I have an 850 foot ficus hedge infested with white fly. What treatment do you recomend? Someone suggested PERMETHRIN or BIFEN to kill adult & larvae and MERRIT or MALLET as a granular systemic? Also, knowing the PERMETHRIN or BIFEN will not completly eradicate the pesty little bugs on the first pass, how long should I wait for a second treatment and perhaps a third? I am open to suggestions.