Evaluation of fumigant toxicity of cyclohexanone to 5 species of insect pests.

Cyclohexanone is a major precursor for nylon production and is also used as a pesticide solvent. In this study, cyclohexanone was evaluated as a fumigant against rice weevil adults, confused flour beetle adults, western flower thrips larvae and adults, spotted wing drosophila adults, and subterranean termite workers. Cyclohexanone fumigation was effective against all 5 insects, and there were considerable variations in susceptibility to cyclohexanone fumigation among the 5 species. At 20 °C, complete control of spotted wing drosophila adults was achieved in 1-h fumigation with 25 µl/l of cyclohexanone and complete control of eastern subterranean termite workers was achieved in 3-h fumigations with 50 µl/l dose of cyclohexanone. Stored-product insects confused flour beetle, and rice weevil adults were more tolerant to cyclohexanone fumigation. Fumigations of 24 h with 75 µl/l dose of cyclohexanone caused 100% mortality of rice weevil adults and 98% mortality of confused flower beetle adults. Even at a 100 µl/l dose, the 24-h fumigations did not achieve 100% mortality of confused flour beetle adults. At 5 °C, complete control of western flower thrips was achieved in 3- and 6-h fumigations with 100 and 50 µl/l doses of cyclohexanone, respectively. Cyclohexanone vapor concentrations were measured using cyclohexanone detector tubes. Vapor concentrations were far below the expected saturation concentration indicating that most cyclohexanone did not exist as vapor in fumigation chambers. The results of effective control of all 5 insect species suggest that cyclohexanone has the potential to be used as a fumigant for postharvest pest control.

Effects of Long-Term Low Oxygen Storage Treatment on Survival of Rice Weevil (Sitophilus oryzae) and Confused Flour Beetle (Tribolium confusum).

There is a need for alternative treatments for postharvest pests on stored products. In this study, 45-d long-term controlled atmosphere (CA) treatments with 3, 5, 6.5, and 8% O2 were studied to determine effects on survival and development of rice weevil (Sitophilus oryzae) and confused flour beetle (Tribolium confusum) eggs and susceptibility of different life stages to a 14-d 5% O2 treatment. Low oxygen treatments were effective against S. oryzae and T. confusum. The 45-d CA treatments with 6.5, 5, and 3% O2 resulted in 0.26, 0.004, and 0% survival rates from egg to adult respectively for S. oryzae and 6.51, 0.14, and 0% survival rates from egg to later stages respectively for T. confusum. For both species, eggs were more susceptible to low oxygen treatment than larvae or pupae. A 14-d CA treatment with 5% O2 resulted in 4.9 and 3.3% survival of eggs of S. oryzae and T. confusum, respectively, as compared with over 50% survival of larvae and pupae for both species. S. oryzae adults, however, were very susceptible to low oxygen treatment and 14-d exposure to 5% O2 atmosphere resulted in zero survival. In contrast, the 14-d exposure to 5% O2 atmosphere resulted in over 94% survival for T. confusum adults. This study suggested there were considerable differences between stored product insects in susceptibility to low oxygen treatment and that long-term CA storage treatments with a low oxygen level of ≤6.5 and ≤5% have potential in controlling S. oryzae and T. confusum, respectively.

Nitric Oxide Fumigation for Control of Ham Mite, Tyrophagus putrescentiae (Sarcoptiformes: Acaridae).

