Fumigation Period Research Articles

Efficacy of the Fumigant Ethanedinitrile to Control the Ham Mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), and Its Sorption on Dry-Cured Ham.

Management of stored-product pests has historically relied on fumigation when pest populations become large. However, the ban of the fumigant methyl bromide and the ineffectiveness of other pesticides stress the need for alternative fumigants. Therefore, laboratory studies were conducted to evaluate the efficacy of ethanedinitrile (EDN) against different life stages of the mite Tyrophagus putrescentiae and to determine the sorption and desorption of EDN by dry-cured ham meat. The results showed that eggs were the most tolerant life stage to EDN fumigation, with an estimated LC50 of 0.6 mg/L. Tyrophagus putrescentiae mixed life-stage colonies were controlled at 1.3 mg/L, and less than 0.05% of the population survived following treatment with 0.6 mg/L within 24 h at 25 °C. The free-headspace concentrations of EDN in fumigation chambers containing ham decreased by 97% of the initial concentrations applied (2.6 and 4.8 mg/L) after the 24 h fumigation period. The EDN sorption in ham followed the first-order kinetics, with half-life values of 5.0 and 4.9 h for 2.6 and 4.8 mg/L, respectively. The percentage losses of EDN per hour were calculated to be 12.8 and 13.2% at 2.6 and 4.8 mg/L, respectively. Our study indicates that EDN controls T. putrescentiae in the laboratory.

Optimizing phosphine fumigation efficiency in hazelnut industry: Determining optimal exposure time for stored product pest control

Hazelnut, as with many other stored products, are susceptible to infestation by a variety of stored insect pests. Phosphine fumigation is a widely used method to control pests in stored products, including hazelnut kernels. This study aimed to determine the optimal exposure time for phosphine fumigation for management of stored product pests in hazelnuts. Four treatments with different exposure times (3, 4, 5, and 6 days) were conducted using various development stages of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), Tribolium confusum Jaqcquelin du Val, (Coleoptera: Tenebrionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) together with the control group. The trials were conducted in a commercial chamber of a hazelnut processing facility. The insects were placed in plastic containers within jute sacks filled with hazelnuts, fumigations were done under gas-proof sheet and the survival rate was assessed after treatments. The results showed that a 3-day exposure period was sufficient to fully eradicate the pupal and adult stages of O. surinamensis. For T. castaneum, 100% mortality was achieved in both larvae and adults from 3 days of exposure, but the pupal stage required at least 5 days. For T. confusum, all larvae and adults died in all exposure periods, but the pupal stage required at least 4 days. In the case of the moth species, a 100% mortality rate was achieved in the larval and pupal stages of both E. kuehniella and P. interpunctella at all exposure periods. The mortality rate of E. kuehniella eggs was 99% after 3 and 4 days of exposure, and a fumigation period of 5 days was required to control the entire population. However, only 67% of P. interpunctella eggs were controlled after 3 days of exposure. The time and stage factors were found to be significant in the egg stage of P. interpunctella. The results suggest that a 5-day exposure period is the most effective for controlling tested stored product pests in hazelnuts.

Evaluation of Ethanedinitrile as a Potential Fumigant against Plasmodiophora brassicae, the Clubroot Pathogen

Clubroot, caused by Plasmodiophora brassicae Woronin, is one of the most challenging diseases to control in oilseed rape (Brassica napus L.) and other crucifers globally. Ethanedinitrile (EDN) is a promising fumigant shown to be effective against various pests and soil-borne pathogens. However, its efficacy against P. brassicae is yet to be tested. Therefore, the current study is focused on evaluating the effectiveness of EDN against P. brassicae at different rates, applied for different durations of exposure. Clubroot-susceptible oilseed rape plants, grown in fumigated soil, were evaluated for disease severity and growth parameters in greenhouse conditions. EDN exhibited good efficacy against the pathogen, with 81.39% disease suppression compared to the control. Complete control of the disease was achieved at the rates of 42 g/m3 and 50 g/m3 as well as in the treatment variant of 35 g/m3-48 h. In addition, EDN improved plant health by increasing shoot weight by 58.24%. However, the combination of a prolonged fumigation period and higher rates resulted in a decline in the seedling emergence rate and plant shoot weight, indicating a potential adverse residual effect of higher rates and longer durations of exposure in plants.

