Nematodes associated with dipterous stem-boring larvae (Chloropidae and Opomyzidae) in ryegrass

Associations between different species of nematodes and stem-boring larvae were studied over two years. Howardula oscinellae was rarely found in stem-boring larvae. Usually mermithids were also uncommon, but in one Italian ryegrass (Lolium multiforum) variety trial over 12.5% of stem-boring larvae were attacked, with different levels of parasitism in larvae from the different ryegrass varieties. Panagrolaimus rigidus nematodes were also identified from stem-boring larvae and Oscinella frit larvae were the most common host. Greater infestation levels of P. rigidus were found in larvae from grazed swards than from cut swards. P. rigidus may cause the death of some stem-boring larvae.