Population density and spatial distribution of immature stages of Callosobruchus maculatus (Col.: Bruchidae) on cowpea in Tehran region

Population density, sampling program and spatial distribution pattern of the eggs and larvae of Callosobruchus maculatus on cowpea (var. Parastoo) were determined in Tehran region. Bean pod was selected as a sample unit and the reliable sample size with maximum relative variation of 20% was obtained 50. Taylor's power law and Iwao's patchiness regression, Index of dispersion and Lloyd's mean crowding methods were used for determining the spatial distribution pattern of eggs and larvae of the pest. The relationship between length and diameter of pods with number of laid eggs was determined using linear regression. There was significant positive relationship between number of eggs and the length of pods. The relationship between number of eggs and diameter of pods was also significantly positive. There was no significant relationship between number of larvae and length/diameter of bean pods. Moreover, the spatial distribution pattern of immature stages of pest using Taylor's method, index of dispersion and Lloyd's mean crowding was aggregated. Occurrence of the pest in field was observed early summer and irregular population fluctuation was recorded during growing season.