Sulfuryl fluoride (SF) is currently used as a fumigant for control of drywood termites and insects in building structures, vehicles, wood products, postharvest commodities, and food processing facilities. This research investigated the feasibility of using SF as a preplant soil fumigant for purple nutsedge control in plastic-mulched tomato production. SF treatments included SF injected through drip tapes or SF injected through drip tapes a few hours following shank injection of chloropicrin (Pic). Results revealed that SF alone at 224, 336, or 448 kg ha−1 was generally less effective compared with when it was applied in conjunction with Pic at 168 kg ha−1. SF alone provided inconsistent control of purple nutsedge. In contrast, SF + Pic was as efficacious or more efficacious on purple nutsedge than the industry standards, including 1,3-dichloropropene (1,3-D) plus Pic and metam potassium. None of the fumigant treatments visually injured tomato plants, stunted growth, or adversely affected tomato yield. In one of the four tomato seasons, tomato plants growing in plots fumigated with SF + Pic resulted in taller tomato plants and higher markable yields. Results indicate that soil fumigation with SF + Pic is safe on plastic-mulched tomato and effectively controls purple nutsedge.

Fomesafen is a protoporphyrinogen oxidase (PROTOX) inhibitor that has the potential to be used as an alternative mechanism of action for PRE nutsedge and broadleaf weed control in Florida production of small fruit and vegetables. Fumigation in the raised-bed plasticulture system may increase herbicide persistence. Fomesafen persistence could dissuade Florida growers from using the herbicide for fear of injury to subsequent susceptible crops. Field experiments were conducted in Balm, FL, in 2015 and 2016 to investigate the effect of fumigation on fomesafen dissipation, eggplant tolerance, and purple nutsedge control. Treatments included fomesafen at 0.42 kg ai ha−1, S-metolachlor at 1.06 kg ai ha−1, and a nontreated control in either a fumigated bed injected with a combination of 39% 1,3-dichloropropene and 59.6% chloropicrin at 336 kg ha−1 or no fumigant. Fomesafen concentration in the soil decreased by 83% and 96% from application to harvest in 2015 and 2016, respectively. Fumigation did not affect fomesafen dissipation in either year. At 2 wk after transplant (WATr), fomesafen caused 14% eggplant injury. Injury decreased to less than 5% at 6 WATr. Fomesafen and S-metolachlor treatments did not reduce eggplant height or yields compared with the nontreated control. Fumigation and fomesafen did not decrease purple nutsedge density; however, S-metolachlor applications resulted in a 48% reduction. Further research is needed to assess efficacy on broadleaf and grass weeds.

Weed seed viability is an important parameter to assess the efficacy of soil disinfestation methods like fumigation and steam. In field experiments, seed samples are commonly placed in permeable bags and buried at several depths in soil before the application of soil disinfestation treatments. The seed samples are recovered several days to weeks after treatment and then seed viability is determined in the laboratory. The process of sample installation and recovery is time consuming and may expose personnel to hazardous conditions such as heat or fumigants. Described is a custom soil probe system, developed to simplify installation and recovery of weed seeds from soil. Each soil probe is capable of holding weed seed samples at three different depths up to 30 cm. The following hypothesis was tested: viability of weed seeds is similarly affected by soil disinfestation treatments whether the seeds were contained in the soil probe system or seed bag assays. Two different soil disinfestation trials were conducted: (1) a repeated micro-plot study (USDA Salinas, 1 m-2), using steam as a soil disinfestation treatment and (2) a field study in a commercial strawberry field with 1,3-dicloropropene plus chloropicrin (Pic-Clor 60) as soil disinfestation method. In both studies, seed viability of burning nettle, common knotweed, and common purslane (tetrazolium assay) and germination rates of yellow nutsedge tubers were assessed. Results indicate that the soil probe system can be used as an alternative to the seed bag assay to assess weed control efficacy of described soil disinfestation methods.

