Distribution of Parthenium hysterophorus L. in the Swabi district of Khyber Pakhtunkhwa.
Parthenium weed (Parthenium hysterophorus L.) is an annual, herbaceous invasive weed but it is perennial in Pakistan. Parthenium weed is a weed of a national significance in Pakistan. Although, parthenium weed is infesting many parts of Khyber Pakhtunkhwa province, but more affected regions are Peshawar valley and Hazara division where it has enormously invaded most of the open spaces like roadsides, wasteland and water ways resulting in loss of local biodiversity. Field survey of district Swabi (Peshawar Valley) of Khyber Pakhtunkhwa, was carried out during May-June, 2013-14 to study the distribution of Parthenium weed. Five villages were selected and thirty locations were randomly selected from each village. The data revealed that the flora is predominated by parthenium weed with the highest relative density of 63.4% among all weeds, followed by Cynodon dactylon (L.) Pers., Cannabis sativa L. and Chenopodium album L. with relative density of 11.37, 10.86 and 7.31%, respectively. Moreover, at different locations, the parthenium weed is competing with C. sativa which is not problematic like parthenium weed and replaced by the latter. Mean distribution of parthenium weed infestation was abundant and almost not uniform in all sites, because some sites were in hilly area. The computed data showed that the highest relative frequency of 28.71% was recorded for parthenium weed followed by C. sativa, C. dactylon and C. album having relative frequency of 13.33%, 12.71% and 10.16%, respectively. Comparatively, the other weeds were having a very low relative density and relative frequency at most of the locations studied. Importance value also shows that P. hysterophorus, C. sativa, C. dactylon and C. album were predominant weeds in district.