EVALUATION OF FUNGICIDE FOR SEED TREATMENT TO CONTROL STEM CANKER AND BLACK SCURF DISEASE (RHIZOCTONIA SOLANI) OF POTATO

Authors: M. M. Rahman1, M. A. Ali2, M. U. Ahmad2 and T. K. Dey3

Abstract

M. Rahman, M. A. Ali, M. U. Ahmad and T. K. Dey. 2014. Evaluation of fungicide for seed treatment to control stem canker and black scurf disease (Rhizoctonia solani) of potato. Bangladesh J. Plant Pathol. 30(1&2):23-27.

A field experiment was conducted to evaluate the effectiveness of Amistar 325 SC (Azoxystrobin) @ 0.10%, Provax-200 (Carbixin+Thiram) @ 0.20% and Bavistin 50 WP (Carbendazim) @ 3.00% and 0.10% as pre-plant seed tuber treating fungicides against stem canker and black scurf disease (Rhizoctonia solani) of potato. Infested seed tubers were treated by spraying with the fungicidal suspensions over the tuber surface. Two additional treatments, one with infested tubers and other one with healthy seed tubers were maintained in the experiment for comparison. Efficacy of Provax to reduce disease incidence and to increase plant growth and yield was not considerable. Pre-plant treatments of infected seed tubers with Amistar 325 SC at 0.20%, Bavistin 50 WP at 3.00, Bavistin 50 WP at 0.10%, and planting of healthy seed tubers increased germination by 9.17, 7.86, 7.47 and 8.56%; number of stem per hill by 7.54, 13.07, 12.56 and 9.30%; plant height by 2.31, 10.42, 9.23 and 10.02; and tuber yield by 64.15, 22.06, 20.06 and 7.23% respectively over control-2. The treatments reduced incidence of stem canker and black scurf by 59.45, 54.05, 48.65 and 51.35 and disease severity, in terms of PDI, was reduced by 65.87, 56.09, 48.77 and 48.77% respectively over control-2.  Results of the present investigation reveal that Amistar 325 SC is the most effective fungicide followed by Bavistin 50 WP to improve plant growth, tuber yield and to reduce incidence and severity of stem canker and black scurf disease of potato.

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INTRODUCTION

Potato (Solanum tuberosum) is a leading staple food crop of the world and it ranks next to wheat and rice. In Bangladesh, it is the first leading vegetable crop and grown in almost all areas of the country. During 1999-2000, the production of potato was 2.93 million metric tons from 0.243 million hectares of land. In Bangladesh, average tuber yield is lower compared to other potato growing countries of the world. The major constraint of potato production is prevalence of epidemic diseases and lack of supply of quality seed potato to the farmers. In Bangladesh, a total of 39 diseases of potato have been recorded (Ali and Khan 1990). One of the major diseases is stem canker and black scurf caused by Rhizoctonia solani (Kuhn). It is the most common and   widespread disease throughout the country (Ali and Dey 1994).

            Rhizoctonia solani is a soil-borne fungus and causes ‘black scurf’ on potato tubers and canker on stems. Severe stem canker can kill shoots and delay crop emergence. On the surface of infected tubers the fungus forms dark brown to black sclerotia which vary in size. The sclerotia are resting structures that allow the fungus to survive for long periods under stress conditions. Tuber infested with sclerotia is a significant problem in seed tubers as the sclerotia can act as a primary source of infection for the new plant. The tuber  borne  nature of R. solani  is  an important

component of the disease cycle. Many researchers from different countries reported efficacy of pre-plant seed tuber treatment with fungicides to control stem canker and black scurf diseases (Bolkan 1976, Wenham et al. 1976, De and Sengupta 1992, Akhilash et al. 1996, Anon. 2005, Himel et al. 2007, Djelbali and Bathassel (2010).

Development of effective as well economic control methods against stem canker and black scurf disease is essential in Bangladesh. One of the transmission methods of the disease is infected seed tubers bearing sclerotia of R. solani. Effective seed treatment methods can minimize the primary spread of the disease from seed to progeny tubers; thereby reduce incidence and severity of the disease. So, the present investigation was undertaken to evaluate three promising fungicides for pre-plant treatment of potato seed tubers to control stem canker and black scurf under Bangladesh conditions.

