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1.
The effect of injection of different dosages of dichloropropane-dichloropropene (DD) mixture at 15-cm depth combined with different dosages of dazomet distributed on the surface of the soil on densities ofRotylenchus uniformis was investigated in a field experiment on sandy soil. The treatments were given at the end of October 1970. The water content of the soil was at field capacity and the temperature about 10°C. Distributing 5 g or 10 g dazomet per m2 on the surface of plots treated with 10 ml DD mixture per m2 (mortality 82%) had the same effects as repeating the DD treatment once or twice, respectively. A better horizontal distribution of the DD mixture would probably have made distributing 5 g dazomet per m2 on the surface of soil in which a DD treatment killed 80% of the nematodes in the top 20 cm, equivalent to adding two similar DD treatments.To kill a certain percentage of the eggs ofR. uniformis in the soil, twice as high a dosage of DD mixture was necessary as to kill the same percentage of juveniles and adults. Eggs and active nematodes were equally sensitive to dazomet.Samenvatting De uitwerking op dichtheden vanRotylenchus uniformis van verschillende doses dichloorpropaan-dichloorpropeen(DD)mengsel, op 15 cm diepte in de grond gebracht, gecombineerd met verschillende doses dazomet, die op de oppervlakte van de grond werden gestrooid, werd onderzocht op een proefveld op zandgrond. De behandelingen werden eind oktober 1970 uitgevoerd bij een bodemtemperatuur van ongeveer 10°C (Tabel 1). Het watergehalte van de grond was ongeveer op veldcapaciteit door regenval voor de behandelingen. De werking van de verschillende behandelingen op de aaltjes in de bovenste 20 cm van de grond is weergegeven in de Tabel 2 en 3 en Fig. 2 en 3, die van enkele behandelingen op verschillende diepten in de grond in Tabel 4 en 5 en Fig. 6. Strooien van 5 g en 10 g dazomet per m2 op de oppervlakte van veldjes, die tevens behandeld waren met 10 ml DD mengsel per m2 (sterfte van de aaltjes 82%) had hetzelfde effect als wanneer deze behandeling met DD éénmaal resp. tweemaal herhaald zou zijn. Bij een betere horizontale verdeling van het DD-mengsel in de grond zou een behandeling met dit nematicide, die 80% van de aaltjes in de bovenste 20 cm van de grond doodde, gecombineerd met strooien van 5 g dazomet per m2 op de oppervlakte waarschijnlijk gelijkwaardig zijn geweest aan drie behandelingen met DD-mengsel, die telkens 80% van de bij de behandeling nog aanwezige aaltjes doodden.Volgens berekeningen naar aanleiding van Fig. 7 is voor het doden van een bepaald percentage van de eieren vanR. uniformis tweemaal zoveel DD-mengsel nodig als voor het doden van hetzelfde percentage jonge en volwassen dieren. Alle stadia van het aaltje waren even gevoelig voor dazomet.  相似文献   

2.
In Dutch field experiments with Heterodera rostochiensis Woll. systemic nematicides at low and high nematode densities resulted in unfavourable cost/ benefit relations, as compared to other control procedures; on average, a 50 % reduction of the maximum multiplication of the nematode was observed. In England, better results were obtained at high nematode densities when higher dosages of nematicides were worked into the soil at a depth of 15 cm. In order to obtain a better effect of the mostly used contact nematicide DD-mixture at a moderate dosage, a special treatment of the soil surface with the non-fumigant dazomet was combined with the fumigation. On clay soil more than 99 % kill of stem nematodes was obtained with 30 g dazomet + 50 ml DD-mixture per m When 10 g dazomet was added a 80% kill of Rolylenchus uniformis (Thorne) could be obtained on sandy soil; this was equivalent to 2 applications of the DD-mixture alone. The combined treatment offers the great advantage of increasing the chances by 3 times to make the appropriate choice of the year for the treatment. Eggs of R. uniformis and H. rostochiensis are less susceptible to DD-mixture than free living larvae and adults.  相似文献   

