Many growers have had success using the beneficial nematode Steinernema feltiae as a biocontrol agent for fungus gnat larvae and thrips pupae. The nematodes can be applied to growing media via the irrigation system. Screens should be removed prior to application to avoid damaging the nematodes. Preventative applications to moist potting medium are most effective; like most biocontrols, nematodes are best used to keep pest populations low and will not remedy a serious outbreak already in progress. One of the benefits of using S. feltiae is that there is no REI, an added bonus in propagation houses and retail establishments.
S. feltiae is only effective against the soil-dwelling stages of the fungus gnat and thrips life cycles. Because the nematodes do not attack thrips nymphs or adults, they should not be relied upon as the sole method of thrips control. Note also that S. feltiae does not control shore flies; however, the beneficial nematode Steinernema carpocapsae is available to control shore fly larvae and is also easy to apply. Consult your supplier for more information or see our fact sheet: https://ag.umass.edu/greenhouse-floriculture/fact-sheets/biological-control-using-beneficial-nematodes
- Dr. Angela Madeiras, Extension Educator & Diagnostician, UMass Extension Plant Diagnostic Lab