The ham mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), is a common pest infesting several stored products, particularly the aged hams. In this study, we reported the efficacy of nitric oxide (NO) fumigation, a recently discovered fumigation treatment under the ultra-low oxygen environment, at various concentrations and time under the laboratory conditions at 25°C against different mite stages on both dietary media and ham meat. Our results showed that NO fumigation was effective against all mite stages and 100% control was achieved. Generally, the egg was the most tolerant stage and required 48-, 24-, 16-, and 8-h treatments to achieve 100% mortality at 0.5, 1, 1.5, and 2% NO concentration on dietary media, respectively. Tyrophagus putrescentiae mobile immatures and adult stages were less tolerant, and 100% mortality was achieved after 16-, 8-, 8-, and 4-h treatment at 0.5, 1, 1.5, and 2% NO, respectively. The median lethal concentration (LC50) of NO on egg was 0.86, 0.68, and 0.32% for 8-, 16-, and 24-h treatments. In addition, a confirmatory test was conducted on ham meat at 0.5 and 1.0% of NO and similar efficacy was found. Complete control of egg was achieved after 48- and 24-h treatment at 0.5 and 1.0% of NO, respectively, and larvae and adult mites were 100% controlled after 16 and 8 h at 0.5 and 1.0% of NO, respectively. Our results demonstrated that NO fumigation was effective against T. putrescentiae and can be a potential alternative treatment to methyl bromide for cured-ham pest control.

Thalidomide suppresses angiogenesis and immune evasion via lncRNA FGD5-AS1/miR-454-3p/ZEB1 axis-mediated VEGFA expression and PD-1/PD-L1 checkpoint in NSCLC.

BACKGROUND: Non-small cell lung cancer (NSCLC) accounts for about 80-85% of total lung cancer cases. Identifying the molecular mechanisms of anti-tumor drugs is essential for improving therapeutic effects. Herein, we aim to investigate the role of thalidomide in the tumorigenicity of NSCLC. METHODS: The A549 xenograft nude mouse model was established to explore therapeutic effects of thalidomide. The expression of FGD5-AS1 was evaluated in carcinomatous and paracarcinomatous tissues from NSCLC patients as well as NSCLC cell lines. CCK-8 assay was performed to assess cell viability. The invasive capacity was examined using transwell assay. The tube formation assay was applied to determine cell angiogenesis. Flow cytometry was subjected to validate CD8+ T cell activity. The FGD5-AS1/miR-454-3p/ZEB1 regulatory network was analyzed using luciferase reporter, RIP and ChIP assays. RESULTS: Thalidomide reduced tumor growth and angiogenesis and increased CD8+ T cell ratio in a mouse model. Enhanced expression of FGD5-AS1 was positively correlated with the poor survival of NSCLC patients. Knockdown of FGD5-AS1 notably suppressed the proliferation, invasion and angiogenesis of cancer cells as well as the apoptosis of CD8+ T cells. Thalidomide targeted FGD5-AS1 to exert its anti-tumor activity in NSCLC. FGD5-AS1 acted as a sponge of miR-454-3p to upregulate ZEB1, thus increasing the expression of PD-L1 and VEGFA. Simultaneous overexpression of FGD5-AS1 and silencing of miR-454-3p reversed thalidomide-mediated anti-tumor effects in NSCLC. CONCLUSION: Thalidomide inhibits NSCLC angiogenesis and immune evasion via FGD5-AS1/miR-454-3p/ZEB1 axis-mediated regulation of VEGFA expression and PD-1/PD-L1 checkpoint.

Effectiveness of Nitrogen Dioxide Fumigation for Microbial Control on Stored Almonds.

ABSTRACT: Quality of stored almonds is compromised by insect infestations and microbial contamination. Nitric oxide (NO) is a potent fumigant for postharvest pest control on fresh and stored products. NO fumigation must be conducted under ultralow oxygen conditions, and it always produces nitrogen dioxide (NO2), depending on the O2 level in the fumigation chamber. NO and NO2 have proven antimicrobial effects but have not been tested for efficacy against microbes in almonds. We evaluated, in this study, fumigation of unpasteurized almonds with NO2 at different levels for inhibition of bacteria and fungi. Almonds were fumigated with 0.1, 0.3, or 1.0% NO under ambient O2 to generate 0.1, 0.3, or 1.0% NO2 conditions; the fumigation treatments lasted 1 or 3 days at 25°C. GreenLight rapid enumeration tests on diluted wash-off almond samples from NO2 fumigation treatments showed either greatly reduced microbial loads or complete control of microorganisms, depending on NO2 concentration and treatment duration. NO2 fumigation was more effective against fungi than against bacteria. These results suggest that postharvest NO fumigation with proper levels of NO and NO2 can be used for insect and microorganism control on stored almonds.