3.
An assay, based on amplification of cDNA synthesized from genomic viral RNA, has been developed to detect tobacco rattle virus in infected plant material and viruliferous nematodes. A range of different TRV strains could be detected using the procedure developed. The presence of one to three viruliferous nematodes in a nematode suspension was sufficient for the detection of TRV. The minimum amount of purified virus detectable in the assay was 15 fg, indicating an increased sensitivity of the PCR-based assay as compared to serological detection methods, like ELISA. A dot-blot hybridization procedure was developed for the detection of the PCR products, making agarose gel electrophoresis dispensable.  相似文献   

4.
为筛选防治西瓜根结线虫(Meloidogyne incognita)的安全、高效防治技术,本研究对浅耕、深耕、浅耕+棉隆、深耕+棉隆4种土壤连作障碍处理耕作机械化技术防治西瓜根结线虫的效果及对土壤微量元素的影响等进行了评价。结果表明,与对照普通耕作模式相比,4种处理均能显著降低土壤中西瓜根结线虫的数量,提高对根结线虫的防治效果,增加西瓜的产量。其中,以深耕+棉隆处理的防治效果和增产效果最好。深耕+棉隆处理可以增加交换性镁和有效硒的含量,对交换性钙和有效铜的含量没有显著影响。综合评价认为深耕+棉隆处理适于在西瓜根结线虫发生非常严重的地区推广应用,而对于根结线虫发生特别轻的地区,仅以浅耕处理就能有效控制其危害。本研究提供了一种耕作措施与化学农药熏蒸相结合防治根结线虫的新方法,对于减少化肥农药用量,保护农业生态环境安全具有重要意义。  相似文献   

5.
ABSTRACT The vertical distribution of Pratylenchus penetrans was monitored in four fields cropped with maize, black salsify, carrot, or potato. Soil samples were collected at 21-day intervals from May 2002 until April 2003 from five plots (2 x 5 m(2)) per field. Per plot, 15 cores were taken to a depth of 70 cm and split into seven segments of 10 cm each. Within the plots, segments from corresponding depths were pooled. After mixing, 200-g subsamples were taken and nematodes were extracted by zonal centrifugation from the root fraction and the mineral soil fraction separately. In most crops, the root fraction contained more than 50% of the total number of P. penetrans. Because the ratio between the numbers of nematodes in the root fraction and mineral soil fraction changes during the growing season, numbers of P. penetrans found in the mineral soil fraction cannot be used to estimate the total number in the soil. Therefore, both fractions have to be processed to obtain a reliable estimate of the density. No nematodes were recovered below 50 cm soil depth, except in the maize field where nematodes were found at 70 cm. The optimum sampling depth for maize, black salsify, carrot, and potato was 45, 25, 25, and 35 cm, respectively. The percentage of nematodes per soil layer was independent of the sampling date, indicating that a defined optimum sampling depth will be applicable throughout all seasons. The cumulative vertical distribution, modeled with a logistic equation, can be used to estimate the sampling error when samples are collected at different depths.  相似文献   

6.
In pots containing soil fumigated with DD before planting the growth of white clover was considerably better than in untreated pots. A similar effect was obtained both with cis- or trans-1,3-dichloropropene. Some other components of DD, including 1,2-dichloropropane, had no influence on clover growth in the concentration at which they occur in DD. Of the compounds not associated with DD, EN 18,133 and sugar showed a favourable effect on clover growth, but X 323 had no influence. In the untreated pots with poorly growing clover many roots had died. On the places where dead lateral roots had been attached many fungi were present in the tissue, especiallyRhizoctonia sp. andFusarium spp. These pots contained also more clover cyst nematodes and more springtails (Collembola). In one of the pot experiments poor growth could probably be attributed to an attack by the clover cyst nematode (Heterodera trifolii Goffart). The nematode level above which damage to the plants occurred was calculated at 1000–3000 eggs (larvae inclusive) per 100 ml of soil. In the other pot experiment, however, poor growth could not be explained by cyst nematodes only. In field experiments clover growth was promoted by soil fumigation with DD, also when only a few cyst nematodes were present. These observations increase the evidence that attack of white clover by pathogens is a complex phenomenon in which nematodes as well as fungi and perhaps insects too are involved. Apart from a small increase in growth at the beginning, soil fumigation with DD did not raise the yield of perennial rye grass.In this article the name DD is used as abbreviation for the trade name Shell D-D.  相似文献   

