There are two reasons for the rise of the price of onions. One is the farmers don't produce enough onions and the other is onions are exported. There is one reason which is not to be ignored that is in order to make the farmers produce more onions, the price of the oinions are purposely raised. If there is black marketing, the people or public must be responsible for not carrying out the necessary actions.
Control over traders would help to control the price to some extent. Onion is not essential item, we also should ignore the consumption a when the price goes high. Let it get rotten at traders place.