Studies were conducted to determine lethal temperatures for Cyperus esculentus and Cyperus rotundus tubers using diurnal oscillations in soil temperature with maxima of 40, 45, 50, and 55 C and a minimum of 26 C. Growth of Cyperus spp. plants was faster at 40 C than at a constant temperature of 26 C. The 45 C treatment delayed Cyperus spp. emergence but was not lethal to tubers. Tuber mortality was 100% for both Cyperus spp. with the 50 and 55 C temperature regimes. Soil solarization with thermal-infrared-retentive (TIR) films resulted in higher soil temperatures than with a 30-μm low-density polyethylene (LDPE) clear film. With TIR films, greater proportions of emerged C. rotundus plants were killed by foliar scorching, and 6 wk of soil solarization was more effective at reducing C. rotundus density than with the LDPE film. Four weeks after film removal, the lowest level of control was obtained with the LDPE film. For C. rotundus tubers planted 5 and 10 cm deep, 62% control was obtained with the LDPE film, and it decreased to 32% with a 15-cm planting depth. The best residual control was 95 and 92% with the 75-and 100-μm TIR films, respectively. With the TIR films, there was no significant change in C. rotundus control with planting depth.

Soil solarization is a process of soil disinfestation that involves solar heating of moist soil covered with transparent polyethylene film. This nonchemical approach to controlling soil-borne pests is being investigated as an alternative to methyl bromide fumigation. Summer solarization controlled annual weed species and suppressed purple nutsedge. Although some nutsedge tubers sprouted despite the solarization treatment, the resulting shoots were almost always trapped under the clear solarization film. Conversely, in rows that were mulched with black film, nutsedge rhizomes punctured the film so that leaf expansion occurred above the film. In controlled pot experiments conducted in darkness, yellow nutsedge rhizomes readily penetrated 19- and 30-μm clear films as effectively as opaque films. Thicker clear films and bubble film reduced nutsedge penetration. In the greenhouse and laboratory, nutsedge penetration of transparent polyethylene film was inversely related to irradiance levels when the film was in direct contact with the soil. However, when there was a 5- to 10-mm space between the soil and the film, the lowest irradiance level (30 μmol m−2 s−1) was as effective as 320 μmol m−2 s−1 in reducing penetration by purple nutsedge. The film penetration by nutsedge rhizomes appears to be linked to a light-dependent morphological change from rhizome growth to leaf development, which occurs before film penetration with clear mulch and after film penetration with opaque mulch. The alternate sprouting and foliar scorching of nutsedge shoots trapped under clear films could potentially be exploited to deplete nutsedge tubers that occur at soil depths that do not develop lethal temperatures under soil solarization.

The effect of soil disinfestation with methyl bromide (MB) or by soil solarization (solar heating) and the fungicides TMTD (tetramethylthiuram disulfide) and fentin acetate (triphenyltin acetate) on the degradation of terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-methylthio)-s-triazine] and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] were investigated. The degradation of terbutryn appeared to follow first-order kinetics with a half-life of about 2 weeks and was much slower in MB-treated or solarized soils, i.e. half-life of about 11 weeks. Suppression of terbutryn degradation in the MB-treated soil was still evident 8 months after soil fumigation, similar to that found in autoclaved soil. TMTD and fentin acetate at 20 μg/g soil strongly inhibited degradation of terbutryn in soil. Degradation of atrazine was affected to a lesser extent by soil disinfestation. Results from the present study suggest that biocidal soil treatments may slow herbicide degradation. Thus, herbicide dosages in disinfested soil should be adjusted in order to avoid phytotoxicity. Moreover, lower dosages might be sufficient to attain weed control, and combined disinfestation or fungicides with herbicide treatments might be intentionally used to extend herbicide activity.

