The swarms of locusts which first invaded parts of northeastern Kenya are now in Masinga, Machakos County.
On Monday evening, the first swarm landed in Kivaa Ward, spreading fear and panic among residents who expect a bumper harvest this season and whose crops are still in the fields.
According to Kivaa Ward representative Justus Kiteng'u, the swarm crossed over from Embu County.
He said he had notified the county government which mobilised a team to the site.
Agriculture County Executive Urbanus Wambua said the local government and the Kenya Plant Health Inspectorate Services visited the affected area early Tuesday morning.
"We had our team visit Masinga area where the locusts were sighted last evening. At around 11 am Tuesday, spraying had started and we expect to give a full report by the end of the day," he said.
The devolved unit has been on high alert after the Ministry of Agriculture last week set up a surveillance team that has been monitoring the locusts' movement.
Mr Wambua also urged farmers not to panic as the locusts will be put under control.
The county says it has dispatched three vehicles to the border of Kitui for surveillance and monitoring in Masinga and Yatta.
CAUTION OVER PESTICIDES
Residents, including environmentalist Dr John Musingi and University of Nairobi's Dr Jonathan Nzuma, called for caution with regard to spraying of the insects.
They said the insecticides used should be safe to the environment and livelihoods of the residents.
"Let us have our experts investigate the effect of those insecticides on humans, environment and wildlife. The government is currently using fenitrothion/malathion for control," said Dr Nzuma.
Dr Musingi suggested that the government should instead use nets to trap the insects when they are resting at night.
Non-governmental organisations have also voiced concern about the use of chemical sprays to control the locusts.
In a statement issued by Route to Food Initiative (RTFI), the Biodiversity and Biosafety Association of Kenya (BIBA-K), Kenya Organic Agriculture Network (KOAN) and Resources Oriented Development Initiatives (RODI Kenya) on Monday, the organisations called for use of "less toxic" pesticides.
"Although some of the government interventions have been commendable, our position is that they should use the least toxic pesticides to deal with the menace. People living in the treated areas should be alerted to take precautions to avoid adverse after-effects on human health and the environment at large," said the organisations in a statement.
The team is behind a petition in Parliament to demand withdrawal of harmful toxic pesticides from the Kenyan market.
The petition is currently before the National Committee on Health.