programs focus primarily on plant aesthetic qualities and not on disease tolerance, often leaving crops susceptible to diseases ( Sances, 2005 ). Metham sodium, chloropicrin, 1,3-dichloropropene, and iodomethane are potential substitutes for MB in
Robert E. Uhlig, George Bird, Robert J. Richardson, and Bernard H. Zandstra
Sally M. Schneider and Bradley D. Hanson
nematode, pathogen, or weed control in trials in various production systems ( De Cal et al., 2004 ; Gilreath et al., 2005 ; Mann et al., 2005 ) but are not currently approved for certified nursery production in California. Iodomethane [IM (previously
Steven A. Fennimore, Milton J. Haar, Rachael E. Goodhue, and Christopher Q. Winterbottom
runner plant yield results and this article describes weed control results in strawberry nurseries. Some fumigant alternatives to MB currently under investigation are Pic (trichloronitromethane; Niklor Chemical Co., Long Beach, CA), iodomethane (IM
James S. Gerik
Field trials were conducted to test fumigants as alternatives to methyl bromide (MB) for production of hybrid freesia (Freesia × hybrida). One trial compared rates of 1,3-dichloropropene (DP) combined with chloropicrin (CP); the second trial compared iodomethane (IM) together with CP, DP:CP, and furfural with and without metham sodium; and the third trial compared rates and formulations of IM:CP to the standard MB:CP treatments. Most treatments reduced populations of Pythium spp. and controlled weeds compared to the untreated controls. Formulations of IM:CP reduced the incidence of disease caused by Fusarium oxysporum. Treatments of IM:CP performed as well as MB:CP, and treatments of DP:CP performed as well as IM:CP. Presently only the DP, CP and metham sodium formulations are registered for use on ornamental crops. Registration of the IM formulations will improve the options available to cut flower growers for management of plant pathogens and weeds.
James S. Gerik, Ian D. Greene, Peter Beckman, and Clyde L. Elmore
Two field trials were conducted from 2002 until 2004 to evaluate several chemicals as alternatives to methyl bromide for the production of calla lily (Zantedeschia sp.) rhizomes. Various rates and chemical combinations were tested. The chemicals were applied through a drip irrigation system. The chemicals included iodomethane, chloropicrin, 1,3-dichloropropene, metham, sodium furfural, and sodium azide. None of the treatments reduced the viability of seed of mallow (Malva parviflora) previously buried in the plots. Propagules of nutsedge (Cyperus esculentus) and seed of mustard (Brassica nigra) were controlled by iodomethane + chloropicrin, 1,3-dichloropropene + chloropicrin, chloropicrin alone, 1,3-dichloropropene alone, and furfural + metham sodium. Propagules of calla were controlled by all of the treatments except sodium azide and furfural + metham sodium. In the first trial, all treatments reduced the populations of soilborne plant pathogens, including Pythium spp., Phytophthora spp., and Fusarium oxysporum, except for sodium, which did not reduce the population of Phytophthora spp. In the second trial, all treatments controlled Pythium spp. but only a high rate of iodomethane + chloropicrin reduced the population of F. oxysporum. For all treatments, the incidence of disease caused by soilborne pathogens was reduced compared to the nontreated control. The number and value of harvested rhizomes were greater among all of the treatments, except for sodium azide, compared to the control. The harvested value of the crop for the best treatments increased significantly compared to the control. A successful crop of calla rhizomes can be produced by combinations of iodomethane, chloropicrin, 1,3-dichloropropene, and metham sodium.