7.
Soil samples from the coastal bulb-growing areas in the provinces of North- and South-Holland and the North-East Polder in the Netherlands were examined for trichodorid nematodes and tobacco rattle virus (TRV) serotypes. At least one of a total of eight species of Trichodoridae, of whichParatrichodorus pachydermus was most prevalent, was found in 93% of the samples from the provinces of North- and South-Holland and TRV, including four serotypes, was obtained from 49% of these samples. In the North-East Polder one of three species of trichodorids, of whichP. teres occurred most frequently, was present in 72% of the samples, and TRV of one serotype was obtained from 28% of these samples. The TRV isolates recovered from these samples reacted serologically with one of four antisera to strains of TRV. Virus transmitted byP. pachydermus reacted to the PRN-, byTrichodorus viruliferus to the RQ-, byP. teres to the N5- and byT. similis, to the TS-antiserum, respectively.  相似文献   

8.
A rapid bait leaf method, using detached leaves ofNicotiana tabacum ‘White Burley’, for determining infestation of soil samples with TRV-transmitting trichodorids is briefly described. Bait leaf infection may already occur three hours after leaf burial and is apparently associated with trichodorid adherence to the leaf surface. Virus could always immediately be detected by inoculation onto attached ‘White Burley’ leaves with homogenates from bait leaves that had been buried for two days and more. After burial for shorter periods bait leaves first required additional exposure to light (for three days) to permit virus multiplication. Chances to detect viruliferous trichodorids were highest after keeping the bait leaf in soil for three days followed by a three-day incubation under light.  相似文献   

9.
BACKGROUND: Termiticides are applied at concentrations much higher than those used in agricultural settings. The longevity of fipronil has not yet been examined at the rates used for termite control, nor has the compound's movement in the soil been addressed. RESULTS: Fipronil was detected in the eluates of treated soil cones, increasing initially and then decreasing to a steady concentration of about 1 µg mL?1. In larger PVC pipe plots, fipronil in the top treated soil depth (0–7.5 cm) dissipated more rapidly (half‐life of 11–13 months) than in treated soil at the next treated depth (7.5–15 cm; half‐life of 20–29 months). The presence of vegetation had no significant effect on the mobility, longevity or movement into untreated depths. Treated soil remained toxic to termites throughout the duration of the study. Fipronil moved into the 15–22.5 cm soil depth in sufficient concentration to cause 100% mortality to eastern subterranean termites in 3 day bioassays. CONCLUSION: Fipronil remains in treated soil at levels toxic to termites for at least 30 months. Movement of the active ingredient was observed in sufficient amounts to kill termites in non‐treated soil directly below the treated soil. Published 2010 by John Wiley & Sons, Ltd.  相似文献   

