Combinations of reduced rates of 1,3-dichloropropene and dazomet as a broad spectrum soil fumigation strategy in view of methyl bromide replacement

Almost no single commercially available or registered compound is able to replace the broad spectrum activity of methyl bromide. However, combinations of for long known fumigants or their generators, showing good activity in the control of specific groups of soil borne diseases or pests, show interesting broad spectrum activity and even synergism. Well-known combinations are 1,3-dichloropropene (1,3-D) and chloropicrin, applied by injection or through irrigation lines. A few decades ago, combination products containing 1,3-D and methyl isothiocyanate (MITC) were developed and commercialized but were not Longer supported. As 1,3-D is an excellent nematicide with other target groups depending on contact time and tarping, and dazomet as a MITC generator shows fungicidal, nematicidal, insecticidal and herbicidal activities, studies with combinations of both were started again. Laboratory trials with different combinations of 1,3-D and Basamid (97 % dazomet) in soil columns showed interesting results both with Basamid solved in 1,3-D, although limited by temperature, and with simultaneously applied products, even at half dose of each, or even tess. In a further stage, small greenhouse trials were performed with tomato and lettuce crop and could confirm synergistic activity through the evaluation of crop stand and harvest results. Other trial work was performed in collaboration between Certis Europe branches and local research groups in both Italy and Spain. There again it was demonstrated that the combination of 1,3-D (injectable as well as emulsifiable formulations) with Basamid are able to control different phytosanitary problems in different crops. In parallel with the above mentioned trial work, emphasis is also made on careful and appropriate tarping of the soil, preferentially by improved gastight barrier film. The latter allows dose reduction as well as improvement of the fumigation performance. Barrier properties of commercially available fumigation film are now studied for both 1,3-D and MITC. Finally, it is emphasized that appropriate application systems and machinery need more attention to achieve good results with this type of fumigants, i.e. less volatile and with less good diffusion capacity as compared to methyl bromide.     

Genotoxic effects of methyl isothiocyanate

Aim of the study was to investigate the genotoxic effects of methyl isothiocyanate (MITC), a compound widely distributed in the environment as a constituent of certain vegetables, a soil fumigant and breakdown product of carbamate pesticides. MITC caused only marginal mutation induction in reversion assays with Salmonella strains TA100 and TA98 and, the maximum effect (<2-fold increase over the background rate) was seen at 100microg/ml. In differential DNA-repair assays with E. coli (strains 343/763 uvrB/recA and 343/765 uvr(+)/rec(+)), a pronounced dose-response effect (induction of repairable DNA-damage) was seen at low concentrations (>/=4microg/ml). In both bacterial assays, addition of activation mix (rat liver S-9) led to a reduction of the genotoxic effects. In micronucleus assay and in single cell gel electrophoresis assay with human hepatoma cells (HepG2), clear cut positive results were obtained at exposure concentrations of <5microg/ml. On the contrary, only marginal effects were seen in differential DNA-repair host-mediated assays where E. coli indicator cells were recovered from different inner organs of mice that had been treated orally with a high dose (90mg/kg bw) of the test compound. Further in vitro experiments showed that MITC is inactivated by body fluids (saliva, gastric juice) and that its DNA-damaging properties are attenuated by non-enzymatic protein binding. Since exposure of HepG2 cells to MITC led to formation of thiobarbituric acid reactive substances, it is likely that its DNA-damaging effects involve lipid peroxidation processes. Overall, our findings show that MITC induces only marginal effects at extremely high (almost lethal) doses in inner organs in vivo, but it causes DNA-damage at low concentrations in vitro.     

Methyl iodide: an alternative to methyl bromide for insectary fumigation

Methyl bromide is a powerful fumigant that has been widely used in soil, structural and commodity fumigations for many years. Because of its designation as an ozone-depleting chemical and resulting federal and international laws, it is scheduled to be removed from production in the year 2001. In experiments testing the suitability of methyl iodide as a replacement chemical for insectary and quarantine fumigations, the chemical appears to be as effective or more effective than methyl bromide. Increased symptoms of plant toxicity to methyl iodide are evidenced only at concentrations above those required to kill insect pests.     

