromide Alternatives Emissions Reductions.
Interpretive Summary: Cut flower and ornamental bulb industries rely heavily on a methyl bromide/chloropicrin (MB/Pic) mixture as a key pest management tool. The loss of MB will seriously affect the cut flower and bulb industry, and, in the future, will require growers to use alternative fumigants. Therefore, efficacy of shank and drip-applied alternative fumigants (normal and reduced label rates) under high barrier film (virtually impermeable film, VIF) to control weeds, soil-borne pathogens and to produce a marketable ranunculus crop was tested in flower fields in Carlsbad relative to the standard MB/Pic shank fumigation at 350 lb/acre and an untreated soil. The primary goals of this project are to (1) demonstrate alternative fumigation systems at on-farm trials to facilitate the implementation of alternative pest management strategies by the California cut flower and ornamental bulb industry, and to (2) establish an outreach and educational program on alternative pest management practices that decreases the MB dependency of the cut flower industry, minimizes fumigant rates and emissions, while maintaining or increasing floricultural productivity and/or economical viability. Results indicate that the alterative treatments yielded similar stand densities, weed control, pathogen control and yields as the standard methyl bromide treatment.
Studies were initiated in November 2007 at commercial flower fields in Carlsbad, California to grow ranunculus following commercial standard production practices. Per bed 2 drip tapes (flow rate, 0.4 gpm/100 ft) were laid, and beds were covered with virtually impermeable film (VIF), with exception of methyl bromide shank standard treatments, which were covered with standard polyethylene tarp (PE). The experimental design was a randomized complete block design with each treatment unit replicated 4 or 3 times for the drip and the shank trial, respectively. The total plot area consisted of 52 beds (42” center-to-center) each 150 ft long. The shank trial included the following treatments: Untreated, MB/Pic (67/33) (350 lbs/acre, standard PE mulch), and Paladin/Pic (83% dimethyl disulfate, 17% Pic; 600 lbs/acre, VIF). The drip trial included the following treatments: Untreated, untreated followed by (fb) metam potassium (Kpam, 50 GPA), InLine (62% 1, 3-D, 35% Pic; 270 lbs/acre), InLine fb Kpam (270 lbs/acre fb 50 GPA), Kpam fb InLine (50 GPA fb 270 lbs/acre), chloropicrin (Pic; 200 lbs/acre), and Pic fb Acrolein (200 fb 270 lbs/acre). Primary drip fumigants were applied on November 19, 2007, and sequential pesticide applications were conducted 7 days past the first fumigant application on November 26, 2007. Shank fumigants were applied on December 6, 2007. Ranunculus was seeded 3 weeks after fumigation on December 27 and 28, 2007, and conventional production practices and pest management were followed. Crop response, and weed control were evaluated on February 22 and April 2, 2008. Control of soil-borne pathogens was evaluated on soil samples collected prior to seeding, at peak cut flower harvest, and at bulb harvest. Ranunculus crop yield comprises of cut flowers and flower bulbs. Cut flower harvest was conducted by a commercial crew from April 11 to May 8, 2008. Flower bulbs were harvested on July 17, 2008.
Results Stand density: At 6 weeks after seeding, shank applied MB/Pic at 350 lb/acre and Paladin/Pic at 600 lbs/acre resulted in similar ranunculus densities and both fumigants had higher crop densities than the untreated soil (data not shown). All tested drip-applied fumigants resulted in significantly lower ranunculus densities than shank-applied fumigants.
Weed control: Major weed species at this location are clover spp., which are hard to control by fumigation. Shank-applied Paladin/Pic provided lower weed control than the MB/Pic shank standard. Selected drip applied alternative pesticides showed better weed control than shank-applied MB/Pic, although differences were not significant. Treatments with improved weed control included Kpam fb InLine, Pic, InLine fb Kpam, and Pic fb Acrolein.
Pathogen control: Fusarium control was improved by 35 and 100% in MB/Pic and Paladin/Pic shank fumigated soils, respectively, compared to untreated soils. There were no significant differences in Pythium control between untreated soils and shank fumigated soils. Pathogen control was significantly improved in soils fumigated with drip alternative fumigants relative to the MB/Pic shank standard.
Cut Flower Yield: There were no significant differences in total flower yields between the MB/Pic shank standard and the Paladin/Pic shank treatment, and both fumigants had higher cut flower yields than untreated soils. Total flower yields were significantly higher in all drip fumigant treatments than in the MB/Pic shank standard, except for the untreated fb Kpam treatment.