Alternative Fumigants Research Articles

Propilen Oksit'in Kuru Meyve Güvesi Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)'ya karşı Metil Bromüre Alternatif Bir Fumigant Olarak Değerlendirilmesi

Propilen Oksit'in Kuru Meyve Güvesi Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)'ya karşı Metil Bromüre Alternatif Bir Fumigant Olarak Değerlendirilmesi

The Fumigation Toxicity of Three Benzoate Compounds against Phosphine-Susceptible and Phosphine-Resistant Strains of Rhyzopertha dominica and Sitophilus oryzae.

Phosphine (PH3) has been widely used as a fumigant in food storage, but increasing PH3 resistance in major pests makes finding alternative fumigants urgent. Methyl benzoate (MBe), a volatile organic compound regarded to be a food-safe natural product, has recently demonstrated significant toxicity against a variety of insect pests. This study is the first evaluation of the fumigation toxicity of three benzoate compounds, MBe, vinyl benzoate, and ethyl benzoate, against PH3-susceptible and PH3-resistant strains of Rhyzopertha dominica and Sitophilus oryzae. All strains were exposed to the compounds at concentrations up to 20 µL/1.5 L air for 24 h. Compared to vinyl benzoate and ethyl benzoate, MBe induced higher mortality rates in all strains at all concentrations. When food was made available, the lethal median concentration for MBe was 10-17-fold higher than when tested without food. Moreover, no significant differences were observed between the responses of the PH3-susceptible and PH3-resistant strains to the compounds. Notably, S. oryzae was more susceptible to MBe. In laboratory settings, MBe successfully controlled PH3-resistant strains of R. dominica and S. oryzae, making it a viable option for PH3-resistance management. Thus, MBe might be suitable for food security programs as an environmentally benign alternative fumigant.

Impacts of the Ban on the Soil-Applied Fumigant Methyl Bromide.

The loss of the soil fumigant methyl bromide (MeBr) and adoption of soil fumigant alternatives has been challenging for farmers, particularly for those crops in which pathogens previously controlled by MeBr have emerged as significant problems, but it has resulted in some unanticipated benefits for the scientific community and the environment. Applauded as one of the most effective environmental agreements to date, the universally accepted Montreal Protocol on Ozone Depleting Substances has had a significant impact on the environment, reducing the release of halogenated compounds from anthropogenic sources enough to mitigate global warming by an estimated 1.1°C by 2021. The funding associated with various MeBr transition programs has increased collaboration across scientific disciplines, commodity groups, industry, and regulatory agencies. Chemical alternatives and improved application strategies, including the development of gas-retentive agricultural films, coupled with sound efficacy data and grower ingenuity have resulted in the sustained production of many of the impacted crops; although there has been some loss of acreage and value, particularly for Florida fumigated crops, for some, value has continued to increase, allowing production to continue. The loss of a single, broad-spectrum tool for pest control has led to a deeper understanding of the specific pest complexes impacting these at-risk crops, as well as the development of new, biologically based management tools for their control while increasing our understanding of the role of the soil microbiome in pest control and crop production.

The Effects of Propylene oxide Fumigation on the Mortality of Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae)

This study was carried out in 2014-2015 at Kahramanmaraş Sütçü İmam University, Faculty of Agriculture, Department of Plant Protection, Entomology Laboratory. This study aims to evaluate the viability of propylene oxide (PPO) as an alternative fumigant to methyl bromide (MeBr) for the efficient control of Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) and to model the mortality rates of P. interpunctella insects using different regression techniques. The biological effectiveness of PPO was assessed across all life stages of P. interpunctella during a brief exposure period (4 hours) under three conditions: normal atmospheric pressure (PPO alone), low pressure (PPO+Vacuum), and an atmosphere enriched with carbon dioxide (CO2) (PPO+CO2). For all PPO treatments, PPO was directly introduced into the fumigation chamber at seven or more concentrations using different micro-syringes of different volume ranges: 2.5-25 µl l-1, 1.5-45 µl l-1, 1.5-30 µl l-1, and 0.5-15 µl l-1 for eggs, larvae, pupae, and adults, respectively. The results indicate that 100% mortality was observed in eggs at concentrations of 25 µl l-1, 20 µl l-1 and 20 µl l-1; in larvae at concentrations of 45 µl l-1, 30 µl l-1 and 40 µl l-1; in pupae at concentrations of 30 µl l-1, 15 µl l-1 and 25 µl l-1; and in adults at concentrations of 15 µl l-1, 10 µl l-1 and 10 µl l-1 for the PPO alone, PPO+Vacuum, and PPO+CO2 treatments, respectively. The results obtained from the developed regression models for insect mortality reveal that these models generally exhibited a better fit when described by exponential and third-order polynomial functions. In summary, this study indicates that PPO treatments hold significant promise for rapid insect control, particularly in the case of the Indian meal moth, rendering them invaluable for quarantine purposes.

