Seasonal phenology of diamondback moth populations in southern Australia

摘要

In the last two decades in Australia，diamondback moth，Plutella xylostella(L.)(Lepidoptera：Plutellidae)，has caused major problems in vegetable Brassica crops due to the increase in levels of resistance to synthetic pyrethroid insecticides.During this time，there has also been a dramatic increase in the area of non-vegetable brassicaceous plants(canola，forage brassicas and brassicaceous weeds)growing in Australia that has provided additional resources for P.xylosteUa.Outbreaks of P.xylostella in these areas are sporadic and appear to be primarily related to climatic conditions. In southern Australia，moths are very abundant in spring and decrease in numbers during summer.We have analysed eight years of pheromone trapping data from Victoria to quantify variations in timing of these spring moth peaks in relation to climatic conditions. The timing of the initial spring peak，using a physiological timescale，was not consistent between years.Low numbers of moths appeared to be overwintering in the crop and most spring peaks could be related to prior peaks，though on some occasions moth peaks were not derived solely from local populations.Major P.xylosteUa outbreaks occurred in canola production areas in Western Australia in 2000 and 200 1 and New South Wales in 2002.We have used climatic analyses and data from insecticide resistance assays to investigate these recent outbreaks.Clear associations between severity of outbreaks of P.xylostella with temperature and rainfall were not demonstrated.However，our analysis suggests that the canola-growing regioas of Western Australia would be more prone to P.xylostella outbreaks than those in New South Wales becanse of the potential for a hiisher number of generations. In both areas，we demonstrated that the level of resistance to permethrin，a synthetic pyrethroid，had risen in P.xylostella and was a contributing factor to the difficulties that growers had in controlling the outbreaks.More long term datasets are needed to validate climatic models for eventual prediction of outbreaks of P.xylostella in Australian canola crops.