Methyl bromide has been widely used for weed control in polyethylene-mulched tomato production. With the phaseout of methyl bromide in the United States, an effective alternative is needed. Field experiments were conducted in 2007 and 2009 to determine if allyl isothiocyanate (ITC) would provide substantive weed control in tomato along with crop tolerance under low-density polyethylene (LDPE) and virtually impermeable film (VIF) mulch. Treatment factors included two mulch types (LDPE and VIF) and six rates of allyl ITC (0, 15, 75, 150, 750, 1,500 kg ha−1). A standard treatment of methyl bromide : chloropicrin (67 : 33%) at 390 kg ha−1 under LDPE mulch was also established. Allyl ITC was broadcast applied and incorporated in soil before forming raised beds and laying plastic mulch. Tomatoes were transplanted 3 wk after applying allyl ITC or methyl bromide treatments. Tomato injury was ≤ 8% in all treatments at 2 wk after transplanting (WATP). Allyl ITC at 913 (± 191) kg ha−1 was required to control yellow nutsedge, Palmer amaranth, and large crabgrass equivalent to methyl bromide at 6 WATP and maintain marketable tomato yield equivalent to methyl bromide treatment. VIF mulch was not effective in increasing weed control or improving the marketable yield of tomato over LDPE mulch. This research demonstrates that allyl ITC under an LDPE mulch can have a practical application for weed control in polyethylene-mulched tomato in the absence of methyl bromide.

Fresh market tomato is an important and valuable crop in Florida, accounting for 630 million dollars farm-gate value, which was 45% of the total value of the U.S. crop in 2010. In order to maintain or increase its productivity, labeled herbicide alternatives to methyl bromide are important to limiting seed production of weeds emerging between the raised plasticulture beds. A study was conducted inside a greenhouse where carfentrazone was applied as a drench at 0.03125×, 0.0625×, 0.125×, 0.25×, 0.5×, 1×, 2×, 4×, and 8× and as a subsurface irrigation at 0.0625×, 0.125×, 0.25×, 0.5×, 1×, 2×, 4×, 8×, and 16× rates. The 1× rate equaled the maximum labeled rate of carfentrazone (35.1 g ai ha−1) that would be applied to an area of 0.360 m2. Both the drench and subsurface trials showed an increase in plant injury and reduced growth as the rate of carfentrazone increased. The drench trial, however, was observed to have higher visible injury and greater growth reduction (based on plant measurement) than the subsurface trial, when comparing similar rates. For the 1× rate of carfentrazone in the drench trial vs. the subsurface trial, injury was 66 and 24.5%, respectively. For the 1× rate the tomato plants had estimated growth, based on the curves fit for the data, of 4.8% vs. 39.9% for the drench and subsurface trials, respectively. The subsurface trial better represents what happens in the field when carfentrazone root uptake injury is observed since it is normally observed to be around 10% or less. This still leaves a level of concern; once a 10% injury level in the subsurface trial was estimated to have reduced tomato growth, fruit weight, and total shoot dry weight by 33, 15, and 9.5%, respectively.

Potassium azide (PA) (112 kg/ha), oxadiazon + 1,3-dichloropropene (1,3-D) (168 kg/ha + 140 L/ha), dazomet (392 kg/ha), dazomet + chloropicrin (392 + 168 kg/ha), dazomet + 1,3-D (392 kg/ha + 140 L/ha), iodomethane (IM) (336 kg/ha), metam-sodium (MS) (748 L/ha), MS + chloropicrin (748 L/ha + 168 kg/ha), and MS + 1,3-D (748 + 140 L/ha) were evaluated at Jay and Arcadia, FL, in 1998 and 1999 as alternatives to methyl bromide (MeBr) fumigation for the management of common turfgrass weeds. Potassium azide was as effective as MeBr in controlling ‘Coastal’ bermudagrass, yellow and purple nutsedges, alexandergrass, broadleaf signalgrass, tall and sharppod morningglories, and various winter annual broadleaf weeds, but it failed to provide acceptable control of redroot pigweed. 1,3-Dichloropropene + oxadiazon did not control yellow nutsedge, purple nutsedge, or Coastal bermudagrass. Similarly, this combination treatment failed to control carpetweed but did provide 83% control of the winter annual weed species, 71% control of alexandergrass and broadleaf signalgrass, and ≥ 80% control of tall morningglory, sharppod morningglory, and redroot pigweed. Dazomet + combination treatments provided control of Coastal bermudagrass at Jay; however, control of common bermudagrass, alexandergrass, and broadleaf signalgrass was not acceptable at Arcadia. Sedge species control with dazomet + combinations was poor (< 63%) at both sites. Iodomethane, a treatment not yet registered by the U.S. Environmental Protection Agency (EPA), controlled weedy grass species, sedge species, and broadleaf weeds present at the two locations under different environmental conditions. Metam-sodium alone and MS + chloropicrin, tarped and untarped, and MS + 1,3-D provided acceptable weed control; however, MS + chloropicrin covered with a plastic tarp for 48 h was the best MS treatment. Metam-sodium + chloropicrin, with plastic tarp, controlled weedy grass and broadleaf species equal to MeBr; however, unacceptable sedge species control at Jay and Arcadia was 56 and 79%, respectively. Metam-sodium applied alone failed to control redroot pigweed; however, MS + combinations provided control. These studies confirm that no EPA-registered fumigant alternative to MeBr, applied alone or in combination for preplant turf soil fumigation, exists. Consequently, until such time that an effective alternative is identified, turf managers will be forced to forego fumigation, or they will have to choose a less-effective alternative and accept the consequences of contamination.

