Experiments were conducted in the laboratory and in greenhouses. Of three neem preparations sprayed upon eggs, only neem oil (NO) exerted a negative impact on the hatching rate of Coccinella septempunctata and Chrysoperla carnea. First instar larvae of Episyrphus balteatus proved to be highly susceptible, when feeding 24 h on aphids sprayed with neem kernel water extract (NKWE). First instar larvae of C. septempunctata showed a very high mortality when feeding on aphids sprayed with different neem preparations. Aphid feeding and live span was reduced. When NKWE had been applied to the soil, the mortality of larvae of E. balteatus and C. septempunctata were lower, when feeding on aphids. Second instar larvae of C. septempunctata were far less susceptible when feeding 48 h on neem‐sprayed aphids than first instars; the time of their development was prolonged, and aphid consumption reduced. Larvae of C. carnea proved to be less susceptible, when feeding on neem‐sprayed aphids, than E. balteatus and C. septempunctata. In C. carnea, however, significant influences were also observed in aphid consumption, time of development, mortality, longevity, and rate of deformity. NO, containing a very low concentration of azadirachtin A, had stronger negative effects than NeemAzal‐T/S®, in all observations. In the parasitoid Diaeretiella rapae, NKWE application to the soil induced negative reactions, when aphids on these plants were parasitized: low percentage parasitization, lowered mummy weight, low emergence rate of adults of F1 and even of F2. Foliar sprays of NKWE had less severe effects in this parasitoid species. The results are discussed with regard to their theoretical and practical significance.

The present study was stimulated by the problem of onion seed production where seed production is possibly only winter period after whichrapid increase in temperature as well as early shower adversely affect the quality of seed. To overcome this situation a field experiment wasundertaken to find out the optimum planting time for maximizing quality true seeds of onion. The experiment was laid out in a randomizedcomplete block design with four replications. The treatments were five planting dates viz. 1 October, 15 October, 30 October, 15 Novemberand 30 November to achieve the objective. The research work was done at On-Farm Research Division, BARI, Bogra during September, 2010to June, 2011. The results revealed that the growth parameters, seed yield components, health and quality of harvested seeds were significantlyinfluenced by the different treatments. Results showed that among different planting dates, 15th November was the best for seed and quality.DOI: http://dx.doi.org/10.3126/ijasbt.v3i1.11847     Int J Appl Sci Biotechnol, Vol. 3(1): 67-72

Experiments were carried out to evaluate the toxicity of six botanicals, Bazna (Zanthoxylum rhetsa), Ghora-neem (Melia sempervirens), Hijal (Barringtonia acutangula), Karanja (Pongamia pinnata), Mahogoni (Swietenia mahagoni) and Neem (Azadirachta indica) against red flour beetle, Tribolium castaneum Herbst. Leaf and seed extracts were prepared by using acetone, methanol and water as solvents. The results showed that extracts of all the six plants had direct toxic effect on red flour beetle. Among them, Neem seed extract showed the highest toxic effect (mortality, 52.50%), whereas Hijal leaf extract possessed the lowest toxic effect (mortality, 22.24%). Among the solvents, acetone extract showed more toxic effect than other extracts. Seed extracts of respective plants were slightly more toxic than leaf extract. The effectiveness of most of the plant extracts increased proportionally with the increase of doses and decreased with time.

The aphid incidence and its correlation with environmental factors were studied. Mustard variety "Sampad" was used as test crop. Aphid incidence varied significantly at various parts of mustard plant and time of the day. The highest number of aphid was observed in the vegetative parts of the mustard plant in the morning. High cloudiness, relative humidity and dew point favoured the aphid population and slight rain fall quickly declined the aphid population. Among the different environmental factors maximum temperature, dew point and sun shine hours were positively correlated with aphid population and minimum temperature, relative humidity and wind speed were negatively correlated with aphid population.

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A study was carried out during July 2010 to April 2012 to understand the effect of weather prevalence on sigatoka disease of banana suckers in different areas of Bangladesh and to develop an environment friendly disease management practice. Four locations viz. Dinajpur, Bogra, Rangpur and Madhupur were surveyed. To find out suitable and ecofriendly management practices for controlling sigatoka disease of banana, seven treatments were used viz. i) Soil drenching with BAU-Biofungicide (2%), ii) BAU-Biofungicide as foliar spray (2%), iii) Soil drenching with BAU-Biofungicide (2%) plus foliar spray (2%), iv) Bavistin (carbendazim) spray (0.2%), v) Dithane M-45 (mancozeb) spray (0.2%), vi) Soil drenching with BAU-Biofungicide (2%) plus Bavistin spray (0.2%); and vii) control. The average highest incidence (26.42%) and severity (22.84%) of sigatoka disease of banana suckers were recorded during October at Bogra, while the lowest incidence (9.75 %) and severity (8.51%) were recorded during January at Dinajpur. Out of the control measures employed, BAU-Biofungicide (2%) either alone or in combination with Bavistin (0.2%) was found as an excellent biocontrol means for controlling sigatoka disease of banana suckers.

Abstract:The study was carried out to quantify the purity of different marketed brands of three insecticide namely diazinon, acephate and cypermethrin using suitable protocols GC-FID and GC-ECD. Nineteen marketed brands of these insecticides collected from retailers of Jessore, Gazipur and Rangpur region were analyzed and estimated their purity in two seasons of 2006-2007 and 2007-2008. Among six marketed brands of diazinon, only one brand (RSN) had 96.71-100% purity in both the seasons in all locations which considered to be standard product, but four brands (DZN, SBN, HZN, DNN) in other regions, contained <95% pure which were substandard product. The remaining 2 brands (DNN, AZN) contained 33.71-51.94% purity in 2006-07 and the other two brands (SBN, DZN) had very small amount of active ingredient (0.16-0.84% purity) in 2007-08 and all these were impure in quality. All five tested brands of acephate had 57.14-88.59% purity in 2006-07 which were substandard but in 2007-08, three brands (SNT, BNS, ATF) showed >90% purity and the remaining 2 had <80% purity which were less AI than required. Of eight tested brands of cypermethrin, three brands were almost to have >95% pure in 2006-07 in all locations. The other two brands (CPR, AMT) contained >90% purity. In 2007-08, two brands of cypermethrin (RCD, SCR) contained >95% pure, another two brand (CRN, RLT) had 88.77-91.15% purity. The brands UTD was standard in purity in 2006-07 but this brand was below standard in quality in 2007-08 in all locations. Most of the tested brands of cypermethrin were found standard and sub standard level of purity in comparison to diazinon and acephate.