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Feras Almasri, Husein A. Ajwa, Sanjai J. Parikh, and Kassim Al-Khatib

). Research showed that the soil fumigants that are alternatives to MeBr are generally less effective pest control agents. These alternatives to MeBr include chloropicrin (CP), 1,3-dichloropropene (1,3-D), methyl isothiocyanate (MITC) generators such as metam

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Douglas V. Shaw and Kirk D. Larson

Yield for annual California strawberry (Fragaria ×ananassa Duch.) production systems in soils treated with combinations of methyl bromide–chloropicrin (MB:CP) were compared with four alternative soil treatment systems using meta-analysis. Studies represent 11 production seasons, and were conducted at three distinct locations in California. Fumigation with mixtures of methyl bromide (MB) and chloropicrin (CP) increased yield significantly compared with any and all alternatives lacking MB. In a combined analysis of 45 studies, fumigation with MB:CP compounds increased yield an average of 94.4% (d+ = 2.874 ± 0.098) compared with yields for plants in nonfumigated (NF) soils. Further, the effect of MB:CP fumigation increased over the first three strawberry cultivation cycles: MB:CP–fumigated soils provided a 59.2% (d+ = 2.166 ± 0.146) yield advantage when one cycle of fumigation was omitted, a 100.2% (d+ = 3.000 ± 0.143) advantage when two cycles were omitted, and a 148.4% (d+ = 6.201 ± 0.348) yield advantage when three or more cycles of MB:CP were omitted. In a combined analysis that included 34 studies, soil fumigation with MB:CP conferred a 9.6% (d+ = 0.751 ± 0.087) yield advantage over fumigation with CP alone. Soils treated with MB:CP yielded 6.8% (d+ = 0.437 ± 0.114) more fruit than those treated with very high rates of CP (336–396 kg·ha–1), and 15.4% (d+ = 1.190 ± 0.134) more than soils treated with commercially realistic rates (168–224 kg·ha–1). Similar to the comparison using NF soils, the efficacy of very high rates of CP appeared to diminish over cycles of strawberry cultivation; MB:CP increased yield 2.2% (d+ = 0.043 ± 0.162) in the first CP production cycle, 10.6% (d+ = 0.588 ± 0.174) and 13.7% (d+ = 2.054 ± 0.401) in the following two cycles. Combinations of dichloropropene (DP) and CP were no more effective than were lower rates of CP alone, and MB:CP conferred a 14.4% (d+ = 0.962 ± 0.162) yield advantage over mixtures of DP:CP. Mixtures of MB:CP increased yield 29.8% (d+ = 3.199 ± 0.287) compared with metam sodium (MS). The standardized effect was similar when comparing MB:CP combinations with either MS or NF soils, suggesting little effect of MS on the yield response. Chemical names used: trichloronitromethane (chloropicrin); 1,3-dichloropropene (dichloropropene); sodium N-methyldithiocarbamate (metam sodium).

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James P. Gilreath and Bielinski M. Santos

nutsedge densities below 30,000 plants/acre. Fig. 1. Effects of methyl iodide plus chloropicrin (MI + Pic) 98:2 (v/v) rates on nutsedge densities at 5 and 9 weeks after transplanting (WAT) and on relative tomato marketable fruit weight in plots treated with

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Bielinski M. Santos, James P. Gilreath, and Timothy N. Motis

Field trials were conducted from 1999 to 2003 to determine whether chloropicrin (Pic) stimulates nutsedge (Cyperus spp.) emergence through polyethylene mulch, and to examine at which Pic rate the stimulatory effect is maximized. Shank-injected Pic rates were 0, 50, 100, 150, 200, and 250 lb/acre. Application rates between 107 and 184 lb/acre of Pic stimulated nutsedge sprouting through polyethylene mulch by 60%, 400%, 58%, and 120% more than the nontreated control during four of the seasons. Rates above 250 lb/acre eliminated the stimulatory effect on nutsedge, reducing densities to the same levels as the nontreated control. The exact physiological mechanism of this stimulation is still unknown.

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Jayesh B. Samtani, Husein A. Ajwa, Rachael E. Goodhue, Oleg Daugovish, Zahanghir Kabir, and Steven A. Fennimore

). Total annual applications of 1,3-D are however restricted in an area of 93.2 km 2 (defined as township) in California as a result of air quality concerns ( California Department of Pesticide Regulation, 2009 ). Chloropicrin being volatile and toxic can

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Robert E. Uhlig, George Bird, Robert J. Richardson, and Bernard H. Zandstra

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

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Sally M. Schneider and Bradley D. Hanson

township caps that are shared by all 1,3-D-using crops on a first-come-first-served basis [ California Department of Pesticide Regulation (CDPR), 2002 ]. Metam sodium and chloropicrin (Pic) are currently registered in the United States and have provided

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Johan Desaeger and Alex Csinos

