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1.
A study was conducted of the behaviour of oxamyl in Israeli soils of varying clay and organic matter contents. The adsorption isotherms for oxamyl were linear, and the adsorption coefficient (Kd) could be correlated to the clay content of the soils, as well as to the organic matter content of the soil. Oxamyl adsorption was underestimated by using published correlations between the adsorption and the chemical properties of pesticides, such as their solubility or octan-1-ol-water partition coefficient. The decomposition of oxamyl in soils followed first-order kinetics. The half-life ranged from 4 to 33 days in a Bet Dagan soil. The reaction rate increased with increasing moisture content of the soil until field capacity was reached, at which point it levelled off. The Arrhenius relationship was followed, with degradation proceeding more rapidly at higher temperatures. In several soils of varying composition, which were kept at field capacity, no difference in the degradation rates was observed. Oxamyl was applied to a Bet Dagan soil from a point source in a single pulse, as a split application, and on a continuous basis. The distribution patterns of oxamyl under the various treatments differed significantly. After the single-pulse application, oxamyl was leached out of the emitter zone. While the split application decreased the oxamyl-free zone, the best results were obtained by continuous application, which gave a nearly uniform distribution of oxamyl in the soil.  相似文献   

2.
BACKGROUND: Fluensulfone, a new nematicide of the fluoroalkenyl group, has proved to be very effective in controlling root‐knot nematodes, Meloidogyne spp., by soil application. The systemic activity of this compound against M. incognita on peppers via soil drenching and foliar spray was evaluated. RESULTS: Root application of fluensulfone via soil drenching showed slight and no nematode control activity when applied 4 and 10 days, respectively, after inoculation. A single foliar spray of peppers with a fluensulfone solution at 3.0 g L?1 prior to inoculation reduced the galling index by 80% and the number of nematode eggs by 73–82% of controls. The reduction in these parameters by fluensulfone was much higher than that obtained with oxamyl or fenamiphos at the same concentration. This activity was also observed when the plants were sprayed 21 days before inoculation. A series of experiments suggested that foliar spray with fluensulfone prior to inoculation reduces nematode invasion. However, foliar spray after inoculation did not inhibit nematode development inside roots. CONCLUSION: Fluensulfone showed relatively high nematode control activity when sprayed on the foliage before inoculation. Fluensulfone may be used as a foliar application, in addition to soil application, for root‐knot nematode control. Copyright © 2011 Society of Chemical Industry  相似文献   

3.
BACKGROUND: Soil application of systemic neonicotinoid insecticides can provide opportunities for long‐term control of insect pests in vineyards, with minimal risk of pesticide drift or worker exposure. This study compared the effectiveness of neonicotinoid insecticides applied via irrigation injection on key early‐season and mid‐season insect pests of vineyards in the eastern United States. RESULTS: On vines trained to grow on drip irrigation, early‐season application of imidacloprid, clothianidin, thiamethoxam and dinotefuran provided high levels of control against the potato leafhopper, Empoasca fabae. Protection of vines against Japanese beetle, Popillia japonica, and grape berry moth, Paralobesia viteana, was also observed after mid‐season applications. Efficacy was poor in commercial vineyards when treatments were applied to the soil before irrigation or rain, indicating that vines must be grown with an irrigation system for efficient uptake of the insecticide. CONCLUSIONS: In drip‐irrigated vineyards, soil‐applied neonicotinoids can be used to provide long residual control of either early‐season or mid‐ to late‐season foliage pests of vineyards. This approach can reduce the dependence on foliar‐applied insecticides, with associated benefits for non‐target exposure to workers and natural enemies. Copyright © 2012 Society of Chemical Industry  相似文献   

4.
Soft-rotting bacteria affecting bell peppers crops represent an economically destructive disease of growing importance worldwide. In Venezuela since 2006, soft-rot symptoms have been occasionally observed in bell pepper fruits grown under greenhouse conditions. Affected fruits presented water-soaked lesions that progressed to complete fruit maceration. Bacteria were isolated from water-soaked lesions in order to identify the causal agent of this disease. Of 13 bacterial isolates recovered from affected fruits, only isolate AGPim1A was able to produce a hypersensitive reaction in tobacco plants and to reproduce soft-rot symptoms in bell peppers fruits. Several methods, including classical bacteriological tests and carbon utilization profiling, alongside with sequence analysis of 16S rRNA and housekeeping genes gyrB and groES-groEL, allowed identification of the soft-rotting bacterium as Serratia marcescens. To our knowledge, this is the first report showing a S. marcescens strain associated with soft-rot disease in bell pepper fruits.  相似文献   

