Growth Of Flue-cured Tobacco Research Articles

The Effect of Flame Sterilization on the Microorganisms in Continuously Cultivated Soil and the Yield and Quality of Tobacco Leaves

Flame disinfection is a new technology that uses high temperatures to kill pathogens and control soil-borne diseases. In order to determine the feasibility of applying flame disinfection technology to flue-cured tobacco, a field experiment was conducted in Pianpo Village (test site I) and Lühuai Village (test site II), Luquan County, Yunnan Province. The effects of flame disinfection on soil-borne disease control, flue-cured tobacco growth agronomic traits, the tobacco yield and quality, and the soil microbial community in the flue-cured tobacco field were investigated. The results were as follows. (1) After flame disinfection, the control rates of the four main soil-borne diseases—black root rot, root rot, wilt, and root knot nematodes—were all over 70%. (2) Samples were taken from the experimental site of Pianpo Village at 0 and 114 days after disinfection (tobacco boom period) to study the effects of soil microbial communities by high-throughput sequencing. Compared with the control group, after 0 days of flame disinfection, the abundance of bacterial actinobacteria, Nocardia, Streptomyces, and fungal ascomycetes decreased, while the abundance of bacterial Proteobacteria, Bacteroidetes, Arthrobacter, and mycospora increased. After 114 days of disinfection, the abundance of bacterial actinobacteria, Proteobacteria, chloromyces, and fungal ascomycetes decreased. The abundance of Mortierella was recovered, the abundance of Gibberella and Fusarium increased, and the abundance of Trichospora and Basidiomycetes decreased in both periods. (3) After flame disinfection treatment, the tobacco yield in the two experimental areas was increased by 50.80% and 54.70%, respectively, and the proportion of high-quality tobacco was also increased. In conclusion, flame disinfection before tobacco planting can improve the soil conditions, effectively control soil-borne tobacco diseases, and improve the quality and yield of tobacco leaves.

Tobacco/Salvia miltiorrhiza Intercropping Improves Soil Quality and Increases Total Production Value

Unreasonable cultivation methods and management measures have led to widespread obstacles in tobacco continuous cropping in planting areas, resulting in reduced tobacco yield and soil degradation. Therefore, intercropping tobacco with other crops is an effective strategy to improve continuous cropping barriers. In this study, flue-cured tobacco NC102 and conventional planting varieties of Salvia miltiorrhiza were used as materials, and four treatments of flue-cured tobacco monoculture (CK), flue-cured tobacco, and Salvia miltiorrhiza at a ratio of 1:1 (TS11), 2:2 (TS22), and 2:3 (TS23), respectively, were set up to study their effects on soil microorganisms, physical and chemical properties, and yield and quality of flue-cured tobacco. The results showed that intercropping Salvia miltiorrhiza increased the number of soil bacteria and actinomycetes, decreased the number of fungi, and increased the activity of urease and sucrase. The content of available nitrogen and available phosphorus in intercropping Salvia miltiorrhiza soil was significantly higher than that of the flue-cured tobacco monoculture, while the content of available potassium was lower than that of the flue-cured tobacco monoculture. The soil environment was more conducive to the growth of flue-cured tobacco. Compared with the flue-cured tobacco monoculture, the proportion of superior tobacco in intercropping Salvia miltiorrhiza increased by 2.2–3.4%, and the ratio of potassium to chlorine in leaves of different parts of flue-cured tobacco increased by 12.3–75.0%. The content of total sugar and soluble sugar in middle and upper leaves of intercropping flue-cured tobacco was higher than that of the flue-cured tobacco monoculture, which improved the quality of flue-cured tobacco. From the analysis of the chemical composition of tobacco leaves, TS11 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 1:1) had the best treatment effect, potassium content, total sugar, reducing sugar content, and potassium chloride ratio of flue-cured tobacco were the highest, the chlorine content was the lowest, and the quality was better than other treatments. From the analysis of total output value, the total output value of TS22 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 2:2) was higher than that of other intercropping treatments. In 2018 and 2019, the total output value increased by 21.3% and 22.4%, respectively, compared with the flue-cured tobacco monoculture. The intercropping advantage was obvious, and the treatment effect was the best.

