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1.
To study the relationship between temperature regimes and loss of viability of Dematophora necatrix in soil, two field experiments were conducted to determine the effectiveness of soil solarization on reducing the population of D. necatrix colonizing avocado root segments buried at a depth of 15–60cm. Increase of maximum hourly temperatures attributable to soil solarization reached, depending on depth, 6.7–4.6°C in unshaded areas and 3.9–1.5°C for shaded areas in the first experiment (starting in early June, 1995). The better environmental conditions in the second experiment (starting by mid-July, 1995) led to higher temperature increases (8.6–5.6°C, depending on depth) when solarization was conducted in unshaded areas. One, 4, 5 and 6 weeks of solarization were required to eliminate the viability of D. necatrix at 15, 30, 45 and 60cm depths in the first experiment, whereas only 8, 10, 15 and 22 days of solarization were needed for the loss of viability of D. necatrix at the same depths in the second experiment. In shaded areas, however, soil solarization attained significant effectiveness at 15cm depth.Regression analyses of fungal viability (ln-transformed data) over accumulated temperature–time showed best fits when the minimum threshold temperature was 30°C. Although eradication of D. necatrix in soil can be achieved down to 60cm depth in solarized plots, and at 15cm depth in unsolarized unshaded plots, the accumulation of temperature–time appeared less effective in reducing inoculum viability in the latter.  相似文献   

2.
The potential of solarization to control Meloidogyne incognita in piles of soil used at olive nurseries in southern Spain was studied in 1999 and 2000. Kaolin and soil infested with free eggs and egg masses of the nematode in nylon bags were buried 20 and 40 cm deep inside conical piles of soil 80 cm high and with a base diameter of 1 m. Soil piles were solarized for 3 weeks in July and August. The effect of various periods of solarization was assessed by egg hatch bioassays in sterile water, and by infectivity to tomato plants. Maximum soil temperature at 20 cm depth in solarized piles was 47·4°C in 1999 and 48·2°C in 2000, compared with 32·9°C and 31·7°C in nonsolarized piles. Solarization reduced egg hatch by > 95% compared with nonsolarized samples, irrespective of type, burial depth and location of inocula in a soil pile. Egg hatch of egg mass-infested samples buried at 20 cm depth was higher than that of free eggs buried at the same depth. The differential effect associated with burial depth and type of inoculum was not found in solarized piles. In nonsolarized piles, hatch of free eggs from samples buried at 40 cm depth was higher than that from samples buried at 20 cm depth. Egg hatch in samples from solarized piles was lower than that from nonsolarized piles. A bioassay of tomato plants in 2000 confirmed the reduction in infectivity of free eggs buried in solarized soil piles. Under the conditions in southern Spain, solarization of 40 cm-high piles of soil for 3 weeks can therefore be used for the control of root-knot nematodes in potting soil for olive nursery production.  相似文献   

3.
Apricot ( Prunus armeniaca ) and almond ( P. dulcis ) trees at the first leaf stage were planted in soil infested with Verticillium dahliae and mulched with transparent or black polyethylene film, or not mulched, in the San Joaquin Valley of California, March-August 1990. During the 19-week mulching treatment, summer soil temperatures reached as high as 46, 41, and 33°C at 18 cm depth; and 41, 37, and 32°C at 30 cm depth under clear film, black film, and no film, respectively. Trees mulched from the time of planting with transparent polyethylene (solarization) did not survive or grow as well as those mulched with black film or not mulched. Incidence of foliar symptoms due to Verticillium wilt was reduced by 86–100% in both apricot and almond trees by black, as well as transparent film mulch the following season. Incidence of vascular discoloration symptoms of trunks and primary scaffolds due to Verticillium wilt was similarly reduced by both mulches. Mulching with black polyethylene film gave better overall results than solarization with transparent film. The intermediate soil temperatures produced did not chronically harm trees, as judged by tree survival and annual growth of trunk diameter, yet the prolonged period of soil heating provided control of Verticillium wilt equivalent to that of solarization with transparent polyethylene. These studies provided further evidence that in-season mulching can be used to conserve water during establishment of new orchards or replant trees in warm, arid climates.  相似文献   