Sulfur Dioxide Fumigation for Postharvest Control of Mealybugs on Harvested Table Grapes.

Laboratory fumigations with sulfur dioxide (SO2) were conducted under ultralow oxygen (ULO) and normal atmosphere to determine their effects on mortality of grape mealybug, Pseudococcus maritimus (Ehrhorn), and vine mealybug, Planococcus ficus Signoret, and postharvest quality of table grapes. Three- and 4-d fumigation treatments with 100 ppm SO2 under 30 ppm ULO condition and normal atmosphere resulted in 100% mortality of eggs and nymphs/adults of vine mealybug. The 3- and 4-d SO2 fumigations under the ULO condition and the normal atmosphere were also effective against grape mealybug with egg mortalities of 85.8% and 98.8% and nymph/adult mortalities of 99.0% and 100%, respectively. There was no significant difference between SO2 fumigations under ULO and the normal atmosphere in insect mortality. One-day fumigation treatments with 400 and 500 ppm SO2 achieved 89.8% and 95.8% mortality of grape mealybug eggs, respectively, and achieved 100% mortality of grape mealybug nymphs and adults. None of the treatments used in this study adversely affected quality of the six table grape cultivars used in the studies. SO2 fumigation under either ULO or normal atmosphere is potentially a useful means for postharvest control of mealybugs on harvested table grapes.

Nitric oxide fumigation for postharvest pest control on lettuce.

BACKGROUND: The lettuce aphid, Nasonovia ribisnigri, and western flower thrips, Frankliniella occidentalis, are quarantine pests of lettuce in Asian markets and, therefore, require treatments on lettuce exported from USA to Japan and Taiwan, respectively. Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control and has been demonstrated as safe to fresh fruit and vegetables. In this study, small-scale NO fumigations were conducted to determine effective treatments and large-scale confirmatory tests were conducted to determine the efficacy against N. ribisnigri and F. occidentalis on commercially packed lettuce. The safety of NO fumigation to postharvest quality of lettuce was also evaluated. RESULTS: In small-scale experiments, complete control of N. ribisnigri was achieved in 3, 8, and 16 h fumigations with 2.0%, 1.0%, and 0.5% NO, respectively, at 2 °C on both iceberg and romaine lettuce. In a large-scale experiment, complete control of both N. ribisnigri and F. occidentalis was achieved in a 16 h fumigation with 0.5% NO at 2 °C. The fumigation treatment had no effect on either external or internal postharvest quality of lettuce at 14 days after treatment. CONCLUSION: Nitric oxide fumigation was demonstrated to be effective against both N. ribisnigri and F. occidentalis and safe to lettuce quality in large-scale fumigations of commercially packed lettuce. The study suggests that NO fumigation has the potential to be an alternative treatment to methyl bromide for postharvest pest control on harvested lettuce. © 2018 Society of Chemical Industry.

Nitric Oxide Fumigation for Control of Spotted Wing Drosophila (Diptera: Drosophilidae) in Strawberries.

Nitric oxide (NO) fumigation was conducted to determine the efficacy of controlling spotted wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), in strawberries and the effects on postharvest quality of strawberries under ultralow oxygen conditions at 2°C. Eight-hour fumigations with 1.0 and 3.0% NO were tested against different life stages of the insect to determine an effective treatment, and a 16-h fumigation was tested to determine the impact on strawberry quality. Complete control of eggs and larvae in strawberries was achieved in an 8-h fumigation with 3.0% NO, and the treatment achieved 98.8% mortality of pupae. The first and second instars were more susceptible to NO and were completely controlled with 1.0% NO fumigation. The 16-h fumigation treatment with 3.0% NO had no negative impact on strawberry quality as there were no significant differences from the control in berry damage score. The NO fumigation, however, significantly reduced mold 2 wk after fumigation, indicating that NO fumigation had potential to preserve strawberry quality. The results of this study demonstrated that NO fumigation is effective for control of SWD and safe to strawberries, and therefore, NO fumigation has potential to control SWD on harvested strawberries.