An optimized biofumigant improves pepper yield without exerting detrimental effects on soil microbial diversity

BackgroundBiofumigation is a non-chemical sustainable approach that reshapes soil microbiota to overcome challenges in way of continuous cultivation. However, the type and quantity of substrate have a significant impact on microbiota shifts and the subsequent success of biofumigation. Moreover, studies on the effects of biofumigant concentration in combination with fumigation duration on soil microbiota dynamics are very rare.Research methodsWe performed microcosm experiments to investigate how a biofumigant (Korean canola cultivar, HanRa) at various concentrations (0.5%, 1%, 2–4% w/w: biofumigant/soil) and fumigation periods (2–4 weeks) affects the soil bacterial and fungal communities. Subsequently, pot experiments employing two Korean canola cultivars (HanRa and YongSan) at 1% (w/w) were carried out.ResultsIllumina MiSeq analysis revealed that 2–4% biofumigant, regardless of incubation period, had a significant negative impact on microbial diversity and network complexity. In contrast, 1% biofumigant transformed the bacterial, fungal, and inter-kingdom networks into a highly connected and complex network without affecting microbial diversity. Bacillus, Clostridium, and Pseudomonas were the most highly stimulated bacterial genera in the biofumigated soils, whereas the abundance of Acidobacteria members was greatly reduced. The 2–4% amendments had substantially and more differentially abundant Fusarium than the 1%. Soil nutrition (e.g., pH, nitrate, ammonium, and exchangeable potassium), fruit yield, and weed suppression were enhanced in subsequent pot experiments. Of the nine soil chemical properties, phosphate and exchangeable potassium were the main factors influencing the microbial community assembly.ConclusionsOptimized biofumigation-mediated increase in nitrate, ammonium, and potassium availability in the soil without causing any negative effects on soil microbial diversity indicates its potential as a preplant to improve crop productivity. This study contributes significantly to our understanding of how an optimal biofumigant can help ameliorate obstacles in continuous cropping.Graphical

Estimating discriminating doses of phosphine for adults of eight species of psocids of genera Liposcelis (Psocodea: Liposcelididae) and Lepinotus (Psocodea: Trogiidae)

Phosphine (PH3) resistance and tolerance contribute to the increased importance of psocids (Psocodea: Liposcelididae) as stored-product pests. This study estimated the discriminating doses (DDs) of phosphine for laboratory susceptible adults of Liposcelis bostrychophila (Badonnel), L. entomophila (Enderlein), L. decolor (Pearman), L. paeta Pearman, L. rufa Broadhead, L. obscura Broadhead, L. fusciceps Badonnel, and Lepinotus reticulatus Enderlein. Discriminating dose is defined as the upper limit of the 95% confidence interval (95% CI) of the concentration that kills 99% of the individuals in a test sample (LC99). Psocids were exposed to incremental phosphine concentrations of 0.0–300.0 ppm and 0.0–150.0 ppm over a 20-h and 72-h fumigation period, respectively, at 25 °C using a modified FAO Method No.16. The estimated DDs had a range of 65.6–697.3 ppm and 18.1–194.5 ppm over a 20-h and 72-h fumigation period, respectively. For the 20-h fumigation period, the eight psocid species had higher DDs than those established for all stored-product insect pests in the FAO Method No.16 publication. Liposcelis entomophila and L. decolor were the most tolerant psocid species over a 20-h and 72-h fumigation period, respectively. Moreover, L. entomophila required approximately 9.3 and 6.7x higher phosphine concentration compared to the most susceptible L. obscura and L. reticulatus over a 20-h and 72-h fumigation period, respectively, to achieve similar levels of LC50 mortality. The higher heterogeneity values in the standard 20-h fumigation period indicate the potential for increase in phosphine resistance in field populations subjected to phosphine fumigation. Discriminating doses estimated in this study can be used for detection of phosphine resistance and estimation of resistance frequencies in field-collected populations of the psocid species investigated.

