A STUDY OF SOME FACTORS AFFECTING THE PATHOGENICITY OF VERTICILLIUM ALBO-ATRUM R. & B.

1943 ◽  
Vol 21c (3) ◽  
pp. 95-117 ◽  
Author(s):  
Colin D. McKeen
Keyword(s):  
Soil Moisture ◽  
Verticillium Wilt ◽  
Sandy Loam ◽  
Disease Incidence ◽  
Plant Residues ◽  
Infested Soil ◽  
Clay Loam ◽  
Susceptible Host ◽  
Soil Temperatures ◽  
Verticillium Albo Atrum

An epidemic of Verticillium wilt, which occurred in the Niagara Peninsula in 1940, involved many hosts, from seven of which the fungus was isolated; the isolates were compared with respect to cultural characters and pathogenicity. Although the isolates varied slightly in morphology and pathogenicity, they are all referred to Verticillium albo-atrum R. & B.A considerable residuum of inoculum was demonstrated in the soil in May, 1941, following the 1940 epidemic. The optimum temperature for vegetative growth of the fungus is about 24 °C. which closely approximates the optimum for disease incidence. Wilt symptoms appear slightly sooner and the temperature range of heavy disease incidence is broader (18° to 29 °C.) at high than at optimum soil moisture (21° to 27 °C.). The fungus persisted and was equally aggressive after three months in fine sandy loam, medium clay loam, and red clay loam under cropped and fallow conditions, except when the soil was fallow and dry during the period. Growing a susceptible host in infested soil for three months did not influence the activity of Verticillium more than did an immune host. Inoculum in a resting condition must be incorporated in moist soil a few days before it can readily infect plants. The addition of green plant residues and two organic acids caused a slight suppression of fungous activity.Air and soil temperatures and precipitation for May, June, July, and August for 1939, 1940, 1941, and 1942 have been examined. It was found that soil temperatures high enough for disease development are not likely to be encountered before late June and then the disease developed seriously only when the soil moisture was uniformly high during the months of May, June, and July. The relative infrequency of serious outbreaks of Verticillium wilt on the Niagara Peninsula thus appears to be due to the low soil moisture that ordinarily pertains during that part of the growing season when soil temperatures are high enough to favour the fungus.

Soil Persistence of Dinitramine

Weed Science ◽  
1980 ◽  
Vol 28 (6) ◽  
pp. 650-654 ◽  
Author(s):  
J. A. Poku ◽  
R. L. Zimdahl
Keyword(s):  
Mathematical Model ◽  
Soil Moisture ◽  
Field Data ◽  
Soil Moisture Content ◽  
Sandy Loam ◽  
Clay Loam ◽  
First Order ◽  
Soil Persistence ◽  
Herbicide Concentration ◽  
Increasing Temperature

The effects of soil temperature, moisture, and herbicide concentration on the rate of degradation of dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) were measured in clay loam and sandy loam in the laboratory. In sandy loam, the rate of degradation increased with increasing temperature. In clay loam, the rate of degradation increased from 10 to 30 C and decreased at 40 C. Soil moisture content influenced the rate of degradation in the following order: 22>11>>2.2% (air-dry) for clay loam and 12.0 = 6.0>>0.5% (air-dry) for sandy loam. First-order half-lives ranged from 3.2 at 30 C to 47 weeks at 10 C in clay loam, and 2.3 at 40 C to 31 weeks at 10 C in sandy loam. Applications in 2 yr did not cause buildup of dinitramine in the field. A mathematical model was used in an attempt to correlate laboratory and field data.

The effects of soil compaction, soil moisture and soil type on growth and nodulation of soybean and common bean

1998 ◽  
Vol 78 (4) ◽  
pp. 571-576 ◽  
Author(s):  
B. R. Buttery ◽  
C. S. Tan ◽  
C. F. Drury ◽  
S. J. Park ◽  
R. J. Armstrong ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Adverse Effects ◽  
Plant Growth ◽  
Water Supply ◽  
Common Bean ◽  
Soil Type ◽  
Soil Compaction ◽  
Sandy Loam ◽  
Clay Loam ◽  
Reduced Water