Low-Temperature Fumigation of Harvested Lettuce Using a Phosphine Generator.

A research-scale phosphine generator, QuickPHlo-R, from United Phosphorus Ltd. (Mumbai, India) was tested to determine whether it was suitable for low-temperature fumigation and oxygenated phosphine fumigation of harvested lettuce. Vacuum cooled Iceberg and Romaine lettuce (Lactuca sativa) were fumigated in 442-liter chambers at 2°C for 24 and 72 h for control of western flower thrips [Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)] and lettuce aphid [Nasonovia ribisnigri (Mosely) (Homoptera: Aphididae)]. Oxygenated phosphine fumigation for 48 h under 60% O2 was also conducted at 2°C with Iceberg and Romaine lettuce for control of lettuce aphid. The generator completed phosphine generation in 60-90 min. Complete control of western flower thrips was achieved in 24-h treatment, and the 48-h oxygenated fumigation, and 72-h regular fumigation treatments completely controlled lettuce aphid. Lettuce quality was evaluated 14 d after fumigation. There was increased incidence of brown stains on fumigated Iceberg lettuce, and the increases were more obvious in longer (≥48 h) treatments. Both Iceberg and Romaine lettuce from all treatments and controls had good visual quality even though there was significantly higher brown stain incidence on fumigated Iceberg lettuce in ≥48-h treatment and significant differences in quality score for both Iceberg and Romaine lettuce in the 72-h treatment. The brown stains were likely due to the high sensitivity of lettuce to carbon dioxide. The study indicated that QuiPHlo-R phosphine generator has potential in low-temperature phosphine fumigation due to the quick establishment of desired phosphine levels, efficacy in pest control, and reasonable safety to product quality.

Procedures of Laboratory Fumigation for Pest Control with Nitric Oxide Gas.

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on fresh products and procedures for residue analysis and product quality evaluation. An airtight fumigation chamber containing fresh fruit and vegetables is first flushed with nitrogen (N2) to establish an ultralow oxygen (ULO) environment followed by injection of NO. The fumigation chamber is then kept at a low temperature of 2 - 5 °C for a specified time period necessary to kill a target pest to complete a fumigation treatment. At the end of a fumigation treatment, the fumigation chamber is flushed with N2 to dilute NO prior to opening the chamber to ambient air to prevent the reaction between NO and O2, which produces NO2 and may damage delicate fresh products. At different times after NO fumigation, NO2 in headspace and nitrate and nitrite in liquid samples were measured as residues. Product quality was evaluated after 2 weeks of post-treatment cold storage to determine effects of NO fumigation on product quality. Keeping O2 from reacting with NO is critical to NO fumigation and is an important part of the protocols. Measuring NO levels is challenging and a practical solution is provided. Possible protocol modifications are also suggested for measuring NO levels in the fumigation chambers as well as residues. NO fumigation has the potential to be a practical alternative to methyl bromide fumigation for postharvest pest control on fresh and stored products. This publication is intended to assist other researchers in conducting NO fumigation research for postharvest pest control and accelerating the development of NO fumigation for practical applications.

Nitric Oxide Fumigation for Control of Bulb Mites on Flower Bulbs.

In this article, the efficacy of nitric oxide (NO) fumigation to control bulb mites in the genus Rhizoglyphus and its effects on germination and growth of flower bulbs were studied. Bulb mites on infested peanuts were fumigated with NO at different concentrations under ultralow oxygen conditions in 1.9-liter jars for 4-48 h at various temperatures ranging from 2 to 20 °C. Bulb mites were susceptible to NO fumigation treatment. Efficacy of fumigation treatment increased with increased concentration, treatment time, and temperature within the ranges tested. Complete control of bulb mites was achieved in 24-h fumigation with 3.0% and 5.0% NO at 10 °C and with 2.0% NO at 20 °C. A fumigation treatment with 3.0% NO at 20 °C for 24 h, which was stronger than necessary for bulb mite control, was tested on bulbs of four flower varieties to determine its safety on germination and growth of the flower bulbs. The NO fumigation treatments did not significantly affect germination and growth of flower bulbs. This study showed that NO fumigation was effective against bulb mites on peanuts and did not affect germination and growth of flower bulbs. Therefore, NO fumigation has potential for postharvest control of bulb mites on flower bulbs.

