New swarms of desert locusts are threatening the livelihoods of millions of people in the Horn of Africa and Yemen despite a year of control efforts, the United Nations has warned.
The UN says there have been good breeding conditions in eastern Ethiopia and Somalia, with Kenya also at risk.
And breeding underway on both sides of the Red Sea poses a new threat to Eritrea, Saudi Arabia and Yemen.
This year had already seen the worst East Africa invasion in 70 years.
"For Kenya, the threat is imminent, it could happen any time now," Keith Cressman, the UN Food and Agriculture Organisation's senior locust forecasting officer told the BBC.
"It could be as bad as what we've seen in the past year because the area of breeding ground in these countries is as big as 350,000 sq km (135,000 sq miles)."
Between January and August this year East Africa saw billions of the insects destroying crops across the region.
"We lost so much of our pastures and vegetation because of the locusts and as a result we are still losing a good number of our livestock," said Gonjoba Guyo, a pastoralist in North Horr sub-country in northern Kenya.
"I have lost 14 goats, four cows and two camels because of the locust outbreak and now there is lots of fear that we may face similar or worse consequences."
FAO officials said countries in the region were now much better prepared than for the last invasion.
They say surveillance is high, and preparedness - such as spraying pesticides on the ground or from aeroplanes - is much better, with over one million acres of land treated for infestations in 10 countries.
But there are fears that communities might be overwhelmed if the swarms are really big.
So, how could the locusts breed again on such a threatening scale?
Experts say central Somalia and eastern Ethiopia received higher than average rainfall in the rainy season from September and November.
That meant the ground saw significant generation and expansion of vegetation.
"That became a really good breeding ground for the locusts," said Mr Cressman. "And these areas are really huge breeding areas."
With these conditions, within a couple of months locusts move from single insects to acting as a part of a group.
This then leads to small bands of wingless hoppers and small swarms of winged adults.
According to a report by the FAO and the World Meteorological Organisation, desert locusts can multiply massively and within a year there can be 160,000 times as many as at the outset.
Given its arid topography, northern Somalia was expected to make things difficult for the locusts.
But in November, Cyclone Gati did just the opposite when it made landfall there.
It brought two years of rainfall within two days and what could have been a hostile terrain for the locusts turned into a favourable breeding ground.
After the floods, the moist soils became ideal for the locusts to lay eggs and they also had an unexpected growth of vegetation to feast on.
Somalia was also one of the countries in the region worst affected by the desert locust upsurge this year.
Experts say increased surveillance in several affected regional areas have helped keep locusts away.
But they say it has not been possible where the security situation is not under control.
"For instance, there has been no surveillance in southern Somalia," said Mr Cressman.
Yemen is another country that has several breeding grounds of desert locusts.
But the conflict there has meant surveillance has not been possible in several areas.
Experts say locusts have also been migrating to Saudi Arabia from Yemen.
They can also regularly cross the Red Sea, a distance of 300km, as they can stay in the air for long periods.
Countries in the region have also prepared themselves to use pesticides on the ground and from the air.
"Control operations have prevented the loss of an estimated 2.7 million tonnes of cereal, worth nearly $800m in countries already hard hit by acute food insecurity and poverty," the FAO said in a statement.
But experts say more funding is needed to match the challenge.
"We are doing the surveillance but we have not been given any equipment or pesticides to spray," said Jeremiah Lekoli, an environmental scientist who is also working as a locust surveillance scout in the Marsabit county of northern Kenya.
"It is very important we have those things, otherwise by the time they arrive the locusts will have caused the damage and have left."
The FAO has warned that more than 35 million people are already acutely food insecure in the five most-impacted countries.
It says that number could increase by another 3.5 million if nothing is done to control the latest outbreak.