Soil fumigation with methyl bromide: the phytotoxicity of inorganic bromide to carnation plants

Rooted carnation cuttings often developed phytotoxic symptoms when planted in soil previously fumigated with methyl bromide, and many died. Those which recovered suffered a marked check in growth and flower production was reduced. Plant injury and effects on flower yield were more severe at high rates of fumigant application, but were reduced by flooding the soil with water or by incorporating peat into the growing medium.
Plant survival and flower yield were inversely related to the concentration in soil of inorganic bromide formed by the breakdown of the fumigant. Injury to plants occasionally occurred in the presence of soil concentrations of inorganic bromide as low as 5 pglg. Flooding the soil or incorporating peat into it were beneficial because these treatments reduced the soil concentration of inorganic bromide.
Carnation plants which were grown in soil previously fumigated with methyl bromide or supplemented directly with potassium bromide accumulated bromide in their leaves, and a bromide gradient was eventually established, the concentrations decreasing from the bottom to the top of the plants.
The evidence that inorganic bromide is the cause of the injury to carnations is discussed, and the role of peat in alleviating the incidence and seventy of the injury is considered.     

Control of clubroot by soil partial sterilization with particular reference to the treatment of small natural foci of infection

Experiments were made on field plots with four soil partial sterilants applied at different dose rates or as combination treatments. The effects of treatments on clubroot were assessed by growing cabbages on the field plots or in a glasshouse in soil removed from the plots. In two experiments, no plants grown on plots or seedlings grown in soil samples from plots treated with Dowfume M.C.2 or Telone were infected with clubroot, whilst only one infected seedling was found in soil samples from those plots treated with chloropicrin. Although relatively few infected plants were recovered from Basamid treated plots, many infected seedlings were found in soil samples from those plots. The effectiveness of these treatments as indicated by seedling survival was Dowfume M.C.2 < chloropicrin < Telone < Basamid. At five sites a combination of Dowfume M.C.2 at 98 g/m² with 40 g/m² Basamid resulted in all cabbage seedlings grown in soil samples being disease free.     

Preliminary glasshouse and field tests of soil partial sterilants for clubroot control

Experiments were made on field plots and in individually dosed pots to investigate the effects of ten soil partial sterilants on percentage infection of cabbage with clubroot. Additionally, cores of naturally-infested soil or samples of artificially infested and buried soil removed from some treated plots were also sown with cabbage in a glasshouse and the seedlings then assayed for the presence of clubroot. There was evidence that the partial sterilants were optimally effective at different depths. Dowfume M.C.2 and Basamid having the unique properties of effectiveness at deep and shallow horizons of the soil respectively. Chloropicrin at 60 ml/m² and Dowfume M.C.2 at 98 g/m² were the most effective partial sterilants in controlling clubroot while Basamid and Telone were also considered to merit further testing. All other partial sterilants reduced percentage infection in pot experiments and field crops to varying extents although formaldehyde was least effective.     

High-Resolution Melt Analysis for Rapid Comparison of Bacterial Community Compositions

In the study of bacterial community composition, 16S rRNA gene amplicon sequencing is today among the preferred methods of analysis. The cost of nucleotide sequence analysis, including requisite computational and bioinformatic steps, however, takes up a large part of many research budgets. High-resolution melt (HRM) analysis is the study of the melt behavior of specific PCR products. Here we describe a novel high-throughput approach in which we used HRM analysis targeting the 16S rRNA gene to rapidly screen multiple complex samples for differences in bacterial community composition. We hypothesized that HRM analysis of amplified 16S rRNA genes from a soil ecosystem could be used as a screening tool to identify changes in bacterial community structure. This hypothesis was tested using a soil microcosm setup exposed to a total of six treatments representing different combinations of pesticide and fertilization treatments. The HRM analysis identified a shift in the bacterial community composition in two of the treatments, both including the soil fumigant Basamid GR. These results were confirmed with both denaturing gradient gel electrophoresis (DGGE) analysis and 454-based 16S rRNA gene amplicon sequencing. HRM analysis was shown to be a fast, high-throughput technique that can serve as an effective alternative to gel-based screening methods to monitor microbial community composition.     

Microorganisms participating in the biodegradation of modified polyethylene films in different soils under laboratory conditions

The degree of biodegradation of low-density polyethylene (LDPE) films modified with Bionolle^® polyester in different soils under laboratory conditions was evaluated. Films were incubated in soils from waste coal, a forest and an extinct volcano crater. Prior to degradation studies, soils underwent chemical and microbiological analysis. Film weight loss and mechanical properties, as well as the surface of the polymeric samples determined via scanning electron microscopy, were evaluated after 75, 150 and 225 days of biodegradation. Important chemical changes in the polymeric chains were detected by Fourier Transform Infrared Spectroscopy (FTIR). Fungal and bacterial species that were able to grow on the film surfaces were monitored in order to see whether the films were easily colonised by autochthonous microorganisms (i.e., typical to each soil). Identification of microorganisms was based on their cellular fatty acid methyl ester (FAME) profiles. Biodegradation of modified polyethylene films in soils led to significant changes (i.e., elongation at brake of 98%) in their mechanical properties that were caused by biochemical modifications of both polyester and polyethylene. Compared to waste coal soil, films underwent rapid biodegradation in soils that were rich in organic matter. Bacteria belonging to the genus, Bacillus, and the fungi, Gliocladium viride, Aspergillus awamori and Mortierella subtilissima, were easily able to colonise both polyethylene and polyethylene modified with Bionolle^®.     