Efficacy of Nitric Oxide Fumigation for Controlling Codling Moth in Apples.

Nitric oxide (NO) fumigation under ultralow oxygen (ULO) conditions was studied for its efficacy in controlling codling moth and effects on postharvest quality of apples. NO fumigation was effective against eggs and larvae of different sizes on artificial diet in 48 h treatments. Small larvae were more susceptible to nitric oxide than other stages at 0.5% NO concentration. There were no significant differences among life stages at 1.0% to 2.0% NO concentrations. In 24 h treatments of eggs, 3.0% NO fumigation at 2 °C achieved 100% egg mortality. Two 24 h fumigation treatments of infested apples containing medium and large larvae with 3.0% and 5.0% NO resulted in 98% and 100% mortalities respectively. Sound apples were also fumigated with 5.0% NO for 24 h at 2 °C to determine effects on apple quality. The fumigation treatment was terminated by flushing with nitrogen and had no negative impact on postharvest quality of apples as measured by firmness and color at 2 and 4 weeks after fumigation. This study demonstrated that NO fumigation was effective against codling moth and safe to apple quality, and therefore has potential to become a practical alternative to methyl bromide fumigation for control of codling moth in apples.

Effects of Ultralow Oxygen and Vacuum Treatments on Bed Bug (Heteroptera: Cimicidae) Survival.

Control of bed bugs is problematic, balancing among efficacy, safety, and cost. In this study, ultralow oxygen (ULO) and vacuum treatments were tested on bed bugs to develop a safer, effective, and environmentally friendly solution to kill bed bugs on infested items. ULO treatments were established by flushing sealed enclosures with nitrogen. All life stages of bed bugs were found to be susceptible to ULO and vacuum treatments, and efficacy of the treatments increased with reduced oxygen levels, increased treatment time, and temperature. In the ULO treatments, 100% mortality of bed bug nymphs and adults and >98% mortality of bed bug eggs were achieved in the 8-h treatment under 0.1% O 2 atmosphere at 30°C. Different levels of vacuum that yielded different oxygen levels were tested on all life stages of bed bugs. The susceptibility of different stages to vacuum treatments increased from nymphs to adults to eggs. Complete control of all life stages was achieved in 12 h under -982 mbar (-29.0 inHg) vacuum at 30°C. This study demonstrated that bed bugs were very susceptible to low oxygen stresses and ULO and vacuum treatments have potential to be used as effective and safe treatments to decontaminate bed bug-infested removable objects.

Oxygenated Phosphine Fumigation for Control of Light Brown Apple Moth (Lepidoptera: Tortricidae) Eggs on Cut-Flowers.

Light brown apple moth, Epiphyas postvittana (Walker), eggs were subjected to oxygenated phosphine fumigation treatments under 70% oxygen on cut flowers to determine efficacy and safety. Five cut flower species: roses, lilies, tulips, gerbera daisy, and pompon chrysanthemums, were fumigated in separate groups with 2,500 ppm phosphine for 72 h at 5°C. Egg mortality and postharvest quality of cut flowers were determined after fumigation. Egg mortalities of 99.7-100% were achieved among the cut flower species. The treatment was safe to all cut flowers except gerbera daisy. A 96-h fumigation treatment with 2,200 ppm phosphine of eggs on chrysanthemums cut flowers also did not achieve complete control of light brown apple moth eggs. A simulation of fumigation in hermetically sealed fumigation chambers with gerbera daisy showed significant accumulations of carbon dioxide and ethylene by the end of 72-h sealing. However, oxygenated phosphine fumigations with carbon dioxide and ethylene absorbents did not reduce the injury to gerbera daisy, indicating that it is likely that phosphine may directly cause the injury to gerbera daisy cut flowers. The study demonstrated that oxygenated phosphine fumigation is effective against light brown apple moth eggs. However, it may not be able to achieve the probit9 quarantine level of control and the treatment was safe to most of the cut flower species.

