Gypsy Moth Population in Hovsgol Region, Mongolia
Baigal-Amar Tuulaikhuu and Paul W. Schaefer
The gypsy moth (Lymantria dispar dispar) is a serious pest of deciduous trees in temperate areas of the northern hemisphere. In Europe and in parts of eastern United States a non-flying female form (European (EGM) or North American (NAGM)) occurs, while in eastern Asia, a flight capable female Asian gypsy moth (AGM) form occurs. Historically, rather little has been written about the Asian Gypsy Moth (AGM) in Mongolia but in 2002-2004, this moth has come to the attention of everyone from local herdsman to government official. In late July and August, literally millions of female moths have taken to the air and drawn the attentions of all. In villages, towns and cities, female moths fluttered most everywhere and created a nuisance by laying their eggs masses on drying cloths, fabrics, buildings, both outside and in. The moth proved to be a widespread general nuisance during the flight of female moths. The suddenly occurred outbreak of gypsy moth required to monitor continuously, to clarify the biology and ecology of Asian gypsy moth in Mongolia, illustrate the periodicity of its population dynamics and to identify causative agents affecting the outbreak and to find biological control agents for population suppression
In an unpublished internal government report, Tegshjargal (2002) reported that outbreaks had occurred as early as 1928, again in 1970-74, and in 1989 in northeast Khangai and at Khentii Mountain. Tsendsuren, Dubeshko (1989) and Tegshjargal (2001) in listing forest insect pests in Lake Hovsgol Region, omit any mention of this insect as a defoliating pest.
According to Hatgal meteorological station, in the project Study site, until 2000, summer average air temperatures never reached 12OC, which appears near the threshold necessary to support successful larval development.
We monitored population density, body size and reproductive capacity of the cyclic lepidopteron, the Asian gypsy moth (Lymantria dispar dispar), from outbreak phase to the latent density phase in northern Mongolia. Larval density of the species increased exponentially from 2001 to 2002 and remained at the outbreak level also in 2003. Then rapidly decreased in 2004 and 2005 year density was the latency for this species. In the outbreak years, the body size and fecundity of individuals was smaller and in latent years these same measurements increased as analyzed from several parallel datasets on adults. Possible factors responsible for the reduced size and fecundity of individuals in the Mongolian gypsy moth population were quantitative shortage of foliage, rapid and delayed inducible resistances of the host, Siberian Larch (Larix sibiricus), as well as crowding-induced responses of larvae.
While the gypsy moth are surveying, 53 species, including in 5 orders, 22 families, of forest pest insects were recorded. For feeding group, 25 of them are foliage eating, 20 of species of them are bark and stem insects, 5 species are root insects, and 3 species are corn insects.