Toxicity of fungal endophyte secondary metabolites to plant parasitic nematodes and soil-borne plant pathogenic fungi

Fungi isolated from the cortical tissue of surface sterilized tomato roots collected from field plots produced secondary metabolites in nutrition broth that were highly toxic toMeloidogyne incognita. Especially strains ofFusarium oxysporum were highly active with 13 of 15 strains producing culture filtrates toxic to nematodes. The mechanism of action of the toxic metabolites produced by the non-pathogenicF. oxysporum strain 162 with proven biological control ofM. incognita in pot experiments was investigated. These metabolites reducedM. incognita mobility within 10 min of exposure. After 60 min, 98% of juveniles were inactivated. Juveniles were initially inactivated within a few minutes of exposure, but with exposure of 5 h 50% of the juveniles were dead and 24 h exposure resulted in 100% mortality. In a bioassay with lettuce seedlings metabolite concentrations > 100 mg/l reduced the number ofM. incognita juveniles on the roots comparing to the water control. TheF. oxysporum toxins were highly effective towards sedentary parasites and less effective towards migratory endoparasites. Nonparasitic nematodes were not influenced at all. Metabolites of strain 162 also reduced significantly the growth ofPhytophthora cactorum, Pythium ultimum andRhizoctonia solani in vitro. Secondary metabolites of endophytic fungi on plant-parasitic nematodes and soil-borne fungi should be considered for control of plant parasitic nematodes and plant pathogenic fungi. The results also show the need for proper selection of target nematodes inin vitro bioassays.     

溴甲烷熏蒸对桃蛀果蛾的毒力作用

对溴甲烷熏蒸处理桃蛀果蛾结果进行机率值法分析,推算出在25℃温度条件下溴甲烷熏蒸处理1.5h和2h,达到桃蛀果蛾Carposina sasakii Matsumura幼虫死亡率99%的浓度时间乘积(CT值)分别为43.79g·h/m3和46.77 g·h/m3;15℃和10℃温度条件下熏蒸处理3h,达到桃蛀果蛾幼虫死亡率99%的溴甲烷浓度分别为50.84 g·h/m3和118.55 g·h/m3.研究表明,溴甲烷熏蒸对桃蛀果蛾幼虫的毒性作用随着溴甲烷熏蒸浓度的增加而增加,相同熏蒸剂浓度条件下,随着温度升高,溴甲烷熏蒸效果明显增加.     

棉隆及氯化苦对几种生姜土传病原物的毒力

以侵染生姜的茎腐病菌Pythium myriotylum Drechsler、姜瘟病菌Ralstonia solanacearum和南方根结线虫Meloidagrne incognila为指示病原物,比较了两种土壤处理剂棉隆和氯化苦的熏蒸毒力。采用密闭玻璃容器熏蒸,结合菌丝生长速率法测得棉隆和氯化苦对生姜茎腐病菌的EC50值分别为0.284 和0.096 mg/L,EC90值分别为18.106 和0.312 mg/L。通过密封盘内摇床振荡(25 ℃,45 r/min)培养(24 h),结合菌悬液比色法评价了两药剂对姜瘟病菌的毒力。结果表明:氯化苦的活性较高,EC50和EC90值分别为0.176和1.280 mg/L,而棉隆的毒力较低,其EC50和EC90值分别达1 984和5 701 mg/L。采用线虫悬浮液密闭熏蒸法处理48 h,发现棉隆对南方根结线虫的EC50和EC90值分别为0.175和0.634 mg/L,氯化苦毒力略低于棉隆,其EC50和EC90值分别为1.211和3.772 mg/L。     

Dose response of weeds to methyl iodide and methyl bromide

Labonuory bioassay and field experiments were conducted to characterize the dose response of weeds to methyl iodide and methyl bromide as soil fumigants. The patterns in potency of both fumigants and in sensitivity of diffcretit weed species to the fumigants were distinguished with the use of logistic dose-response models. Similar to its response to methyl hromide fumigation. Amaranthus retrofleus L. was the most sensitive to methyl iodide fumigation. Cyperus rotundtis L. was the least sensitive to methyl iodide fumigation, whereas Portuloca oleracea L. was the least sensitive to methyl hromide. Lolium multiflorum Lam. Abutilon theophrasti Medik. Chenopodium album L. P. ateracea . Brassica kaber (D.C.) L.C. Wheeler and Cyperus escuden-tus L. were similar in sensitivity to methyl iodide. Methyl iodide was as potent as methyl bromide for A. retroflexus but more potent than methyl bromide for L. multiflorum , A. theophrasti. C. album. P. oleracea. B. kaber, C. esculentus and C. rotundus. The dose response for weeds in the field was similar to that obtained in laboratory bioassays. Under fieid conditions. 280 kg ha^-1 methyl iodide killed all species tested except Solanum nigrum L Methyl iodide appears to be a suitable replacement for meihyl bromide because it can be used in situations simitar to methyl bromide fumigation, has superior efficacy against a broad spectrum of pests and has a low potential for degrading the earth's ozone lavers.     