5.
Second-stage juveniles (J2) and egg masses of root-knot nematodes as well as root debris heavily infected by the latter were exposed for different periods of time to six different doses of the nematicides cadusafos and fenamiphos. The efficacy of the nematicides increased significantly with increasing exposure time. Both nematicides were more effective against J2, although they could not provide acceptable control of J2 inside egg masses or heavily galled root debris. The effect of different application strategies on the efficacy and persistence of certain nematicides was also assessed in a field study. Cadusafos, fenamiphos, fosthiazate and oxamyl were applied in field micro-plots either as a single full dose at the time of crop establishment or as multiple reduced-rate applications at 14-day intervals throughout the cropping period, and their efficacy and persistence were determined using bioassays and analytical studies. Fosthiazate was the most efficient nematicide studied, and this was mainly attributed to its long soil persistence. Oxamyl also provided adequate nematode control for the first 48-56 days after its application, regardless of the application method used and its relatively rapid field dissipation. Fenamiphos and cadusafos failed to provide adequate nematode control, although cadusafos was the most persistent of the nematicides tested. The failure of fenamiphos to provide adequate nematode control was mainly attributed to its rapid degradation by soil micro-organisms, which were stimulated after its repeated low-rate application at 14-day intervals. In contrast cadusafos failure was attributed to the inability of the nematicide to reduce nematode populations even at relatively high concentrations in soil.  相似文献   

6.
Current environmental awareness has led to a greater demand for alternative nematode control strategies. Three field experiments were established to compare management tactics on cucumber in commercial greenhouses naturally infested with root-knot nematodes (Meloidogyne spp). Cucumber rootstocks which have shown resistance to soil-borne diseases were tested to reveal any resistance/tolerance to root-knot nematodes, and integration of these rootstocks with nematicides was investigated. Metham-sodium and 1,3-dichloropropene (1,3-D) provided good control of nematode populations when their application was followed by the application of a non-fumigant nematicide such as cadusafos or oxamyl. Neither fumigant could provide season-long control of nematode populations, and a further application of cadusafos was required for satisfactory control. The efficacy of metham-sodium was significantly increased when injected into soil in comparison with its application through the drip irrigation system. The use of rootstocks resistant to soil-borne fungal pathogens used together with chemical means of nematode control provided promising results for their further use in integrated strategies as alternatives to methyl bromide. However, the latter was the superior treatment for the control of root-knot nematodes in soil infested with residues of galled roots. Dazomet, metham-sodium nor the non-fumigant nematicides oxamyl and fenamiphos could reduce nematode population as efficiently as methyl bromide. None of the chemicals tested except methyl bromide could enter galled roots and kill surviving nematodes.  相似文献   

7.
D. V. CLAY 《Weed Research》1980,20(2):97-102
The tolerance of strawberries to herbicides was tested by applications to the roots of plants growing in sand and by foliage applications to plants grown in compost, and compared with tolerance in the field. Dimefuron was safe as a foliar application but much more toxic than simazine when applied in sand or in the field. Metamitron caused slight injury as a foliar spray; in sand and in the field it was intermediate in toxicity between simazine and lenacil. At normal rates propachlor was safe as a foliar spray and much safer than lenacil when applied in sand. High rates had no adverse effect in the field. Ethofumesate and pendimethalin caused some temporary stunting when applied to foliage, but were less toxic than lenacil when applied to roots in sand. Field applications of both herbicides at 1–1.5 kg/ha were safe. Foliage sprays of bentazone, oxadiazon and oxyfluorfen severely damaged the sprayed leaves, but these herbicides were less active than lenacil when applied to the roots. In the field they caused severe leaf damage, but by the end of the growing season the plants had recovered. The experiments demonstrated the value of separate root and shoot activity tests for indicating which herbicides merit further field testing.  相似文献   

