Grasshopper Problems in Yacutia (Eastern Siberia, Russia) Grasslands

Abstract

The zone of natural Yacutia grasslands is situated between 60-64'N and 130-1350E. Vegetation of the meadow-steppe occupies vast glades dispersed in woodlands. These glades are inhabited by a dozen grasshopper species, three of which (Chorthippus albomarginatus, Aeropus sibiricus, and Omocestus haemorrhoidalis) are of economic importance. Most (up to 98%) of the grasshopper population consists of C. albomarginatus, which can produce mass outbreaks in years with deficient rainfall. Overgrazed pasture grasslands are particularly subject to grasshopper depredation. A recent outbreak took place in 1986-87, and an upsurge was observed in 1992. Prospective control strategies are under discussion-including rotational grazing, grassland management, and effective utilization of appropriate chemical measures on limited areas based on phenology forecasts. Special consideration is given to the search for and possible utilization of alternative control agents. Locusts and grasshoppers are pests of major economical im- portance in the countries of the former USSR: in the late 80s and early 90s of the twentieth century, they were controlled by insec- ticide treatments on the surface more than 4 million ha annually. In Russia, the annual average area of anti-locust and grasshopper treatments usually does not exceed 300,000 ha. However, in years of heavy outbreaks, it can reach (as it did, for example, in 1993) more than 600,000 ha. A remarkable zone in Russia where grasshoppers systemati- cally inflict damage is Yacutia, a vast region situated in the northeastern part of Siberia between 550 and 751N and 1070 and 162?E. It extends over 3,103,000 km2 (more than one-fifth of the entire area of Russia). The greatest part (80%) of Yacutia is covered by coniferous forest, the taiga, where the larch, Larix gmelini predominates. However, in the central area, the landscape is characterized by the alternation of forests and natural glades with grassland vegetation of a meadow-steppe type that is unique for this boreal region. It is in this zone, which is intensely exploited for cattle and horse breeding-the main occupation of Yacutians- that the principal sites of grasshopper outbreaks are concentrated.