Exploring the effect of different application rates of biochar on the accumulation of nutrients and growth of flue-cured tobacco (Nicotiana tabacum).

Biochar application has become one of the most potential tools to improve soil fertility and plant growth for sustainable and eco-friendly agriculture. However, both positive and negative effects of biochar application have been recorded on plant growth and soil fertility. This study investigated the impact of different application rates (0, 600, 900, 1200, and 1800 kg/ha) of biochar on the soil nutrient contents, accumulation of nutrients and dry matter in different plant parts, and growth of flue-cured tobacco plants under field conditions. Results demonstrated that soil organic carbon pool and carbon/nitrogen ratio were increased proportionally with the increasing dosage of biochar, 25.54 g/kg and 14.07 g/kg compared with control 17 g/kg and 10.13 g/kg, respectively. The contents of soil total nitrogen were also significantly increased after biochar application in the middle (1.77 g/kg) and late-growth (1.54 g/kg) stages of flue-cured tobacco than in control (1.60 g/kg and 1.41 g/kg, respectively). The contents of soil nitrate nitrogen were also higher under low (600 and 900 kg/ha) application rates of biochar and reduced when higher (1200 and 1800 kg/ha) dosages of biochar were applied. However, it was observed that varying application rates of biochar had no impact on soil ammonium nitrogen content during the growth period of flue-cured tobacco plants. The nutrient accumulation (N, P, K) in different parts of flue-cured tobacco plants was significantly increased under a low application rate of biochar, which enhanced the soil and plant analyzer development values, effective leaves number, growth, dry matter accumulation, and leaf yield of flue-cured tobacco. In contrast, the high biochar application rate (1200 and 1800 kg/ha) negatively impacted nutrient accumulation and growth of flue-cured tobacco. Conclusively, the optimum application of biochar (600 and 900 kg/ha) is beneficial for plant growth, soil fertility, accumulation of nutrients, and dry matter in different plant parts. However, excessive biochar application (> 900 kg/ha) could inhibit flue-cured tobacco plant growth. This study provides a theoretical foundation for biochar application in tobacco and other crop production to obtain agricultural sustainability and economic stability.

Moderate Boron Concentration Beneficial for Flue-Cured Tobacco (Nicotiana tabacum L.) Seedlings Growth and Development

Boron (B) deficiency is a common phenomenon in most tobacco-planting areas in Yunnan, China. In 2020 and 2022, hydroponic experiments that contained B in a concentration gradient of 0.000, 0.125, 0.250, 0.750, 5.000, 10.000, 20.000, and 40.000 mmol L−1 were conducted to investigate tobacco cultivar K326′s agronomic traits, photosynthetic performance, antioxidant enzymes, and boron and nicotine concentration. As B concentration increased, indices including leaves biomass and net photosynthetic rate (Pn) generally increased first and then decreased, which was in contrast to antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). With increasing B concentration, boron content in tobacco seedlings increased significantly by 24.00~96.44%, while decreased nicotine content by 21.60~82.03%. The highest biomass and photosynthetic performance were obtained within 0.75 and 5.00 mmol L−1 treatments. The results of the sandy soil pot verification experiment were similar to the hydroponic experiment obtained. The beneficial mechanism of moderate B on tobacco seedlings is to maintain cell structure integrity, enhance photosynthetic capability, and promote root growth. Consequently, the optimum B concentration for tobacco seedlings is 0.75~5.00 mmol L−1, and applying 0.25~0.50 B kg hm−1 in soil under available B insufficiency could meet the needs of the growth of flue-cured tobacco.

Retracted: Cake Fertilizer and Humic Acid on Soil Nutrients and Growth of Flue-cured Tobacco under VR vision

Tobacco is an important economic crop with high economic value. At present, China’s tobacco planting area and total output ranks first in the world, and the tobacco industry plays an important role in China’s economic development. Based on the above background, the purpose of this study was to study the effects of cake fertilizer and humic acid on soil nutrients and growth of Flue-cured Tobacco under VR vision. The effects of humic acid fertilizer and cake fertilizer on the growth, nitrogen, phosphorus, potassium content, nicotine content and chemical composition of flue-cured tobacco were studied by using randomized block test method with no fertilization as blank control. The causes of improving yield and quality of flue-cured tobacco were discussed, The results showed that humic acid and cake fertilizer improved the dry matter quality of root, stem, lower leaves and middle leaves of flue-cured tobacco, which were 22.69%, 16.52%, 27.25%, 15.44% and 41.50% higher than those of conventional fertilization, respectively. It showed that humic acid fertilizer increased the biomass of Flue-cured tobacco, provided material basis for the improvement of yield and quality, and promoted dry matter accumulation of various organs.