8.
The rapid range expansion of naturalized Italian ryegrass (Lolium multiflorum Lam.) in farmland is a serious problem in Fukuroi city in Shizuoka Prefecture, Japan. Glyphosate has been used to control Italian ryegrass in the levees of rice paddy fields and wheat fields for ～20 years, but this weed in Fukuroi city is poorly controlled by glyphosate. In order to elucidate the level of resistance to glyphosate in Italian ryegrass populations, seed bioassays and a foliar application experiment, using seeds collected from 16 wild populations in and around Fukuroi city and from three susceptible cultivars, were conducted. For the susceptible cultivars and one population from a site where glyphosate had not been applied for >10 years, the shoot length in the seed bioassays was greatly suppressed at a glyphosate concentration of 10 mg ai L?1 and no seedling survived after the foliar application of glyphosate at a rate of 2.3 kg ai ha?1. Nine wild populations from levees in the southern part of Fukuroi city showed vigorous shoot growth at a glyphosate concentration of 10 mg ai L?1 and had at least a 78% survival rate after the application of glyphosate at 2.3 kg ai ha?1. Four wild populations from levees in the northern part of Fukuroi city showed a slight suppression of the shoot growth as a result of the glyphosate treatment and their survival rates ranged from 20 to 64%. The results suggested that resistance to glyphosate has evolved in the wild populations of Italian ryegrass that are growing on the levees. This is the first report of a glyphosate‐resistant weed in Japan.  相似文献   

9.
BACKGROUND: The potential of systemic neonicotinoid insecticides to control potato leafhopper, Empoasca fabae (Harris), a damaging pest of wine grapes in the eastern United States, was investigated. Soil or foliar applications were made to potted or field‐grown vines, and the response of leafhoppers was determined in clip cages over the following month on young or mature leaves. RESULTS: Foliar application of imidacloprid caused immediate and long‐lasting reductions in E. fabae survival on both leaf ages, whereas the activity of soil‐applied imidacloprid was delayed. Clothianidin, imidacloprid and thiamethoxam all provided long‐lasting reduction in leafhopper survival on young and mature foliage when applied through either delivery route. However, the percentage of moribund nymphs was significantly greater on foliar‐treated vines and increased over time in mature and immature leaves compared with soil‐treated vines. Residue analysis of foliar‐applied imidacloprid showed an 89% decline in mature leaves from day 1 to day 27, and a 98% decline in immature leaves over the same time period. Comparison of soil‐applied clothianidin, imidacloprid and thiamethoxam in field‐grown vines showed significant reduction in E. fabae only on mature leaves of vines treated with thiamethoxam. CONCLUSIONS: Neonicotinoids can control E. fabae in small vines, even in rapidly expanding foliage where this pest causes greatest injury. Soil application provides superior long‐term vine protection because declining residues on foliar‐treated vines lead to suboptimal activity within 2–3 weeks. Vineyard managers of susceptible cultivars may take advantage of this approach to E. fabae management by using foliar applications of the three neonicotinoids tested here, or by using soil‐applied thiamethoxam. Copyright © 2011 Society of Chemical Industry  相似文献   

10.
ABSTRACT Tomato wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici, is effectively controlled by a foliar spray of validamycin A (VMA) or validoxylamine A (VAA) (>/=10 mug/ml); however, neither VMA nor VAA is antifungal in vitro. In pot tests, the effect of a foliar application of VMA or VAA at 100 mug/ml lasted for 64 days. Plants sprayed with VMA or VAA accumulated salicylic acid and had elevated expression of the systemic acquired resistance (SAR) marker genes P4 (PR-1), Tag (PR-2), and NP24 (PR-5). Foliar spray of VMA also controlled late blight and powdery mildew of tomato. The disease control by VMA and VAA lasted up to 64 days after treatment, was broad spectrum, and induced the expression of PR genes, all essential indicators of SAR, suggesting that VMA and VAA are plant activators. The foliar application of plant activators is a novel control method for soilborne diseases and may provide an economically feasible alternative to soil fumigants such as methyl bromide.  相似文献   

11.
Duration of systemic pesticide activity under field conditions has wide implications for pest management. Our aim was to determine the duration of activity of systemic insecticides commonly used in cultivated tobacco (Nicotiana tabacum) by measuring the levels of insect infestations on field plots and effects on reproduction and survival of the green peach aphid (Myzus persicae) in controlled bioassays using field grown leaves. Plants were treated with different concentrations of two systemic neonicotinoid pesticides, imidacloprid and thiamethoxam, and grown in small field plots. Our results show that these materials are effective under field conditions against aphids for at least 13 weeks after transplant. Pesticides also affected aphid reproduction and nymph survival in bioassays, although some aphids survived on pesticide-treated leaves. We also observed that leaf age affected aphid survival. We showed that neonicotinoids were very effective against M. persicae, aphids are a useful organism to assess pesticide efficacy early in the growing season, but plant characteristics are more important than pesticide concentration in the second half of the growing season.  相似文献   

