The bugs are destroying crops and invading farmhouses on the island, particularly in Ottana and Orani in the central province of Nuoro.
More than 2,000 hectares of farmland has been destroyed, as videos shared by Italian media appear to show fields covered in “carpets” of the insects.
At least a dozen farms have been ravaged, with animal grazing pastures ruined and "little left to harvest", Italy's La Stampa newspaper reported.
The bugs normally appear across Italy in June, July and August. But the unusually large number in Sardinia has been linked to last week's sudden rise in temperatures after months of unusually cold weather.
"There are millions in the countryside," the Italian farmers' association Coldiretti warned in a statement on Monday.
"The locusts emerge on uncultivated land, but then they go to cultivated land to eat," the group said, adding that there was little that could now be done to remedy the situation.
Cultivating land for crops discourages the insects laying their eggs in the autumn and prevents them reaching maturity in the summer warmth, the group advised.ù
Meanwhile, residents of some parts of Northern Italy are reportedly barricading themselves inside their homes as the regions of Lombardy, Piedmont and Emilia-Romagna are battling a plague of brown marmorated stink bugs, Coldiretti added.
The unusual bugs, which Coldiretti said have "few natural enemies" in Italy, have destroyed swathes of fruit trees across the northern regions.