The response of flue-cured tobacco cultivar K326 to nitrogen fertilizer rate in China

AbstractNitrogen is an important element for the growth of flue-cured tobacco and is closely related to its yield and quality. In order to pursue higher economic benefits, excessive fertilizer is generally applied in flue-cured tobacco production, which is unfavourable for the sustainable development of flue-cured tobacco production and for the environment. In 2016 and 2017, experiments using different nitrogen fertilizer application rates in flue-cure tobacco were conducted in Yunnan province, and the changes in agronomic, economic and chemical indices as well as in residual soil nitrogen were compared. Linear and quadratic models were used to compare the response of tobacco to nitrogen fertilizer. With increasing nitrogen fertilizer rate, the proportions of superior to medium tobacco and the average price of flue-cured tobacco leaves initially increased and then decreased, while fresh weight, dry weight and the proportion of inferior tobacco showed the opposite trend. Total sugar and reducing sugar contents decreased with increasing nitrogen fertilizer rates, while total nitrogen and nicotine contents increased. Sensory evaluation scores had the highest value when 90 kg N/ha and 120 kg N/ha were applied. Soil nitrate contents increased as nitrogen fertilizer rate increased. The quadratic model was suitable for the response of cultivar K326 to nitrogen and 90 kg N/ha could meet the needs of cultivar K326.

Study on Climate Changes for Flue-Cured Tobacco Growth in Chenzhou City of Hunan Province

Chenzhou city is the most typical region of Nanling Hill Ecological Zone of flue-cured tobacco with of aroma style of burnt sweet and pure sweet in China and is the largest planting region of flue-cured tobacco in Hunan province. It is of significance to study the changes of climatic parameters with time because climate is the most important factor in determining the growth, yield and quality of flue-cured tobacco. In this study, the data of climatic parameters including cumulative sunshine hours(S), mean temperature (T) and cumulative precipitation (P)from 1952 to 2018 in Chenzhou were used to analyze their changes at the scales of year, whole field period and growing period of flue-cured tobacco. The results showed that at the scale of year, the cumulative S, mean T and cumulative P were ranged from 1029.0 h to 2072.1 h, from 17.1°C to 19.5°Cand from 897.1 mm to 2244.6 mm, with the means of 1449.7 h, 18.1°C and 1482.5 mm, respectively. At the scale of whole field period of flue-cured tobacco, the cumulative S, mean T and cumulative P were ranged from 298.1 h to 807.2 h, from 21.2°C to 23.9°C and from 416.7 mm to 1102.7 mm, with the means of 514.8 h, 22.3°C and 719.0 mm, respectively. At the scale of growing period of flue-cured tobacco, the annual cumulative S were ranged from 70.0 h to 257.2 h, from 77.3 h to 322.5 h and from 131.2 h to 300.3 h in the periods of rooting, flourishing and maturing with the means of 127.8 h, 190.4 h and 197.2 h, respectively. The mean temperatures were ranged from 14.2°C to 18.9°C, from 22.2°C to 26.1°C, and from 25.8°C to 29.6°C with the means of 16.4°C, 24.1°C and 28.0°C, respectively. The annual cumulative P were ranged from 69.9 mm to 553.9 mm, from 133.1 mm to 485.6 mm and from 46.4 mm to 356.8 mm in the periods of rooting, flourishing and maturing with the means of 262.5 mm, 299.9 mm and 153.9 mm, respectively. At the year scale, cumulative S annually decreased by 7.587 h, mean T annually increased by 0.02°C, while cumulative P changed irregularly with insignificantly increasing about by 0.184 mm annually. At the scale of whole field period of flue-cured tobacco, mean T annually increased by 0.0195°C, while both cumulative S and P changed irregularly with insignificantly decreasing by 1.64 h and 1.62 mm annually, respectively. At the scale of growing period of flue-cured tobacco, all climatic parameters changed irregularly except cumulative S in significant positive compound function in the maturing period. Meanwhile, the slight decreasing tendency of cumulative sunshine hours and the slight increasing tendency of cumulative precipitation are disadvantageous while the slight increasing tendency of cumulative precipitation in the maturing period is positive for the growth and quality of flue-cured tobacco.