In field tests we have observed year-to-year differences in the severity of the effects of soil compaction on nodulation and growth of common bean; these differences appeared to be related to the amount of rainfall during the growing season. We decided to use better controlled conditions in the greenhouse, and extend the scope of the study to another legume crop and a different soil type, in order to investigate the hypothesis that copious water supply alleviates the adverse effects of soil compaction on nodulation and plant growth.The effects of two levels of soil compaction and of high and low water supply on the growth and nodulation of common bean and soybean were investigated in separate pot tests using a Fox sandy loam and a Brookston clay loam soil.Root growth of both species was severely restricted by dry compacted conditions. Plant growth as a whole was clearly reduced by both increased compaction and by reduced water supply, presumably mediated by the effects on root growth. The effect of reduced water supply was more severe in the highly compacted pots, and more severe in the clay loam than in the sandy loam.In the sandy loam, low moisture reduced nodule numbers and weights in both species, while increased bulk density reduced the numbers of nodules but not the dry weights. In the clay loam, nodule weights and numbers were very low, presumably, owing to high levels of nitrate, which may have resulted from mineralization of soil organic matter during storage.A generous supply of water obviously alleviated some of the adverse effects of soil compaction on plant growth. This is in general agreement with results of earlier field trials, where severity of the effects of soil compaction varied with the quantity of rainfall. Key words: Soybean, common bean, soil compaction, soil moisture, nodulation, bulk density

scholarly journals Factors Influencing Development of Root Rot on Ginseng Caused by Cylindrocarpon destructans

2005 ◽  
Vol 95 (12) ◽  
pp. 1381-1390 ◽  
Author(s):  
Mahfuzur Rahman ◽  
Zamir K. Punja
Keyword(s):  
Soil Moisture ◽  
Root Rot ◽  
Disease Incidence ◽  
Hyphal Growth ◽  
Infested Soil ◽  
Cylindrocarpon Destructans ◽  
Virulent Isolate ◽  
Weakly Virulent ◽  
Highly Virulent

The fungus Cylindrocarpon destructans (Zins) Scholten is the cause of root rot (disappearing root rot) in many ginseng production areas in Canada. A total of 80 isolates of C. destructans were recovered from diseased roots in a survey of ginseng gardens in British Columbia from 2002-2004. Among these isolates, 49% were classified as highly virulent (causing lesions on unwounded mature roots) and 51% were weakly virulent (causing lesions only on previously wounded roots). Pectinase and polyphenoloxidase enzymes were produced in vitro by C. destructans isolates when they were grown on pectin and phenol as a substrate, respectively. However, highly virulent isolates produced significantly (P < 0.001) higher enzyme levels compared with weakly virulent isolates. Histopathological studies of ginseng roots inoculated with a highly virulent isolate revealed direct hyphal penetration through the epidermis, followed by intracellular hyphal growth in the cortex. Subsequent cell disintegration and accumulation of phenolic compounds was observed. Radial growth of highly and weakly virulent isolates on potato dextrose agar was highest at 18 and 21°C, respectively and there was no growth at 35°C. Mycelial mass production was significantly (P ≤ 0.01) lower at pH 7.0 compared with pH 5.0. To study the effects of pH (5.0 and 7.0) and wounding on disease development, ginseng roots were grown hydroponically in Hoagland's solution. Lesions were significantly larger (P < 0.001) at pH 5.0 compared with pH 7.0 and wounding enhanced disease by a highly virulent isolate at both pHs. In artificially infested soil, 2-year-old ginseng roots were most susceptible to Cylindrocarpon root rot among all root ages tested (1 to 4 years) when evaluated using a combined scale of disease incidence and severity. Root rot severity was significantly (P < 0.002) enhanced by increasing the inoculum density from 3.45 × 102 CFU/g of soil to 1.86 × 103 CFU/g of soil. Disease severity was higher at 20°C compared with 15 and 25°C and at -0.02 MPa soil moisture compared with -0.005 and -0.001 MPa. A significant interaction between soil moisture and temperature was observed for root rot severity.

scholarly journals Relationship Between the Inoculum Density of Verticillium dahliae and the Progress of Verticillium Wilt of Olive