Soil properties affect vapor-phase adsorption to regulate dimethyl disulfide diffusion in soil

Dimethyl disulfide (DMDS) is efficacious against nematodes and other soil-borne pathogens known to reduce crop quality and yield. Previous studies reported inconsistent efficacy and suggested that the diffusion of DMDS varied with different soil types. The effect of soil adsorption on gaseous DMDS diffusion through different soil types is poorly understood. To clarify the role and mechanism of soil adsorption in the diffusion of gaseous DMDS in soil, we have studied the diffusion rate constant (Rt) of gaseous DMDS in soils using a soil column experiment. The adsorption of DMDS at each gas-soil, soil-water and gas-water partition was measured by a batch-equilibrium headspace method. The results showed the DMDS adsorption equilibrium was well-described by the nonlinear Freundlich isotherm and the linear Henry isotherm. Rt values were strongly negatively correlated with the Henry coefficient (Kd) values. The Kd values of dry soil were several orders of magnitude higher than those observed in moist soil within each moisture content range. The Kd values in dry soil were strongly positively correlated with soil pore size (<2 nm). However, when the soil moisture content ranged from 3 to 12% (w/w), the Kd values were strongly correlated with specific surface area (SSA). Elevated temperatures promoted the gaseous phase of DMDS (consistent with Henry's Law) and its diffusion through soil. The soil-water partition coefficient (K'f) ranged from 1.83 to 2.20 μg11/n mL1/n g−1 in tested soils. Our results suggest that the DMDS vapor-phase diffusion in soil was significantly affected by soil adsorption, which in turn depended on the soil's properties especially the SSA and soil moisture content. These findings suggest applicators can reduce the risk of unsatisfactory and inconsistent efficacy results against soil-borne pests by adjusting the DMDS dose and fumigation period according to soil type, moisture conditions, and other environmental factors.

Management of Chrysanthemum Verticillium Wilt through VIF Soil Mulching Combined with Fumigation at Label and Reduced Rates

Pre-plant soil fumigation for managing soilborne pathogens is practiced worldwide in several intensive ornamental and vegetable production areas. However, global regulations are currently implemented to minimize use of these chemicals. According to these policies, the efficacies of dazomet (DZ, Basamid Granulat®) applied alone to soil and under virtually impermeable film (VIF) at reduced (247.5 kg ha−1 a.i.) and label (495 kg ha−1 a.i.) rates were assessed in managing natural infections of Verticillium wilt and in reducing yield losses on greenhouse chrysanthemum plantations in two trials carried out in the 2012 and 2013 seasons. The performances of this fumigant at a lower rate combined with VIF application were also compared with standardized metam-sodium (MS, Divapan®) fumigation applied at 510 L ha−1 a.i. under VIF and application of dazomet at label rate alone to bare soil. Temperatures were monitored at 20-cm depth in plots covered (VIF) throughout the entire fumigation period. Although all fumigation treatments significantly reduced the infection level by V. dahliae on chrysanthemum, the performances differed among them. DZ and MS applied at label rates under VIF showed the most effectiveness in controlling Verticillium wilt of chrysanthemum. However, DZ applied to soil at a low rate under VIF mulching showed good performances, which were always better than application of DZ alone at label rate to bare soil. Moreover, when combining a reduced rate of DZ with VIF mulching, chrysanthemum yield losses were reduced in a similar manner to the label rate application under VIF. Based on these findings, DZ application at a reduced rate could be suggested on a large scale to prevent Verticillium attacks on chrysanthemum cultivated on a protected crop. Future studies should be performed to verify the ability of VIF application in inducing high temperatures in soil and above all in enhancing performances of soil fumigation at low rates performed with other natural and chemical sterilants.