Characteristics and cause analysis of flue-cured tobacco's water requirements during growth periods in low latitude plateau area, China

Abstract This study aimed to identify the future changes in water requirements (ETc) of flue-cured tobacco by comparing estimated ETc values in the future with previous usage. This will provide a basis for estimating irrigation requirements, and help improve agricultural water use efficiency in the future. The Penman–Monteith equation and the single-crop efficient method were used to calculate the flue-cured tobacco ETc, net irrigation requirement (IR) and net irrigation requirement index (IDI) for the period 1956–2015, and the four Intergovernmental Panel on Climate Change (IPCC) AR5 emission scenarios were used to estimate ETc for two future periods (2046–2065 and 2081–2100) in the central Yunnan Province, China. The results showed that the IDI gradually decreased, along with the growth of flue-cured tobacco. The ETc, IR and IDI values increased with latitude in central Yunnan Province. Furthermore, the variations in the ETc over the whole growth period in the mid-21st century and late-21st century also tended to increase with latitude. In addition, based on the influence of climate variation on the ETc as assessed by a principal component analysis, precipitation was the main factor affecting flue-cured tobacco growth. This study contributes to the establishment of suitable irrigation systems for flue-cured tobacco at every growth stage in central Yunnan Province.

Research on Drought Resisting Effect of Water- Retaining Agent in Flue-Cured Tobacco Production

Pot experiment was used to simulate the effect of water-retaining agent on agronomic trait, root growth and yield of flue-cured tobacco under different drought conditions (including drought in root extension period, drought in flourishing growth period, drought in maturation stage, as well as severe, medium and mild drought in the growth duration) in the growth duration of flue-cured tobacco. The results showed that the effect of water-retaining agent on increasing area of flue-cure tobacco leaf was apparent when simulated irrigation amount was 250mm and 100mm, and water-retaining agent could effectively promote growth of flue-cured tobacco root system. While the yield of flue-cured tobacco was the highest when the simulated irrigation amount was 400mm and applied water-retaining agent was 45g/pot.

Growth and Physiological Characteristics of Flue-cured Tobacco (Nicotiana Tabacum L.) under Selenate-Se Stress

ABSTRACTSelenate is chemically similar to sulfate and can be taken up and assimilated by plants. Although selenium (Se) has not been shown to be essential for higher plants, Se is toxic to many crops in excess. To obtain better insights into the effects of the possible mechanism of how plants alleviates the toxicity of selenate-Se stress, the growth, Se subcellular distribution of fresh leaves, antioxidant enzyme activities and photosynthetic traits of flue-cured tobacco (FCT) through a hydroponic experiment were studied. Results revealed that the growth of FCT reduced remarkably, meanwhile the content of proline and malonaldehyde (MDA) enhanced significantly with selenate-Se stress. Selenium was mainly stored in the cytoplasm and the cell wall in fresh leaves. Cell membrane of lipid peroxidation was aggravated, and it stimulated the improvement of the activities of superoxide dismutase (SOD) and catalase (CAT), and reduced the activity of peroxidase (POD) with the selenate-Se stress. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular CO2 concentration (Ci) of FCT were significantly reduced with selenate-Se treatments; whereas chlorophyll a, chlorophyll b, and total chlorophyll contents (chlorophyll a + b) were not significantly difference between the treatments. The above declared that it had inhibitory effect on physiological characteristics and photosynthesis of FCT with selenate-Se stress. It was inferred that the reasons of photosynthesis reduction were the main limiting factors of stomatal closure and supplying of CO2 deterioration of FCT with selenate-Se stress. Meanwhile, synthesized protein or/and amino acids storage in cytoplasm and fixed by cell wall of Se were the important methods to alleviate the toxicity and enhance the tolerance of selenate-Se stress to FCT.