Deliquescence‐induced release of ethyl formate and chlorine dioxide from their precursors‐loaded sachets for in‐package fumigation of spotted wing drosophila (Drosophila suzukii Matsumura)

AbstractThe toxicity and environmental concerns of methyl bromide (MB) have been a significant impetus for research into environmentally benign fumigant alternatives. Ethyl formate (EF) and chlorine dioxide (ClO2) are FDA‐approved agents with potential as alternatives to MB. However, both are chemically unstable and pose considerable end‐use challenges. In this study, we developed moisture‐activated sachets for EF and ClO2 to facilitate their end‐use deployment for in‐package fumigation. The sachets were loaded with EF or ClO2 metastable precursors, citric acid (CA), and a deliquescent salt carrier (e.g., CaCl2 or NaCl). When placed in an elevated relative humidity environment, these combinations activate the release of EF or ClO2 gases, separately. The deliquescence lowering phenomenon and its effect on fumigants release rate were investigated when mixing CA with CaCl2 or NaCl. The mutual deliquescence relative humidity for CA–CaCl2 and CA–NaCl mixtures were 40% and 63%, respectively. CaCl2 enhanced the release rate of fumigants from their sachets, whereas NaCl resulted in a slower release rate. EF and ClO2 sachets were evaluated for fumigation of different life stages of spotted wing drosophila (SWD). Complete control of SWD adults was achieved after exposure to 10.1 mg·h/L EF, while eggs, larval, and pupal stages were more tolerant toward EF vapour and required 110.2 mg·h/L EF to achieve control. ClO2 at low concentrations was more effective than EF against all SWD life stages, excluding pupae. Complete mortality was achieved after fumigating SWD adults, eggs, and larvae with 0.73, 2.39, and 1.21 mg·h/L ClO2, respectively. These results indicated that both EF and ClO2 sachets could be employed safely for EF and ClO2 in‐packaging fumigation to control produce pests.

Effects of Fumigation on the Reduction of Salmonella enterica in Soil.

Due to the phaseout of methyl bromide (MeBr), there is a need for broad-spectrum soil fumigation alternatives for pest management. Little is known about the impact of fumigation alternatives on foodborne pathogens, such as Salmonella, in agricultural soils. This study investigated the effect of MeBr alternative fumigants on Salmonella reduction in soil. Sandy loam soil was collected from a conventional farmed vegetable field and inoculated with either Salmonella Newport J1892 or Typhimurium ATCC 14028 (5.9 ± 0.3 log10 colony-forming unit [CFU]/g). Each of the four fumigants labeled for pest management (1,3-dichloropropene, chloropicrin, dimethyl disulfide, and metam sodium) was applied at labeled maximum application field levels to soil in pots and stored for a 2-week period. Sterile water was used as a control. Following the 2-week period, Salmonella concentrations in soil samples were enumerated at 1, 7, 14, and 21 days postfumigation. The mean concentration of Salmonella Newport was significantly higher than that of Salmonella Typhimurium 1 day after fumigation (p = 0.015). Fumigation using 1,3-dichloropropene or dimethyl disulfide significantly reduced Salmonella Newport and Salmonella Typhimurium concentrations, compared with the sterile water control. The rate of Salmonella reduction in soil treated with dimethyl disulfide was higher (0.17 ± 0.02 log10 CFU/g/day), compared with soil treated with the other fumigants (0.10-0.12 log10 CFU/g/day). Due to the reduction of Salmonella, alternative fumigation treatments may mitigate potential Salmonella contamination in soil within farm environments.

