The influence of nitrogen fertiliser on the population development of the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.) on field grown winter wheat.

摘要

The effect of nitrogen fertilizer on populations of Sitobion avenae and Metopolophium dirhodum on winter wheat was investigated in Cambridge, UK, during 1993-95. Naturally-occurring aphid populations were monitored with 3 nitrogen treatments: none;nitrogen application using Canopy Management guidelines (130-210 kg/ha); and conventional practice (190 kg/ha). Laboratory-reared S. avenae were used to enhance field populations on half the plots. Natural populations of M. dirhodum remained below the current UK spray threshold level of two-thirds of shoots infested at the start of flowering, or 5 aphids/shoot, in all years, whilst populations of S. avenae exceeded the threshold in all years. The response of these species to nitrogen differed. Significantly higher populations of M. dirhodum were recorded in both nitrogen treatments in all years, whilst the response of S. avenae varied between years. In 1994 and 1995, when environmental conditions favoured aphid development, higher populations were recorded in the nitrogen treatments. In 1993 when high rainfall created unfavourable conditions, higher populations were recorded in the plots receiving no nitrogen. Differences in peak density and cumulative aphid index of S. avenae resulted from differences in the rate of population increase between ear emergence and peak density on the different treatments. Populations prior to ear emergence were higher in the plots which received nitrogen, but the differences were not statistically significant. In 1993,higher levels of infection by entomogenous fungi were observed in all treatments, with significantly higher levels of infection in treatments receiving nitrogen.