MATERIALS AND METHODS

Fungicides tested in the experiment were Amistar 325 SC (Azoxystrobin) @ 0.10%, Provax-200 (Carbixin+Thiram) @ 0.2% and Bavistin 50 WP (Carbendazim) @ 3.0% and 0.1%. Two controls consisted of healthy tubers (control-1) and infected tubers carrying sclerotia (control-2) were used in the experiment for comparison. Infected as well as healthy seed tubers of variety Diamant were collected from Breeder Seed Production Centre of Bangladesh Agricultural Research Institute (BARI) at Panchagarh, Bangladesh. The fungicides were suspended in tap water at desired concentrations. The infected seed tubers were spread on the floor and the fungicidal suspensions were sprayed over the seed tubers for treatment. For proper coverage of the surface, the tubers were rotated frequently at the time spray. The treated tubers were air dried overnight and stored in a room until planting.

The experiment was conducted at the Tuber Crops Research Sub-Centre (TCRSC) of BARI in Bogra during 2008-2009. The experiment was laid out in a randomized complete block design with four replications. The unit plot size was 3.0 m x 3.0 m. Block to block and plot to plot distances were 100 cm and 50 cm, respectively. Row to row distance was 60 cm.  Recommended doses of fertilizers and manures were applied as suggested by Tuber Crops Research Centre, BARI, Gazipur (Anon. 2005). Cowdung was incorporated to the soil during land preparation at the rate of 10 t/ha. Urea, Triple super phosphate (TSP), Muriate of potash (MOP), Gypsum, Zinc sulphate and Boric acid were applied at the rate of 360, 220, 250, 120, 14 and 6 kg per hectare, respectively. The entire amount of TSP, MOP, Gypsum, Zinc sulphate, Boron and half of urea were applied at the time of final land preparation. Treated seed tubers were planted on 29 November 2008 maintaining 25 cm seed to seed distance. The 2nd half of urea was applied at 30 days after planting (DAP). Weeding was done at 25 DAP and earthing up was done at 30 DAP. Irrigation was applied at 20 and 40 DAP. The insecticides Dursban (0.5%) and Admire (0.1%) were applied respectively, to control cutworms and aphids. Secure (0.1%) was sprayed at 10 days interval as preventive measures against late blight disease of potato. The crop was harvested on 28 February 2009.

Data on germination, number of stem per hill, plant height were recorded from the field. After harvest, data on healthy and infected tubers were collected. The black scurf infected tubers were separated into three groups such as russet, deformed and sclerotia infected. Number and weight of tubers under each group were recorded. Number and weight of healthy tubers harvested from each plot were also recorded.

            Disease related data such as disease incidence, percent disease index (PDI) were recorded. To record disease incidence, 20 plants were randomly selected from each unit plot at 70 DAP, uprooted carefully, washed with running tap water and checked for infection. Numbers of infected and healthy plants were counted and percent disease incidence was calculated based on total number of plants checked. At 70 DAP, severity of stolon infection was indexed on a  0-6 indexing scale (Dey 2010), where 0= No symptom on stolon, 1 = minute brown lesion on stolon or root, 2 = moderately brown lesion on stolon and curling tendency on central leaf, 3 = stolon symptom discolored accompanied by brown discoloration on roots, 4 = brown to black discoloration on underground parts, tissue discoloration and curling of growing leaves, 5 = profuse emerging of auxiliary leaves, leaf size reduced markedly and pale green on leaf margin, and 6 = production of aerial tuber with green colour. Twenty plants in each plot were randomly selected and uprooted carefully from soil, washed with water. The plants were checked individually and severity of stolon infection was indexed. Number of stem canker infected plants under each grade (0-6 scale) was recorded and the percent disease index (PDI) was calculated using standard formula as shown below:

evaluation-of-fungicide-for-seed-treatment-to-control-stem-canker-and-black-scurf-disease-rhizoctonia-solani-of-potato-1

The black scurf infected tubers were separated into russet, deformed and sclerotia infected tubers. Number and weight of tubers under each symptom category per plot were recorded. Collected data were analyzed statistically following MSTAT-C computer program Differences among treatment means were determined following Duncan’s Multiple Range Test using the same computer program.