Efficacy of the Fumigants Propylene Oxide and Ethyl Formate to Control Two Pest Species of Dry-Cured Hams

The ham mite Tyrophagus putrescentiae and the red-legged ham beetle Necrobia rufipes are harmful pests to several high-valued stored products. The regulatory phase-out of the fumigant methyl bromide necessitates the search for alternative fumigants. Propylene oxide (PPO) and ethyl formate (EF) were therefore evaluated in the laboratory for controlling these pests of dry-cured hams. Concentration–mortality studies at 25 °C of PPO and EF found that the mobile stages of the mites were very susceptible to low concentrations of 10 mg/L and less of each gas, while mite eggs were very tolerant and required 20 mg/L for PPO and 80 mg/L of EF for 100% mortality. Mixed life stage cultures of mites and beetles were treated for 24 h with either PPO or EF at 1× and 2× the estimated 99% lethal doses and confirmed effectiveness for controlling simulated pest populations. The sorptive properties of each gas in chambers with ham pieces, dog food kibbles, or fish meal were minimal for a reduction in mite toxicity when compared to treatments in empty chambers. There was no evidence that any desorbed gas occurred at a level toxic to mite eggs in any of the fumigated commodities. These fumigation studies with ham pests support further work with PPO and EF on any changes in the sensory quality of dry-cured hams for human taste and for commercial-scale fumigations toward regulatory approval.

Radiative efficiencies and global warming potentials of agricultural fumigants

A rounded assessment of the environmental impacts of fumigants used within the agricultural sector must consider the potential climate impacts of their release into the atmosphere. Within policy settings, the 100-year Global Warming Potential (GWP100) is the most commonly used metric. While GWP100 values are available for the widely used fumigant sulfuryl fluoride, no estimates are available for 4 alternative fumigants: ethyl formate, cyanogen, hydrogen cyanide and phosphine. Existing laboratory measurements of the infrared spectra and reaction rate coefficients of these gases are used to produce new estimates of their radiative efficiencies and atmospheric lifetimes, and the first estimates of their GWP100 and other climate emission metrics. Although uncertainties are considerable, their GWP100 values are estimated to be no more than 2% of the GWP100 value of sulfuryl fluoride. These new estimates will enable informed estimates of the climate impact of the use of these fumigants, which must account for the differing usage and release rates to achieve the same fumigant efficacy.

Evaluation of wheat kernel and flour quality as influenced by chlorine dioxide gas treatment

Chlorine dioxide (ClO2) gas, known for its high oxidation and penetration capacity, is a potential alternative fumigant to control stored-product insect pest population. In this study, hard red spring wheat (Triticum aestivum L.) kernels were exposed to varying levels of gaseous ClO2 concentrations (200, 300, 400, and 500 ppm, 1 ppm = 0.0027 mg/L at room condition) and held in a gas-tight bucket assembly for 24 h after achieving desired concentration. ClO2 treatment achieved complete insect mortality of lesser grain borer (Rhyzopertha dominica (Fabricius)) and highest adult progeny reduction at 500 ppm across all vial locations. Significant reduction (37.8–51.1%) in germination percentage resulted after exposure to 300–500 ppm. Flour lightness value significantly increased after kernel treatment at 200–500 ppm. The pH value of wheat flour was significantly reduced from 6.2 to 6.1 after 500 ppm treatment. Peak and final viscosities of wheat flour significantly decreased from 3303.7 to 3073.3 cP, and from 3515.0 to 3208.3 cP, respectively. No significant difference was observed in other investigated flour quality and functionality parameters, including falling number, trough viscosity, breakdown viscosity, starch damage, and Mixolab dough behavior properties. Overall, ClO2 treatment at 500 ppm is effective in killing adult lesser grain borers without negatively affecting wheat flour quality parameters.

A comprehensive review on advances in storage pest management: Current scenario and future prospects

Modernization of the agricultural production system led to a significant increase in annual food production intended to meet the ever-growing consumer demand. In many countries, most of the food grains produced is stored for contingency and regular supply. These stored grains, in general, are directly or indirectly infested by insects, resulting in severe grain damages and storage losses, thus, causing a threat to food safety and security. Although a variety of insect management options, such as physical, mechanical, biological, and chemical methods, are available, fumigation has been practiced for decades in storage. However, opportunities for fumigation are narrowing after the phase-out of methyl bromide. Besides, safe food and health concerns paved the path for green chemistry and non-chemical management practices. This review includes the list of stored-grain insects and their detection methods. The different management strategies such as the modern storage structures (hermetic and low-pressure storages), modified or controlled storage atmosphere, application of ozone as fumigant, irradiation, and physical options are presented. Further, the details on sustainable biological options, such as semiochemicals, natural enemies, biopesticides, and entomopathogenic nematodes, are supplemented. The use of inert dusts as grain protectant and in combination with the biological entity is included. Studies on alternative fumigants', novel management options, such as molecular biology tools (RNAi and CRISPR) and nanotechnology in stored grain protection, are also highlighted. This review helps the reader to understand the overall factors affecting grain storage and the different options to manage the insects causing storage losses.