Effect of continuous cropping on soil nutrients at flue-cured tobacco rhizosphere and non-rhizosphere

In order to clear the effects of flue-cured tobacco continuous cropping on soil nutrients, soil chemical properties in rhizosphere and non-rhizosphere at different continuous cropping years of flue-cured tobacco were analyzed. The results showed that pH both at rhizosphere soil and non-rhizosphere soil, and soil organic matter in non-rhizosphere soil decreased firstly and then increased at different growth and development stages of flue-cured tobacco during continuous cropping years. However, the content of organic matter in rhizosphere increased gradually. The total N and available N both in rhizosphere soil and non-rhizosphere soil, and total K and available K in non-rhizosphere soil showed the trend from decrease to increase, and then decrease again. The total K and available K in rhizosphere, the available P both in rhizosphere and non-rhizosphere soil, and the total P in rhizosphere increased firstly and then decreased. However, the total P in non-rhizosphere soil decreased gradually. With the increase of continuous cropping time, the pH both in rhizosphere and non-rhizosphere soil decreased gradually, however, the contents of organic matter, total N and available N, P and K both in rhizosphere and non-rhizosphere soil appeared to enrichment at different degrees. The pH at rhizosphere soil was lower than that at non-rhizosphere soil, however, the content of organic matter, total N and available N, P and K in rhizosphere soil were higher than those in non-rhizosphere soil. Continuous cropping of flue-cured tobacco changed a reasonable proportion of available nutrients both in rhizosphere and non-rhizosphere soil, which could not meet the vast demand for the growth of flue-cured tobacco. Compared with available N and P, continuous cropping resulted in the lack of available K in rhizosphere soil and the enrichment of available K in non-rhizosphere soil.

Selenium uptake, speciation and stressed response of Nicotiana tabacum L.

The research on the function and mechanism of selenium (Se) is of great significance for the development of Se-enriched agricultural products. In this paper, uptake, speciation distribution, the effects on the flue-cured tobacco growth and antioxidant system of Se at different levels (0–22.2mgSekg−1) were studied through a pot experiment, aiming to clarify flue-cured tobacco's response to Se stress and the relationship between Se speciation and antioxidant system. The results showed that the leaf area and number, the biomass and the chlorophyll content reached the maximum at 4.4mgkg−1 of Se treatment. Selenium at low levels (≤4.4mgkg−1) stimulated the growth of flue-cured tobacco by elevating the capability of antioxidant stress and reducing the malondialdehyde (MDA) content to 0.6–0.8 times of that of the control. However, high Se levels (≥11.1mgkg−1) depressed the capability of antioxidant stress and raised the MDA content to 1.5-fold of that of the control, and meanwhile the biomass of the aboveground parts and underground parts declined notably. The Se content in different parts of flue-cured tobacco significantly increased with the growth of Se levels. The range of Se content in roots, leaves and stems at 2.2–22.2mgkg−1 of Se treatment were 16.7–58.6mgkg−1, 2.6–37.3mgkg−1 and 2.2–10.3mgkg−1, respectively. According to the detection of different Se speciation, only selenocysteine (SeCys) was detectable in leaves at 2.2mgkg−1 Se treatment; SeCys, selenite [Se(IV)]and selenate [Se(VI)] were detected in flue-cured tobacco leaves at Se treatment (≥4.4mgkg−1), which accounted for 4.6–10%, 9–18.7% and 71–86% respectively; SeCys, selenomethionine (SeMet) and Se(IV) were detected in roots, and organic selenium(66–84%) was the main Se species at Se≤11.1mgkg−1 treatment; four Se species [SeCys, SeMet, Se(IV) and Se(VI)] were detected in flue-cured tobacco roots, and the main Se species was inorganic Se (60%) at 22.2mgkg−1 Se treatment. That was to say, the percentage of organic Se species (SeCys and SeMet in flue-cured tobacco leaves and root) declined, whereas the ratio of inorganic Se species [Se(IV) and Se(VI)] increased with the growth of Se levels. The correlation analysis showed that the superoxide dismutase (SOD) activity as well as the glutathione (GSH) and MDA contents were positively correlated with the Se(IV) and Se(VI) contents at P<0.01 and excessive inorganic Se might destruct the reactive oxygen species (ROS) balance and enhance the MDA content, thus causing damage to the plant growth. In a word, the present study suggested that the ratio of inorganic Se [Se(IV) and Se(VI)] was closely related with the growth and the antioxidant capacity of flue-cured tobacco and the excessive application of Se led to the higher proportion of inorganic Se and poorer antioxidant capacity, which ultimately inhibited the growth of flue-cured tobacco.