4.
The efficacy of summer irrigation and soil solarization combined with cruciferous residues was tested against the dry root rot pathogen Macrophomina phaseolina in an arid climate. In irrigated amended soil, polyethylene mulching during May increased the soil temperature to 57°C and 50°C at depths of 0–15 and 16–30 cm, respectively. As a result, within l5 days the population of M. phaseolina was almost eradicated (93–99%) at both soil depths. A considerable reduction (75–96%) was also achieved by natural heating of irrigated soil (46–53°C) for l5 days after amending with cruciferous residues. Mulching alone was only partially effective (69–89% reduction). These results suggest a new approach to controlling soil-borne pathogens in hot, arid regions by combining summer irrigation with soil amendment. Amendment with residues alone or in conjunction with soil solarization also increased the population of lytic bacteria against M. phaseolina .  相似文献   

5.
Soil solarization provided effective control of bacterial canker of tomato in plastic houses. Trials in plastic houses in Preveza County, Greece, during the period 1990–1992 showed that soil solarization (approximately 6 weeks of soil mulching with transparent polyethylene sheets) drastically reduced disease incidence throughout the cropping season. In contrast, soil fumigation with a recommended rate of methyl bromide (70 g/m2) was ineffective. Both wild-type and antibiotic-resistant strains of Clavibacter michiganensis subsp. michiganensis , growing on Nutrient Agar Glycerol (NAG) medium within covered and screwed vials and embedded at various soil depths (5, 15 or 25 cm) before soil solarization, were studied. Weekly sampling of bacteria during treatment showed a sharp decline of populations in the solarized soil compared to the non-treated control plots 4–6 weeks after soil tarping. Populations of marked strains infiltrated into tomato stem segments and buried in the soil decreased significantly after 5–6 weeks of solarization compared to non-treated control plots. The data presented here suggest that soil solarization is useful for the control of bacterial canker of tomato in plastic houses in Greece.  相似文献   

6.
Summary Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 °C . Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38–60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2–5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively.  相似文献   

7.
Soil solarization (SoSol) with a single layer of transparent polyethylene (PE) film, traps considerable heat and moisture in soil. Solarization of field soil with two layers of 1 mil (25 μm thick) PE film, separated by a 6-cm air layer, caused soil temperatures at 15 cm depth to rise by 12.7°C and 3.6°C over those in noncovered soil or soil covered by one layer of film, respectively; at 30 cm depth the respective differences in temperature were 11.2°C and 2.7°C. Viability of propagules (mainly chlamydospores) ofFusarium oxysporum f. sp.vasinfectum that had been buried at 30 cm depth, was reduced after 31 days of solarization by 97.5%, 58%, and 0% under a double film layer, a single layer, and in non-covered soil, respectively. The insulating effect of a double layer of PE film improved heat retention in soil and the solarization effect.  相似文献   

8.
Ganoderma boninense causes severe losses to oil palm in South East Asia. The disease typically manifests itself as basal stem rot, but there remains controversy over the route of infection and source of inoculum. Using isolates differing in aggressiveness, infection via roots was confirmed; it was also shown that large inoculum provided as Ganoderma -infested palm- or rubber-wood blocks (12 × 6 × 6 cm) is necessary for soil infection of seedlings after 6–8 months. Smaller blocks (3 × 3 × 3 cm) produced rapid (≤ 3 months) infection of roots and lower stem when physically attached to roots. Therefore fragmentation of infested palm wood from a felled, mature plantation before subsequent replanting may provide inoculum. Failure of G. boninense to grow through non-sterile soil or organic debris from frond bases, suggests it is a poor competitor and that roots must contact inoculum directly. Severe disease occurred after 8 months on inoculated seedlings under shade, but not on seedlings exposed to sun. Soil temperatures in sunlight frequently rose above 40°C and reached 45°C, whereas in shade they never exceeded 32°C. Ganoderma boninense is probably inhibited in exposed soil since optimal growth in vitro was 25–30°C, and there was no recovery from 45°C. Soil temperature may explain why symptoms often first appear in mature plantations when canopy formation creates shade. Infection is not peculiar to senescing palms but can occur throughout the growth cycle.  相似文献   

