▁effective ▁to ▁reduce ▁field ▁population ▁levels ▁to ▁below ▁economic ▁damage ▁th resh olds . ▁ ▁Ne wer ▁methods ▁ ▁An ▁area ▁of ▁on going ▁research ▁is ▁using ▁orn amental ▁species ▁to ▁reduce ▁in oc ul um ▁levels ▁of ▁n emat odes ▁in ▁the ▁fields . ▁ ▁G row ing ▁Tag etes ▁mar ig olds ▁has ▁been ▁shown ▁to ▁reduce ▁Pr aty len chus ▁numbers ▁by ▁ 9 0 %. ▁ ▁Other ▁orn ament als ▁such ▁as ▁H elenium , ▁Ga ill ard ia , ▁and ▁E ri oph yll um ▁also ▁suppress ▁P . ▁pen etr ans . ▁ ▁All ▁of ▁these ▁tact ics ▁require ▁accurate ▁diagn osis ▁of ▁species ▁and ▁identification ▁of ▁population ▁levels ▁ass essed ▁from ▁soil ▁and ▁root ▁samples ▁taken ▁from ▁the ▁field . ▁ ▁C ertain ▁factors ▁like ▁exp ense ▁and ▁types ▁of ▁cro ps ▁have ▁influ ences ▁on ▁the ▁types ▁of ▁control ▁methods ▁employed . ▁ ▁When ▁comb ating ▁Pr aty len chus ▁pen etr ans ▁several ▁methods ▁of ▁control ▁and ▁management ▁are ▁usually ▁employed ▁for ▁cont rolling ▁the ▁disease . ▁ ▁Import ance ▁ ▁Root ▁les ion ▁n emat odes ▁are ▁third ▁behind ▁root ▁kn ot ▁and ▁c yst ▁n emat odes ▁for ▁the ▁greatest ▁economic ▁impact s ▁on ▁cro ps ▁world wide . ▁ ▁It ▁is ▁the ▁most ▁important ▁n emat ode ▁p est ▁in ▁the ▁n ort he astern ▁United ▁States . ▁Plant ▁vari eties ▁sus cept ible ▁to ▁the ▁respective ▁fung i ▁are ▁dam aged ▁even ▁more ▁when ▁the ▁plants ▁are ▁inf ected ▁with