Isothiocyanates (ITCs) were evaluated as an alternative to methyl bromide (MeBr) for control of Palmer amaranth, large crabgrass, and yellow nutsedge; reduction of tuber density; and increase in marketable tomato yield in low density polyethylene (LDPE)-mulched tomato production. Allyl ITC was applied at 450, 600, and 750 kg ai ha−1; metham sodium (methyl ITC generator) was applied at 180, 270, and 360 kg ai ha−1; and MeBr plus chloropicrin (mixture of MeBr and chloropicrin at 67 : 33%, respectively) was applied at 390 kg ai ha−1. A nontreated weedy check was included for comparison. There was no injury to tomato plants following allyl ITC, metham sodium, or MeBr application. Allyl ITC at 750 kg ha−1 or metham sodium at 360 kg ha−1 controlled Palmer amaranth ≥ 79%, large crabgrass ≥ 76%, and yellow nutsedge ≥ 80% and was comparable to the weed control with MeBr. Highest rates of allyl ITC and metham sodium reduced yellow nutsedge tuber density (≤ 76 tubers m−2) comparable to the MeBr application. Total marketable tomato yield was ≥ 31.6 t ha−1 in plots treated with allyl ITC at 750 kg ha−1 or metham sodium at 360 kg ha−1. Marketable tomato yield from the highest rate of allyl ITC or metham sodium were similar to the yield (38.2 t ha−1) with MeBr treatment. Therefore, allyl ITC at 750 kg ha−1 and metham sodium at 360 kg ha−1 are effective alternatives to MeBr for Palmer amaranth, large crabgrass, and yellow nutsedge control in LDPE-mulched tomato.

Field experiments were conducted in 2006 and 2007 to evaluate the herbicidal activity of phenyl isothiocyanate (ITC) on yellow nutsedge, Palmer amaranth, and large crabgrass in tomato grown on two polyethylene-mulched types. Treatments included two mulch types (low density polyethylene [LDPE] mulch and virtually impermeable film [VIF] mulch) and phenyl ITC at 0, 15, 75, 150, 750, and 1,500 kg ha−1. A standard rate of methyl bromide/chloropicrin (67 : 33%) at 390 kg ha−1 under LDPE mulch was included for comparison. Regardless of mulch type, phenyl ITC at 1,452 (±133) and 1,719 (±426) kg ha−1 was required for broad-spectrum weed control equivalent to methyl bromide in 2006 and 2007, respectively. Tomato injury was ≥ 44% at the highest phenyl ITC rate of 1,500 kg ha−1 at 2 wk after transplanting (WATP) both years, irrespective of mulch type. Greater crop injury was observed from 750 kg ha−1 of phenyl ITC in 2006 (≥ 27%) than in 2007 (≤ 10%). The greater injury in 2006 was attributed to a higher phenyl ITC concentration because holes in the plastic mulch for transplanting were punched at the time of transplanting in 2006; whereas, in 2007 holes were punched 2 d before transplanting, allowing 2 d of aeration before transplanting. Tomato marketable yield at all rates of phenyl ITC was lower than with methyl bromide in 2006. However, in 2007, marketable yield in plots treated with phenyl ITC at 750 kg ha−1 was equivalent to methyl bromide. Overall, VIF mulch was no more effective than LDPE mulch at increasing weed control or improving the marketable yield of tomato either year.

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.