Germination and Seedling Parameters of Wheat as Affected by Storage Conditions

A storage experiment was carried out from 27th April to 27thDecember, 2019 to study the effect of storage conditions i.e. methods (open air, under sunshade and in stores), packages type (normal, gunny, polyethylene and metal containers) and periods of seeds fumigation with phosphine (15, 30 and 45 days) on germination and seedling parameters of wheat. The experiment was arranged in a factorial experiment in randomized complete block design (R.C.B.D.) with four replications. Stored wheat seeds under sunshade produced the highest values of final germination percentage, germination index, mean germination time, plumule length, radical length, seedling vigor index and seedlings dry weight, followed by stored wheat seeds in stores. The highest germination index, mean germination time, plumule and radical lengths, seedling vigor index and seedlings dry weight were recorded in the samples of wheat seeds sealed stored in metal containers, followed by normal stored in gunny packages. The highest percentage of final germination was obtained by normal stored in gunny packages, followed by sealing storage in metal containers. The highest final germination percentage, germination index, mean germination time, plumule length, radical length, seedling vigor index and seedlings dry weight and the lowest abnormal seedlings percentage, rotten and sold seeds percentages, speed germination index, co-efficient of germination and germination energy percentage were recorded when treated with phosphine at the rate of 3 tablets/m3after 15 days from beginning the storage. This study recommended that stored wheat seeds under sunshade in metal packages and treating with phosphine at the rate of 3 tablets/m3 after 15 days from beginning the storage to enhance germination and seedlings parameter of wheat under the environmental conditions of Dakahlia Governorate, Egypt.

Antifungal effect of volatile organic compounds produced by Streptomyces salmonis PSRDC-09 against anthracnose pathogen Colletotrichum gloeosporioides PSU-03 in postharvest chili fruit.

Application of volatile organic compounds (VOCs) from Streptomyces salmonis PSRDC-09 (VOCs PSRDC-09) grown on sterile wheat seeds against chili anthracnose pathogen was investigated in vitro and in vivo. Among 10 isolates of Colletotrichum species tested, Colletotrichum gloeosporioides PSU-03 was selected as the most aggressive anthracnose pathogenic strain on chili fruit against VOCs produced by Streptomyces species. Among 11 isolates, the strain PSRDC-09 exhibited the highest antifungal activity and was identified as S. salmonis PSRDC-09. The antagonistic mechanism of the VOCs PSRDC-09 on morphological of C. gloeosporioides PSU-03, observed by scanning electron microscope (SEM), revealed the irregular distortions in the fungal hyphae. The effect of inoculum size and spore concentration of S. salmonis PSRDC-09 prepared as a wheat seed inoculum on the suppression of C. gloeosporioides PSU-03 was studied both in vitro and on chili fruit. The optimum inoculum size (45g 0·31l-1 ) and spore concentration (107 spores per ml) of the wheat seed culture of S. salmonis PSRDC-09 exhibited the complete suppression (100% inhibition) on C. gloeosporioides PSU-03. The optimum fumigation period of the VOCs PSRDC-09 (45g 1·38l-1 ) was found to be 24h. Based on gas chromatography-mass spectrometry (GC-MS) analysis, 14 major VOCs (produced by the strain PSRDC-09) were detected and l-linalool was the main volatile component. The results indicated that the VOCs from S. salmonis PSRDC-09 could effectively control the chili anthracnose disease caused by C. gloeosporioides. These findings suggest that S. salmonis PSRDC-09 may have the potential to become a promising biofumigant for biocontrol of chili anthracnose disease in the postharvest system.