Allelopathic influence of leek (Allium porrum) seeds on germination and radical growth of flue-cured tobacco of different cultivars

Leeks (Allium porrum L.) are increasingly included in the rotation or inter-planting with tobacco in many provinces of China and worldwide. Therefore, we examined the possible allelopathic potential of leek seeds on the germination, seedling emergence and root elongation of flue-cured tobacco of different cultivars. The effects of imbibed leek seeds, their aqueous leachates and extracts of the seed on the germination and root elongation of the seeds of four test flue-cured tobacco cultivars, K 326, Yunyan 85, Zhongyan 100 and NC 89, under both aseptic and soil conditions, were investigated. Inhibitory effects were evident in all of the bioassays of these tobacco seeds. The leachates of the leek seeds and the aqueous seed extract were highly inhibitory, but the seeds themselves were less inhibitory. The observations indicate a release of inhibitory substances from the leek seeds leading to the observed inhibitory effects. The results of this study may be very useful for the management of crop rotations/systems involving leek as a component. Key words: Allium porrum L., allelopathy, flue-cured tobacco, inhibitory effects, seed germination, seed extract.

EVALUATION OF GROWTH REGULATORS AND RIPENING AGENT USED IN FLUE-CURED TOBACCO WHEN SPRAY-SOLUTION APPLICATION IS DELAYED

Information is limited concerning the effect on efficacy of flue-cured tobacco growth regulators and a ripening agent resulting from delayed application after solution preparation. Efficacy of C8-C...

Evaluation of tobacco soil fertility suitability of the Sanmenxia area, China, based on geographic information systems

The growth of flue-cured tobacco is sensitive to changes in environmental conditions. Excellent tobacco leaf production is strictly restricted by regional cultivated lands. For the purpose of reasonable utilization and scientific management of Sanmenxia tobacco fields, it is meaningful to evaluate the soil fertility suitability of tobacco crops quantitatively and objectively. In this study, the global positioning system (GPS) technology was used to obtain sample point information automatically. Based on the analysis of fertility properties of soil samples collected from the Sanmenxia tobacco planting regions in Henan Province, we present the index system of soil fertility suitability for tobacco crops. The integrated evaluation of soil fertility suitability was studied with six indices, including organic matter, pH value, available nitrogen (N), available phosphorus (P), available potassium (K), and chlorine (Cl−1) content of surface soil. The subjective grade value was calculated according to S-type and parabola-type functions of the effect of evaluation factors on tobacco crops. Further, the weight value of soil fertility suitability indices was calculated by the method of Hiberarchy analysis. The soil fertility suitability level was evaluated and classified. The suitability map of the Sanmenxia tobacco planting regions in Henan Province was then drawn with the geographic information system (GIS) software mapGIS. It was found that highly suitable fields were mainly distributed in the high mountains in the Southwestern part of the investigated regions where soil pH value and the contents of organic matter were medium, but the contents of available P and available K were higher, accounting for 79.36% of the whole area. Suitable fields were 17% of the whole area, mainly distributed in the middle part of the investigated regions where soil pH value was higher. Unsuitable fields existed in the northern-east and middle part of the Sanmenxia where the contents of soil Cl− was very high, accounting for 3.51% of the whole regions.

Effects of Nematicides on Pratylenchus penetrans, Soil Nitrification, and Growth of Flue-Cured Tobacco

Effects of Nematicides on Pratylenchus penetrans, Soil Nitrification, and Growth of Flue-Cured Tobacco

Effects of pesticides on soil enzymatic activities, Pratylenchus penetrans populations, black root rot, and growth of flue-cured tobacco