Yellow nutsedge, a weed commonly present in Florida vegetable fields, may substantially reduce crop yields when not controlled. Soil fumigation with methyl bromide effectively controls nutsedges, but methyl bromide is being phased out of production and use in the United States. Therefore, nutsedge management in bell pepper is a cause for concern. An experiment was conducted during four seasons (spring and fall of 1999 and 2000) to determine the tolerance of bell pepper grown at two in-row spacings (23 and 31 cm) to interference resulting from planted yellow nutsedge tuber densities (0 to 120 tubers/m2). Relative to yields with no nutsedge, pepper fruit yields in each season were reduced 10% with fewer than 5 planted tubers/m2. Yield losses increased more rapidly with an increase in initial nutsedge density from 0 to 30 than from 30 to 120 tubers/m2. With 30 nutsedge tubers/m2, large fruit yield was reduced 54 to 74% compared to that with no nutsedge. Nutsedge shoots overtopped the pepper plants as early as 6 wk after treatment when, with 15 planted tubers/m2, nutsedge interference reduced pepper plant biomass by 10 to 47%. In the absence of methyl bromide, weed control strategies with high efficacy against yellow nutsedge will be needed for bell pepper production.

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.

Methyl bromide has been a key fumigant for broad-spectrum weed control in polyethylene-mulched bell pepper. However, the ozone-depleting nature of methyl bromide has led to its scheduled phaseout from U.S. agriculture. Thus, an effective alternative to methyl bromide is needed. Field trials were conducted in 2007 and 2009 to evaluate the crop response and weed control efficacy of allyl isothiocyanate (ITC) in polyethylene-mulched bell pepper. The experiment included various combinations of two mulch types (low density polyethylene [LDPE] and virtually impermeable film [VIF] mulch) and six rates of allyl isothiocyanate (0, 15, 75, 150, 750, 1,500 kg ha−1). Additionally, a standard treatment of methyl bromide/chloropicrin (67 : 33%) at 390 kg ha−1 under LDPE mulch was included for comparison. Bell pepper injury was < 3% in all treatments, except 11% injury at 1,500 kg ha−1 allyl isothiocyanate under VIF mulch at 2 wk after transplanting (WATP). VIF mulch did not provide additional weed control and marketable pepper yield over LDPE mulch. Allyl isothiocyanate at 932 (± 127) kg ha−1 controlled yellow nutsedge (90%), Palmer amaranth (97%), and large crabgrass (92%) through 6 WATP and maintained the marketable yield equivalent to methyl bromide treatment. This research demonstrates that allyl ITC under an LDPE mulch can serve as a potential alternative to methyl bromide for weed control in polyethylene-mulched bell pepper.

It has been hypothesized that differentially applied environmental regulations create pollution havens, as firms will choose to invest in countries with lax environmental standards. Using a theoretical model of pest control adoption and an empirical spatial equilibrium model, we examine one such environmental regulation, a U.S. ban on methyl bromide, to determine if an agricultural pollution haven will be created in Mexico. Alterations in agricultural production location, trade patterns, and methyl bromide use are determined. We find that, under the assumptions held, Mexico will not dramatically increase its use of methyl bromide following the ban. Sensitivity analysis to this result is conducted.

This study evaluates the economic impact of a ban on methyl bromide on the U.S. winter fresh vegetable market for six major crops: tomatoes, green peppers, cucumbers, squash, eggplant, and watermelons. Florida is the primary domestic supplier of these products. Mexico and Texas are the competing suppliers of the five vegetable crops and peppers, respectively. Leontief technologies represent both monocrop and double-crop production systems; linear inverse demand functions represent four demand regions in the U.S. and Canada. By increasing production costs and reducing yields, a ban on methyl bromide decreases Florida's FOB revenues by 54% and increases those of Mexico by 65%. Price increases to U.S. fresh vegetable consumers range from near zero to over 10%, depending upon the commodity and location.

Methyl bromide (MBr) has been widely used as a fumigant to control pests in the agricultural sector, but it is also an ozone depleting substance. After 2005, methyl bromide could only be produced when a critical use exemption was agreed to by the signatories to the Montreal Protocol. This paper examines how the EPA’s ex ante cost analyses for open field fresh strawberries in California for the 2006–2010 seasons compare to an ex post assessment of costs. A key input into the ex ante cost analysis is the assumed yield loss associated with methyl bromide alternatives. The EPA used conservative assumptions given the wide range of estimates in the literature at the time, but it appears that a number of viable MBr alternatives – either new fumigants or new ways of applying existing fumigants – may have become available more quickly and resulted in lower yield loss than initially anticipated. Likewise, it appears that farmers who substituted away from methyl bromide did so without imposing large negative impacts on production in prime California strawberry growing areas. Ex post evaluation also confirms the effect of California regulatory restrictions in limiting the use of various economically competitive alternatives. It is worth noting that unanticipated complications after switching away from methyl bromide, such as new diseases, slowed the transition to MBr alternatives.