溴甲烷土壤消毒替代技术研究进展

概述了溴甲烷替代品的新进展。在土壤消毒方面,新的进展有化学替代品:氯化苦胶囊、氯化苦乳剂、氯化苦+噻唑磷混用、C₂N₂、氰铵化钙、异硫氰酸烯丙酯、异硫氰酸甲酯、1,3—二氯丙烯和氯化苦混剂、碘甲烷、环氧丙烷、叠氮化合物、硫酰氟等。在使用技术上,采用化学灌溉和注射施药技术进一步提高药剂分布的均匀性。在非化学替代技术上,生物熏蒸和有机质补充正受到重视。减少溴甲烷的技术正在快速地发展。     

Effect of soil physical factors on methyl iodide and methyl bromide

Production and importation of methyl bromide is scheduled to be banned by 2001. Methyl iodide was evaluated as a possible replacement soil fumigant. The effects of soil moisture, temperature, soil texture and fumigation time on the efficacy of methyl iodide for the control of two common weeds, Abutilon theophrasti and Lolium multiflorum, were characterized and compared with those of methyl bromide. The optimal soil moisture for methyl iodide to kill both weed species in sandy soils was 14% water content (w/w). Greater efficacy was obtained when the temperature during fumigation was above 20°C. Compared to methyl bromide, the efficacy of methyl iodide was more consistent in different soils. Time to 100% mortality of weeds was 24 h for methyl iodide fumigation and 36 h for methyl bromide when 200 μM of fumigant was used. On a molar basis methyl iodide was consistently more effective than methyl bromide across the range of environmental factors tested. In terms of application technology and spectrum of activity, methyl bromide can be directly replaced by methyl iodide. © 1998 SCI     

Status of chemical alternatives to methyl bromide for pre-plant fumigation of soil

ABSTRACT None of the chemical alternatives currently registered and available has the full spectrum of activity and versatility of methyl bromide as a pre-plant soil fumigant. Chloropicrin and 1,3-dichloropropene (Telone) can provide significant control of many plant pathogens in soil and growth stimulation in annual crops. These compounds, however, provide limited control of weeds or other residual plant materials in soil of concern in nursery production systems, and some perennial replant diseases. Methyl isothiocyanate generators such as metam sodium have broad biocidal activity in soil, but are more difficult to apply effectively. In most soil applications, the available alternatives are likely to be used in combinations, either as mixtures (e.g., 1,3-dichloropropene and chloropicrin) or sequentially (e.g., chloropicrin followed by metam sodium). They may also be supplemented with other more specific pesticides and cultural controls. Among the alternatives currently under active development but not yet available, methyl iodide and propargyl bromide probably have activity that most closely parallels that of methyl bromide in soil. However, all of the chemical alternatives to methyl bromide will be subject to continuing review and more regulation. Furthermore, we do not know the actual prospects for registration of the new fumigants currently under development and there is a risk that registered fumigants will not be available for large-scale use in soil indefinitely.     

溴甲烷在草莓田的替代及减少其散发的技术

溴甲烷是一种消耗臭氧层的物质，根据《蒙特利尔议定书哥本哈根修正案》，发展中国家将于2015年淘汰。在我国溴甲烷消费量最大的地区，河北省满城县实施了中-意“溴甲烷土壤消毒替代技术及能力建设项目”。试验结果表明：威百亩和威百亩＋VIF，采用化学灌溉技术施药，是有前景的溴甲烷替代品，2001～2002年威百亩和威百亩＋VIF处理“达赛莱克特”品种的产量分别为26816kg／hm^2和23672kg／hm^2，而溴甲烷处理的产量为28346kg／hm^2；威百亩和威百亩＋VIF处理“理念”品种的产量分别为19844kg／hm^2和15989kg／hm^2而溴甲烷处理的产量为19657kg／hm^2；2002～2003年威百亩和威百亩＋VIF处理“达赛莱克特”品种的产量分别为23073kg／hm^223446kg／hm^2而溴甲烷处理的产量为25285kg／hm^2威百亩和威百亩＋VIF处理“全明星”品种的产量分别为：29594kg／hm^227677kg／hm^2而溴甲烷处理的产量为32191kg／hm^2产量结果经统计分析表明，威百亩、威百亩＋VIF与溴甲烷均无显著差异。溴甲烷＋VIF采用热法施药，其产量与溴甲烷无明显差异，但溴甲烷＋VIF能减少溴甲烷25％的用药量。太阳能消毒＋生物防治制剂的产量高于空白对照，有一定的防病增产效果，但显著低于溴甲烷处理的产量，不能作为溴甲烷的替代品。进口品种“理念”和当地主栽品种“全明星”对土传病害的抗性较差，在长势、产量方面均显著差于新引进品种“达赛莱克特”。虽然“达赛莱克特”对土传病害有一定的抗性，但与溴甲烷和威百亩处理区比较，空白对照区的产量仍显著低于药剂处理区的产量。     

