ry , ▁con if ers , ▁ros es , ▁tom ato , ▁pot ato , ▁corn , ▁on ion ▁and ▁sugar be ets , ▁and ▁orn ament als ▁such ▁as ▁N arc iss us . ▁More ▁than ▁ 1 6 4 ▁hosts ▁for ▁P . ▁pen etr ans ▁have ▁been ▁recorded . ▁ ▁In ▁the ▁host ▁range ▁there ▁are ▁some ▁hosts ▁that ▁are ▁sus cept ible , ▁such ▁as ▁whe at , ▁o at , ▁field ▁pe a , ▁f aba ▁bean , ▁and ▁ch ick pe a , ▁and ▁some ▁that ▁are ▁moder ately ▁sus cept ible , ▁such ▁as ▁bar ley ▁and ▁can ola . ▁ ▁Some ▁general ▁sympt oms ▁that ▁are ▁produced ▁on ▁inf ected ▁plants ▁include ▁poor ▁growth , ▁fruit ▁spot , ▁and ▁ch lor otic ▁fol i age . ▁ ▁These ▁secondary ▁sympt oms ▁are ▁often ▁due ▁to ▁plant ▁root ▁stress . ▁ ▁These ▁make ▁it ▁rather ▁difficult ▁to ▁diagn ose ▁n emat ode ▁dise ases ▁in ▁general . ▁ ▁The ▁roots ▁when ▁inf ected ▁produce ▁ne c rot ic ▁les ions , ▁which ▁are ▁dark ened ▁areas ▁of ▁dead ▁t issue , ▁on ▁the ▁surface ▁and ▁throughout ▁the ▁cor tex ▁of ▁the ▁inf ected ▁roots . ▁ ▁These ▁les ions ▁turn ▁the ▁root ▁to ▁re dd ish - b rown ▁to ▁black ▁and ▁are ▁initially ▁spot ty . ▁ ▁As ▁the ▁n emat ode ▁continues ▁to ▁feed , ▁the ▁les ions ▁can ▁co ales ce ▁to ▁become ▁large ▁ne c rot ic ▁areas ▁of ▁t issue ▁that