9.
Monthly inoculations of both intact plants and excised shoots of Quercus suber with the pathogenic species Botryosphaeria stevensii and Phytophthora cinnamomi were performed to investigate seasonal changes in susceptibility of this forest tree species in relation to environmental parameters and plant water status. Infection symptoms were mainly detected on seedlings inoculated from spring to autumn (April through October) with either pathogen. Mean canker sizes also showed a seasonal pattern, the higher values being recorded in the same period as above. Lesion lengths were significantly ( P  < 0·001) related to environmental minimum temperature. Mean daily minimum temperatures within the range of 5–12°C clearly inhibited lesion development of P. cinnamomi , whereas B. stevensii showed a less pronounced decrease in canker expansion at the same temperature range. In excised shoots of Q. suber inoculated monthly with B. stevensii , a negative linear relationship was found between the studied range of plant relative water content (81–91%) and canker length. In contrast, the lesions caused by P. cinnamomi were not significantly ( P  = 0·32) related to any seasonal change in water content. Some control measures for the diseases caused by both pathogens are discussed on the basis of the seasonal changes in host susceptibility observed in this study.  相似文献   

10.
The efficacy of solarization in weed control under field conditions of the United Arab Emirates was evaluated by two methods: on-farm weed assessment and a seed germination test. In the on-farm weed assessment method, the weed frequency, density, and dry weight were compared in the solarized and non-solarized plots that were cultivated with cabbage. Prior to solarization, the soil was artificially infested with the seeds of 10 weeds. Generally, the densities of seven species and dry weights of five species were significantly lower in the solarized plots as compared to the control. Launea mucronata , Capsella bursa-pastoris , and Echinochloa colona were very sensitive to solarization, as they did not appear in the solarized plots. However, Portulaca oleracea and Melilotus indica were not significantly affected by soil solarization. In the second method, the germination was assessed for the seeds of four weedy species buried at three depths for different durations of solarization. The results confirmed the great sensitivity of L. mucronata and C. bursa-pastoris seeds to solarization, as all had not germinated after 15 days of solarization, even at the 15 cm depth. The seeds of E. colona , however, were less sensitive after 15 days of solarization, especially at 7.5 cm and 15 cm, respectively. The seed germination method confirmed the resistance of the P. oleracea seeds to solarization. The results emphasized the importance of the germination test to provide accurate predictions about the spatial and temporal changes of the soil seed bank in solarized farms. This would help to determine the optimal duration of solarization in each farm, depending on the kind of weeds infesting the farm.  相似文献   

11.
The effects of pre-planting solarization or fumigation with metham-sodium of sand-mulched soil on fusarium wilt of watermelon in plastic house culture were investigated at Almeria, south-eastern Spain. In two trials, 2 months' solarization increased the average maximum soil temperature by c. 5°C to 44-48° C at 10 cm depth and by 4-5° C to 40-42° C at 20-30 cm. The amount of Fusarium oxysporum in the upper 15 cm of a naturally infested soil was reduced by solarization and by fumigation. During the 9 months following treatment, the F. oxysporum population stabilized at a low level in soil solarized for 2 months, but fluctuated in soil solarized for 1 month and increased in fumigated soil. The amount of wilt in watermelon sown into this soil after treatment was generally low; plants growing in solarized or fumigated soil suffered less wilt than plants in untreated soil but the differences were not significant. In a soil artificially infested with the highly pathogenic race 2 of F. oxysporum f. sp. niveum, F. oxysporum populations were greatly reduced following solarization or fumigation, and fluctuated erratically thereafter. Solarization for 2 months completely controlled wilt in watermelon and gave a fruit yield almost five times that of plants in untreated soil. Solarization for 1 month only slowed disease development slightly but gave a yield more than twice that in untreated soil. Fumigation with metham-sodium retarded disease development considerably and tripled fruit yield. Plant performance was significantly better in soil solarized for 2 months than in uninfested control soil, suggesting beneficial effects of this treatment additional to wilt control.  相似文献   