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1372-1378 ◽  
Author(s):  
F. J. López-Escudero ◽  
M. A. Blanco-López
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Disease Incidence ◽  
Olive Tree ◽  
Temporal Variations ◽  
Inoculum Density ◽  
Infested Soil ◽  
Initial Inoculum ◽  
Progress Curve ◽  
Olive Trees

An experiment was conducted in microplots which were artificially infested with a defoliating isolate of Verticillium dahliae using seven different treatments of inoculum densities ranging from 0 to 10 microsclerotia per gram of soil (ppg). The experiment was conducted in Andalucía (southern Spain), and the susceptible Spanish olive cv. Picual was used to determine the relationship between pathogen inoculum density and the progress of Verticillium wilt of olive (VWO). The inoculum, produced on a sodium pectate cellophane medium, was found to efficiently infect olive trees. Symptoms first appeared 30 weeks after the trees were transplanted into infested soil. Periods of increasing disease incidence in the following seasons and years were mainly during spring and autumn, particularly in the second year after planting. Olive trees exhibited a high susceptibility to the defoliating pathotype of the pathogen, even at very low inoculum levels; in fact, diseased plants were encountered throughout the experiment regardless of the inoculum density treatment. Inoculum densities greater than 3 ppg in the soil resulted in final disease incidence greater than 50% for the trees after 2.5 years. Therefore, these inoculum densities must be considered very high for olive trees. There were no differences in final disease incidence, mean symptom severity, or area under the disease progress curve between plots infested with 10 or 3.33 ppg, whereas other treatments exhibited lower values for each of these disease parameters. The temporal variations of disease incidence and severity were highly correlated for the higher inoculum density treatments, with r2 values ranging from 0.92 to 0.84 for disease incidence and from 0.93 to 0.88 for severity. However, r2 was slightly lower for the treatments involving lower inoculum densities of the pathogen in microplots. The slopes of the linear regression curves were statistically different for nearly all the inoculum density treatments. Positive correlation was found between the initial inoculum density and final disease incidence values after the study period that was accurately explained by mathematical models. The results suggest that susceptible olive cultivars should not be planted in soils infested with virulent defoliating pathotypes of V. dahliae. Results also clarify that inoculum density levels obtained from field soil analyses can be used for establishing a risk prediction system with a view to controlling VWO in olive tree plantations.

Effects of Incorporating or Burning Straw, and of Different Cultivation Systems, on Winter Wheat Grown on Two Soil Types, 1985–91

1995 ◽  
Vol 124 (2) ◽  
pp. 173-194 ◽  
Author(s):  
R. D. Prew ◽  
J. E. Ashby ◽  
E. T. G. Bacon ◽  
D. G. Christian ◽  
R. J. Gutteridge ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Sandy Loam ◽  
Disease Incidence ◽  
Soil Types ◽  
Silty Clay ◽  
Clay Loam ◽  
Silty Clay Loam ◽  
Cultivation Systems ◽  
Sharp Eyespot ◽  
Take All

SUMMARYDisposal methods for straw from continuous winter wheat were tested on two soil types, a flinty silty clay loam and a sandy loam, over 7 years (1985–91). The methods tested were burnt or chopped straw in full factorial combination with four cultivation methods (tined to 10 cm, tined to 10 cm then to 20 cm; ploughed to 20 cm; tined to 10 cm then ploughed to 20 cm). Measurements were taken to determine the effects on crop establishment and growth, pest and disease incidence, and the consequent effects on yield. Another experiment (1985–91) on the flinty silty clay loam site, investigated the interactions between straw treatments (burnt, baled or chopped in plots that were all shallow cultivated to 10 cm) and five other factors; namely, time of cultivation, insecticides, molluscicides, fungicides and autumn nitrogen. All the straw x cultivation systems allowed satisfactory crops to be established but repeated incorporation of straw using shallow, non-inversion cultivations resulted in very severe grass-weed problems. Early crop growth, as measured by above-ground dry matter production, was frequently decreased by straw residues, but the effect rarely persisted beyond anthesis. Pests were not a problem and their numbers were not greatly affected either by straw or cultivation treatments, apart from yellow cereal fly which, especially on the heavier soil, was decreased by treatments which left much straw debris on the soil surface. Incorporating straw also caused no serious increases in the incidence of diseases. Indeed, averaged over all sites and years, eyespot and sharp eyespot were both slightly but significantly less severe where straw was incorporated than where it was burnt. Eyespot, and even more consistently sharp eyespot, were often more severe after ploughing than after shallow, non-inversion cultivations. Effects on take-all were complex but straw residues had much smaller effects than cultivations. Initially the disease increased most rapidly in the shallow cultivated plots but these also tended to go into the decline phase more quickly so that in the fourth year (fifth cereal crop) take-all was greater in the ploughed than in the shallow cultivated plots. On average, yields did not differ greatly with straw or cultivation systems, although there were clear effects of take-all in those years when the disease was most severe. In the last 2 years, yields were limited by the presence of grass weeds in the plots testing chopped straw incorporated by tining to 10 cm.

