Farmers in Tharaka-Nithi County have lost at least 2,403 metric tonnes of food crops to desert locusts.
More than 30,000 acres were invaded by the insects in Tharaka North Sub-County, according to Governor Muthomi Njuki.
Green grams, millet, sorghum, cowpeas and peas had started maturing for harvest when the insects invaded last month and munched through most of it.
Speaking on Wednesday at Kathangacini area in Tharaka North Sub-County during the commissioning of 100 National Youth Service (NYS) youths who joined hundreds of locals in spraying hatched locusts, Mr Njuki said they target to kill new swarms in the next one week.
Some 15,000 acres have been sprayed so far and the locusts had died, he said.
"The earlier swarms laid eggs in all the 30,000 acres of farms and bushes ... a big population of a new generation of swarms had hatched posing a big threat to locals," said Mr Njuki.
He said the county government had procured 150 pumps, 122 litres of chemicals and is providing water to locals who are also using their farm knapsack sprayers to battle the nymphs before they develop wings and fly away.
Governor Njuki, who is also the Council of Governors' Committee on Agriculture Chairperson, said the NYS team led by Inspector Jacob Barwecho will remain in the region until all swarms are killed.
He also praised the collaboration between the affected counties and the national government in combating the ravenous insects that threaten food security in the country.
The county boss noted that the spraying exercise, which started a week ago in Kamaguna Village, was progressing well but urged more locals to volunteer.
County Agriculture Executive Njagi Njue asked locals to keep livestock away from sprayed vegetation for at least one week to avoid poisoning their animals.
He asked the residents to always report to the village managers whenever they notice hatching of new swarms for immediate spraying.
"We want to make sure that we kill the hatched locusts before they grow wings because, at that age, they are easily managed," said Mr Njue.