Comparisons of seasonal fluctuations in Uroleucon nigrotuberculatum (Hemiptera: Aphididae) densities between 2003–2004 and 2015–2016 in northern areas of its distribution range in Japan

Abstract

Seasonal fluctuations in herbivore densities are affected by various factors. Solidago altissima was introduced from North America and has spread widely over Japan. Then, an aphid Uroleucon nigrotuberculatum and a lace bug Corythucha marmorata, both associated with S. altissima, invaded Japan in the late 1980s and 2000, respectively. In Miyagi, northeastern Japan, U. nigrotuberculatum and C. marmorata were established in the 1990s and 2012, respectively. We conducted periodic surveys of U. nigrotuberculatum in 2003–2004 and 2015–2016, and of C. marmorata in 2016 in Miyagi. Then, a competition experiment was performed to examine the relationship between them. In 2003, the average maximum daily temperature did not exceed 30 °C and the aphid was continuously confirmed on S. altissima during the census period. In other census years, the temperature exceeded 30 °C and the aphid disappeared in summer. At these sites, C. marmorata was continuously found on S. altissima. The presence of C. marmorata did not negatively affect U. nigrotuberculatum in the competition experiment. In addition, peak densities of U. nigrotuberculatum were higher in 2015–2016 than in 2003–2004. Based on these results, we conclude that U. nigrotuberculatum populations were at least partly affected by high temperature during the summer, but not by C. marmorata invasion in Miyagi.