The Potential of Five Winter-grown Crops to Reduce Root-knot Nematode Damage and Increase Yield of Tomato

Broccoli (Brassica oleracea), carrot (Daucus carota), marigold (Tagetes patula), nematode-resistant tomato (Solanum lycopersicum), and strawberry (Fragaria ananassa) were grown for three years during the winter in a root-knot nematode (Meloidogyne incognita) infested field in Southern California. Each year in the spring, the tops of all crops were shredded and incorporated in the soil. Amendment with poultry litter was included as a sub-treatment. The soil was then covered with clear plastic for six weeks and M. incognita-susceptible tomato was grown during the summer season. Plastic tarping raised the average soil temperature at 13 cm depth by 7°C.The different winter-grown crops or the poultry litter did not affect M. incognita soil population levels. However, root galling on summer tomato was reduced by 36%, and tomato yields increased by 19% after incorporating broccoli compared to the fallow control. This crop also produced the highest amount of biomass of the five winter-grown crops. Over the three-year trial period, poultry litter increased tomato yields, but did not affect root galling caused by M. incognita. We conclude that cultivation followed by soil incorporation of broccoli reduced M. incognita damage to tomato. This effect is possibly due to delaying or preventing a portion of the nematodes to reach the host roots. We also observed that M. incognita populations did not increase under a host crop during the cool season when soil temperatures remained low (< 18°C).     

Mechanical,barrier and morphological properties of pea starch and peanut protein isolate blend films

Mechanical, barrier and morphological properties of edible films based on blends of Pea starch (PS) and Peanut protein isolate (PPI) plasticized with glycerol (30%, w/w) were investigated. As PPI ratio in PS/PPI blends increased, the thickness of films decreased, the opacity slightly elevated and color intensified. The addition of PPI to the PS film significantly reduced tensile strength from 5.44 MPa to 3.06 MPa, but increased elongation from 28.56% to 98.12% with the incorporation of PPI into PS at 50% level. Film solubility value fell from 22.31% to 9.78% upon the incorporation of PPI ranged from 0 to 50% level. When PPI was added into PS film at 40% level, the WVP and WVTR of the films markedly dropped from 11.18% to 4.19% and 6.16 to 1.95%, respectively. Scanning electron microscopy (SEM) of the surface of films showed that many swollen starch granules were presented in the 100% PS film, while 100% PPI film was observed to have rougher surfaces with presence of pores or cavities. The PS/PPI blend films upon the incorporation of PPI at 20% and 50% level were not homogeneous. However, the smoother film surface was observed in PS/PPI blend films with the addition of PPI at 40% level. SEM image of the cross-sections of the films revealed that the 100% PS film showed a uniform and compact matrix without disruption, and pore formation and 100% PPI film displayed a smooth structure. Rougher and flexible network was shown in blend film with the addition of PPI reaching 40% level.     

Soil fumigation with methyl bromide: the uptake and distribution of inorganic bromide in tomato plants

Tomato plants grown in soil previously fumigated with methyl bromide accumulated inorganic bromide in the foliage. The concentration present depended on the rate of application of methyl bromide to the soil and on the interval between, soil fumigation and planting, two factors determining the concentration in the soil of inorganic bromide arising from the breakdown of the fumigant. The concentration of bromide in the leaves decreased from the base to the tip of the plant, and increased with the age of the tissue. Bromide was accumulated in the fruit, but to a lesser extent than in the leaves. Mature fruit from plants grown in soil fumigated at the commercially applied rate of 1.5 lb/100 ft² (73 g/m²) contained at the most 45 μg/g of fresh tissue, and generally not more than half this value. The concentration of bromide in fruit was related to the concentration of inorganic bromide present in the soil, but not to the state of ripeness or the position of the fruit on the plant. Similar results were obtained for leaves and fruit from plants grown in soil supplemented with inorganic bromide.     