12.
Soil solarization is not broadly adopted as a soil deinfestation method mainly because of its long duration (4–6 weeks). We present evidence showing that the duration of solarization can be reduced to nearly half using impermeable plastics and/or low doses of methyl bromide, while still ensuring effective control of Fusarium oxysporum f. sp. cucumerinum. Chlamydospores of a pathogenic isolate of F. o. cucumerinum, formed in sterile soil, were inserted into nylon mesh envelopes and incorporated into the soil prior to treatment at 20‐ and 30‐cm soil depths. Soil treatments included untreated control, soil solarization with polyethylene or impermeable plastics (LMG), and soil solarization with polyethylene or impermeable plastics plus 20 g m?2 methyl bromide. According to the effects on artificial inocula of F. o. cucumerinum checked at weekly intervals for 4 weeks, soil solarization with impermeable plastics was most effective in destroying pathogen populations even two weeks after soil covering.  相似文献   

13.
MTB-951 is a potential mycoherbicide using a fungal plant pathogen ( Drechslera monoceras ) isolated from native Echinochloa species in Japan. Conidia of this pathogen were used as the active ingredient and its herbicidal performance was examined in a greenhouse. The efficacy of MTB-951 on Echinochloa crus-galli L. was higher in deep water (7–9 cm) than in relatively shallow water (3–5 cm). In a postemergence application, the efficacy decreased as the leaf stage of E. crus-galli proceeded between the 1 and 2.5 leaf stage. For example, the control ratio (%) of E. crus-galli was 95% when applied at the 1 leaf stage, and 72% at the 2.5 leaf stage in 5 cm water. Generally, mycoherbicidal efficacy was less when applied pre-emergence rather than postemergence. Efficacy was also influenced by the duration of submergence in deep water. For example, when water depth was kept at 5 cm for more than 7 days after application and then decreased down to 3 cm, the efficacy was high. However, when the water depth was kept at 5 cm for less than 7 days, the efficacy was low. Efficacy was lower under high temperatures (35°C/25°C, day/night) than under low temperatures (25°C/15°C, day/night). Water management, application timing and temperature are important factors on herbicidal efficacy of MTB-951 to control E. crus-galli .  相似文献   

14.
G. BROD 《Weed Research》1968,8(2):115-127
Summary. 1. Echinochloa crus-galli is a typical grass weed of root crops in warmer regions, germinating late and thus covering the soil at a late stage. It originates in central and east Asia and is now a weed of world-wide importance.
2. High temperatures are necessary for germination which begins in spring, but not before the soil temperature reaches 15° C. Minimum, optimum and maximum germination temperatures of 13° C, 20–30° C and 40° C were found in S.W. Germany.
3. Seeds of E. crus-galli are dormant during the first 3–4 months after harvest. Those developing relatively early in the growing season require rather longer for after-ripening than seeds which mature later.
4. For optimum germination, water saturation of the soil of 70–90% is required.
5. Soil acidity has some influence, and there is an apparent germination optimum around neutrality. Light also induces germination.
6. Seeds can emerge from a relatively wide range of depths. Greatest emergence and the strongest plants resulted from seeds at 2–6 cm, but even from 10 cm a high percentage of seedlings is likely to emerge.
7. Further development proceeds rapidly. The first panicles arc already formed 6–7 weeks after emergence in favourable conditions, but full maturity is possible only if there are high temperatures in late summer.
8. E. crus-galli is a hygrophilous species, with best development on medium heavy soil, sandy loam or loamy sand with sufficient water supply.
9. E. crus-galli is indifferent to the lime content of the soil.
10. Best development occurs with high fertility, and a rich supply of nitrogen is especially important.
Recherches sur la biologie et écologie du panic Echinochloa crus-galli (L.) Beauv.  相似文献   