Evaluation of dosimeter tubes for monitoring phosphine fumigations

Within integrated pest management options, fumigation of stored products is one method to help control post-harvest insect infestations in our food and agricultural products. Fumigant gas concentration monitoring is important to confirm that the treatment was adequate to achieve the desired insect control, but monitoring can be relatively expensive and labor intensive. This study evaluated how accurately dosimeter tubes could monitor phosphine fumigation treatments. The dosimeter tube is designed to continuously react with phosphine gas during the fumigation period and yields a measurement in terms of concentration ∗ time product or CT, which can be interpreted as cumulative exposure. Two models of dosimeter tubes were evaluated (high range and low range). The reference method for these trials were wireless phosphine monitoring sensors, which recorded gas concentrations at hourly intervals during an exposure, and from this a CT product was also calculated. Model LPG-1, high-range dosimeter tube, measured within ± 25% of the phosphine monitoring sensors for CT dosages less the 70,000 ppm∗hr. Model LPG-2, low-range tube, tended to significantly over-estimate phosphine CT dosage by 50%–100% of the phosphine monitoring sensor references. Secondly, bioassays of fumigant efficacy were performed using susceptible and resistant adult Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), lesser grain borers, and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), red flour beetle, for estimating insect control at the varied fumigation CT treatments. For the susceptible strains, CT dosages ∼5000 ppm∗hr controlled both species. However, the insect control varied from 60% to 100% for resistant adults at CT dosages of ∼20,000 ppm∗hr. The dosimeter tubes function in these ranges of dosages where each insect species are controlled and the dosimeter tube model LPG-1 provides reasonable estimates of the fumigation dosage for a given treatment level.

Fumigant toxicity of some essential oils against Red Flour Beetles, Tribolium castaneum (Herbst) and its safety to mammals.

Fumigant activities for three essential oils; Garlic oil (Allium sativum L); Chili pepper (Capsicum annuum L.) and Nigella (Nigella sativa L.) were assessed at different concentrations against the adult and 20-days old larval stages of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in the laboratory. The accumulative mortality was observed at different exposure periods (3, 5 and 7 days). The residual effect of garlic oil that was the effective oil, on the treated wheat grains was evaluated with respect to histological changes in the liver, kidney, and stomach of rat fed on this treated wheat. The results showed that the mortality rates of treated stages increased with increasing the time of fumigation treatment. Moreover the highest essential oils toxicity at the Median lethal concentration (LC50) values for exposure periods (3, 5 and 7 days) to fumigation were (126, 53, and 47 mg/L air) for adult stage and were (79, 62, and 41 mg/L air) for larval stage, respectively in the case of Garlic oil treatment. While, the lowest essential oils effective was Nigella oil at the Median lethal concentration (LC50) values for exposure periods (3, 5 and 7 days) to fumigation were (3594, 629, and 335 mg/L air) for adult stage and were (1040, 416, and 227 mg/L air) for larval stage, respectively. The toxicity effect of various essential oils against adults and larvae of T. castaneum at the LC50at 7 days fumigation could be arranged in descending order as follows: Garlic oil, Chili pepper oil, and Nigella oil. The histological changes showed that the organs slightly affected at the fumigation for 3 days. It may be concluded that the garlic essential oil is the good effective fumigant to control T. castaneum in the stored products and it recommended that the fumigation period does not exceed 3 days. The garlic essential oil has the potential for applications in IPM programs for stored-grain pests because of its high volatility and fumigant activity and its safety.

Phosphine resistance in saw-toothed grain beetle, Oryzaephilus surinamensis in the United States

Phosphine (PH3) fumigation resulting in sub-lethal exposure has led to the development of phosphine resistance in many stored-product insect species worldwide and is a major challenge to the continued effective use of phosphine. In 2016 phosphine resistance was found in Tribolium castaneum (Herbst) and Plodia interpunctella (Hübner) collected from California dried fruit and nut processing facilities. Although Oryzaephilus surinamensis (L.) infests grain, dried fruit, and nuts in storage and processing facilities, phosphine resistance in this species has not been studied in the United States. In this study, the discriminating dose of phosphine for O. surinamensis eggs was estimated using a laboratory susceptible strain; it was found to be 28.4 ppm over a 72-h fumigation period (1 mg/L of phosphine = 714.18 ppm or 1 ppm = 0.0014 mg/L). Discriminating dose bioassays were used to determine phosphine resistance in both eggs and adults of 14 different populations collected from California and Oklahoma. Resistance to phosphine was detected in four out of 14 populations in adults and nine out of 14 populations in eggs and ranged from 2 to 100%. Phosphine percent survival values in both adults and eggs of three populations, namely, Box BR, Box BF, and OKWat were >90%. Lethal concentration values required to kill 99% of individuals in samples for adults of these three populations were predicted as 320.5, 290.7, and 263 ppm, respectively, and those for eggs were 1030.7, 1055.9, and 564.5 ppm, respectively, over a 72-h fumigation period. This study confirms that phosphine resistance is present in O. surinamensis in the United States.