Oxygenated phosphine fumigation for control of Epiphyas postvittana (Lepidoptera: Tortricidae) eggs on lettuce.

Light brown apple moth, Epiphyas postvittana (Walker), is a quarantined pest in most countries. Its establishment in California and potential spread to other parts of the state and beyond make it urgent to develop effective postharvest treatments to control the pest on fresh commodities. Fumigation with cylindered phosphine at low temperature has emerged to be a practical methyl bromide alternative treatment for postharvest pest control on fresh commodities. However, its use to control E. postvittana eggs on sensitive commodities such as lettuce is problematic. E. postvittana eggs are tolerant of phosphine and long phosphine treatment also injures lettuce. In the current study, E. postvittana eggs were subjected to oxygenated phosphine fumigations to develop an effective treatment at a low storage temperature of 2 degrees C. In addition, soda lime as a CO2 absorbent was tested to determine its effects in reducing and preventing injuries to lettuce associated with phosphine fumigations. Three-day fumigation with 1,000 ppm phosphine under 60% O2 achieved 100% mortality of E. postvittana eggs in small-scale laboratory tests. In the presence of the CO2 absorbent, a 3-d large-scale fumigation of lettuce with 1,700 ppm phosphine under 60% O2 resulted in a relative egg mortality of 99.96% without any negative effect on lettuce quality. The 3-d fumigation treatment without the CO2 absorbent, however, resulted in significant injuries to lettuce and consequential quality reductions. The study demonstrated that oxygenated phosphine fumigation has the potential to control E. postvittana eggs and the CO2 absorbent has the potential to prevent injuries and quality reductions of lettuce associated with long-term oxygenated phosphine fumigation.

Radio-sensitization by Piper longumine of human breast adenoma MDA-MB-231 cells in vitro.

BACKGROUND: The current study investigated the effects of Piper longumine on radio-sensitization of human breast cancer MDA-MB-231 cells and underlying mechanisms. MATERIALS AND METHODS: Human breast cancer MDA-MB-231 cells were cultured in vitro and those in logarithmic growth phase were selected for experiments divided into four groups: control, X-ray exposed, Piper longumine, and Piper longumine combined with X-rays. Conogenic assays were performed to determine the radio-sensitizing effects. Cell survival curves were fitted by single-hit multi-target model and then the survival fraction (SF), average lethal dose (D0), quasi-threshold dose (Dq) and sensitive enhancement ratio (SER) were calculated. Cell apoptosis was analyzed by flow cytometry (FCM).Western blot assays were employed for expression of apoptosis-related proteins (Bc1-2 and Bax) after treatment with Piper longumine and/or X-ray radiation. The intracellular reactive oxygen species (ROS) level was detected by FCM with a DCFH-DA probe. RESULTS: The cloning formation capacity was decreased in the group of piperlongumine plus radiation, which displayed the values of SF2, D0, Dq significantly lower than those of radiation alone group and the sensitive enhancement ratio (SER) of D0 was1.22 and 1.29, respectively. The cell apoptosis rate was increased by the combination treatment of Piper longumine and radiation. Piper longumine increased the radiation-induced intracellular levels of ROS. Compared with the control group and individual group, the combination group demonstrated significantly decreased expression of Bcl-2 with increased Bax. CONCLUSIONS: Piper longumine at a non-cytotoxic concentration can enhance the radio-sensitivity of MDA- MB-231cells, which may be related to its regulation of apoptosis-related protein expression and the increase of intracellular ROS level, thus increasing radiation-induced apoptosis.