Residual free methyl bromide in fumigated commodities

The extent to which methyl bromide was retained by fumigated material after treatment was followed in laboratory studies on a range of commodities exposed to the vapour at atmospheric pressure. Amounts of methyl bromide, recovered by solvent extraction and determined using gas-liquid chromatography, were related to the temperature, moisture content and manner of post-treatment storage. Immediately after exposure, the initial amount of free methyl bromide present was more dependent on the gas concentration used than on the time of exposure. Under the experimental conditions of exposure, the residual free methyl bromide in all commodities fumigated at 25°, except cocoa beans and groundnuts, fell to below 1 ppm within a few days when they were held at that temperature, whether spread in thin layers on trays or kept sealed in glass bottles. At lower temperatures, the rate of loss was slower, small amounts of methyl bromide being extracted from several commodities one month after treatment. The disappearance of fumigant from wheat and sultanas was more rapid from samples with higher moisture contents. A mathematical treatment of the data is presented, to assist in prediction of the behaviour of residual fumigant under storage conditions before processing. It is concluded that the risk of ingestion of harmful quantities of free methyl bromide by the consumer is small and that the occasions when relatively high residues might occur can be predicted.     

Permeability of plastic films to methyl bromide: a comparative laboratory study

The permeability of plastic films to the fumigant methyl bromide (MB) was measured by two different methods, in order to facilitate the selection of films which are impermeable to the gas. Polyethylene-based films are highly permeable to MB, as evidenced by both methods. In contrast, multilayer coextruded films which have a layer of barrier material such as polyamide (PA) or ethylene-vinyl alcohol copolymer (EVOH) were significantly less permeable to MB, as reflected by the parameters permeability rate, time to 90% concentration (TC₉₀, by the diffusion method) and lag-time values (by the variable-volume method). A significant correlation was found between the permeability rate assessed by the diffusion method and that obtained with the variable-volume method. Permeability of all films increased with temperature as evidenced by all tested parameters. This increase was more pronounced with polyethylene films, the permeabilities of which increased five- to six-fold when the temperature was increased from 20°C to 60°C. The effect of temperature on barrier-film permeability was less significant. Permeability of films to MB was affected by additional factors such as additives, the length of the monomer side-chain, and the thickness and density of polyethylene films. © 1998 SCI     

威百亩对西葫芦常见土传病原菌的毒力及田间防效

为明确威百亩对西葫芦常见土传病原菌的活性及田间防治效果,以1,3-二氯丙烯为对照药剂,采用改进的密封盘法比较了2种熏蒸剂对西葫芦菌核病菌等4种病原菌的毒力及对菌核萌发的影响,并于田间采用密闭熏蒸法比较了2种药剂对西葫芦茎基腐病的防治效果.室内结果显示:威百亩对西葫芦菌核病菌、茎基腐病菌、枯萎病菌及绵腐病菌的EC₅₀分别为0.060、0.945、1.380、2.953 mg/L,而1,3-二氯丙烯对这4种病原菌的EC₅₀为516.654、928.558、633.784、77.242 mg/L,威百亩0.228 mg/L可完全抑制菌核的萌发.田间药效试验表明:威百亩150、90、75、60 kg/hm²及1,3-二氯丙烯200 kg/hm²均能不同程度控制西葫芦茎基腐病的发生,防治效果分别为88.94%、87.58%、83.76%、80.60%和64.80%,且各试验剂量均对西葫芦安全并能在一定程度上起到增产作用,威百亩150 kg/hm²处理增产率最高,达34.82%.从防治效果及经济效益分析,在西葫芦田推荐使用威百亩防治土传病害.     

Influence of methyl bromide soil fumigation method on fungicidal efficacy and bromide residues

Highest inorganic bromine residues (30 ppm) were found when soil was fumigated with liquid methyl bromide (MB) introduced by conventional means into evaporating dishes. With preheated (vaporized) MB or injection of MB/chloropicrin (CP) mixtures, bromide concentrations were reduced by 50%. They were uniform throughout the soil (0 to 60 cm) except after MB/CP injection, when larger residues were found in the 30-60 cm layer. Leaching with 2000 m^p3/ha (20 cm) of water always reduced bromide content to 7.5 and 10 ppm at the 0-30 and 30-60 cm depth, respectively. Organic amendments to soils substantially increased bromide levels up to 118 ppm, most of which was found in the upper soil layers; two teachings with 2000 m^p3 /ha water were required to return the soils to their normal state.Sclerotium rolfsii andFusarium oxysporum f. sp.dianthi cultures buried in soil were eliminated from the upper 30 cm with MB applied either conventionally or preheated. At 50 cm, 500 kg/ha of the preheated gas was superior to 1000 kg/ha of the cold gas. All MB fumigations suppressed carnation flower yields compared with CP alone but were superior to no treatment. After leaching, MB-fumigated soils yielded the highest number of flowers.     

