M. M. Rahman
TCRSC, Bangladesh Agricultural Research Institute (BARI), Bogra
M. A. Ali
Department of Plant Pathology Bangladesh Agricultural University, Mymensingh
M. U. Ahmad
Department of Plant Pathology Bangladesh Agricultural University, Mymensingh
T. K. Dey
Director, Regional Agricultural Research Station, BARI, Ishurdi, Pabna, Bangladesh
Fungicide, Seed treatment, Stem canker, Rhizoctonia solani, Control
Breeder Seed Production Centre of Bangladesh Agricultural Research Institute (BARI) at Panchagarh, Bangladesh
Pest Management
Fungicides tested in the experiment were Amistar 325 SC (Azoxystrobin) @ 0.10%, Provax-200 (Carbixin+ Thiram) @ 0.2%, Boric acid @ 3.0% and Bavistin 50 WP (Carbendazim) @ 0.10%. 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. 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, 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 follows: PDI = [Class frequency/ (No. of plants checked X highest score)] x 100. 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.
Bangladesh J. Plant Pathol. 30(1&2):23-27, 2014; ISSN 1012 9279
Journal