A field experiment on eco-friendly pest control in cucumber (Cucumis sativa L.) field was conducted at Rajshahi University during April, 2011 to June, 2011 with eight botanical pesticides prepared from the leaves and seeds of Bangladeshi plants. These botanicals are mahogany seeds, (Swietenia mahagoni), chirata leaves (Swertia chirata), jute seeds (Corchorus olitorius L.), garlic (Allium sativum L.), marigold leaves (Tagetes erecta) and carrot leaves (Daucus carota). One control treatment without botanicals was maintained during this experiment where only water was sprayed. Out of these botanicals, a less number of insect attacks on cucumber leaves (1.33 ± 0.19) were found in combined treatment of mahogany and chirata whereas a high number of insect attacks were observed in combined treatment of garlic and jute seed (5.89 ± 0.40) and control (4.66 ± 0.33). Individual application of chirata extract also showed good protection of cucumber leaves (1.67 ± 0.19) from insect attack. A smaller number of leaves perforations were found in the combined treatment of mahogany and chirata (3.44 ± 0.29) compared to control (14.22 ± 1.05). Chirata extract also showed good performance (4.00 ± 0.19) against leaves perforation of insect. Besides the pest control, botanical pesticides also have enormous effect on plant growth. The tallest cucumber plant was observed in the combined treatment of mahogany and chirata (469.00 ± 63.51 cm) and shortest in garlic treatment (84.56 ± 15.24 cm). The cucumber production was also high in combined treatment of mahogany and chirata (1863.33 ± 196.32 g) compared to control (1260.00 ± 501.63 g). From this study, it is found that combined application of mahogany and chirata extract not only showed good protection of cucumber plant from insect attack but also increased the cucumber production. Therefore, we conclude that farmers should use botanical pesticides from mahogany seeds and chirata leaves instead of toxic chemical insecticides for controlling pest in cucumber field.

Bangladesh produces a huge amount of potatoes every year. This research was carried out to find the optimum conditions for bioethanol production from potato of Bangladesh. From this study, optimum growth of yeast (Saccharomyces cerevisiae CCD) was observed at pH 6.0 and temperature 31°C. Addition of a small amount of alpha-amylase enzyme to potato solution was found to enhance the potato starch degradation and made the fermentation process quicker. This study observed that 1750 unit alpha-amylase is enough to degrade the starch in 15% of 500 ml potato starch solution. From fermentation time study, 6-day incubation time was found to be enough to complete the fermentation process and optimum production of bioethanol form potato starch. Suitable concentration of potato in fermentation process was determined using five different potato solutions (5%, 10%, 15%, 20% and 30%). A highest production of bioethanol was found in  20% potato treatment. Therefore, 20% potato solution is recommended for high-scale production of bioethanol from potato starch.