Vol. 16 No. 2 (2018)

Predatory mite Paraphytoseius cracentis (Acari: Phytoseiidae)is a natural enemy of thrips found on some vegetables such as green beans, cucumbers, green squash, egg plant, and peppers in the Red River Delta. The purpose of this study was to investigate the morphological and biological characteristics of P. cracentisfed on Frankliniella occidentalis(Thysanoptera: Thripidae) and Carpoglyphus lactis(Acari: Acaridae) at 29°C, 75% RH. The predatory mite fed on C. lactiswas similar in size to that of mite fed on F. occidentalis.The developmental times of immature females and males of the mite fed on C. lactis(4.24 and 4.26 days, respectively) were not significantly different from mites fed on thrips (4.23 days with female and 4.26 days with male). The daily oviposition rate and total number of eggs of P. cracentisreared on C. lactis(1.62 eggs/female/day and 18.48 eggs/female, respectively) were significantly higher than that of females reared on thrips (1.24 eggs/female/day and 13.77 eggs/female, respectively). The intrinsic rate of natural increase of P. cracentisfed on C. lactis(0.215 females /female/day) was significantly higher than that of mites fed on thrips (0.189 females /female/day). In conclusion, predatory mite P. cracentiswas able to survive and increase its population when fed on F. occidentalisand C. lactiscould be used formass rearing of this predatory mite.

Seven genotypes of groundnut (DM1, DM2, DM3, DM4, HL11, HL22 and LDDL) provided by the Agricultural Genetics Institute were evaluated for growth and physiological characteristics under drought conditions at seedling stage. A pot-experiment in nethouse was arranged according to a completely randomized design. Drought stress was imposed on three true leaf seedlings (15 days after sowing) by withholdingt irrigation untill the soil osmotic pressure reached -80 KPa. Meanwhile, regular irrigation schedules were perfomed for maintaining the soil moisture at 70% saturation in the control and in non-drought periods. Drought stress inhibited growth and photosynthesis, transpiration and significantly reduced dry matter of groundnut at seedling stage and the inhibition varied with genotype. Three indexes showing close correlations with dry weight included drought susceptibility index (DSI); drought tolerance efficiency (DTE) and drought tolerant index (DTI) with correlation coefficients of r = -0.55 and -0.602, r = 0.55 and 0.83, and r = 0.53 and 0.98 at drought and recovery periods, respectively. The chlorophyll stability index (CSI) showed no correlation with dry weight and did not reflect drought tolerance. The results also showed that the genotypes HL22 and DM4 possessed higher drought tolerance comparing to the others.

This study aimed to evaluate the situation of hygiene conditions of pig slaughterhouses in Lam Dong province. A total of 24 slaughterhouses from 3 representative districts of the province were chosen for the survey. The awareness of abattoir workers was evaluated using a semi-structured questionnaire. The conditions of food hygiene and safety were assessed through analysis of microbial contamination in the samples collected from the investigated slaughterhouses including surfaces of pork, water, and equipment. Results showed that only a small number of the slaughterhouses were trained on the slaughtering procedure (11.11% and 50.0% of small and medium slaughterhouses, respectively). All the slaughterhouses carried out the slaughter operations on the floor. Most of the abattoir workers showed litte knowledge nor proper practices for hygiene of facilities, their individual hygiene, and the pork. Almost all equipment items were contaminated with the total aerobic bacteria and Enterobacteriaceae atunacceptable levels. Coliformswere found exceeding the specified standards in a relatively high proportion of the water samples from both types of slaughterhouses. 90.74% and 88.89% from the small and medium slaughterhouses were contaminated above the standards with the total aerobic bacteria, 66.67% and 72.22% with E. coli, 5.56% and 27.78% with Salmonella, respectively. It is therefore concluded that pig slaughterhouses in Lam Dong province are not yet satisfactory concerning food hygiene and safety and proper solutions should be warranted to improve the present status.

The aim of the study was to evaluate the growth, survival rate, yield and quality of the oysters with seeds originated from Ben Tre, Tra Vinh and Ca Mau provinces. Oysters were cultured in the canal at Dam Doi district, Ca Mau province. Oysters with initial shell length of 8-9 cm were cultured in the net frame with a density of 140 individuals/m2. After 7 months of culture, the survival rate of Ca Mau oysters was higher than that of Ben Tre and Tra Vinh but the difference was not significant (p > 0.05). Ca Mau oysters reached highest shell length (120.20 ± 0.71 mm), total weight (147.37 ± 1.62 g) and productivity (22.62 ± 0.33 kg/m2) and there were significant difference with oysters originated from Ben Tre and Tra Vinh (p < 0.05). Quality evaluation of oysters showed that the appearance of shell, deliciousness of flesh oysters were not significantly different among oyster sources (p>0.05). Oysters derived from Ben Tre and Tra Vinh provinces can be cultured successfully in canal at Dam Doi district, Ca Mau province. The findings from this study are helpful for aquaculture practices in order to supply oyster seeds from the places that have spat collectors for oyster culture activities in Ca Mau province if neccessary.