The effects of drip-applied 1,3-dichloropropene (1,3-D) and chloropicrin on fumigant soil gas levels and growth of vegetable seedlings were investigated in three separate tests in Tifton, Ga. Tests were conducted in Spring 2002, Fall 2002, and Spring 2003. Phytotoxicity of 1,3-D + chloropicrin was induced in the 2002 tests by applying progressively higher rates (0 to 374 L·ha–1) of drip-irrigated InLine (an emulsifiable formulation (EC) containing 60.8% 1,3-D and 33.3% chloropicrin) and planting vegetable seedlings within four days after application. Vegetables evaluated were tomato, pepper and cucumber (Spring 2002), and tomato and squash (Fall 2002). In Spring 2003, the effects of 1,3-D formulation (InLine versus Telone EC, an EC containing 94% 1,3-D), plastic mulch type [low density polyethylene (LDPE) versus virtually impermeable film (VIF)] and drip tape configuration (one versus two drip tapes) on fumigant soil gas levels and growth of tomato were investigated. Tomato was planted after the recommended 3-week waiting period. Fumigant concentrations in soil were measured using Gastec detection tubes at 1 to 4 days after drip fumigation in all three tests. Measured fumigant soil gas concentrations were correlated with fumigant application rates in Spring 2002, but not in Fall 2002. Vegetables were visibly affected by residual fumigant levels in the soil and showed symptoms such as leaf chlorosis (cucumber, squash and pepper), leaf bronzing (tomato) and stem browning and stunting (all crops). Fumigant soil air levels were negatively and linearly correlated with different plant growth parameters, in particular plant vigor. The cucurbit crops showed an immediate response and high mortality within 1 week after planting. Surviving plants recovered well in fall. The solanaceous crops showed a more delayed response and lower mortality rates. However, phytotoxic effects with tomato and pepper were more persistent and plants did not seem to recover with time. Overall, fumigant residue levels and potential phytotoxicity were greater in spring than in fall. Greater fumigant soil concentrations were measured under VIF as compared to LDPE plastic mulch. The effect of drip-tape configuration varied with the type of plastic mulch that was used. The double-tape treatment resulted in lower fumigant levels at the bed center under LDPE mulch, and higher fumigant levels at the bed shoulder under VIF mulch. The formulation containing 94% 1,3-D resulted in higher soil fumigant levels as compared to the formulation containing 61% 1,3-D and 33% chloropicrin, especially with VIF mulch. Early plant vigor of tomato was negatively correlated with fumigant soil gas levels, and was especially poor following drip fumigation with 94% 1,3-D under VIF mulch.

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S.M. Schneider, B.D. Hanson, J.S. Gerik, A. Shrestha, T.J. Trout, and S. Gao

-inject 300 to 400 lb/acre a.i. of 98% MB plus 2% chloropicrin (Pic) covered with high-density polyethylene (HDPE) tarpaulins. The MB component of this treatment provides consistent, effective control of nematodes, fungi, and weeds over a wide range of soil

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Carlene A. Chase, William M. Stall, Eric H. Simonne, Robert C. Hochmuth, Michael D. Dukes, and Anthony W. Weiss

An evaluation of the effect of bed width (24, 28, 32, and 36 inches) on the control of a mixed population of nutsedge [yellow nutsedge (Cyperus esculentus) and purple nutsedge (C. rotundus)] was conducted with an emulsifiable concentrate formulation of a 1,3-dichloropropene (1,3-D) and chloropicrin (CP) mixture (1,3-DCP) for application through drip irrigation systems. Beds were mulched with either 1.4-mil-thick virtually impermeable film (VIF) or 0.75-mil-thick high-density polyethylene (HDPE) and 1,3-DCP was applied at 35 gal/acre by surface chemigation or via subsurface chemigation 6 inches deep within the bed. HDPE was more permeable to gaseous 1,3-D than VIF so that 1 day after treatment (DAT), 1,3-D gas concentration at the bed centers under VIF was significantly higher than under HDPE. Dissipation of 1,3-D gas with HDPE occurred within 7 DAT, but dissipation with VIF took ∼10 days. In bed centers, 1,3-D concentrations 1 DAT were in the range of 2.3 to 2.9 mg·L–1 whereas in bed shoulders concentrations ranged from 0.1 to 0.55 mg·L–1. In 2002 and 2003, 1,3-D concentration in shoulders of narrower beds was significantly higher than in the wider beds, but dissipated more rapidly than in wider beds. Lower initial 1,3-D concentrations were observed with HDPE film in shoulders than with VIF and the rate of dissipation was lower with VIF. At 14 DAT, nutsedge plants were densely distributed along bed shoulders (19 to 27 plants/m2) with little or no emergence in the centers of beds (fewer than 5 plants/m2), but with no response to bed width. Nutsedge density increased with time, but the nature of the increase differed with bed width. The most effective nutsedge suppression was achieved with 36-inch beds, which had densities of 11–13 plants/m2 on bed centers and 53 plants/m2 on bed shoulders by 90 DAT. Nutsedge suppression was initially more effective with VIF than with HDPE film, so that no nutsedge emerged in the centers of beds mulched with VIF compared with 2–7 plants/ m2 with HDPE by 14 DAT. On bed shoulders there were 2–7 plants/m2 with VIF and 32–57 plants/m2 with HDPE. Increase in nutsedge density with time was greater with VIF so that by 90 DAT nutsedge densities on bed centers and shoulders were greater than with HDPE in 2002 and the same as with HDPE in 2003. Subsurface chemigation did not consistently improve suppression of nutsedge when compared with surface chemigation. Concentrations of 1,3-D in bed shoulders irrespective of bed width were nonlethal. Initial superior nutsedge suppression with VIF did not persist. Nutsedge control in a sandy soil with 1,3-DCP chemigation is unsatisfactory with one drip-tape per bed.