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An in vitro experiment was carried out to evaluate the effectiveness of antibiotics at different concentrations on growth and development of Trichoderma harzianum, Phytophthora infestans, Colletotrichum gloeosporioides, Corticium theae and Fusarium oxysporum found in tea plantation. Three samples viz. sample-1 (Validamycin 60% w/w) @ 45, 60 and 75 ppm, sample-2 (Hexaconazole 2.5% w/w+Validamycin 8.5% w/w) @ 55, 82.5 and 110 ppm and sample-3 (Streptomycin 9% w/w+Tetracyclin hydrochloride 1% w/w) @ 50, 75 and 100 ppm were tested. The result showed that Antibiotics have inhibitory effects on T. harzianum. Unsatisfactory performances in terms of per cent growth inhibition (<80) were recorded on crop infecting fungi. C. theae treated with sample-1 @ 75 ppm and C. gloeosporioides with sample-2 @ 110 ppm had shown maximum 25.50 and 54.19 per cent growth inhibition, respectively. The highest 70.53 per cent growth inhibition of C. theae was observed in sample-3 treated @ 100 ppm. Considering the findings it can be recommended not to use above antibiotics with their respective concentrations in plant agriculture for controlling diseases caused by the said fungi.

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Jute is the most important fibre crop for Bangladesh and second important for world. Bangladesh requires about 6000 tons of jute seed. Among this quantity Bangladesh produce whole amount of Corchorus capsularis L. (white jute) seed but only very little amount of Corchorus olitorius L. (tossa jute) seed. Production of tossa jute seed is not too profitable because of high production cost for that reason farmers of Bangladesh are not interested to produce seed of tossa jute. And production cost of jute seed is mainly associated with labor cost that is mainly for weeding. This study was conducted to assess the best herbicide application time to enhance seed productivity, quality and reduction the cost of production. In this experiment two Corchorus species were grown using three different herbicide application times and no herbicide application used as control. The results indicated that for tossa jute (BJRI tossa pat-8) maximum plant population, plant height, branch/plant, capsule/plant, seed/capsule, seed yield, germination capacity, field emergence capacity, seed vigour and CVG were found in Control plot. Maximum 1000 seed weight and MGT were recorded in herbicide applied at 13th days after cutting transplanting. Maximum capsule length found at 10th days of herbicide application. For white jute (CVL-1) highest plant population, plant height, branch/plant, seed/capsule, capsule length, germination capacity, field emergence capacity, seed vigour and CVG were recorded in control plot. Highest capsule/plant, 1000 seed weight and seed yield were found in herbicide applied at 13th days after cutting transplanting. Maximum MGT found in herbicide applied at 16th days after cutting transplanting. Result revealed that herbicide use reduce the production cost of jute seed compare to manual seed production technology.

Only leaf reduction (Cultural measure), in treatment T4 [treated with leaf removal above 15 inches (38.10 cm) from ground level], maximum yield (2185.00 kgha-1) was found resulted 21.64% more over the control. T3 [10 inches (25.40 cm)] and T5 [20 inches (50.80 cm)] gave similar response having 20 and 20.68% increased yield over the control. The lowest severity (21.38 PDI) was found in T5 [20 inches (50.80 cm)] that was statistically identical to T4 [15 inches (38.10 cm)] and T3 [10 inches (25.40 cm)] having a decrease trend of 58.28%, 50.26% and 42.59% respectively. There is 92.99% impact of leaf reduction in reducing disease severity of red rust having a decrease trend of 7.2 PDI for removal of leaf by 5 inches (12.70 cm) from the soil level. Similarly there is 81.44% impact of leaf reduction in increasing yield of made tea (kg ha-1) having an increase trend of 103.01 unit for removal of leaf by 5 inches (12.70 cm) from the soil level. In leaf reduction (Cultural measure) with one round chemical application, treatment T13 [treated with leaf removal above 15 inches (38.10 cm) from ground level with one round of Carbendazim 50 WP] gave maximum yield (2,310.00 kgha-1) resulted 28.61% more over the control followed by T15 [20 inches (50.80 cm) with one round of Carbendazim 50 WP] and T14 [20 inches (50.80 cm) with one round of Copper-oxichloride 50 WP] having 28.18 and 27.69% increased yield of made tea.  Lowest severity (9.63 PDI) was found in T15 [20 inches (50.80 cm) with one round of Carbendazim 50 WP] having 41.21% reduction over control followed by identical PDI in T12 [15 inches (38.10 cm) with one round of Copper-oxichloride 50 WP], T13 [15 inches (38.10 cm) with one round of Carbendazim 50 WP] and T14 [20 inches (50.80 cm) with one round of Copper-oxichloride 50 WP] having 77.40, 77.31 and 77.79% reduction respectively. There is 78.24% impact in reducing disease severity of red rust having a decrease trend of 2.23 PDI for removal of leaf by 5 inches (12.70 cm) from the soil level with one round chemical fungicide application. Similarly there is 51.76% impact in increasing yield of made tea (kg ha-1) having an increase trend of 30.21 unit for removal of leaf by 5 inches (12.70 cm) from the soil level with one round chemical fungicide. From the benefit cost analysis it is projected that the treatment T3 [10 inches (25.40 cm)] received the highest marginal rate of return (1202.17%) followed by 1152.17% in treatment T4 [treated with leaf removal above 15 inches (38.10 cm). One round of systemic fungicides like Carbendazim 50 WP with this cultural practice gave 1034.21% and 1091.42% marginal rate of return respectively. Considering yield of made tea, disease severity and benefit cost analysis viewpoint, it can be concluded that, the cost effective treatment is removal of soil touching old leaves attached with tea bushes of MSK and LSK pruned sections within 10 inches (25.40 cm) to 15 inches (38.10 cm) from the soil level.