Sorption of ethanedinitrile in fumigated commodities and its impact on efficacy for Rhyzopertha dominica (Coleoptera: Bostrichidae) and Lasioderma serricorne, (Coleoptera: Anobiidae) control

The present study evaluated sorption and desorption of ethanedinitrile (EDN) by different agricultural commodities at 2.6 and 4.8 mg/L during a 24 h fumigation period at 25 Cº. This study also investigated the impact of EDN sorption on the toxic efficacy against the lesser grain borer, Rhyzopertha dominica, and the cigarette beetle, Lasioderma serricorne. Results showed that decrease in the free-headspace concentration of EDN was high in all tested commodities. The concentrations of EDN declined by average levels of 99.8, 98.9, 98.5, 96.2 and 84.3% of the initial applied doses for wheat flour, wheat kernels, pinto beans, corn and tobacco leaves, respectively, at both doses by the end of the 24 h exposure periods. The relationship between the decrease in the free-headspace of EDN concentration over time followed the first order kinetics equation which was described as Ct = 1.77e−0.183t, Ct = 0.22e−0.215t, Ct = 2.03e−0.169t, Ct = 2.59e−0.136t, Ct = 2.17e−0.071 at 2.6 mg/L and Ct = 3.32e−0.179t, Ct = 0.41e−0.222t, Ct = 3.55e-0.165t, Ct = 4.42e0.14t, Ct = 3.87e0.071t at 4.8 mg/L for wheat kernels, wheat flour, pinto beans, corn and tobacco leaves, respectively. Moreover, we found that sorption of EDN (mg EDN/kg of commodity) by wheat flour, wheat kernels, pinto beans, corn and tobacco leaves was 12.84, 12.57, 12.66, 12.17 and 37.52 mg/kg at 2.6 mg/L, and 23.73, 22.74, 23.33, 22.73 and 69.37 mg/kg at 4.8 mg/L indicating that more than 99.0, 97.0, 98.0, 96.0 and 90.0% of the initial applied doses were sorbed, respectively. Desorption of EDN from the treated commodities after 1 h aeration and during 1 week of observation was very low, ranging from less than 0.016 mg/L for pinto beans to 0.002 mg/L for wheat flour at day 1. Results also showed that sorption of EDN by wheat kernels or wheat flour led to reductions in the insecticidal activity against L. serricorne and R. dominica mixed life stages cultures.

Coleus cultivars (Solenostemon scutellarioides (L.) Codd.) as potential bioindicators of chronic ozone exposure

Sensitivity of plant under ozone exposure can indicate its potency of being important bioindicator. Early studies have found that coleus plant (Solenostemon scutellarioides (L.) Codd.) has a potency to be ozone bio-indicator. This study aims to investigate the effect of chronic ozone exposure on root and leaf biomass and to quantify any change based on the plant appearance. Four different cultivars of coleus plant with different colour namely fully green (FG), green purple (GP), yellow purple (YP), and reddish (RD) had been selected. These four cultivars were fumigated with three different concentrations of ozone gas (≤ 10 ppb, 40 ppb, and 150 ppb) for 8 hours fumigation during 30-day period of experiment. All cultivars showed a stable leaf biomass after 30-day period of ozone exposure. Similarly, root biomass of all cultivars was not significant changed after fumigation period. Nonetheless, magnitude of ozone symptoms on leaf showed variation in certain cultivars. FG cultivar showed a significant number of chlorosis leaves under 40 and 150 ppb ozone exposure. The exposure of 150 ppb ozone also caused a noticeable percentage of curling leaves on RD cultivar. Moreover, the purple area in YP and GP showed a larger ratio under exposure of 150 ppb ozone. Consequently, coleus plants displayed resistance responds in terms of biomass. On the other hand, the plants also revealed variation in leaf symptom magnitudes and colour patterns under ozone exposure. However, these cultivars are potential to be bio-indicator due to their sensitivity in terms of appearance.