Sorption and desorption dynamics of ethyl formate and propylene oxide as fumigants in durable agricultural commodities

Ethyl formate (EF) and propylene oxide (PPO) are promising alternative fumigants for stored products. Sorption and desorption behaviors of EF and PPO were studied in five commodities. EF and PPO were highly and moderately sorptive, respectively, into the treated commodities. Pinto beans, wheat flour and corn were highly sorptive compared to wheat kernels and tobacco leaves. The headspace concentrations of EF decreased after 24 h of fumigation by the average percentages of 93.5, 65.0, 78.9, 98.6 and 52.6% fumigated at 50 mg/L, while similar percentages of 93.5, 61.1, 78.7, 98.0, and 52.3 fumigated at 100 mg/L were found for wheat flour, wheat kernels, corn, pinto beans and tobacco leaves, respectively. Declines in percentages for headspace concentrations of PPO by wheat flour, wheat kernels, corn, pinto bean and tobacco leaves were 90.7, 43.5, 77.6, 97.6, and 77.0 at 50 mg/L, and were 90.3, 41.9, 77.8, 96.6 and 78.7% at 100 mg/L, respectively, by the end of the 24-h exposure period. Sorption rates of EF (mg/kg commodity) in wheat flour, wheat kernels, corn, pinto bean and tobacco leaves were 280.4, 192.2, 233.0, 295.6, 525.8, at 50 mg/L and were 560.2, 361.3465.1, 588.2, and 1046.4 at 100 mg/L, respectively after 24 h of fumigation. Sorption rates of PPO (mg/kg commodity) were 271.9, 128.6, 229.5, 292.8, 770.7 at 50 mg/L and were 541.6, 247.8, 459.9, 579.7, 1573.2 at 100 mg/L for wheat flour, wheat kernels, corn, pinto bean and tobacco leaves, respectively. Pinto beans were the most sorptive commodity for EF and PPO and wheat kernels were the lowest. EF and PPO desorbed from all commodities except pinto beans 24 h after ventilation. These results may improve understanding of sorption and desorption of EF and PPO for commercial fumigations.

Supplemental Fumigant Placement Improves Root Knot and Fusarium Wilt Management for Tomatoes Produced on a Raised-Bed Plasticulture System in Florida's Myakka Fine Sand.

Fresh-market tomatoes are produced on a raised-bed plasticulture system that relies heavily on soil-applied preplant fumigants for the management of soilborne pathogens, nematodes, and weeds. Since the transition from methyl bromide to alternative fumigants, growers have experienced a resurgence of several soilborne pests and pathogens, including root-knot nematode caused by Meloidogyne spp. and Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici race 3. This resurgence is attributed to the inability of the alternative fumigants to effectively disperse through the soil in the same manner as methyl bromide. Two supplemental fumigation strategies, the application of chloropicrin (PIC) below bed edges (herein "supplemental PIC") and broadcast deep-shank applications of 1,3-dichloropropene (1,3-D), were evaluated in conjunction with standard raised-bed applications of Pic-Clor 60, Pic-Clor 80, and Pic 100 covered with a virtually impermeable film or a totally impermeable film. Large-plot replicated studies were conducted in two separate commercial tomato fields with a history of production losses caused by root-knot nematode and Fusarium wilt. Deep-shank 1,3-D applications significantly reduced the recovery of root-knot and total parasitic nematodes across field sites before the preparation of raised beds. Both supplemental PIC and deep-shank 1,3-D reduced root-knot galling and Fusarium wilt incidence, but the latter supplemental treatment statistically had the greatest impact. Fumigant applied within raised beds or plastic film had no significant effect on root-knot galling or Fusarium wilt. Although both supplemental fumigation strategies had a significant effect on pest and disease pressure, neither statistically improved tomato yields based on small subplot harvests. Controlled laboratory experiments confirmed the fungicidal activity of 1,3-D against F. oxysporum f. sp. lycopersici, with 75, 90, 95, and 99% lethal doses corresponding to estimated field application rates of 56.1, 93.5, 121.6, and 184.7 liters/ha, respectively. The results demonstrate how fumigant placement can improve pest and disease control activity with current fumigant alternatives to methyl bromide and further support the broader pesticidal activity of some chemical fumigants.