10.
The effect of 0.35, 0.5, 0.7, 1, 1.4 and 2 g aldicarb/m2, applied at planting time, on the multiplication of small densities ofGlobodera rostochiensis on potato was investigated in an experiment on sandy loam. The chemical was applied broadcast to the soil and rotavated into the top 15 cm on half the plots of each treatment. The plots were ridged three times, the first time immediately after the planting of the potatoes. Nematodes multiplied at the same rate in the top 20 cm of the soil on rotavated and non-rotavated plots treated with the same dosage of the chemical. The relation between log dosage and probit reduction of the multiplication rate in the top 20 cm after the plots had been levelled was linear between 0.35 g and 1.4 g aldicarb/m2. The dosage-increase efficiency was 0.3 probit units per doubling of the dosage and the reduction of the multiplication rate at 0.5 g aldicarb/m2 76%, whereas 2 g aldicarb/m2 was not more effective than 1.4 g. However, multiplication rates in the centre of the ridges of rotavated plots were reduced by 96.5% at 1 to 2 g aldicarb/m2 but only by about 60% below the furrows and by 60% to 80% below the ridges. The latter reduction was the greater the larger the dosage of the chemical.The observations were in accordance with the supposition that multiplication of nematodes was totally inhibited in the top 20 cm of plots treated with 1.4 g and 2 g aldicarb/m2 and that postharvest populations there consisted entirely of non-hatched eggs of the pre-plant population. The poor performance of the chemical in the deeper layers of the soil makes application less effective in reducing population build-up than in preventing yield losses.Samenvatting Het effect van 0,35, 0,5, 0,7, 1, 1,4 en 2 g aldicarb/m2, toegediend vlak voor het poten, op de vermenigvuldiging vanGlobodera rostochiensis op aardappel werd onderzocht in een veldproef op zavel. Het middel werd breedwerpig over de oppervlakte van de grond verdeeld. Daarna werd de helft van de met elke dosis behandelde en van de onbehandelde veldjes gefreesd tot 15 cm diepte. Er werd drie maal aangeaard. Er was geen verschil in de vermenigvuldiging van de aaltjes in de bovenste 20 cm van de grond tussen wel en van het middel van probit vermindering van het vermenigvuldigingsgetal van het aaltje ten opzichte van onbehandeld in de bovenste 20 cm van de grond was rechtlijnig tussen 0,35 g en 1,4 g aldicarb/m2. Het effect van dosisvergroting was 0,3 probit eenheid per verdubbeling van de dosis en de vermindering van het vermenigvuldigingsgetal bij 0,5 g aldicarb/m2 77%. Het effect van 1,4 g en 2 g aldicarb/m2 was gelijk. De resultaten zijn in overeenstemming met de veronderstelling, dat in de met 1,4 en 2 g aldicarb/m2 behandelde veldjes de vermenigvuldiging van de aaltjes in de bovenste 20 cm van de grond geheel was verhinderd. Met een voor praktische toepassing aanvaardbare dosis aldicarb kon een sterke vermeerdering van aardappelcystenaaltijes beneden 20 cm onder de oppervlakte van de grond niet worden voorkómen. Daardoor is de bruikbaarheid van dit systemische nematicide (en van overeenkomstige middelen) in een bestrijdingssysteem, dat streeft naar het (zeer) laag houden van dichtheden van aardappelcystenaaltjes, problematisch.  相似文献   

11.
Isolates of the PRN serotype of tobacco rattle virus (TRV) were transmitted with different efficiencies by the nematode vectorParatrichodorus pachydermus. Virus isolates which belonged to other serotypes were not acquired and/or transmitted by this vector, nor were PRN serotype isolates which had been obtained from naturally infected potato plants and maintained by mechanical transmission in the glasshouse for several years. PRN serotype TRV isolates from the Netherlands or from Scotland were equally well transmitted by initially virus-freeP. pachydermus populations from either country. Allowing a naturally viruliferous nematode population access for 3 weeks to uninfected or TRV-infected roots resulted in an increased proportion of the trichodorid population transmitting TRV.  相似文献   

12.
Results of field experiments reported in the literature suggest a linear relation between log dosage of dichloropropene injected into the soil and probit mortality of plant parasitic nematodes. In most cases probit mortality increases by about half a unit per doubling of the dosage of fumigant. This is in accordance with the distribution of sums of concentration-time (CT) products for dichloropropene in the soil according to investigations by Leistra (1971 and in litt.). The relation between log dosagex of the chemical and probit mortalityy can be described by the equationy=ax+b (a andb constants). Fora the name dosage increase efficiency is proposed. It is to be expressed in probit units per doubling of the dosage. The way in which the chemicals spread through the soil can be derived from the relation between dosage and mortality. Experiments should therefore always be done with a fairly large range of dosages including some of which only little effect is expected. Results of field experiments with dazomet, metamnatrium and methyl isothiocyanate, reported in the literature also suggest a linear relation between log dosage and probit mortality. The average dosage increase efficiency for the top 20 cm of the soil was higher than with dichloropropene.  相似文献   

