The experiment was conducted at the Farm of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during the period from March to July 2008. The seeds of BARI Mung-5 were used and the seeds were collected from Bangladesh Agricultural Research Institute, Joydebpur, Gazipur. There were eight treatments used in this experiment and these were: T1 = White polyethylene mulch, T2 = Black polyethylene mulch, T3 = Yellow polyethylene mulch, T4 = Blue polyethylene mulch, T5 = Yellow pot trap, T6 = Yellow cloth trap, T7 = Reflective tape and T8 = Control. Four different colored (white, black, yellow and blue polyethylene) mulches were placed between two rows of mungbean at 20 DAS in the field. The mulches were withdrawn at 50 DAS. Yellow pot trap was prepared with a yellow plastic container and yellow cloth trap was prepared by using yellow cloth for attracting white fly. Some oily substances (Griz) were kept on yellow plastic container and cloth for trapping whitefly. Two traps were used per plot (3m2). Traps were set at 20 DAS and they stayed upto 50 DAS. Traps were replaced in every week. Reflective tape of cassette was used for avoiding whitefly. The experiment was laid out in Randomized complete Block Design (RCBD) with three replications. The layout of the experiment was prepared for distribution of the treatment combinations in each plot of each block. There were 24 unit plots altogether in the experiment. The size of the plot was 1.5m×1.5m. The distance between two blocks and two plots were 1.0 m and 0.5m, respectively. The selected experimental plot was opened in the first week of March 2008 with a power tiller and was exposed for one week for sun drying. After one week the land was harrowed, ploughed and cross ploughed several times. Fertilizers were applied as per recommendation of Bangladesh Agricultural Research Institute for Mungbean in Bangladesh. Well decomposed cowdung as per treatment was applied at the time of final land preparation. The entire amounts of TSP, MP were applied during final land preparation. Only urea was applied in two equal installments at 20 and 30 Days after sowing (DAS). After emergence of seedlings, various intercultural operations like loosening of the soil, weeding was done for better growth and development. Light over-head irrigation was provided with a watering can to the plots immediate after germination of seed. Irrigation was also applied two times considering the moisture status of field. Weeding was done three times in these plots considering the optimum time for removal. The experimental plots were examined at 10 days interval for the appearance of viral mosaic. The incidence of mosaic was recorded four times. The first counting was made at 20 DAS and the following counting was made at 10 days interval. The mosaic infected plants were identified by visual observation as yellow patches on mungbean leaves coalesced to form a larger patch that develops into a yellow mottle; eventually the entire leaf could turn yellow. The green areas appear as dark green islands interspersed in yellow chlorotic areas; the infected leaf blade appears wavy.
The incidence of yellow mosaic diseases was calculated as follows:
% Yellow mosaic infected plants= Number of infected plant in each plot ÷ Total number of plants in each plot × 100
Yellow mosaic severity was recorded at 20, 30, 40 and 50 DAS. For scoring the severity of both (0-9 scale) of the disease, ten infected plants were selected randomly from each replicate plot. Five trifoliate leaves were selected from each selected plant for scoring the disease severity data.
Disease severity was determined by calculating the PDI as follows:
Percent Disease Index (PDI) = Sum of disease rating ÷ (Total number of leaves observed × Highest grade in scale) × 100
The severity of yellow mosaic disease was recorded following the 0-9 grading scale where, 0 = No visible symptoms on leaves, plant growth, flowering and pod formation normal, 1 = Yellow chlorotic spots or flecks few in number and scattered over younger leaves; plant growth, flowering and pod formation normal, 3 =Yellow chlorotic flecks or mottle larger in size and covered about 25% of leaf area; Some coalesced and formed a patch; plant growth, flowering and pod formation slightly affected, 5 = Yellow chlorotic mosaic covered 50% of leaf area or some leaves. Some coalesced and formed irregular patches, plant moderately stunted, flowering and pod formation moderately reduced, 7 = Yellow chlorotic mosaic covered about 75% of leaf of several leaves, leaves reduced in size, pod formation restricted with yellow and curved pods; plants considerably stunted, 9 = Young leaves completely yellow, plant severely stunted, flowering and pod formation severely affected with very few small yellow curved pods that contained yellow shriveled seeds or without any pod formation. The crop was harvested at full ripening stage. Before harvesting 5 apparently healthy plants and 5 infected plants (which have initially produced the symptoms) in each unit plots were selected randomly and collected data on plant height (cm), number of pods per plant, pod length (cm), number of seeds per pod, yield per plot(kg) and yield per hectare (ton). The data obtained for different characters were analyzed. The analysis of variance was performed by using MSTAT Program. The significance of the difference among the treatment means was estimated by DMRT (Duncan’s Multiple Range Test) at 5% level of probability.