Zahangir Kabir, Steven A. Fennimore, John M. Duniway, Frank N. Martin, Gregory T. Browne, Christopher Q. Winterbottom, Husein A. Ajwa, Becky B. Westerdahl, Rachael E. Goodhue, and Milton J. Haar
For years, strawberry (Fragaria ×ananassa L.) runner plant nurseries have relied on methyl bromide (MB) fumigation of soil to produce healthy transplants. Methyl bromide, however, has been phased out due to its environmental risks. The potential for alternative fumigants to replace MB was evaluated at low and high elevation strawberry nurseries in California. The alternative fumigant iodomethane plus chloropicrin (IMPic) and a nonfumigated control (NF) were compared to methyl bromide plus chloropicrin (MBPic) at a low elevation nursery (LEN) and at a high elevation nursery (HEN) near Susanville, Calif. At a HEN near Macdoel, Calif., MBPic was compared to alternative fumigants IMPic, 1,3-dichloropropene plus chloropicrin mixture (Telone C35) followed by dazomet, chloropicrin (Pic) followed by dazomet and NF. Plants produced at the LEN were transplanted at the Macdoel HEN to measure the effects of soil fumigant history on plant health and runner plant production. Plants produced at both high elevation nurseries were evaluated for fruit yield and quality at two commercial fruit production sites in soils previously fumigated with MBPic or Pic. Runner plant production at the nurseries was similar in plots fumigated with either MBPic or alternative fumigants. All fumigation treatments had higher runner plant production than plants produced for two production cycles on NF soils. Generally, fruit yields from nursery plants produced on soils fumigated with IMPic, Pic followed by dazomet, or Telone C35 followed by dazomet, were similar to fruit yields from plants produced on MBPic fumigated soils. Overall, our results indicate that preplant soil treatments with IMPic, Pic followed by dazomet, and Telone C35 followed by dazomet, are potential alternatives to MBPic fumigation for strawberry runner plant nurseries. Fruit yields by plants in MBPic and Pic fumigated soils were comparable; however, they were more variable in Pic fumigated soils. Chemical names used: 1,3-dichloropropene (1,3-D), methyl bromide, methyl iodide (iodomethane), trichloronitromethane (chloropicrin), tetrahydro-3, 5-dimethyl-2 H-1,3,5-thiadiazine-2-thione (dazomet).
S.M. Schneider, B.D. Hanson, J.S. Gerik, A. Shrestha, T.J. Trout, and S. Gao
trials in various production systems ( De Cal et al., 2004 ; Gilreath et al., 2005 ; Karlik et al., 2001 ; Mann et al., 2005 ), but are not currently approved for certified nursery production in California. Iodomethane (IM), which is not yet registered
James P. Gilreath and Bielinski M. Santos
Two independent field studies were conducted to determine the efficacy of methyl iodide (MI) formulations and rates on mixed nutsedge [purple nutsedge (Cyperus rotundus) and yellow nutsedge (Cyperus esculentus)] stands and their effects on tomato (Solanum lycopersicum) yields. In both studies, treatments were rates of two formulations of MI + chloropicrin (Pic) at the 98:2 (v/v) and 50:50 (v/v) proportions. In the MI + Pic 98:2 study, the fumigant rates were 0, 100, 125, 150, 175, and 200 lb/acre in Spring 2004 and 0, 125, 150, 175, and 200 lb/acre in Fall 2004. In the MI + Pic 50:50 study, the rates were 0, 200, 250, 300, 350, and 400 lb/acre during both seasons. Additionally, a grower standard was included in each study, which consisted of plots fumigated with methyl bromide (MBr) + Pic 67:33 (v/v) at a rate of 350 lb/acre. Higher rates of MI + Pic 98:2 and 50:50 significantly reduced mixed nutsedge densities and increased relative marketable fruit weight of tomato. Plots fumigated with MBr + Pic were weed-free at the sampling times during both studies. Data from both studies indicated that MI + Pic 98:2 and 50:50 rates of 125 and 200 lb/acre, respectively, consistently provided the highest marketable fruit weights and mixed nutsedge control, which were similar to those obtained in plots treated with MBr + Pic.
Inga A. Zasada, Clyde L. Elmore, Lani E. Yakabe, and James D. MacDonald
evaluate propargyl bromide against a diversity of soil-borne pests, 2) to determine propargyl bromide efficacy in three different geographical environments, and 3) to compare propargyl bromide with MBC, iodomethane, and metam sodium. Materials and
Sally M. Schneider, Husein A. Ajwa, Thomas J. Trout, and Suduan Gao
control conveys a high risk to growers of high-value crops. Iodomethane (IM) tested as a soil fumigant has shown a broad spectrum of efficacy against pathogens, nematodes, and weeds similar to that obtained for MBr ( Becker et al., 1998 ; Eayre et al