root-lesion disease, which is caused by pratylenchus loosi , is one of the most important diseases currently impacting iran tea plantations. this disease causes great economic crop impacts. northern provinces, which supply much of iran’s tea production, have been especially hard impact by root-lesion disease.the purpose of this study was to biological control the nematodes as one of the main se...

This paper studies an otherwise standard principal-agent problem with hidden information, but whether there are positive production externalities between agents: the output of any agent depends positively on the e¤ort expended by other agents. It is shown that the optimal contract for the principal exhibits two-way distortion: the e¤ort of any agent is oversupplied (relative to the ...rst-best)...

Contests are a common method to describe the distribution of many di¤erent types of rents. Yet in many of these situations the utilisation of the prize plays an important role in determining agents’payo¤s and incentives. In this paper, we investigate the incentives to expend e¤ort for a prize that produces consumption externalities and consider alternative regulatory policies. We …nd relatively...

ornithobacterium rhinotracheale (ort) has been identified as one of the respiratory bacterial pathogens in turkey and chicken flocks. four live birds displaying severe torticollis were submitted from a 13-week-old commercial broiler breeder chicken flock located in mazandaran province. these birds were suspected to pasteurellosis by the farm veterinarian. no other marked gross lesion except em...

Objective(s): The use of new technologies, which can be realized as nanotechnology, is a novel approach in this sector. Covers made of silver nanoparticles effectively prevent and reduce invasion of microorganisms, compared with other conventional covers. This study was conducted to determine the effects of nanosilver covers in comparison with other conventional covers. <stron...