|Rainbolt, Christine -|
|Samtani, Jayesh -|
|Fennimore, Steven -|
|Gilbert, Celeste -|
|Subbarao, Krishna -|
|Shrestha, Anil -|
|Hanson, Bradley -|
Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 7, 2013
Publication Date: February 1, 2013
Citation: Rainbolt, C., Samtani, J.B., Fennimore, S.A., Gilbert, C., Subbarao, K.V., Gerik, J.S., Shrestha, A., Hanson, B.D. 2013. Steam as a pre-plant soil disinfestant tool in California cut flower production. HortTechnology. 23:207-214. Interpretive Summary: Steam treatment of soil was investigated as an alternative for methyl bromide soil fumigation for the production of ornamental crops. Five trials were conducted in California in flower fields and covered structures using steam for soil disinfestation for the production of calla lily, oriental hybrid lily, sunflower, and bupleurum. Steam disinfestation usually was as effective as methyl bromide for suppression of pathogens and weeds and improving crop growth in cut flower nurseries. However, significant improvements in fuel and treatment time efficiency are needed before this approach can be recommended as a viable alternative to methyl bromide in California cut flower nurseries.
Technical Abstract: Methyl bromide (MB) has been widely used in California cut flower production for effective control of a broad range of soil pests including plant pathogens and weeds. However, MB has been classified as an ozone depleting substance, and its availability to growers is limited according to the Montreal Protocol Act guidelines. The need to find alternatives to MB is imperative, and steam has been suggested as a non-chemical option for pre-plant soil disinfestation. Five trials were conducted in commercial protected structure or open-field cut flower nurseries in Monterey, San Luis Obispo, and Ventura Co., California to evaluate steam application alone or in combination with solarization on soil-borne plant pathogen populations, weed densities, crop production parameters. In a 2007 calla lily [Zantedeschia aethiopica (L.) Spreng.] trial, steam disinfestation provided weed control similar to MB:chloropicrin (MBPic). In a 2008 calla lily trial, the steam (pipe) + solarization treatment was the most effective in reducing weed biomass and density, and as effective as MBPic in control of Verticillium dahliae Kleb. In a 2009 Oriental hybrid lily (Lilium spp.) trial conducted in the spring, steam treatments (drain tile or spike-hose) had fewer Fusarium oxysporum propagules 112 days after treatment (DAT) than the control, and the spike-hose steam treatment also had fewer propagules than the MB treatment. Weed densities in the drain tile steam and MB treated plots were lower than in the control plots, and crop plants were taller in both steam and MB treated plots. In a 2009 Oriental hybrid lily trial conducted in the fall, fewer crop plants emerged in the control than in steam and MB treated plots by 44 DAT, and Pythium spp. populations were lowest in the MB treatment. In a 2010 sunflower (Helianthus annuus L.) and bupleurum (Bupleurum griffithii hort.) trial, there was less Pythium spp. and Phytophthora cactorum survival in steam treatments compared to control plots, and weed densities were lower in spike-hose steam treated plots than in control plots. Steam disinfestation usually was as effective as MB for suppression of pathogens and weeds and improving crop growth in cut flower nurseries. However, significant improvements in fuel and treatment time efficiency are needed before this approach can be recommended as a viable alternative to MB in California cut flower nurseries.