Field studies were initiated in the 2013-14 and 2014-15 growing seasons to evaluate the potential of soil solarization (SS) treatments for their efficacy on weed control and crop yields and to compare SS to 1,3-dichloropropene (1,3-D)+chloropicrin (Pic) fumigation. Each replicate was a bed with dimension 10.6 m long by 0.8 m wide on top. The center 4.6 m length of each bed, referred to as plots, was used for strawberry plug transplanting and data collection. Treatments included: i) 1,3-D+Pic (39% 1,3-dichloropropene+59.6% chloropicrin) that was shank-fumigated in beds at 157 kg ha−1 and covered with VIF on August 30 in both seasons; ii) SS for a 6 wk duration initiated on August 15, 2013 and August 21, 2014 by covering the bed with 1 mil clear polyethylene tarp; iii) SS for a 4wk duration initiated on September 6, 2013 and September 3, 2014; iv) SS 4 wk treatment initiated September 6, 2013 and September 3, 2014 and replaced with black VIF on October 4, 2013 and October 1, 2014 and v) a nontreated control covered with black VIF on October 4, 2013 and October 1, 2014. In both seasons, following completion of the preplant treatments, ‘Chandler’ strawberry was planted in two rows at a 36 cm in-row spacing in plots during the first wk of October. Over both seasons, the 6 wk SS treatment consistently lowered the weed density compared to the nontreated control. Weed density in the 6wk SS treatment was not statistically different from the 4wk SS treatments in the 2013-14 growing season. In both seasons, crop yield in the 4 wk SS was significantly lower than other treatments.

Methyl bromide (MBr) was a widely used fumigant in plasticulture because of its effectiveness against soil-borne pests and weeds in high-value crops; however, it was found to be a class 1 ozone-depleting substance and is no longer available for use in most of the United States. A mixture of 1,3-dichloropropene and chloropicrin (Pic-Clor 60) is an alternative that has been used to control soil-borne pathogens and nematodes, and has marginal control of weeds. Virtually impermeable film (VIF) and totally impermeable film (TIF) retain fumigants in the soil longer than the low- and high-density polyethylene films typically used in plasticulture production systems. The increased retention by these films may result in greater control of recalcitrant weeds such as nutsedge. Four rates of Pic-Clor 60 (112, 168, 224, and 280 kg ai ha−1) used with TIF, 280 kg ai ha−1 of Pic-Clor 60 used with VIF, and one nontreated control with VIF were evaluated for 2 yr to assess control of yellow and purple nutsedge and to determine an efficacious Pic-Clor 60 rate used with TIF. TIF with a lower rate of 224 kg ai ha−1 of Pic-Clor 60 significantly controlled nutsedge populations compared to a high rate of 280 kg ai ha−1 with VIF.

Methyl bromide (MBr) has been an industry standard for soil fumigation in a multitude of crops for decades. However, it has been banned by the United Nations Environment Programme, and alternatives to MBr must be implemented to sustain productivity in many vegetable crops that depend on soil fumigation. One alternative that has been implemented in some areas is methyl iodide (MeI). Efficacy of MeI has been demonstrated on many pest species and has been generally similar to MBr. Methyl iodide is a costly material, which has likely limited its adoption. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low-density and high-density polyethylene film, which can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied MeI : chloropicrin (Pic) (50 : 50 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of MeI : Pic (93.3 L ha−1 [178 kg ha−1 broadcast]) under VIF and TIF, three reduced rates (37.3, 56, 74.6 L ha−1 [71.2, 106.8, 142.5 kg ha−1 broadcast, respectively]) under TIF, and a nontreated control under TIF. Results indicate fumigant use rates may be reduced from a standard 93.3 L ha−1 under VIF to 37.3 L ha−1 (60% reduction) under TIF while providing yellow nutsedge control and maintaining tomato yields.

Methyl bromide (MBr) was widely used as a soil fumigant to manage pests in the planting bed prior to transplanting fresh market tomato; however, it has been banned by the United Nations Environment Programme. Alternatives to MBr must be implemented to sustain productivity in fresh market tomato. Dimethyl disulfide plus chloropicrin (DMDS : Pic) is a fumigant alternative to methyl bromide for the management of yellow nutsedge and other soil-borne pests in tomato. Fumigant costs, environmental concerns, and risk mitigation measures encourage reduced fumigant application rates. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low density and high density polyethylene film, VIF and TIF can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied DMDS : Pic (79 : 21 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of DMDS : Pic (468 L ha−1) under VIF and TIF, a high rate (561 L ha−1) under VIF, three reduced rates (187 L ha−1, 281 L ha−1, and 374 L ha−1) under TIF, and a nontreated control under TIF and VIF. Results indicated rates may be reduced from a standard 468 L ha−1 under VIF to 187 L ha−1 (67% reduction) under TIF while maintaining yellow nutsedge control and tomato yields. In addition, the results indicated that nontreated TIF managed yellow nutsedge better than nontreated VIF because of decreased penetration of the mulch by yellow nutsedge.