The effectiveness of clove oil, its fractions, and clove oil-based fumigant tablet formulations, against Tribolium castaneum (Herbst)

Indonesia has seen an increase and widespread reports of resistance among stored-product insect pests to phosphine. The use of Syzigium aromaticum (clove oil) as an alternative fumigant may be a useful strategy to control infestation by phosphine-resistant varieties of stored-product insects. The objective of this study was to examine the effectiveness of whole (unfractionated) clove oil as well as its component fractions as a fumigant and repellent against the red flour beetle (Tribolium castaneum (Herbst)), and to develop a simple fumigant formulation for this purpose. The experimental design used to test the effectiveness of clove oil and its fractionation was a completely randomized design (CRD). Meanwhile, testing the effectiveness of tablet formulations was carried out by factorial CRD. Fumigation test results gave LD50 and LD95 values of 0.234 and 1.142 ml/l respectively, for crude clove oil used in a fumigation chamber against T. castaneum. An n-hexane fraction of clove oil tested under the same conditions was more lethal, causing 95% mortality of T. castaneum at the dose of 0.801 ml/l during fumigation. Finally, tablets containing a set proportion of clove oil and naphthalene (1:1) reached LD91 against T. castaneum after 7 days’ fumigation.

Cover Image, Volume 66, Issue 12

CSA NewsVolume 66, Issue 12 p. i-i COVER IMAGEFree Access Cover Image, Volume 66, Issue 12 First published: 21 November 2021 https://doi.org/10.1002/csan.20192AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Cover: Grapevines, and the grapes they produce, are an important specialty crop in the California landscape. In 2005, the primary pre-planting fumigant to control soilborne pathogens, methyl bromide, was phased out of use. Two USDA-ARS scientists studied alternative fumigants and their long-term impacts on soil microbes and grapevine health, publishing their findings in the Soil Science Society of America Journal. See p. 8. Cover photo, courtesy of Sadikshya Dangi, shows soil sampling in the vineyard at the San Joaquin Valley Agricultural Sciences Center in 2018. Volume66, Issue12December 2021Pages i-i RelatedInformation

Toxicity of Five Plant Volatiles to Adult and Egg Stages of Drosophila suzukii Matsumura (Diptera: Drosophilidae), the Spotted-Wing Drosophila.

The environmental impact of methyl bromide (MB) has resulted in its phase out as an insecticidal fumigant except for critical use exempted categories. Consequently, there is an urgent need to develop an environmentally sustainable MB alternative fumigant. trans-Cinnamaldehyde (TC), benzaldehyde, allyl isothiocyanate (AITC), hexanal, and ethyl formate (EF) are naturally occurring plant volatiles with insecticidal properties. This study assessed the toxicity of these plant volatiles to adult and egg stages of the spotted-wing drosophila (SWD) (Drosophila suzukii Matsumura). The plant volatile treatments had a significant effect on adult SWD mortality. The descending order of toxicity to adult SWD was benzaldehyde > AITC > TC > hexanal > EF at a headspace concentration of 0.50 μL/L air for 24 h. All the volatiles, at a concentration of 4.00 μL/L air, significantly inhibited larval emergence from SWD eggs in artificial diet compared to the control. At a 0.50 μL/L air level, among the volatiles tested, only AITC exhibited 100% inhibition against larval emergence from SWD eggs in blueberry fruits after 24 h exposure. In summary, this study shows that all volatiles tested elicited varying degrees of toxicity toward SWD adults and eggs. However, AITC was the most efficacious volatile and the one with the greatest promise as a post-harvest fumigant for both adult and egg stages of SWD.

Preliminary study to evaluate ethanedinitrile (C2 N2 ) for quarantine treatment of four wood destroying pests.

