Did you know nematodes are the most abundant animals on earth? Nematodes are microscopic round worms that are extremely common in soils. There are over 25,000 species of nematodes, most of which are considered to be beneficial and feed on bacteria, fungi or insect larvae. The beneficial characteristics of one species of nematode, Steinernema feltiae, are even exploited in some commercial greenhouses in order to reduce pest populations (Fig. 1).
Figure 1. Steinernema feltiae is an entomopathogenic nematode (left) that can be drenched into growing media of ornamental crops in the greenhouse (right) to control western flower thrips and fungus gnats.
S. feltiae are entomopathogenic on western flower thrips larvae and fungus gnat larvae, which are two major greenhouse pests. Applying S. feltiae as a soil drench in the greenhouse reduces the populations of western flower thrips and fungus gnats in greenhouse crops. However, there are some nematodes that can also be considered harmful to ornamental crops, such as the northern root knot nematode, Meloidogyne hapla (Fig. 2).
Figure 2. Meloidogyne hapla is a pathogenic nematode of field-grown ornamental crops such as daylilies.