Does streptobacillary arthritis reduce house mouse population density, activity and damage to sorghum crops?

An experiment to examine the effect of streptobacillary arthritis on mouse populations was conducted in maturing sorghum crops in mouse-proofed pens. There were three treatment pens and three control pens in which mice with and without clinical signs of streptobacillary arthritis were introduced, respectively. A constant mouse density (533 mice ha(-1)) was introduced to the pens by releasing 12 mice in each pen. The sex ratio of introduced mice was also constant by releasing in each pen nine males and three females. Mean track index was lower in treatment pens than in control pens, indicating that streptobacillary arthritis reduced the activity of mice. However, this was not translated into a reduction in other population responses. Mean mouse density at harvest, percentage of female pregnant at harvest, yield loss caused by mice and a feeding index (oil card index) did not differ significantly between treatment and control groups. A plausible explanation for these findings was that mice with the clinical signs might be less active but were able to consume as much grains as mice without the clinical signs because food was in abundant supply

Accuracy assessment of moderate resolution image spectroradiometer products for dust storms in semiarid environment

Dust storms are strongly and negatively associated with the annual cycle of rainfall and coincide with the west and southwesterly winds in west and south west of Iran. Accuracy assessment of particulate matter products of moderate resolution image spectroradiometer was studied in this research. Moderate resolution image spectroradiometer products consist of aerosol optical thickness, its corresponding image red, green and blue and moderate resolution image spectroradiometer/ terra calibrated radiances 5 minutes L1B swath 1 km, which shows the environmental information at terrestrial, atmospheric and ocean phenomenology. Daily aerosol optical thickness data retrieved from moderate resolution image spectroradiometer from May 2009 to May 2010 were compared with the amount of particulate matter measured at ground in Sanandaj, Iran, using non-linear correlation coefficient. Results showed that the moderate resolution image spectroradiometer image / terra calibrated radiances 5 minutes L1B swath 1 km is able to detect dust storms distribution and their blowing direction over study area clearly. The air quality conditions obtained in with dust storm period were unhealthy and correlation coefficients between moderate resolution image spectroradiometer aerosol optical thickness and particulate matter concentration in this period were higher than without dust storm period. The moderate resolution image spectroradiometer aerosol optical thickness values lower than 0.1 were acquired uncertainty level. Comparison of moderate resolution image spectroradiometer images/ terra calibrated radiances 5 minutes L1B swath 1 km and image red, green and blue showed that moderate resolution image spectroradiometer has limitation in retrieval of aerosol optical thickness from the dust storm with high concentration of particulate matter. This study reveals that the algorithm which is applied to refine the aerosol optical thickness is not able to recognize the amount of particulate matter in low and very high concentrations sensitively. No study has previously been conducted to investigate the accuracy of the moderate resolution image spectroradiometer particulate matter products

Rats in rice: Linking crop and pest models to explore management strategies

Context Rodents cause yield losses of 1015% in irrigated lowland rice crops in Vietnam, with farmers spending a lot of time and money trying to control them. Despite this, there is little understanding about the optimal timing of rodent control and the level of reduction required to maximise rice crop yields. This is compounded by the ability of rice crops to compensate for damage, and farmers applying control at the wrong time. Aims We explored the optimal timing and intensity of rodent control required to increase yields of irrigated lowland rice crops in the Mekong Delta, Vietnam. Methods We developed a system analysis framework using the rice model APSIM-Oryza validated against a hand-clipped field experiment, linked with a rodent population model and field data on rodent damage rates in rice crops. A range of intensities of reduced feeding rates and timing were explored in simulated scenarios. The responses were examined over three rice crop seasons in An Giang province, Mekong Delta, Vietnam. Key results The rice crop model was benchmarked, validated and shown to adequately compensate for rodent damage. Highest yield losses occurred in the third rice crop (16% yield loss). A one-off rodent control action at the booting stage of the rice crop with 50% control effectiveness achieved a 5% yield increase. The community trap barrier system (CTBS) with 30% control effectiveness achieved a 5% yield increase. Conclusions The modelling demonstrated the importance of rodent management timing and that control should be applied before the onset of the rodent breeding season, which normally starts at maximum tillering or booting stages. Implications We conclude that modelling can improve pest management decisions by optimising timing and level of effectiveness to achieve yield increases