Population dynamics of wheat aphids Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) at District Mardan, Khyber Pakhtunkhwa Pakistan

摘要

Wheat ( Triticum aestivum L.) is one of the major source of food worldwide. However, it ?suffers from numerous constraints. The aphids, particularly Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) species are among the major causes that severly affect wheat production acrossthe globe. To ?determine the population dynamics of aphids associated with wheat crop in Khyber Pakhtunkhwa, we examined the mean population of both species in the selected areas (Maho Dheri, Sarband, Kandare, Rag Narai and Khazana Dheri) of district Mardan in 2015. The mean population of R. padi and S. avenae per plant were recorded every week by counting the number of aphids on 5 plants picked up randomly from each selected wheat field using the diagonal methods. The results on current study showed that the infestation of both aphid species was started in the 1 st week of February (05 standard weeks). The densities of aphids per plant increased as the vegetative growth proceeded and was highest till the mid of March (10 th and 11 th standard week). The declined in aphid populations for both species were started after mid of March and ended in April. The mean population of both aphid species was found low in the 1 st week of February (05 th standard week) that is probably due to the low temperature. The population density of aphids reached to the its peak in the second week of March due to suitable temperature for aphid infestation.