RESULTS AND DISCUSSION

Germination

Range of germination of potato seed tubers under different treatments including two controls (1 and 2) was 85.54 to 93.38%. The lowest germination was recorded when infected seed tubers were planted (control-2) without treatment, which was statistically similar to the treatment with Provax-200 @ 0.20%. The highest germination was recorded from the treatment with Amistar 325 SC at 0.20%, which was statistically similar to Bavistin 50 WP at 3.00, Bavistin 50 WP at 0.10% and planting of healthy seed tubers. The four treatments increased germination by 9.17, 7.86, 7.47 and 8.56%, respectively and the increase was significant compared to control-2 (Table 1).

Stem number and plant height

Under different treatments, number of stem per hill varied from 3.98 to 4.50 and plant height varied from 57.08 to 63.88 cm. The lowest number of stem per hill and plant height was found under control-2. Treatments with Amistar 325 SC at 0.2%, Bavistin 50 WP at 3.0%, Bavistin 50 WP at 0.1% and planting of healthy tubers increased stem number/hill by 7.54, 8.79, 13.07, 12.56 and 9.30%; and plant height by 2.31, 11.91, 10.42, 9.23 and 10.02, respectively over control-2. The increase in both the parameters was not significant compared to control-2 (Table 1).

Incidence and severity of disease

The highest incidence of 46.26% stem canker and black scurf disease of potato was recorded from control-2. Treatments of infected seed tubers with fungicides and use of healthy tubers caused significant reduction in disease incidence. The reductions obtained with Amistar 325 SC at 0.2%, Bavistin at 3.0%, use of healthy seeds, Bavistin at 0.1% and Provax-200 at 0.2% were 59.45, 54.05, 51.35, 48.65 and 45.95% over control-2. The maximum reduction was obtained with Amistar 325 SC which was statistically similar to two treatments with Bavistin and healthy seeds (Table 1).

The severity, in terms of PDI values of stem canker and black scurf disease of potato was 46.26% under control-2. Treatment of seed tubers with fungicides and planting of healthy tubers caused significant reduction in the parameter within the ranged 48.77-65.87 over control-2. However, the efficacy of all fungicidal treatments and planting healthy seeds to reduce disease severity was statistically similar (Table 1).

Number of russet, deformed and sclerotia infested tubers

Per plot maximum number of russet, deformed and sclerotia infested tubers were 26.50, 10.50 and 65.25, respectively, when infected seed tubers were planted without any treatment (control-2). All fungicidal treatments of seed tubers and use of healthy seeds significantly reduced number of russet, deformed and sclerotia infected tubers over control-2. Treatments with  Amistar 325 SC  at 0.2%, Provax-200  at 0.2%, Bavistin at 3.0% and 0.1% and use of healthy seeds reduced number of russet tuber by 64.15, 21.70, 51.89, 41.51 and 61.32%,  deformed  tubers by  40.48, 21.43, 66.67, 66.67 and 33.33% and sclerotia infested tubers by 55.56, 42.15, 48.28, 48.28 and 91.15%, respectively  over control-2 (Table 2).

Weight of russet, deformed and sclerotia infested tubers

The maximum of 580 kg/plot of deformed tubers were harvested from the plot planted with black scurf infected seed tubers without any treatment (control-2). Application of Amistar 325 SC at 0.2%, Provax-200 at 0.2%, Bavistin at 3.0% and Bavistin at 0.1% reduced the parameter to 37.93 – 450 kg/plot. The reductions under above five treatments were 37.93, 37.93, 39.66 and 39.66%, respectively and the reduction was significant compared to control-2. Difference in weight of deformed tubers harvested from plots planted with infected tuber without treatment (control-2) and healthy tubers was not significant (Table 2).