Efficacy studies on ECO2FUME® phosphine fumigant for complete control of Sitophilus zeamais and Tribolium castaneum in stored maize in Thailand.

ECO2FUME® fumigation of maize bag stacks under gas proof sheets was conducted to establish the optimal dosages (application rate) and exposure times (fumigation period) against mixed-age cultures of Sitophilus zeamais and Tribolium castaneum. The Complete Randomized Design (CRD) experimental design was employed, with 3 replications and 4 treatments. The experiments were divided into three groups: 1) treatment with a 25 g/m3 ECO2FUME® application rate (350 ppm phosphine) for 3, 4, and 5 days and a control treatment; 2) treatment with an ECO2FUME® application rate of 50 g/m3 (700 ppm phosphine) for 2, 3, and 4 days and a control treatment; and 3) treatment with a 70 g/m3 ECO2FUME® application rate (1,000 ppm phosphine) for 1, 2, and 3 days and a control treatment. The three target phosphine concentrations of 350 ppm, 700 ppm and 1,000 ppm were maintained during the whole fumigation period. Results of the studies showed that no insect was alive at all dosages and exposure times. The studies also indicated that fumigation with ECO2FUME® could reduce the fumigation period by increasing the phosphine concentration. The effective fumigation protocols on maize against mixed-age cultures of S. zeamais and T. castaneum were ECO2FUME® application rates of 25 g/m3 for 3 days, 50 g/m3 for 2 days and 70 g/m3 for 1 day. The target phosphine concentration must be maintained throughout the fumigation period to achieve 100% mortality of all stages of insects.

Quantifying phosphine penetration through the bark of pine (Pinus radiata D.Don) logs

Phosphine (PH3) is used as an in-transit phytosanitary treatment (10-d fumigation period) for pine (Pinus radiata D.Don) logs exported from New Zealand to China. The ability of PH3 to penetrate through the bark of the logs is not well known. We designed equipment to accurately quantify PH3 penetration into the bark of wooden blocks (100 × 100 × 50 mm; n = 12) cut from the upper and lower trunk of recently harvested pine trees fumigated at 15 or 25 °C. Fumigations simulated commercial conditions consisting of two phases; phase I with 2.0 g m−3 of PH3 for the first 5 days (1–120 h) and 1.5 g m−3 of PH3 in phase II for the next 5 days (121–240 h). During the 10-d schedule, we achieved the required commercial CT (concentration × time) of ≥48,000 ppm h at both temperatures. Bark thickness (i.e., trunk location) did not significantly affect fumigant penetration. Phosphine penetration through the bark of the wooden blocks was greatest after each application, then the penetrated concentrations diminished over time. Greater penetration occurred at 15 °C than at 25 °C. Further studies are required to better understand the dynamics of PH3 penetration particularly at lower temperatures and through insect-infested blocks.