Methyl bromide is an ozone depleting substance and is still being used for quarantine treatment of wood products and logs. Ethanedinitrile (C2 N2 ) is a new potential alternative fumigant and has been investigated as a timber fumigant because it has shown better penetration through timber and responds fast to insects and nematodes. This article reports on laboratory and commercial-scale trials with C2 N2 for important wood destroying pests namely Tomicus piniperda (Pine bark beetle) adults, Hyphantria cunea (Fall webworm) lavae, Reticulitermes speratus (Japanese Termite) adults and Cryphalus fulvus (Scolytidae) (Yellow minute bark beetle) which naturally infests pine logs. Tomicus pi:niperda adults were more tolerance than H. cunea lavae and R. speratus adults with lethal concentration × time affecting 99% mortality (LCt99 ) values of 27.84, 7.49 and 3.30 g h m-3 , respectively. Ethanedinitrile shows exceptionally high toxicity to adult R. speratus which was almost 26 times more toxic than methyl bromide. The complete control of larvae and adults stages of C. fulvus was achieved at concentration × time (Ct) products from 89.6g h m-3 in a 6-8L fumigation chamber. Temperature-depending trials on C. fulvus were conducted with C2 N2 doses of 30 at 21 ± 6 and 40 g m-3 at 9 ± 3 and 2 ± 2°C for 24 h. The Ct products of 182.2, 227.8 and 268.6g h m-3 were obtained and C. fulvus was completely controlled at all tested temperatures. Ethanedinitrile could offer quarantine treatment for wood products and logs for the control of wood destroying insect pests and termites.

Biofumigation activities of volatile compounds from two Trichoderma afroharzianum strains against Fusarium infections in fresh chilies.

Two Fusarium fungi, F. oxysporum and F. proliferatum, have been recognized as major pathogenic fungi that cause postharvest decay of chili fruits. Ozone and some toxic chemicals are used to control pathogenic infections, leading to longer storage lives of agricultural commodities. However, these chemicals may pose some risks to the applicators and the environment. Therefore, alternative, easy-to-use fumigants for effective control of Fusarium infections in harvested fresh chilies are needed. Two endophytic fungi, Trichoderma afroharzianum strain MFLUCC19-0090 and T. afroharzianum strain MFLUCC19-0091, were isolated from Schefflera leucantha leaves. Their volatile compounds were investigated for antifungal activities against F. oxysporum and F. proliferatum. In vitro results showed that the volatile compounds produced by each strain inhibited pathogen growth. Additionally, the Trichoderma-derived volatile compounds significantly reduced Fusarium-related disease severity and incidence percentages in the inoculated fresh chilies. Antifungal properties of the volatile compounds were found to be specific to the species of the tested pathogens (MFLUCC19-0090 greatly suppressed F. oxysporum and MFLUCC19-0091 greatly suppressed F. proliferatum). Seventy-three volatile compounds were detected from both strains. Among the major volatile compounds detected, phenyl ethyl alcohol was found to possess the strongest antifungal activity against both pathogens. These Trichoderma-derived volatile compounds may be used as alternative fumigants for controlling Fusarium rot in harvested fresh chilies. The successful use of volatile compounds as biofumigants can prevent significant market losses and, more importantly, may reduce the health hazards caused by Fusarium-associated mycotoxin exposures among consumers. © 2021 Society of Chemical Industry.

Identification and evaluation of volatile organic compounds evolved during solarization with almond hull and shell amendments

ABSTRACT Biosolarization is a fumigation alternative that combines solarization with organic amendments to suppress pests and pathogens in agricultural soils. The generation of volatile biopesticides in the soil, stemming from biodegradation of carbon-rich amendments, contributes to pest inactivation. The purpose of this study was to (1) profile volatiles that may contribute to pest control under field conditions and (2) measure volatile compounds that may present nuisance or exposure risks for humans near biosolarized fields where larger-scale anaerobic degradation of residues occurs. Biosolarization was performed using prominent agricultural waste products, hulls and shells from several almond varieties as soil amendments. After 8 days of biosolarization, soil samples were analyzed using solid phase microextraction-gas chromatography coupled to mass spectrometry. Volatile fatty acids and ketones made up 85% of biosolarized soil headspace, but terpenes, alcohols, aldehydes, esters, and sulfides were detected as well. Different almond variety residues produced distinct volatile profiles, and nonpareil-amended soils had a much richer and more diverse profile, as well as a fivefold greater VOC abundance, than pollinator-amended soil. Identified volatiles with low US recommended exposure limits were quantified via internal and external standards, including acetic acid, 2-butanone, butanal, hexanal, and phenylethyl alcohol. Across biosolarization treatments, headspace concentrations of selected compounds did not exceed 1 mg/m3. This study demonstrates that almond processing residues recycled into the soil as biosolarization substrates produce a high diversity of bioactive degradation compounds on a field scale, with low potential of non-target risks to humans. Implications: This manuscript has implications for two policy goals in the state of California: to reduce landfill disposal of organic waste, and to reduce emissions from soil fumigants. Almond hulls and shells are an increasing source of organic waste, and novel recycling strategies must be developed. Here, recycling almond residues as soil amendments promoted the rapid formation of VOCs which may act as alternatives to chemical fumigants. Headspace concentrations of potentially deleterious VOCs produced from treated soil were low, on the order of parts per billion. These results will help achieve policy goals by expanding waste usage and fumigation alternatives.