12.
Garlic bulbs heavily infected withDitylenchus dipsaci were chemically treated to control the nematode. Treatment with ethoprop resulted in greatest reduction of nematodes early in the season; oxamyl provided good control; methomyl was ineffective. Treating the soil with aldicarb or phenamiphos was also effective. Later in the season, nematode populations increased with all treatments and crop damage was severe. In a soil heavily infested with this pathogen, nematode populations in the untreated plots were initially low but had increased rapidly 100 days after planting, resulting in total loss of plants by the end of the season. Excellent control was obtained by treating the soil with methyl bromide (MB) or solar heating with transparent polyethylene sheets prior to planting, although MB treatment caused severe stunting of the plants. Treatment with ethylene dibromide (EDB) controlled the pathogen initially, but later in the season the population level increased. The yields (kg/m2) were: untreated, 0; solar heating, 2.325; EDB, 0.813; and MB, 1.152.  相似文献   

13.
于2013—2014年小麦生长季,在陕西关中地区进行田间喷施试验,设置CK、喷Zn、喷三唑酮、喷Zn+三唑酮4个处理,以揭示锌与三唑酮配合喷施对小麦锌营养品质的影响。结果表明:不同喷施方式对小麦籽粒千粒重及产量均无明显影响;喷三唑酮、喷Zn+三唑酮及喷Zn使籽粒Zn含量由CK的25.9 mg·kg~(-1)分别提高到32.2、52.4 mg·kg~(-1)和52.7 mg·kg~(-1),增加幅度分别为24%、102%和103%;喷三唑酮和喷Zn+三唑酮处理降低了小麦籽粒植酸含量,相比对照分别降低23.8%、15.9%,使植酸/Zn摩尔比明显降低,从而显著提高了籽粒锌生物有效性。Zn与三唑酮配合喷施下提高籽粒锌含量及其生物有效性的效果十分明显,同时还能兼顾防治小麦白粉病、条锈病等。  相似文献   

14.
Pymetrozine, a pyridine-azomethine, is a selective biocide against aphids, whiteflies and plant hoppers with a high plant systemic activity. By means of bioassays and autoradiographic techniques it has been shown that this systemic behaviour originates not only from xylem but also from phloem mobility. After foliar application the growing points of plants are protected by pymetrozine imports mainly from leaves. This indicates a high importance of phloem mobility for the systemic activity of pymetrozine against plant-sucking insects. © 1997 SCI.  相似文献   

15.
The effect of Pochonia chlamydosporia , a facultative fungal parasite of nematode eggs, alone or in combination with oxamyl was evaluated in a double-cropping system of lettuce and tomato in unheated plastic houses infested with Meloidogyne javanica at two sites for two consecutive growing seasons. An additional treatment of methyl bromide fumigation was included to compare crop yield in nematode-free vs. nematode-infested soil. Final population densities, reproductive rate, root gall rating, and egg production were determined after each crop. Pochonia chlamydosporia was isolated from nematode eggs up to nine months after application to soil. The fungus survived in the rhizosphere for the entire growing season at one site, but only at low densities. Final population densities of M. javanica decreased after cultivation of lettuce and increased after tomato, and this pattern of population fluctuation was unaffected by treatment, experiment or site. The reproductive rate on lettuce was equal to or below 1, and it was similar among treatments in both experiments at both sites. Eggs were not found on lettuce roots. On tomato, the reproductive rate in the fungus + oxamyl treatment was significantly lower ( P  < 0·05) than other treatments in experiment 1 at both sites. Fungus + oxamyl consistently reduced root gall ratings on tomato in all cases, but numbers of eggs per g root varied depending on treatment. Methyl bromide-treated plots remained free of M. javanica at the end of the 2-year study.  相似文献   

16.
Microbe-Mediated Germination of Ascospores of Monosporascus cannonballus   总被引：1，自引：0，他引：1  
ABSTRACT Ascospores of Monosporascus cannonballus germinated readily in the rhizosphere of cantaloupe plants growing in field soil. However, little or no germination occurred in the rhizosphere of melon plants growing in field soil that was autoclaved prior to infestation with ascospores. The latter data suggested that root exudates alone do not stimulate ascospore germination and that the soil microflora may be involved in the induction of ascospore germination. Amending field soil with streptomycin (which inhibits gram-negative microorganisms) did not suppress ascospore germination in the rhizosphere of cantaloupe plants. However, amending the soil with penicillin (which inhibits gram-positive microorganisms) did suppress ascospore germination. Pentachloronitrobenzene (PCNB), which inhibits the gram-positive actinomycetes but does not inhibit gram-positive or gram-negative bacteria, also suppressed ascospore germination. These results suggest that actinomycetes, either directly or indirectly, are involved in the induction of ascospore germination in field soil in the presence of exudates from cantaloupe roots. Optimum germination occurred at temperatures ranging from 25 to 35 degrees C, and data indicate that a high percentage (>/=72%) of the ascospore population within 500 mum of a root are capable of germination and subsequent penetration of cantaloupe roots.  相似文献   