This study was conducted in Florida in 1999 and 2000 to examine the impact of alternative crop production practices on soil quality and yields of fresh market pepper (Capsicum annuum). Replicated field plots were established on an organic vegetable farm that had been under certification for 5 years and on a conventional pepper farm that had been fumigated with methyl bromide for 25 consecutive years. Production practices evaluated included raised beds covered by white plastic mulch, soil solarization, no-till in a stubble crop of sunn hemp (Crotolaria juncea) or iron-clay pea (Vigna unguiculata) and the addition of 67 t ha−1 of urban plant debris (UPD). Soil fumigation with methyl bromide–chloropicrin was also evaluated at the conventional farm site. Soil organic carbon significantly increased following the addition of UPD in both years at the organic site but only in the second year at the conventional site. Cation exchange capacity increased significantly after addition of UPD in both years at both sites and a significant interaction with production practices was observed in the second year at the organic site. Soil phosphorus levels were high at both sites but were not impacted by production practices or UPD. In 1999, the addition of UPD significantly decreased soil nitrate levels at the organic site and the conventional site, except under the no-till treatments. In 2000, soil nitrate levels were not affected by UPD or production practice. Stand counts, determined by the number of surviving pepper plants 21–28 days after transplanting, were severely impacted in no-till treatments due to intense competition from weeds. Marketable yields equal to, or above, the 1999/2000 statewide average for conventional production systems were obtained with soil fumigation and soil solarization at the conventional site in 1999. In 2000, an epidemic of Phytophthora blight (Phytophthora capsici) eliminated production at the conventional site. Marketable yield at the organic site approached the statewide average for conventional systems under the solarization treatment. Yields under plastic mulch were increased at both sites with the addition of UPD. The results demonstrated that organic pepper yields from soil-solarized plots were similar to yields obtained by conventional farmers using high inputs of rapidly mobile nitrogen sources. However, no-till systems for fall production do not appear to be a viable alternative under Florida conditions due to the rapid proliferation of weeds under the cover crop stubble. The addition of urban plant debris was associated with an increase in soil organic carbon and cation exchange capacity in sandy soils typical of those found in Florida.

An alternative, low-input production system for fresh market tomato was developed using strip tillage practices in conjunction with established bahiagrass pasture. The alternative system was designed to reduce the impact of soilborne pests, minimize agricultural inputs, improve soil conservation and optimize yields. Field experiments indicate that competition from bahiagrassfor nutrients within the tilled strips significantly impacted yield. Selective colonization of tomato roots by arbuscular mycorrhizal fungi isolated from field plots was observed. Damage from root-knot nematodes was minimized by planting tomato into established bahiagrass pastures. The alternative system was validated on a commercial tomato production farm in a side by side comparison with a conventional production system consisting of raised beds, fumigated with methyl bromide and covered by black polyethylene plastic. Yields were 6.5 t/ha greater under the conventional system. However, the net return was $568/ha greater in the alternative system. The results indicate that the alternative system has the potential to replace or supplement the conventional production system.

A laboratory study was carried out in Egypt to determine the effect of combining treatments of gamma radiation and methyl bromide fumigation applied to adults of Tribolium confusum (Duv.). An interaction between irradiation and insecticidal treatment was obvious, with additive effects noted at most combination treatments. When the irradiation treatments were applied first and fumigation were accomplished within 24 hr., the intermediate dosage of irradiation (6 krad) afforded the insects some protection against marginally effective dosages of methyl bromide after 14 days. On the contrary, it is evident that a possible synergistic effect of irradiation pretreatment followed by chemical exposure, after 21 days, where all of irradiation dosages used (2-10 krad) enhanced the fumigant effectiveness. On the other hand, when the irradiation dosages were increased from 5-50 krad and followed by fumigant treatments after 7 days, the trend did continue where all combination treatments killed more insects than did either treatment applied alone. Conversely, when fumigation preceded treatment with irradiation the sublethal methyl bromide fumigation also apparently leaves the surviving insects in a debilitated state and became more radiosensitive.

In general, the effects from combination of irradiation and fumigation were more effective than were the effects of either treatment given singly, whether irradiation preceded insecticidal treatment or vice versa.