Methyl Benzoate Is Superior to Other Natural Fumigants for Controlling the Indian Meal Moth (Plodia interpunctella).

Simple SummaryGlobally, the Indian meal moth is an insect pest of stored goods and manufactured foodstuffs. Synthetic fumigants, such as phosphine and methyl bromide, are widely used agents to control this species. However, due to the development of resistance and increasing concern about the potential adverse effects of synthetic fumigants, it is now necessary to identify environmentally friendly alternatives. Naturally occurring compounds, such as essential oils (EOs), are perhaps the most promising alternative sources; many have been successfully used as active ingredients in contact-based control products, repellents, and fumigants. Methyl benzoate (MBe) is an environmentally friendly, food-safe, natural insecticide that offers a possible alternative to synthetic equivalents. Here, we evaluated the fumigant toxicity of MBe against adults of the Indian meal moth and found that it had great potential for the control of these insect pests in stored products.The Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), is an insect pest that commonly affects stored and postharvest agricultural products. For the control of insect pests and mites, methyl benzoate (MBe) is lethal as a fumigant and also causes contact toxicity; although it has already been established as a food-safe natural product, the fumigation toxicity of MBe has yet to be demonstrated in P. interpunctella. Herein, we evaluated MBe as a potential fumigant for controlling adults of P. interpunctella in two bioassays. Compared to the monoterpenes examined under laboratory conditions, MBe demonstrated high fumigant activity using a 1-L glass bottle at 1 μL/L air within 4 h of exposure. The median lethal concentration (LC50) of MBe was 0.1 μL/L air; the median lethal time (LT50) of MBe at 0.1, 0.3, 0.5, and 1 μL/L air was 3.8, 3.3, 2.8, and 2.0 h, respectively. Compared with commercially available monoterpene compounds used in pest control, MBe showed the highest fumigant toxicity (toxicity order as follows): MBe > citronellal > linalool > 1,8 cineole > limonene. Moreover, in a larger space assay, MBe caused 100% mortality of P. interpunctella at 0.01 μL/cm3 of air after 24 h of exposure. Therefore, MBe can be recommended for use in food security programs as an ecofriendly alternative fumigant. Specifically, it provides another management tool for curtailing the loss of stored food commodities due to P. interpunctella infestation.

Multi-Encapsulation Combination of O/W/O Emulsions with Polyurea Microcapsules for Controlled Release and Safe Application of Dimethyl Disulfide

Dimethyl disulfide (DMDS), a promising alternative fumigant, has been highly desirable for excellent management of soil pests and diseases. However, high volatility and moderate toxicity of this sulfide limit its application. To address these issues, a novel controlled release formulation of DMDS was proposed employing multiple emulsions and polyurea microcapsules (DMDS@MEs-MCs). The successful combination of the two technologies was revealed by confocal laser scanning microscopy, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared. According to the multiple encapsulation structure, the encapsulation efficiency decreased by only 3.13% after thermal storage, compared with a 15.21% decrease of microcapsules made with only a monolayer film. DMDS@MEs-MCs could effectively control the release of active ingredient, which increased applicator and environmental safety during application. Moreover, it could be facilely used by spraying and drip irrigation instead of a special fumigation device. The innovative formulation exhibited better control efficacy on soil pathogens (Fusarium spp. and Phytophthora spp.) and root-knot nematodes (Meloidogyne spp.) than DMDS technical concentration (DMDS TC). In addition, it did not inhibit seed germination after 10 days when the plastic film was removed from the fumigated soil. This method appears to be of broad interest for the development of safe and handy fumigant application.