bugs inside the main stalk

Hey guys I just got a call from a fellow grower, he told me he just chopped a sick looking plant from his indoor HYDRO grow and there are little bugs inside the main stem.... I have no clue what it is, he cant take pics. Anyone heard of this on an indoor hydro grow? Or know what it could be?

Their are catapillers that do that..Hard to treat..you can get em by sticking the with a straightened fish hook I have read.

I found out its root aphid.....little Fuckers!

oh crap-..if not flowering a systemic pesticide. Never had to use one..*fingers crossed

He got some Sns209 systemic organic pesticide....