This study was conducted to evaluate the effect of salinity stress shock on the growth and survival of postlarval black tiger shrimps (Penaeus monodon). The experiment consisted of 7 treatments. In five treatments for salinity stress, the shrimps taken from 20‰salinity condition were abruptly transferred to 5‰, 10‰, 15‰, 20‰, and 30‰salinity environment. In other two treatments the shrimps reared at 20‰salinity were acclimated for short time (in 3 hours) and long time (in 3 days) to 5‰salinity by adding tap water at stocking density of 2 shrimps/L . After 20 days of nursing, the water condition was in a suitable range for shrimp growth. The growth of shrimp in terms of individual length and weight by sudden salinity changes was not significantly different compared to the control, but the survival was significantly lower. The highest survival rate (98,3%) was observed in the control (20‰) and the lowest survival (60,7%) was found in the salinity shock from 20‰to 5‰. The results indicated that the survival of shrimps was adversely affected when salinity was suddenly shocked at high threshold by 10 - 15‰while the increase in salinity from 20‰to 30‰did not affect shrimp survival. Both short time and long time acclimation did not affect the shrimp survival and growth.

This study was carried out to investigate the suitability of different aquaponic systems to be applied at the suburban household scale. The experimentconsisted of two types of hydroponic sub-systems in three replications;presence and absence of substrate were the main difference of two types of systems. Three leafy vegetables,lettuce (Lactuca sativaL.), curled mint (Mentha spicataL.),and basil (Ocimum basilicumL.) were planted on these two aquaponic systems and watered with water from Tilapia culture at the density of 120 fish/m3. During 70 raising days, the water quality was good especially zero-accumulation of nitrogenous forms NH4-N and NO2-N in spite of daily feeding and zero-water exchange. The two aquaponics systems in this study were suitable for the householdswith a medium size of rooftop and small front yard. Generally, the first system showed sustainabilityand higher potential forfurther developmentas compared to the second system. In order to be applied in the reality, pest management and increasing of fish yield have to be taken into consideration.

This study was conducted to determine selected air pollutant emissions to the atmospheric environment from burning of rice strawin theopen field. The experiments were conducted at six different paddy fields in Gia Lam district, Hanoi. The particulate matter, PM2.5 andPM10, were collected by mini-volume samplers (5L min-1) and CO was sucked into bags and analyzed by UV-VIS spectrophotometer. CO2was determined continuously by Lutron GCH- 2018 gas sensor. Meteorological conditions were measured by handheld device. The results showed that the combustion efficiency were larger than 0.9, meaning that all major combustion processes were flame ignited. The concentrations of CO and CO2from rice straw burning varied between 10.21 ÷ 56.03 mg/m3and 734.5 ÷ 1221.2 mg/m3, respectively, similar to other studies in the same burning mode. PM2.5, PM10concentrations ranged from 0.71 to 29.07 mg/m3and 3.22 to 37.31 mg/m3, respectively, higher than the results of rice straw burning studies in Thailand and similar to the results in China. This emission level was much higher than the background level and much larger than the level justified in QCVN 05:2013 and WHO, causing air pollution and this may affect health of people living around the burning area. The results of the study provide an useful information for further research to determine the emission factors from rice straw burning and more accurate calculation on the amount of emissions from rice straw burning in agricultural production in Vietnam.

The use of a combination of loggers on sloping forest land is common and necessary in northern provinces of Vietnam. It requires safety for people and equipment during operation. The article presents an option for controlling the hydraulic system that holds the timber logger on the sloping land. System pressure can be kept almost unchanged, regardless of the machine's motion condition by automatically controlling the volume of the pump. The authors performed the simulation using MATLAB/Simulink software based on the required data. The operating and control properties of the system indicate that the torsion force is small when the machine speed varies from 0 to 1.7 m/s, the power loss and the duration are not significant. This provides a theoretical basis for the practical application of the system.

Lycopene, one of the natural substances, possesses high antioxidant activity. It is widely used in food, cosmestic, and pharmaceutical industries. Tomato is a rich source of lycopene present in the water insoluble fractions such as skin and pulp. Therefore, solid waste from the tomato processing industry is a potential material for lycopene extraction. This study aimed to optimize factors influencing the drying process of tomato waste to be used for lycopene extraction. Optimal drying temperature and final moisture content were 65oC and 23%, respectively. Under these conditions, the lycopene content of the dried tomato waste was 8.92 mg/g dry matterand the antioxidant activity of the lycopene extract was8.14 µmol TE/g dry matter.

This study aimed to assess the role of the women union in economic development of its member households in Yen Phong district, Bac Ninh province. In addition to the secondary data, 90 members of the women union in three representative communes of the district were selected for direct interviews to collect their assessment on women union’s supportive activities for the household economic development. The study results showed that the women union was very active in dissemination of useful information, transfer of the advanced production techniques to its members, support for the households’ access to loans, and coordination with various agencies in providing vocational trainings and job opportunities for the members, thus significantly contributing to the households’ income improvements. However, results and efficiency of some supporting activities still had some limitations. The enhancement of professional training for the local staff of the women union, more dissemination for raising the members’ awareness, better coodinations with professional agencies, reinforcement of advanced production technique transfers as well as vocational trainings and providing more job opportunities for women, especially the women in poor and vulnarable households should be done for improving the role of the district women union in economic development of its member households in the coming time.

Orange is considered one of the key cash crops in Nghe An, which brings high economic efficiency and contributes significantly to local economy in several districts. The study used data collected from the structured survey with 264 orange producers in three districts and in-depth interviews with extension workers and orange traders. Descriptive and comparative statistics analysis and regression with production function were used. Results showed that orange planting area and productivity increased in the past five years, bringing about VND 143 million /ha/year. The main factors affecting orange production development in Nghe An province included market and marketing of products, climate, pests, capital, planting materials, peicides, water and land. Recommendations for orange production development in Nghe An province were proposed accordingly.