異なる時期のオゾン付加に対するウダイカンバ苗の成長・光合成応答(会員研究発表論文)

異なる時期のオゾン付加に対するウダイカンバ苗の成長・光合成応答(会員研究発表論文)

Fumigant activity of volatile compounds of Streptomyces philanthi RM-1-138 and pure chemicals (acetophenone and phenylethyl alcohol) against anthracnose pathogen in postharvest chili fruit

Application of volatiles from Streptomyces philanthi RM-1-138 grown on sterile wheat seeds (volatiles RM-1-138) and pure commercial volatile compounds (acetophenone and phenylethyl alcohol) against chili anthracnose pathogen were investigated in vitro and in vivo. Among 42 isolates of Colletotrichum species tested, C. gloeosporioides PSU-NY8 was selected as the most aggressive anthracnose pathogenic strain on chili fruit against the volatiles RM-1-138. The optimum inoculum size (15 g L−1) and spore concentration (107 spore mL−1) of the wheat seed culture of S. philanthi RM-1-138 exhibited the complete suppression (100% inhibition) on C. gloeosporioides PSU-NY8. In addition, the in vivo result indicated the optimum fumigation period of the volatiles RM-1-138 (15 g L−1) was at 6 h. Phenylethyl alcohol showed no antifungal activity at all concentrations tested (10–1000 μL L−1) while acetophenone at 100 μL L−1 of airspace exhibited antifungal activity both in vitro and in vivo after 12 h fumigation. The fumigant activity was evidenced by the damage of cell wall of C. gloeosporioides PSU-NY8 illustrated by SEM. Therefore, the volatiles from S. philanthi RM-1-138 have a high potential for biocontrol of chili anthracnose disease in postharvest system.

Use of volatile oils of garlic to control the cowpea weevil Callosobruchus maculatus (Bruchidae: Coleoptera)

Cowpea weevil causes losses of 50–90% in cowpea after harvest. Control has relied on toxic agrochemical fumigants that are no longer available or are dangerous and relatively expensive, making its control difficult for most farmers. This study was initiated to investigate alternative control methods to synthetic pesticides, namely the suitable fumigation period and oil concentration of volatile oils of garlic, Allium sativum, were evaluated as a fumigant against adults of the cowpea weevil, Callosobruchus maculatus (Bruchidae: Coleoptera). Fumigation was carried out in small plastic cups (200 mL) and jute sacks (100 g) after several exposure periods (6–24 h). Insect recoveries were observed for 4 d. The volatile oils were tested at concentrations ranging between 0.1% and 20% (v/v). The oils were effective and caused significant mortalities to the test insects in cups at all concentrations tested. Garlic oil vapour penetrated through jute sacks and caused significant mortality to test insects. Recovery cases were negatively correlated to the dose. The 24 h LD50 and LD90 were 0.036% (equivalent to 175.78 μL volatile oils m−3) and 3.61% (equivalent to 17.63 mL volatile oils m−3), respectively, in the cups and jute sacks. The concentration 10% gave 100% mortality within 24 h of exposure.

Impact of Oriental Fruit Fly Postharvest Treatments on Avocado

The detection in August 2015 of the Oriental Fruit Fly (Bactrocera dorsalis Hendel, Diptera: Tephritidae) in the Redland area in Miami-Dade County, Florida triggered a quarantine that restricted the movement of fruit fly host material in an approximately 99-square mile (256-square kilometer) area. The quarantine affected 4000 acres of fruit bearing commercial avocado groves. Approved post-harvest treatments for B. dorsalis and avocado included in the USDA Treatment Manual were acceptable for immediate certification and movement of fresh avocados from the quarantine area. However, it was unknown if Florida avocados would meet quality standards (US combination grade) after the treatments. Three post-harvest treatments that combine methyl bromide fumigation and cold storage periods were tested on six avocado varieties from Florida. The treatments differed in the durations of the fumigation and cold treatment periods. A seven day transit period at 8.3°C (47°F) was added to account for the time when the fruit leaves the packing house until it is sold by retailers. None of the six varieties had met the US combination grade after the treatments and transit period. Treated fruit exhibited both internal (pulp) and external (skin) damage. Damage was attributed to the fumigation component of the treatment, but the six varieties tolerated the cold portion of the treatment. Damage by fumigation ranged from 26% - 100%. In general, the longer the fumigation period the worse the effect. The need for alternative post-harvest treatments for Florida avocados is discussed.