Moscow - Swarms of locusts are threatening thousands of hectares of farmland in southern Russia, state media said on Friday, broadcasting striking images of what they claim to be the worst locust invasion in years.Darkening southern Russia's blue skies, a locust invasion is raging in sixteen districts of the southern region of Stavropol, forcing authorities to treat about 90 000 hectares of farmland with pesticides, regional officials said this week. Russian authorities downplayed the scale of the infestation, saying its results would not be catastrophic."The locusts have settled in a few corn fields," the state RIA Novosti news agency quoted a spokesperson of the agriculture ministry as saying on Friday."About 10% of these fields' crops have been destroyed."A recent heat wave that saw temperatures rise to nearly 40°C is thought to have caused the invasion.The insects are now reportedly migrating to neighbouring regions. "We treat a field, but the locusts fly off to the next one," Alexander Bublov, a pilot of an aircraft spraying pesticides over the affected fields, said on national television. "This is the first time I see this in my 30 years of work."