i have found a white maggot in my begonias and what can i do to get rid of it so it wont destroy the begonias

If this 'maggot' is small, hasa reddish brown head and is curled up in the form of a letter 'c' then it is a vine weevil grub and will eat the roots of your begonias. You need to remove the tubers and empty the compost into the waste bin as there will other grubs or eggs in the compost; the little b...s don't come in ones. Make sure that the tubers are clean and then replant in fresh compost.

There is a vine weevil killer that you can water onto the pots but it only works when the weather is warm. Full details on the packaging.

yes its called pravado vine weevil killer. please check all your pots if there in one you can bet there in others..i bought an infected plant some years ago and i still find the little blighters..sometimes in the evening you can find the adults munching on the leaves.. squish them