Effects of phosphine fumigation on survivorship of Epiphyas postvittana (Lepidoptera: Tortricidae) eggs.

Light brown apple moth, Epiphyas postvittana (Walker), eggs were subjected to phosphine fumigations under normal atmospheric and elevated oxygen levels in laboratory-scale chamber experiments to compare their susceptibilities to the two different fumigation methods. In fumigations conducted under atmospheric oxygen at 5 and 10 degrees C, egg survivorship decreased with increase in phosphine concentration but then increased at a concentration of 3,000 ppm; this increase was significant at 10 degrees C. Based on egg survivorship data, phosphine fumigations conducted in a 60% oxygen atmosphere were significantly more effective than those conducted under atmospheric oxygen conditions. Oxygenated phosphine fumigations at 5 and 10 degrees C killed all 1,998 and 2,213 E. postvittana eggs treated, respectively, after 72 h of exposure. These results indicate the great potential of oxygenated phosphine fumigation for the control of E. postvittana eggs.

Postharvest treatment of fresh fruit from California with methyl bromide for control of light brown apple moth (Lepidoptera: Tortricidae).

Methyl bromide (MB) chamber fumigations were evaluated for postharvest control of light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), in fresh fruit destined for export from California. To simulate external feeding, larvae were contained in gas-permeable cages and distributed throughout loads of peaches, plums, nectarines (all Prunus spp.), apples (Malus spp.), raspberries (Rubus spp.), or grapes (Vitis spp.). Varying the applied MB dose and the differential sorption of MB by the loads resulted in a range of exposures, expressed as concentration x time cross products (CTs) that were verified by gas-chromatographic quantification of MB in chamber headspace over the course of each fumigation. CTs > or = 60 and > or = 72 mg liter(-1) h at 10.0 +/- 0.5 and 15.6 +/- 0.5 degrees C (x +/- s, average +/- SD), respectively, yielded complete mortality of approximately 6,200 larvae at each temperature. These confirmatory fumigations corroborate E. postvittana mortality data for the first time in relation to measured MB exposures and collectively comprise the largest number of larval specimens tested to date. In addition, akinetic model of MB sorption was developed for the quarantine fumigation of fresh fruit based on the measurement of exposures and how they varied across the fumigation trials. The model describes how to manipulate the applied MB dose, the load factor, and the load geometry for different types of packaged fresh fruit so that the resultant exposure is adequate for insect control.

Nitric oxide as a potent fumigant for postharvest pest control.

There is a great demand for safe and effective alternative fumigants to replace methyl bromide and other toxic fumigants for postharvest pest control. Nitric oxide, a common signal molecule in biological systems, was found to be effective and safe to control insects under ultralow oxygen conditions. Four insect species including western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera Thripidae); aphid, Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae); confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae); and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), at various life stages were fumigated with 0.1-2.0% nitric oxide under ultralow oxygen levels of < or = 50 ppm in 1.9-liter glass jars at 2-25 degrees C depending on insect species. Fumigations were effective against all four insect species. Efficacy of nitric oxide fumigation increased with nitric oxide concentration, treatment time, and temperature. There were also considerable variations among insect species as well as life stages in susceptibility to nitric oxide fumigation. Complete control of thrips was achieved in 2 and 8 h with 2.0 and 0.2% nitric oxide, respectively, at 2 degrees C. At the same temperature, complete control of the aphid was achieved in 3, 9, and 12 h with 1.0, 0.5, and 0.2% nitric oxide, respectively. Larvae, pupae, and adults of confused flour beetle were effectively controlled in 24 h with 0.5% nitric oxide at 20 degrees C. Complete mortality of confused flour beetle eggs was achieved in 24 h with 2.0% nitric oxide at 10 degrees C. Rice weevil adults and eggs were effectively controlled with 1.0% nitric oxide in 24 and 48 h, respectively, at 25 degrees C. These results indicate that nitric oxide has potential as a fumigant for postharvest pest control.