Properties and Antioxidant Action of Actives Cassava Starch Films Incorporated with Green Tea and Palm Oil Extracts

There is an interest in the development of an antioxidant packaging fully biodegradable to increase the shelf life of food products. An active film from cassava starch bio-based, incorporated with aqueous green tea extract and oil palm colorant was developed packaging. The effects of additives on the film properties were determined by measuring mechanical, barrier and thermal properties using a response surface methodology design experiment. The bio-based films were used to pack butter (maintained for 45 days) under accelerated oxidation conditions. The antioxidant action of the active films was evaluated by analyzing the peroxide index, total carotenoids, and total polyphenol. The same analysis also evaluated unpacked butter, packed in films without additives and butter packed in LDPE films, as controls. The results suggested that incorporation of the antioxidants extracts tensile strength and water vapor barrier properties (15 times lower) compared to control without additives. A lower peroxide index (231.57%), which was significantly different from that of the control (p<0.05), was detected in products packed in film formulations containing average concentration of green tea extracts and high concentration of colorant. However, it was found that the high content of polyphenols in green tea extract can be acted as a pro-oxidant agent, which suggests that the use of high concentration should be avoided as additives for films. These results support the applicability of a green tea extract and oil palm carotenoics colorant in starch films totally biodegradable and the use of these materials in active packaging of the fatty products.     

Soil fumigation with methyl bromide: bromide accumulation by lettuce plants

Lettuce plants grown in beds of soil previously fumigated with methyl bromide accumulated water-extractable bromide, the amount present in the tissues depending on the concentration of inorganic bromide produced in the soil by the breakdown of the fumigant. Samples of lettuce plants from commercial nursery soils fumigated with methyl bromide at rates of 1–2 lb/ 100 ft² (49–98 g/m²) gave rise to soil bromide levels of n-6i/μg/g. The corresponding bromide concentrations in the plants ranged from i-6 to io-1 mg/g of dry tissue. The bromide concentrations in whole lettuce plants grown in pots of soil supplemented with 0–5 mg/g inorganic bromide, as potassium bromide, ranged up to 100 mg/g of dry tissue. Bromide taken up from the soil by lettuce plants was located mainly in the outer leaves. Lettuce was relatively insensitive to the presence of bromide in the soil; no phytotoxic symptoms were observed in plants growing in soils containing 5 mg/g inorganic bromide. Implications in relation to possible tolerance limits for the bromide content of lettuce plants are discussed.     

Effects of midas® on nematodes in commercial floriculture production in Florida

Cut flower producers currently have limited options for nematode control. Four field trials were conducted in 2006 and 2007 to evaluate Midas® (iodomethane:chloropicrin 50:50) for control of root-knot nematodes (Meloidogyne arenaria) on Celosia argentea var. cristata in a commercial floriculture production field in southeastern Florida. Midas (224 kg/ha) was compared to methyl bromide:chloropicrin (98:2, 224 kg/ha), and an untreated control. Treatments were evaluated for effects on Meloidogyne arenaria J2 and free-living nematodes in soil through each season, and roots at the end of each season. Plant growth and root disease were also assessed. Population levels of nematodes isolated from soil were highly variable in all trials early in the season, and generally rebounded by harvest, sometimes to higher levels in fumigant treatments than in the untreated control. Although population levels of nematodes in soil were not significantly reduced during the growing season, nematodes in roots and galling at the end of the season were consistently reduced with both methyl bromide and Midas compared to the untreated control. Symptoms of phytotoxicity were observed in Midas treatments during the first year and were attributed to Fe toxicity. Fertilization was adjusted during the second year to investigate potential fumigant/fertilizer interactions. Interactions occurred at the end of the fourth trial between methyl bromide and fertilizers with respect to root-knot nematode J2 isolated from roots and galling. Fewer J2 were isolated from roots treated with a higher level of Fe (3.05%) in the form of Fe sucrate, and galling was reduced in methyl bromide treated plots treated with this fertilizer compared to Fe EDTA. Reduced galling was also seen with Midas in Fe sucrate fertilized plots compared to Fe EDTA. This research demonstrates the difficulty of reducing high root-knot nematode population levels in soil in subtropical conditions in production fields that have been repeatedly fumigated. Although soil population density may remain stable, root population density and disease can be reduced.     

Biodegradation of Halogenated Hydrocarbon Fumigants by Nitrifying Bacteria

Three species of nitrifying bacteria were tested for the ability to degrade the halocarbon fumigants methyl bromide, 1,2-dichloropropane, and 1,2-dibromo-3-chloropropane. The soil nitrifiers Nitrosomonas europaea and Nitrosolobus multiformis degraded all three fumigants, while the marine nitrifier Nitrosococcus oceanus degraded only methyl bromide under the conditions tested. Inhibition of biodegradation by allylthiourea and acetylene, specific inhibitors of ammonia monooxygenase, suggests that ammonia monooxygenase is the enzyme which catalyzes fumigant degradation.     