13.
Adequate concentration, exposure time and distribution uniformity of activated fumigant gases are prerequisites for successful soil fumigation. Field experiments were conducted to evaluate gas phase distributions of methyl isothiocyanate (MITC) and chloropicrin (CP) in two forest-tree nurseries. Concentrations of MITC and CP in soil air were measured from replicated microplots that received dazomet, metam-sodium and CP. Half of the plots were covered with high-density polyethylene tarp immediately after fumigation; the other half were not covered but received daily sprinkler irrigation for 1 week to create and maintain a water seal. The magnitude of MITC concentrations was similar between nurseries for metam-sodium in both tarp and water seal treatments and for dazomet in the tarp treatment. Consistently greater MITC and CP concentrations were found in the upper 30 cm of soil in the tarped plots compared with the water-sealed plots. Despite potential environmental and economic benefits with the water seal method, tarp covers were more reliable for achieving and maintaining higher MITC and CP concentrations and less prone to variations due to irrigation/rain, soil bulk density and other environmental conditions.  相似文献   

14.
Annual applications of the herbicides atrazine, simazine, linuron and diuron at 45 kg/ha were made to the same plots for 9 consecutive years from 1963 to 1971 in a peach (Prunus persica (L.) Batsch.) orchard located on sandy loam soil near Harrow, Ontario. Soil samples from these plots were collected in late October for the last 3 years (1969–1971) and trees were cut down in December, 1969. Herbicide residues were determined by bioassays based on the fresh and dry weight of oats (Avena sativa L.) and in one year results were confirmed by chemical analysis. Significant accumulation of herbicides was not observed. The maximum residue levels measured in October over the 3 years of sampling were 7′3 kg/ha for diuron, 3–8 kg/ha for linuron, 1–6 kg/ha for simazine and 04 kg/ha for atrazine in the top 15 cm of the soil profile. Simazine and atrazine showed a rapid decrease in amount after treatment but diuron and linuron were degraded more slowly. Measurable residues of all herbicides were confined to the upper 15 cm of the soil profile and the majority of herbicide remained in the 0–5-cm soil layer. Oats were planted in the orchard plots from 1972 to 1974 to follow the disappearance of the herbicides. All herbicides caused highly significant yield decreases in 1972, atrazine causing the least (38%) and diuron the greatest (86%) reductions. Diuron reduced the yield of oats in 1973 and caused a highly significant decrease in the weight of young oat plants in 1974.  相似文献   

15.
Soil core samples taken from a sandy loam soil at Woburn during January 1972, following spring beans during the previous year, indicated that half the rhizome dry weight of Equisetum arvense (L.) occurred in the uppermost 25 cm of soil and 10% between 75 and 100 cm. Tubers occurred relatively more deeply with half the number and three-quarters of the weight deeper than 50 cm. However, after a 2-year fallow 80% of the rhizomes and tubers were in the uppermost 25 cm of soil. In general, the weight of individual tubers increased with increasing depth in the soil. In pots in the glasshouse, tubers that were formed in one season lost weight when new shoots emerged in the following year; those formed during summer germinated readily in warmth indoors when detached in the autumn, but not until June of the following year in the field. Burial of tubers at a range of depths down to 25 cm did not affect the number of shoots emerging but emergence was delayed. Plants made more growth in neutral than in acid or basic soil, more in silty clay loam than in sandy loam and appeared well adapted to growth in soils with little nitrogen. In general, rhizome growth was less affected by variations in pH and nitrogen level than were shoots and tubers. Plants grown from tubers were suppressed greatly by wheat sown densely and given a moderate amount of nitrogen fertilizer but had negligible effect on the wheat. With fewer wheat plants given less nitrogen, the species partitioned more of its assimilate into tubers than when it was grown alone. The significance of tubers in the biology of the species is briefly discussed and areas meriting further study are highlighted.  相似文献   

16.
At present most of the begonia growers around Ghent disinfect their fields annually or biennially to control nematodes, weeds, and also fungi. Investigations therefore were carried out on the influence of this annual application of nematicides on the soil fauna. Samples were taken in September from two adjacent experimental plots; one plot was disinfected for five consecutive consecutive years with 6 ml of DD per m2, the other was used as a control. It was found that the annual disinfection of begonia fields with DD did not depress the saprophagic fauna and that earthworms, enchytraeids, mites and collembola were mainly in the upper 5 cm of the soil.Samenvatting We constateren dat tegenwoordig de meeste begoniakwekers jaarlijks of tweejaarlijks hun cultuurgrond ontsmetten met het doel aaltjes, onkruiden en ook wel schimmels te bestrijden.We hebben een aanvang gemaakt met de invloed van dit jaarlijks toedienen van nematiciden op de bodemfauna na te gaan. Hiervoor werden bemonsteringen in september uitgevoerd op, twee naast elkaar gelegen proefpercelen: het ene vijf opeenvolgende jaren met DD aan 6 liter per are ontsmet, het andere als getuige gehouden.We hebben vastgesteld dat het jaarlijks ontsmetten van begoniavelden met DD de saprofage fauna niet heeft gedrukt en dat de regenwormen, enchytraeiden, mijten en collembolen zich hoofdzakelijk in de bovenste 5 cm van de bodem bevinden.Research subsidized by the Institute for the Encouragement of Scientific Research in Industry and Agriculture (IWONL).  相似文献   