Abstract Field experiments were conducted on Fox loamy sand with nine treatments and three varieties of flue‐cured tobacco (Nicotiana tabacum) to study the effect of nematicides, Telone II, Telone C17, Vorlex, Vorlex CP, fenamiphos, and a fungicide, propamocarb on soil enzyme activities, populations of Pratylenchus penetrans (Cobb) Filip. and Stek, black root rot, and growth of tobacco. Fumigants and fungicide were applied on May 10 and fenamiphos was applied on May 17. Levels of NH4 +‐N in the soil were higher after treatment with most pesticides on May 24 and July 25 in the urease experiment. Dehydrogenase activity was inhibited by treatments of Telone C17 until June 27, and with Vorlex CP and propamocarb until June 13. Nematode counts before application of pesticides were 2000 to 4000/kg of soil. Populations of P. penetrans were lower in the fumigant‐nematicide treated plots throughout the experiment. Nematode population counts in tobacco roots of three varieties were sometimes lower with Telone II, Vo...

Effects of nematicides on population of pratylenchus penetrans and growth of flue-cured tobacco

Abstract Field studies were conducted on loamy sand at Tamscu farm, Delhi, Ontario, to compare the spring ridge application of Telone C17 at 73 and 101L/ha, Vorlex at 28 and 84L/ha, Vorlex CP at 50L/ha, and spring rotovated application of oxamyl at 2.24kg/ha respectively for the control of Pratylenchus penetrans (Cobb) Filip. and Stek., and for effects on the yield and quality of fluecured tobacco. Experiments were conducted on May 9 in an area that had been summer fallowed in previous year. Nematode densities of P. penetrans per kilogram of soil were lower than other treatments and controls with Telone C17 at 73 L/ha treated plots on May 24; with Vorlex at 28 L on June 7; Vorlex at 84 L on May 24 and on June 7; Vorlex CP on June 7, and with oxamyl on Sept. 6. The nematode population counts per gram dry weight of root were lower with Telone C17 at 73 L/ha on June 7, July 5, and at 101 L/ha on July 5; with Vorlex at 28 L/ha on June 7, July 5, and Sept. 6; with Vorlex at 84 L/ha on June 7, June 21, July 5 and Sept. 6, and with Vorlex CP at 50 L/ha on June 7, July 5 and Sept. 6 in the ridged soil. The population was lower with oxamyl on June 21, July 5, and Sept. 6 in the rotovated soils. There was no difference in the agronomic data on yield, indices of grade, crop and maturity, while tobacco plant height and dry weight in the ridged fanning were greater with treatments of Vorlex at 84 L and Vorlex CP at 50 L/ha. The ridged farming had greater yield of tobacco than rotovated farming. Vorlex was the most effective of all nematicides used in the experiment.

Effect of tobacco etch virus on the seasonal growth of flue-cured tobacco

The effect of tobacco etch virus (TEV) infection on flue-cured tobacco ( Nicotiana tabacum L.) plant growth was invisaged under field conditions in 1985 and 1986. Natural field infection of TEV was allowed to develop a patchy distribution of healthy plants and plants infected at various times of the season. Plants showing symptoms of TEV infection early in the season had significantly less leaf area by season's end (2 weeks after topping) than healthy plants or plants infected late in the season. Significant stunting was evident in plants first showing symptoms as late as 7 weeks after transplantation. Harvestable green leaf weight was not correlated with time of first TEV symptom expression. However, leaf weight per unit area was significantly correlated with time of plant infections, with earlier-infected plants having greater weight per unit area than later-infected plants or healthy plants. Yield, quality and value of the harvested tobacco were not correlated with number of infected plants per plot, however, probably because of compensation by neighbouring plants.

Effect of Early-Season Infestations of the Tobacco Flea Beetle (Coleoptera: Chrysomelidae) on the Growth and Yield of Flue-Cured Tobacco

The effect of Epitrix hirtipennis (Melsheimer) on the yield and growth of flue-cured tobacco was investigated in Virginia during 1981. Beetles (0, 5, 10, 15, and 20 per plant) were confined to individual tobacco plants in sleeve cages for a 3-week period immediately after transplant. Cages were then removed, and the plants were protected from other insects for the rest of the season. All populations caused significant ( P = 0.05) reductions in fresh- and cured-leaf yield, plant height, leaf area, and root weight. Cured-leaf yield was reduced by 18, 25, 38, and 38% for tobacco infested with 5, 10, 15, and 20 beetles per plant, respectively. Fresh-leaf yield was reduced by 21 g per beetle plant.