Spatial distribution of the canola false chinch bug, Nysius cymoides (Hem.: Lygaeidae)

The false chinch bugs, Nysius cymoides appears in many canola fields of the country at harvesting time. Spatial distributions of different stages of the bug were studied in canola fields of the Broojerd Agricultural Research Station during years 2006-2007. Twenty to twenty five samples were randomly taken via an aspirator from a 25 cm2 rimmed-quadrate twice a week. Each sample was kept in alcohol and carried to the laboratory for counting number of eggs, different nymphal instars and adult females and males. Spatial distribution pattern of each stage was determined by both Taylor’s power law and Iwao’s regression method. Aggregated pattern was detected by both models for most immature stages and adults. However, the data showed a better fit to Taylor’s model. Both methods demonstrated different patterns for variance-mean model. Iwao’s method predicted larger or negative sample size for low densities of the bug, which is inapplicable. Overall, Taylor’s power law had a better estimation of spatial distribution parameters and predicted smaller sample size than those of Iwao’s regression method for N. cymoides.