15.
ABSTRACT Soil solarization was shown to be cost effective, compatible with other pest management tactics, readily integrated into standard production systems, and a valid alternative to preplant fumigation with methyl bromide under the tested conditions. Solarization using clear, photoselective, or gas-impermeable plastic was evaluated in combination with metham sodium, 1,3-dichloropropene + chloropicrin, methyl bromide + chloropicrin, pebulate, or cabbage residue. Strip solarization, applied to 20-cm-high, 0.9-m-wide beds, was conducted to achieve compatibility with standard production practices and resulted in soil temperatures 2 to 4 degrees C above those temperatures resulting when using conventional flatbed solarization. Soil temperatures were 1 to 2 degrees C higher at the edges of the raised beds, eliminating any border effects associated with solarization. Following a 40- to 55-day solarization period, the plastic was painted white and used as a production mulch for a subsequent tomato crop. The incidence of Southern blight and the density of Paratrichodorus minor and Criconemella spp. were lower (P < 0.05) in solarized plots. No differences (P < 0.05) in the incidence of Fusarium wilt and the density of nutsedge and Helicotylenchus spp. were observed between plots receiving solarization and plots fumigated with a mixture of methyl bromide + chloropicrin. The severity of root galling was lower (P < 0.05) when soil solarization was combined with 1,3-dichloropropene + chloropicrin (16.2 + 3.4 g/m(2)) and a gas-impermeable film. The incidence of bacterial wilt was not affected by soil treatments. Marketable yields in plots using various combinations of soil solarization and other tactics were similar (P < 0.05) to yields obtained in plots fumigated with methyl bromide + chloropicrin. The results were validated in several large scale field experiments conducted by commercial growers.  相似文献   

16.
The soil-borne plant pathogen Phytophthora cinnamomi is widely distributed in the jarrah ( Eucalyptus marginata ) forest of Western Australia. Infested areas of the forest are mined for bauxite and the presence of the pathogen could after the survival of trees re-established after mining. Monitoring of 21 revegetated bauxite mined areas found that survival of jarrah and marri ( Eucalyptus calophylla ) trees was high (85–92% and 93–99%, respectively) after 5–7 years but P. cinnamomi was recovered from dead trees. To identify trees for more detailed study, plant symptoms of stress such as suppressed growth, wilting, yellowing of crown, coppice and epicormic growth and visible stem lesions were used. Over a period of 15 months, 30 E. marginata and 28 E. calophylla were carefully excavated and examined for lesions and the presence of P. cinnamomi. P. cinnamomi was consistently isolated from the lignotuber and collar regions of both hosts but never from the roots alone, except in one instance from E. calophylla where it was isolated from a non-lesioned root. In E. calophylla , the lignotuber appears to be very susceptible to invasion by P. cinnamomi in contrast to the roots which appear resistant. The invasion of the pathogen into the lignotuber and collar regions of both species was consistently associated with ponding of water around the plants. This ponding persists for many hours to days after rain and appears to provide an infection court for P. cinnamomi. Development of rehabilitation procedures to reduce this ponding will minimize the risk of tree deaths caused by this pathogen.  相似文献   

17.
Mimosa pudica (common sensitive plant) is a problematic weed in many crops in tropical countries. Eight experiments were conducted to determine the effects of light, seed scarification, temperature, salt and osmotic stress, pH, burial depth, and rice residue on the germination, seedling emergence, and dormancy of M. pudica seeds. Scarification released the seeds from dormancy and stimulated germination, though the germination of the scarified seeds was not influenced by light. The scarification results indicate that a hard seed coat is the primary mechanism that restricts germination. The germination increased markedly with the exposure to high temperature "pretreatment" (e.g. 150°C), which was achieved by placing non-scarified seeds in an oven for 5 min followed by incubation at 35/25°C day/night temperatures for 14 days. The germination of the scarified seeds was tolerant of salt and osmotic stress, as some seeds germinated even at 250 mmol L−1 NaCl (23%) and at an osmotic potential of −0.8 MPa (5%). The germination of the scarified seeds was >74% over a pH range of 5–10. The seedling emergence of the scarified seeds was 73–88% at depths of 0–2 cm and it gradually decreased with an increasing depth, with no seedling emergence at the 8 cm depth. The rice residue applied to the soil surface at rates of ≤6 t ha−1 did not influence the seedling emergence and dry weight. The information gained from this study identifies some of the factors that facilitate M. pudica becoming a widespread weed in the humid tropics and might help in developing components of integrated weed management practises to control this weed.  相似文献   

