Explanation:
In order for cultural change to take place, the colonizers must begin by introducing their religion. They attempt to allay fears by coming on a platform of peace, but their ultimate goal is to fundamentally change the beliefs of the tribe.
And at last the locusts did descend. They settled on every tree and on every blade of grass; they settled on the roofs and covered the bare ground.
While the quote is a symbolic representation, it accurately reflects the arrival of the intruders who have every intention to take over the Igbo by introducing monotheistic religion and undermining the things that had previously been valued. We see Okonkwo and his son torn apart because Okonkwo cannot accept that his son has forsaken his tribe for Christianity. The tribe is in trouble, and Okonkwo knows there is nothing he can do to stop the death of all he holds dear, as is reflected in the following passage:
The white man is very clever. He came quietly and peaceably with his religion. We were amused at his foolishness and allowed him to stay. Now he has won our brothers, and our clan can no longer act like one. He has put a knife on the things that held us together and we have fallen apart.