PEA APHID CONTROL AND DI-SYSTON RESIDUES IN GREENHOUSE PEAS AS AFFECTED BY RATES OF APPLICATION, SOIL TYPE, AND SOIL MOISTURE

1965 ◽  
Vol 45 (6) ◽  
pp. 571-577 ◽  
Author(s):  
H. B. Specht ◽  
D. Chisholm
Keyword(s):  
Soil Moisture ◽  
Acyrthosiphon Pisum ◽  
Sandy Loam ◽  
Exchange Capacity ◽  
Pea Aphid ◽  
Clay Loam ◽  
Base Exchange ◽  
Application Rates ◽  
Aphid Control ◽  
Pea Aphids

Furrow applications of Di-syston (O,O-diethyl S-2- (ethylthio)ethyl phosphorodithioate) for control of pea aphids, Acyrthosiphon pisum (Harris), on peas under greenhouse conditions showed that the Di-syston content of the plants reflected the application rates; absorption of Di-syston by the plants was greater on sandy loam than on clay loam; concentrations of Di-syston tended to be highest in the basal third of the pea vines and progressively lower in the middle and top thirds of the plants; slight phytotoxicity occurred on the lower leaves at 4 and 32 lb per acre (4.48 and 35.87 kg/ha) of toxicant but yields were not affected; soil moisture did not affect the uptake of Di-syston in the plant. Differences in uptake may be attributed to differences in the base exchange capacity of the soils.

scholarly journals Effect of Grafting on Growth, Yield, and Verticillium Wilt of Eggplant

HortScience ◽  
2003 ◽  
Vol 38 (2) ◽  
pp. 183-186 ◽  
Author(s):  
Fotios Bletsos ◽  
Costas Thanassoulopoulos ◽  
Demetrios Roupakias
Keyword(s):  
Verticillium Wilt ◽  
Wild Species ◽  
Disease Incidence ◽  
Yield Reduction ◽  
Infested Soil ◽  
Total Production ◽  
Solanum Torvum ◽  
Average Value ◽  
Positive Effects ◽  
Early Production

Eggplant (Solanum melongena L.) seedlings (`Tsakoniki') were grafted by hand on the Verticillium dahliae Kleb. resistant wild species Solanum torvum Sw. (GST) and Solanum sisymbriifolium Lam. (GSS). Grafted and nongrafted eggplants were transplanted to a fumigated soil with methyl bromide and to infested soil with microsclerotia of V. dahliae. Grafted plants were more vigorous, as measured by plant height, main stem diameter, and root system weight, than the nongrafted `Tsakoniki'. This resulted in an increased early production (GST, 45.5%; GSS, 18.4%) and late production (GST, 69.3%; GSS, 59.2%) as compared to the noninfected controls. The mean yield reduction (over years) in early production caused by the disease, as compared to the controls grown in fumigated soil, was 29.4%, 36.6%, and 77.9% for eggplant grafted on S. torvum, S. sisymbriifolium, and nongrafted plants, respectively. This yield reduction in total production was 6.9%, 20.5%, and 56.8%, respectively. The disease incidence in ungrafted plants was 96% and 100% during early and late harvest periods. In contrast, the disease incidence in grafted plants was significantly lower, averaging 28.1% (GST) and 52.6% (GSS) in early production, and 37.6% and 79.3%, respectively, in late production. Solanum torvum was found more resistant than S. sisymbriifolium, because grafted infected plants developed mild symptoms, as indicated by significantly lower leaf symptom index (average value 1.2 and 2.22) and disease index (average value 1.55 and 3.38), respectively. In conclusion, grafting of eggplant on either wild species had positive effects on growth, production, and verticillium wilt control.

