Data from a comparative study of the efficacy of Steinernema feltiae for the control of three species of leafminer formed the basis of an application schedule which successfully suppressed an outbreak of the statutory leafminer pest, Liriomyza huidobrensis. All three instars of Liriomyza bryoniae and L. huidobrensis were similarly susceptible to S. feltiae at 20oC and > 90% relative humidity (RH). Although all larval instars of Chromatomyia syngenesiae were susceptible to S. feltiae, mortality was lower than for L. bryoniae. Repeat applications of S. feltiae to L. bryoniae and C. syngenesiae indicated that a nematode treatment to the second/early third instar larvae was more effective than applying higher rates of nematodes when humidities were less than 90% RH. In a trial on lettuce at a commercial glasshouse a mean L. huidobrensis mortality of 82 +/- 5% was recorded after an S. feltiae application, significantly higher than the chemical treatment, heptenophos.