18.
Downer AJ  Menge JA  Pond E 《Phytopathology》2001,91(9):847-855
ABSTRACT A series of samples were taken from mulched and unmulched trees starting at the surface of mulch or soil to a 15 cm soil depth, forming a vertical transect. Saprophytic fungi isolated from the soil samples on rose bengal medium and surveyed visually were most abundant in mulches and at the interface of mulch and soil (P < 0.05). Microbial activity as assayed by the hydrolysis of fluorescein diacetate was significantly greater in mulch layers than in soils. Cellulase and laminarinase enzyme activities were greatest in upper mulch layers and rapidly decreased in soil layers (P < 0.05). Enzyme activities against Phytophthora cinnamomi cell walls were significantly greater in mulch than in soil layers. When Phytophthora cinnamomi was incubated in situ at the various transect depths, it was most frequently lysed at the interface between soil and mulch (P < 0.001). Roots that grew in mulch layers were significantly less infected with Phytophthora cinnamomi than roots formed in soil layers. In mulched soil, roots were commonly formed at the mulch-soil interface where Phytophthora populations were reduced, whereas roots in unmulched soil were numerous at the 7.5 cm depth where Phytophthora cinnamomi was prevalent. Enzyme activities were significantly and positively correlated with each other, microbial activity, and saprophytic fungal populations, but significantly and negatively correlated with Phytophthora recovery.  相似文献   

19.
From 1999 to 2001, a survey on the occurrence of Phytophthora spp. in the rhizosphere soil of healthy and declining oak trees was conducted in 51 oak stands in Turkey. Seven Phytophthora spp. were recovered from six out of the nine oak species sampled: P .  cinnamomi , P .  citricola , P .  cryptogea , P .  gonapodyides , P .  quercina , Phytophthora sp. 1 and Phytophthora sp. 2. The most frequently isolated species, P .  quercina , was very common on slopes susceptible to drought. It occurred in four different climatic zones and on six Quercus spp., suggesting that it is native to oaks. The second most common species, P .  citricola , was separated into three subgroups: type C was recovered only in Anatolia, whereas A and B occurred only in the European part of Turkey. Phytophthora cinnamomi was recovered at one site only, and may not be involved in oak decline in Turkey. The other four species were recovered sporadically. On affected sites there was a significant association between deteriorating crown status and the presence of Phytophthora spp., particularly P .  quercina . The occurrence of Phytophthora species was significantly influenced by soil pH. Stem inoculation tests on oak seedlings revealed that Q .  petraea was the most susceptible species.  相似文献   

20.
Very little research has been done on weed seedbank communities in the northern Great Plains region of the USA. The objectives of this study were to evaluate the effects of management systems on the weed seed banks and to assess the relationship between the weed seed banks and the above-ground weed communities. The seed banks were sampled along a range of areas of above-ground weed diversity in organic and conventional spring wheat production fields near Big Sandy, Montana, over 2 years. Eight 1 m × 0.33 m areas were selected in each field to encompass a wide range of above-ground weed diversity and soil cores were taken in each area to a depth of 20 cm and split in half at 10 cm. The number of seeds recovered from the top 10 cm of soil and the 10–20 cm depth were significantly affected by the sampling year and an interaction between the cropping system and the sampling year. The year was the only significant predictor affecting the weed seedbank diversity at both depths. A significant interaction between the management system and the year observed at the 10–20 cm sampling depth reflected the higher rate of decrease in diversity occurring between 2005 and 2006 in the conventionally managed fields compared with the organic fields. A multivariate ordination indicated that, although the year played a significant role in determining the weed seedbank communities, the management system had a role only during 2006. We failed to detect strong correlations between the above-ground and underground weed communities. The results of this study suggest that, in the studied region, yearly fluctuations in environmental factors have significant impacts on the weed seed banks.  相似文献   

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