甲酸乙酯对松材线虫的熏蒸效果

【背景】在溴甲烷面临禁用的情形下,探讨新熏蒸剂甲酸乙酯对松材线虫的处理效果,可以科学地评估甲酸乙酯的使用前景。【方法】采用松材线虫分离液和带疫松木段,设置甲酸乙酯5个剂量梯度、5个处理温度和5个处理时间,测定其对松材线虫的毒力及CT值。【结果】在25℃下处理3、6、12、24、48h,甲酸乙酯对松材线虫的Lc50分别为2．63、1．60、0．99、0．41、0．20mg·L-1。温度对毒力有显著影响,在10～29℃,随温度升高,甲酸乙酯对松材线虫的毒力降低,19和29℃下,1．85mg·L-1甲酸乙酯处理松材线虫的死亡率分别为63％和100％。甲酸乙酯熏蒸12h内,能完全杀灭木段中的松材线虫。在23℃下处理6和12h,松材线虫死亡率达到99％时,甲酸乙酯的cr值分别为453．94和424．14mg·h-1·L-1。【结论与意义】甲酸乙酯可用于松材线虫的检疫处理。     

The influence of nemagon fumigation on the major nutrients of a fertilized soil

Summary The effect of nemagon fumigation on the soil chemistry and microbiology of major nutrients in a fertilized saline soil provided interesting and consistent results. Nemagon at 0.2 ml per kg of soil produced optimum significant availability in ammonium nitrogen with all fertilizer treatments from 30 to 45 days. The effect then declined due to nitrification resulting from the dissipation of the chemical. Though initially toxic a higher dose of the fumigant produced more positive results after 60 days as far as ammonified nitrogen was concerned. The results were in agreement with the nitrite, nitrate and halide transformations. All doses of the fumigant resulted in an initial positive response to phosphorus availability. The influence then declined. The results have been explained on the basis of solubilisation caused by microbial activity. Both in amended and unamended soil potassium availability generally increased with passage of time. Fluctuating responses due to changes in the biological activity were produced with increase in the dose of the fumigant.     

生物降解地膜应用与地膜残留污染防控

地膜是农业生产中重要的生产资料之一,过去30多年,地膜用量和农作物覆膜面积一直稳定增长,2014年地膜用量达到了144万t,覆膜面积超过1 800万hm~2,该技术对保障我国农产品安全供给作出了重大贡献。与此同时,地膜残留污染问题越来越严重,一些农田的地膜残留量超过250 kg/hm~2,在我国西北的局部区域,地膜残留已经对农田土壤、作物生长发育、农事作业等造成严重影响和危害。生物降解地膜成为替代普通PE地膜、解决地膜残留污染的一种有效措施和手段,目前生物降解地膜正处于产品研发和评价试验的关键阶段,部分生物降解地膜产品在马铃薯、花生、烟草生产上显示出良好的效果,但总体上还面临巨大挑战,主要包括需要进一步提高地膜产品质量,提高地膜产品破裂和降解可控性,改善地膜的增温保墒能力,实现满足农作物对地膜覆盖功能的要求;此外,需要降低生物降解地膜综合成本,促进生物降解地膜规模化应用。总体上,随着技术进步和农业生产环境的变化,生物降解地膜应用将具有良好的前景。     

Mechanical and water barrier properties of starch/PVA composite films by adding nano-sized poly(methyl methacrylate-co-acrylamide) particles

The aim of this work is to prepare starch/PVA composite films added nano-sized poly(methyl methacrylate-co-acrylamide) (PMMA-co-AAm) particles and to investigate the mechanical properties, water barrier properties, and soil burial degradation for the films. Composite films were prepared by using corn starch, polyvinyl alcohol (PVA), nano-sized PMMA-co-AAm particles, and additives, i.e., glycerol (GL), xylitol (XL), and citric acid (CA). Nano-sized PMMA-co-AAm particles were synthesized by emulsion polymerization. The results of the evaluation of properties for prepared films indicated that compared with films without PMMA-co-AAm particles, the mechanical properties and water resistance were improved up to 70-400% by the addition of nano-sized PMMA-co-AAm. In addition, the results of the soil burial biodegradation revealed that films added PMMA-co-AAm particles were degraded by about 45-65% after 165 days.