17.
Foliar application of a number of broad-spectrum systemic fungicides (particularly conazole fungicides) to loose smut-infected plants of wheat and barley in a 3-spray programme resulted in a marked reduction in the percentage of plants producing infected ears. Such foliar fungicides may have a previously unseen role in reducing the levels of loose smut infection in wheat and barley.  相似文献   

18.
P. JONES 《Plant pathology》1997,46(6):946-951
Foliar application of the broad-spectrum systemic fungicide triadimefon to loose smut-infected plants of wheat and barley produced a marked curative effect. Triadimefon was particularly effective when applied at the beginning of and during stem extension. In addition to reducing percentage plant infection, foliar application of this fungicide (particularly prior to flag leaf emergence) resulted in an increased proportion of infected ears which were only partially smutted. The curative effect of these early fungicide applications resulted in significant yield increases, as a consequence of increased grain number per m2. Application of triadimefon to crops at ear emergence had no significant effect on percentage plant infection but resulted in lower levels of re-infection following artificial or natural inoculation of healthy ears, apparently as a result of a protectant effect of fungicide residues on or in the ovaries.  相似文献   

19.
ABSTRACT Subsurface drip irrigation and associated mandatory minimum tillage practices significantly reduced the incidence of lettuce drop (Sclerotinia minor) and the severity of corky root on lettuce compared with furrow irrigation and conventional tillage. Three possible mechanisms for the drip irrigation-mediated disease suppression were examined in this study: qualitative and quantitative differences in the soil microflora under furrow and subsurface drip irrigation; their antagonism and potential bio-control effects on S. minor; and the physical distribution of soil moisture and temperature relative to the two irrigation methods. To determine if the suppressive effects under subsurface drip irrigation were related to changes in soil microflora, soils were assayed for actinomycetes, bacteria, and fungi during the spring and fall seasons. The effects of the irrigation methods on microbial populations were nearly identical during both seasons. In the spring season, the total number of fungal colonies recovered on potato dextrose agar amended with rose Bengal generally was greater in soils under drip irrigation than under furrow irrigation, but no such differences were observed during the fall. Numbers of actinomycetes and bacteria were not significantly different between irrigation methods during either season. No interaction between sampling time and irrigation methods was observed for any of the microbial populations during both seasons. Thus, the significant effect of sampling time observed for actinomycete and bacterial populations during the spring was most likely not caused by the irrigation treatments. There were also no qualitative differences in the three groups of soil microflora between the irrigation treatments. Even though some fungal, actinomycete, and bacterial isolates suppressed mycelial growth of S. minor in in vitro assays, the isolates came from both subsurface drip- and furrow-irrigated soils. In in planta assays, selected isolates failed to reduce the incidence of drop in lettuce plants. The soil moisture under subsurface drip irrigation was significantly lower at all depths and distances from the bed center after an irrigation event than under furrow irrigation. The soil temperature, in contrast, was significantly higher at both 5 and 15 cm depths under drip irrigation than under furrow irrigation. The suppression of lettuce drop under subsurface drip irrigation compared with furrow irrigation is attributed to differential moisture and temperature effects rather than to changes in the soil microflora or their inhibitory effects on S. minor.  相似文献   

20.
BACKGROUND: The potential for enhanced degradation of the carbamoyloxime nematicides aldicarb and oxamyl and the organophosphate fosthiazate was investigated in 35 UK agricultural soils. Under laboratory conditions, soil samples received three successive applications of nematicide at 25 day intervals. RESULTS: The second and third applications of aldicarb were degraded at a faster rate than the first application in six of the 15 aldicarb‐treated soils, and a further three soils demonstrated rapid degradation of all three applications. High organic matter content and low pH had an inhibitory effect on the rate of aldicarb degradation. Rapid degradation was observed in nine out of the ten soils treated with oxamyl. In contrast, none of the fosthiazate‐treated soils demonstrated enhanced degradation. CONCLUSION: The potential for enhanced degradation of aldicarb and oxamyl was demonstrated in nine out of 15 and nine out of ten soils respectively that had previously been treated with these active substances. Degradation of fosthiazate occurred at a much slower rate, with no evidence of enhanced degradation. Fosthiazate may provide a useful alternative in cases where the efficacy of aldicarb and oxamyl has been reduced as a result of enhanced degradation. Copyright © 2009 Society of Chemical Industry  相似文献   

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