Control of soil-borne pathogens with living bacteria and fungi: Status and outlook

This review addresses some of the current problems with soil-borne pathogens and their economic importance in comparison to the total plant protection market- Possible opportunities for biological control solutions in view of the various constraints of western agricultural production are discussed. More specifically, we address the scientific, economic and conceptual hurdles which have slowed down the development of biocontrol agents. In addition, examples of biological control of soil-borne pathogens which have already reached the market or are likely to be exploited commercially within the next few years are presented. Finally, we speculate on certain developments which might become important for the further commercial development of biological control products.     

五种挥发性化合物对土传病原真菌及线虫的生物活性

为明确挥发性化合物反式-2-己烯醛、香茅醛、1-辛烯-3-醇、芳樟醇、1-戊烯-3-醇对土传病害及线虫病的防治潜力,采用密封盘菌丝生长速率法比较了挥发性化合物对辣椒疫霉等7种植物土传病原真菌、南方根结线虫和禾谷孢囊线虫的生物活性。反式-2-己烯醛和香茅醛的生物活性高于1-辛烯-3-醇、芳樟醇及1-戊烯-3-醇,21.0μL/L反式-2-己烯醛处理能够完全抑制供试病原真菌菌丝的生长。10.5μL/L反式-2-己烯醛或香茅醛处理对花生冠腐病菌孢子及棉花黄萎病菌色素的产生均有较强的抑制作用,且42.0μL/L处理能够完全抑制黄瓜菌核病菌菌核的萌发。2.62μL/L反式-2-己烯醛处理南方根结线虫和禾谷孢囊线虫的2龄幼虫,24h的死亡率均为100%;2.62μL/L香茅醛处理24 h的死亡率分别为95.4%和89.5%,而对照处理的死亡率分别为2.5%和3.0%。研究表明反式-2-己烯醛及香茅醛具有较好的熏蒸抑菌及杀线虫活性。     

Chemical alternatives to methyl bromide for the control of root-knot nematodes in greenhouses

The complete phase-out of methyl bromide from use in developed countries by 1 January 2005 will cause many problems in agricultural industries that are now heavily reliant on its use. Three field experiments were established to compare management tactics on tomato and cucumber in commercial greenhouses naturally infested with root-knot nematodes (Meloidogyne spp). Reduction of nematode juveniles in soil and roots to nil detection levels was observed in all plots following soil fumigation with methyl bromide. A significant reduction of nematode juveniles and root-galling index was observed in plots treated with metham-sodium, dazomet and 1,3-dichloropropene compared with the control and plots treated with non-fumigant nematicides. Reduction of the nematode population led to an increase in fruit yield. However, data collected from the second cultivation season indicated that single control methods such as fumigant or contact nematicides alone cannot drastically decrease initial nematode population and those nematodes which escape control lead to population increase by the end of the cropping season.     

应用不渗漏膜减少溴甲烷的渗漏

2002～2003年在河北省满城县的温室中进行了低量溴甲烷覆盖不渗漏膜 (VIF膜 )土壤消毒试验。在田间相同条件下 ,用溴甲烷对常年种植草莓的土壤进行消毒处理 ,分别覆盖不渗透膜 (VIF膜 )和常规聚乙烯膜 (PE膜 )。试验结果表明 ,溴甲烷低量处理41g/m²,覆盖VIF膜与常规用量 55 g/m²,覆盖PE膜比较 ,在杀灭病原菌效果、杂草控制以及草莓产量上均无显著差异 ,但使用VIF膜可显著减少溴甲烷渗漏 ,减少用量 25%以上 ,从而减少对臭氧层的破坏。     

Allium spp thiosulfinates as substitute fumigants for methyl bromide

Methyl bromide, the most widely used fumigant, is considered to be one of the major factors causing depletion of the ozone layer, and this is likely to lead to it being banned in the near future. Allium sulfur volatiles (thiosulfinates, R-S-SO-R′; R, R′=Me, Pr, y Allul), known to be nematicides, have been evaluated as insecticides against insect pests in stored products, in comparison with their degradation compounds (disulfides) which have already been tested. Methyl and allyl thiosulfinates, with 24-h LD₅₀ values of 0.02–0.25 mg litre⁻¹, were more active than disulfides against six test insects and were superior to methyl bromide; it is suggested that they could be used as alternatives to methyl bromide in stored product control. ©1999 Society of Chemical Industry