17.
乌兰布和沙漠流动沙地土壤水分动态、土壤水势特征的研究   总被引：12，自引：2，他引：10  
通过对乌兰布和沙漠流动沙地土壤水分动态的研究表明:沙土含水量的时空变化与降雨季节和降雨量有密切关系。100mm左右的降雨量对沙地和丘间地的影响深度主要在60cm左右,因此0-60cm土层为土壤水分受降雨影响的活跃层;通过对土壤含水量与土壤水势的关系研究表明:在相同土壤含水量下沙土水分对植物的有效性远大于粘土;通过降雨量对沙地贮水量影响的研究表明:只有38%左右的降雨量增加了土壤贮水量,其余62%被蒸散。  相似文献   

18.
湖北省武穴市佛手山药是“农产品地理标志产品”, 近年佛手山药线虫病害严重, 为此在病源地采集山药土样进行了病害发生调查及病原鉴定?通过形态特征观察?形态特征测计值比较, 以及基于rDNA 28S D2/D3区序列构建短体线虫属线虫群体系统进化树并进行SCAR验证, 对引起佛手山药线虫病的病原线虫进行种类鉴定?结果表明:危害佛手山药的病原线虫的群体特征与咖啡短体线虫Pratylenchus coffeae相似?系统进化树显示:该病原群体与中国香港群体(HQ688677.1)聚类在一个分支上, 置信度达99%?因此, 将该群体线虫鉴定为咖啡短体线虫Pratylenchus coffeae?此外田间调查表明:线虫主要集中分布于10~20 cm深度的土层中, 线虫密度随土壤深度的增加而呈递减趋势, 且连作1年地较连作2年地的线虫数量少, 施用阿维菌素的地块较未施用的线虫数量少?上述结果表明, 在佛手山药生产中实行轮作和科学选择药剂防治, 避免连作, 可降低该线虫发生量?  相似文献   

19.
Plant-parasitic nematodes can cause serious plant diseases and adversely affect crop production. We investigated the temporal and vertical dynamics of plant-parasitic nematodes in northeast China to determine if long-term fertilizer application suppresses the population of plant-parasitic nematodes and influences their vertical distribution in the black soil region. The long-term fertilizer application lasted for 14 years, and included three treatments: pig manure combined with chemical fertilizer (MCF), chemical fertilizer (urea and ammonium phosphate, CF), and no fertilizer (NF). A 3-year corn-wheat-soybean rotation was grown on the field site, soil samples were obtained in the corn phase and nematodes were extracted, identified and counted. Six plant-parasitic nematode genera with relative abundance over 0.1% were found in this study. Heterodera was the dominant genus in all three fertilizer treatments, and its relative abundance was highest in NF (45.4%) and lowest in MCF (32.8%). Fertilizer application had a significant effect on abundance of total soil nematodes but not on either plant-parasitic nematodes or Heterodera. Significant differences in the abundance of total soil nematodes, plant-parasitic nematodes and Heterodera were observed among soil depths and interaction of fertilizer × soil depth. Total soil nematodes were mainly distributed in the 0–20 cm soil layer, and plant-parasitic nematodes and Heterodera were mostly distributed in the 10–30 cm soil layer. Fertilizer application did not show a significant effect on plant-parasitic nematodes or Heterodera at any of the sampling depths from 0 to 80 cm. The results indicated that fertilizer has no effective control on plant-parasitic nematodes when dominant genera and their respective plant hosts exist in relatively high abundance.  相似文献   

20.
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.  相似文献   

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