Submitted to: Methyl Bromide Alternatives and Emissions Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 25, 2005
Publication Date: October 31, 2005
Citation: Gerik, J.S. 2005. Drip applied alternatives for floriculture production. Methyl Bromide Alternatives and Emissions Research Conference Proceedings. Published in 2005 Conference Proceedings, pgs. 105-1 - 105-4. Interpretive Summary: Three per-plant soil fumigation trials were conducted in cut flower fields to compare InLine and Midas soil fumigants to the traditional methyl bromide and chloropicrin fumigation during 2004. The alternative fumigants controlled populations of the soilborne pathogen, Pythium, as well as the traditional fumigants. Midas controlled Fusarium oxysporum better than the traditional fumigants. Weed control and plant growth were as good with the alternative fumigants as the traditional ones. It appears that in this situation the alternative fumigant could be used to successfully grow cut flower crops.
Technical Abstract: Cut flower growers in California have routinely used methyl bromide and chloropicrin for pre-plant soil fumigation to control soilborne pathogens and weeds. Because of the pending prohibition on methyl bromide production and import, alternative treatments will be required. Combinations of 1, 3-dichloropropene and chloropicrin, and of iodomethane and chloropicrin are potential alternatives to methyl bromide and chloropicrin. In June of 2004, three field trials were established near Goleta, CA in flower production fields to test alternative treatments. Fumigants and irrigation water were applied under plastic mulch through three irrigation tapes evenly spaced over the width of the bed. All three trials contained the same four treatments: 1) 448 kg ha-1 methyl bromide + chloropicrin (50:50); 2) 448 kg ha-1 iodomethane + chloropicrin [50:50 (Midas; Arvesta, San Francisco)]; 3) 443 kg ha-1 1, 3-dichloropropene + chloropicrin [61:33 (Inline; Dow AgroSciences, Indianapolis)]; and 4) a water control. All chemicals were emulsified by the formulator and the rates given are based on the active ingredient and bed width. Trial 1 was an open field, had plots 7 m long, and had 6 replications in a randomized complete block design. The soil was Baywood loamy sand (sand: 88%, silt: 3%, clay: 9%, organic matter: 1.9%). Trials 2 and 3 were under shade, had plots 3 m long and had 5 replications in a randomized complete block design. The soil was Camarillo fine sandy loam (sand: 77%, silt: 12%, clay: 11%, organic matter: 2.0%). The treatments were made on 23 June 2004 in 106 L of water per plot. Soil populations of Pythium spp. and Fusarium oxysporum were determined for soil samples from each field by dilution plating on selective media. Four weeks after treatments, trial 1 was seeded with stock (Matthiola spp.), trial 2 was transplanted with seedlings of snapdragon (Antirrhinum majus), and trial 3 was planted with bulbs of Dutch iris (Iris xiphium). Stem rot, caused by Sclerotinia sclerotiorum, appeared in trial 1 and counts of infection centers were made on 2 December 2004. The results indicate that all the chemical treatments reduced the populations of Pythium spp. relative to the control plots, but there were no significant differences among the three chemical treatments. F. oxysporum was more difficult to control. Only in trial 3 did the iodomethane + chloropicrin treatments significantly reduce the population of this soilborne fungus. All three chemical treatments significantly reduced the number of weeds in trial 1. Weed pressure was extremely light in trials 2 and 3 and there were no differences among treatments. Plant height was not significantly different among any treatment for all 3 trials, but the control consistently had the lowest value in all three trials. In trial 1 stem rot was not significantly reduced by any of the treatments. At this time the iodomethane + chloropicrin treatment is not registered for use on flower crops; the 1, 3-dichloropropene + chloropicrin treatment is registered for use on flower crops, but only at a maximum rate of 237 kg ha-1; a higher rate is needed for these crops. In conclusion, these two alternative treatments appear to perform as well as the standard methyl bromide + chloropicrin treatments. Weed and pathogen pressures in these trials were extremely light and the evaluation under more strenuous conditions is warranted.