Field trials were conducted to determine the effect of fumigant-pebulate combinations on purple nutsedge density in fresh market tomato. Treatments consisted of methyl bromide plus chloropicrin (MBr plus Pic) [67:33] at rates of 270 and 130 kg/ha, respectively; Pic plus pebulate at 400 and 4.5 kg/ha, respectively; metham (MNa) plus pebulate at 485 and 4.5 kg/ha, respectively; dazomet plus pebulate at 950 and 4.5 kg/ha, respectively; and 1,3-dicholopropene plus Pic (C-17) [87:13] plus pebulate at 392 and 4.5 kg/ha, respectively. At 12 wk after treatment, MBr plus Pic controlled purple nutsedge more effectively (10 plants/m2) than the fumigant-pebulate combinations (50 to 70 plants/m2). Compared to MBr plus Pic, Pic plus pebulate had a 14% lower marketable yield. No differences in marketable yield were noted with dazomet plus pebulate or C-17 plus pebulate compared to MBr plus Pic. However, MNa plus pebulate produced a 15% higher yield than MBr plus Pic. Additionally, MNa plus pebulate had 15% higher marketable fruit weight than MBr plus Pic.

A study was conducted to compare the effect of 1,3-dichloropropene (1,3-D) + chloropicrin (Pic) in a 83:17 ratio (C-17) used alone or in combination with herbicides on tomato. Treatments evaluated included 1,3-D (325 kg ai/ha) plus Pic (67 kg ai/ha) used either alone or with pebulate (4.5 kg ai/ha), napropamide (4.5 kg ai/ha), metolachlor (1.1 and 2.3 kg ai/ha), lactofen (2.3 kg ai/ha), or flazasulfuron (0.4 kg ai/ha). Pebulate was consistently more effective in controlling purple nutsedge than the other herbicides tested. Purple nutsedge was more effectively controlled with C-17 in combination with pebulate than with the fumigant alone. Shallow incorporation of pebulate failed to improve weed control and tomato fruit yield.

Field trials were conducted to compare the effect of various soil fumigants along with in-bed pebulate and row-middle metribuzin applications on purple nutsedge control and on tomato and bell pepper growth and yield. Treatments consisted of combinations of soil fumigants, pebulate, and metribuzin. Fumigants levels were (1) untreated control, (2) methyl bromide (MBr) + chloropicrin (Pic) (67 + 33%, respectively), (3) Pic, (4) metham, (5) dazomet, and (6) 1,3-dichloropropene (1,3-D) + Pic (83 + 17%, respectively). Pebulate levels were either applied in-bed or not applied. Row middles were either sprayed with metribuzin or untreated. In both crops, purple nutsedge populations were independently influenced by fumigants and pebulate applications, with the highest number of purple nutsedge plants in the untreated control. The addition of pebulate reduced purple nutsedge populations in all treatments. In tomato trials, the yield was affected by fumigants, with the highest losses (53 and 50% reductions in fruit number and weight) observed in the nonfumigated control. In pepper trials, fruit number and weight were individually influenced by fumigants and metribuzin sprayings. Application of metribuzin to row middles increased yields 10% relative to nontreated plots.

Integrated management programs are becoming increasingly necessary for nutsedge control in the absence of methyl bromide. In 2012, field studies were established and maintained for a period of 2 yr at two locations to evaluate the additive effect of fallow programs and preplant fumigants for nutsedge control in bell pepper. The study included eight fallow programs consisting of eight combinations of glyphosate (G) and cultivation (C), and two fumigants; 1,3-dichloropropene + chloropicrin, dimethyl-disulfide + chloropicrin, and a nontreated check. All fallow programs provided greater late-season control of nutsedge compared to the nontreated, with the greatest control of nutsedge observed with glyphosate fb (followed by) glyphosate (GG) and glyphosate fb cultivation fb glyphosate (GCG) fallow programs. Fumigation provided additional nutsedge control in single-input fallow programs. Increased marketable yield was observed in 2012 with the application of either fumigant compared to a nonfumigated control. Furthermore, increased marketable yield was observed with more intensive fallow programs in 2013. Nutsedge control in bell pepper was significantly increased when a fallow program was used in combination with other weed-management practices.