Maximum of 1280 and 4800 kg/plot of russet and sclerotia infested tubers were found under control-2. Both the parameters were significantly reduced over control due to treatments with fungicides and use of healthy seeds. Treatment of black scurf infected seed tubers with Amistar 325 SC at 0.2%, Provax-200  at 0.2%, Bavistin at 3.0%, Bavistin at 3.0%, Bavistin at 0.1% and use of healthy seeds caused 45.31, 39.06, 58.59, 58.59 and 35.16%  reduction in russet tubers and 62.71, 37.93, 22.41, 45.80, 57.71 and 91.67% reduction in sclerotia infested tubers, respectively (Table 2).

evaluation-of-fungicide-for-seed-treatment-to-control-stem-canker-and-black-scurf-disease-rhizoctonia-solani-of-potato-2

Tuber yield

The lowest tuber yield of 16.32 t/ha was harvested from plots planted with black scurf infected seed tubers without treatment (control-2). Treatment of black scurf infected seed tubers with Amistar 325 SC at 0.2%, Provax-200 at 0.2%, Bavistin at 3.0%, Bavistin at 0.1% and use of healthy seeds increased tuber yield by 64.15, 12.13, 22.06, 20.06 and 7.23% over control-2. The increase was significant in case of Amistar 325 SC at 0.2%, Bavistin at 3.0% and Bavistin at 0.1% (Table 2).

Results of the present investigation reveal that pre-plant treatment of seed tubers with the fungicides Amistar 325 SC at 0.1%, Provax-200 at 0.2%, Bavistin 50 WP 3.0% and Bavistin 50 WP at 0.1% is effective to control stem canker and black scurf disease of potato. The treatments increased germination, plant growth and tuber yield but decreased incidence and severity of the disease. The fungicides also reduced number and weight of russet, deformed and sclerotia infested tubers. Planting of healthy seed tubers without treatment gave similar results as recorded from fungicidal treatments. Among the fungicides Amistar 325 SC (0.1%) was the most effective one followed by Bavistin 50 WP (3%) to improve plant growth parameters, tuber yield and to reduce incidence and severity of stem canker and black scurf disease of potato. The findings of the present investigation are in agreement with the findings of other researchers (Bolkan 1976, Wenham et al. 1976, De and Sengupta 1992, Akhilash et al. 1996, Anon. 2005, Himel et al. 2007, Djelbali and Bathassel (2010). Djelbali and Bathassel (2010) agreed that seed tuber treatment and in furrow application of Amistar gave effective control of stem canker and black scurf of potato.

evaluation-of-fungicide-for-seed-treatment-to-control-stem-canker-and-black-scurf-disease-rhizoctonia-solani-of-potato-3

LITERATURE CITED

Akhilesh, S., Tyagi, P. D. and Singh, A. 1996. Evaluation of chemicals dip treatments for the control of black scurf of potato. Himachal J. Agril. Res. 22(1-2): 142-145.

Ali, M. S. and Dey, T. K. 1994. Pathological research on tuber crops in Bangladesh. In: Proc. Workshop on Tubers Crops on Transfer of Technology of CDP crops under Research Extension  LinkageProgramme. pp. 159-165.

Anonymous. 2005. Annual report 2004-2005. Tuber Crops Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur, 75 pp.

Bolkan, H. A. 1976. Seed tuber treatment for the control of black scurf disease of potatoes. New-Zealand J. Exp. Agril. 4 (3): 357-361

De, B. K and Sengupta, P.C. 1992. Evaluation of different chemicals to control of black scurf of potato in the West-Bengal Plains. J. Indian Pot. Assoc. 19: (1): 81-83.

Dey, T. K. 2010. Tuber crops diseases-their identification, method of recording, rating scale and grading system. Oilseed Res. Center, Bangladesh Agril.Res. Inst. Gazipur. pp.28-31.

Djelbali, N. and Bethassel, T. 2010. Field study of the relative susceptibility of eleven potato (Solanum tuberosum L.) varieties and the efficacy of two fungicides against Rhizoctonia solani. Tunisia Crop Prot. 29:9.

Himel, M. K., Akand, A. M. and Khair, A. 2007. Controal of Rhizoctonia solani infecting potato. Abstract of Annual Botanical Conference, March 7-9, 2008. Jahangir-nagar University, Savar, Dhaka.

Wenham, H. T., MacKintosh, B. L. and Bolkan, H. A. 1976. Evaluation of fungicides for control of potato black scurf disease. New-Zealand J. Exp. Agric.  4 (1): 97-101.

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1Principal Scientific Officer, TCRSC, Bangladesh Agricultural Research Institute (BARI), Bogra, 2Professor, Department of Plant Pathology Bangladesh Agricultural University, Mymensingh, 3Director, Regional Agricultural Research Station, BARI, Ishurdi, Pabna, Bangladesh
[Part of Ph.D dissertation of the first author]

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