FLIGHT ACTIVITY OF <i>PLUTELLA XYLOSTELLA</i> (L.) (LEPIDOPTERA: YPONOMEUTIDAE)

Abstract

Abstract The flight activity of P. xylostella in Victoria was studied with the aid of suction traps during 1971–74. Flights occurred all the year round with the peaks in the aerial populations coinciding with those of crop populations. There were no indications of discrete generations. The aerial populations were dominated by males, but a large influx of migrant moths in September, October 1973 increased the population of female moths in the area. Onset of flight occurred during the 2 h period prior to sunset, with male and female flight activities peaking at 2–4 and 4 h after sunset respectively. Flights ceased several hours after sunrise, but males had a longer flight period (19 h) than females (16 h). The light thresholds for flight occurred at 1 h after sunset and 1 h before sunrise. The lower temperature threshold was 7 °C and the upper threshold appeared to be above the maximum of 26 °C recorded in this study. At wind speeds of 0.8–2.2 ms ‐1 flights decreased with increasing wind speed. The lower wind speed threshold was below 0.4 ms ‐1 and the upper threshold was determined as 1.7 ms ‐1 . A lunar periodicity of flight activity was demonstrated with maximum flights occurring at full moon. There were 2 minor flight peaks, a few days before and after the day of new moon.