Trajectory Analysis Of Wheat Aphids During Long-distance Migration Using HYSPLIT Model

Wheat aphids, predominantly Sitobion miscanthi (Takahashi), Rhopalosiphum padi (Linnaeus) and Schizaphis graminum (Rondani), are important insect pests which damaged about 16.7 million hm2 of wheat in north China in 2009. Understanding the long-range migration of wheat aphids is therefore of great importance to the area-wide pest management in wheat producing regions.Wheat aphids make long-distance migrations with the aid of the prevailing winds. The internet-based HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model of NOAA (the National Oceanic and Atmospheric Administration, USA) provides a means of simulating the migration trajectories of small insects, such as aphids. The profile of aphid density was determined with a series of balloon-supported yellow traps located vertically at heights of up to 100 m above ground level, and migration trajectories of aphids at the various heights was simulated with the HYSPLIT model.The helium-filled balloon of about 55 m3 volume was tethered at height of 110m by three chinlon cords. A fourth cord carried the series of sticky yellow traps (Jiaduo Scientific and Industrial Ltd) suspended beneath the balloon. The sticky traps took the formed of cylinders (diameter = 25 cm, height = 60 cm) attached to the vertical cord at intervals of 10 m. The balloon-suspended trapping system was operated between 21 and 28 April, 2009 at Luoning ( E111°39′11″,N34°22′58″) of Henan province. The aphids trapped were predominantly Sitobion miscanthi and Rhopalosiphum padi. The aerial density of aphids (number per trap) showed stratification according to height above ground.(1)The backward trajectories of aphids starting at Luoning at 11h, at heights of 10 m, 40m, 70m and 100m were simulated with the HYSPLIT model (http://www.arl.noaa.gov/HYSPLIT.php). The simulated migration distance starting at a height of 100 m, with a duration of 24 h, was generally greater than trajectories starting at other heights. In most of the cases (6 out of 8) the aphids migrated towards the north and the maximum distance moved within 24 h was 500 km or 490 km on 28 April.(2)Between 28 April and 19 May, 2010 at Luoning ( E111°39′11″,N34°22′58″) of Henan province. May 5-May 8 was the peak of immigration of Sitobion miscanthi. Sitobion miscanthi which immigrated within 24h using backward trajectory might come from Nanyang city, Henan province; Shangluo, Weinan, Tongchuan, Shanxi province. May 14-May 16 was the peak of emigration of Sitobion miscanthi. Sitobion miscanthi might move north to Shanxi, Hebei, Anhui, Shandong province using forward analysis of dispersion model。The maximum distance moved within 24 h was 600 km or 590 km.