Influence of Soil Temperature and Moisture on Terbutryn Activity and Persistence

Weed Science ◽  
1974 ◽  
Vol 22 (6) ◽  
pp. 571-574 ◽  
Author(s):  
Chu-Huang Wu ◽  
P. W. Santelmann ◽  
J. M. Davidson
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Incubation Temperature ◽  
Sandy Loam ◽  
Distribution Coefficients ◽  
Measured Parameter ◽  
Soil Conditions ◽  
Soil Temperatures ◽  
Dry Soil ◽  
Soil Temperature And Moisture

The phytotoxicity of soil-applied terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] to wheat (Triticum aestivumVill.) was significantly affected by soil moisture and soil temperature. Distribution coefficients (Kd) provided a better indication of the phytotoxicity of terbutryn to wheat than any single measured parameter contributing to herbicide adsorption by the soil. Soil temperatures and soil moisture levels suitable for good plant growth tended to enhance the phytotoxicity of terbutryn. No phytotoxic levels of terbutryn to wheat were detected in Teller sandy loam after 20 weeks of incubation at above 10C and 14% soil moisture by weight. However, phytotoxicity to wheat was observed in air-dry terbutryntreated soil after an incubation period of 20 weeks, regardless of incubation temperature. Significant quantities of terbutryn may remain in the field under dry soil conditions.

SOIL MOISTURE AND TEMPERATURE RESPONSE TO SHALLOW TILLAGE IN THE EARLY SPRING

1981 ◽  
Vol 61 (2) ◽  
pp. 455-460
Author(s):  
A. L. DARWENT ◽  
W. G. BAILEY
Keyword(s):  
Soil Moisture ◽  
Surface Soil ◽  
Temperature Response ◽  
Early Spring ◽  
Clay Loam ◽  
Surface Soil Moisture ◽  
Clay Loam Soil ◽  
Soil Temperatures ◽  
Loam Soil

Surface soil moisture was conserved in a loam to clay loam soil receiving a single shallow cultivation in the early spring, while in an unfilled soil it declined markedly. Tillage effects were less marked at deeper depths. Soil temperatures were found to differ only slightly between tilled and untilled soils.

scholarly journals Effect of Planting Configuration, Spring Cover Crop, and Reservoir Tillage on Onion

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 853A-853
Author(s):  
Harlene Hatterman-Valenti* ◽  
Paul Hendrickson
Keyword(s):  
Soil Moisture ◽  
Cover Crop ◽  
Wind Erosion ◽  
Sandy Loam ◽  
Total Yield ◽  
Growing Season ◽  
Field Trials ◽  
Clay Loam ◽  
Raised Bed ◽  
Erosion Protection

Field trials were initiated near Carrington and Absaraka, N.D., on a Heimdal clay loam and a Spottswood sandy loam, respectively to evaluate onion grade and yield in response to planting configuration, spring cover crop, and reservoir tillage. Results from the Carrington and Absaraka locations during 2002 and 2003 showed that colossal-sized onion was the largest grading size obtained (Carrington, 2003) and that the greatest number of colossal onion were from the bed configuration that had a reservoir tillage treatment. The coarser soil texture at Absaraka allowed for spring and fall formed raised bed comparison (2003) in which the fall formed raised bed tended to have greater yields and more marketable onion. Planting configuration resulting in the greatest total yield varied among locations and years but generally increased with reservoir tillage. Soil moisture and temperature monitoring during the early growing season did not differ greatly. However, differences in soil water potentials at the 6“ depth were observed during the last part of the growing season. Cover crop results indicated that a row of canola planted between onion rows for wind erosion protection will reduce onion yields even when ample water is available through routine irrigation. Herbicides for broadleaf control were not applied until onion had two true-leaves due to label restrictions. This delay enabled the canola to grow beyond the recommended stage for broadleaf control and to quickly outgrow the herbicide injury.

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