Steinernema carpocapsae is a beneficial nematode, a microscopic roundworm, used in biological pest control. These parasitic organisms infect and kill various insect pests in agricultural and horticultural environments. They are considered a natural and environmentally sound method for managing insect populations, offering an alternative to chemical pesticides.
How It Controls Pests
The life cycle of Steinernema carpocapsae involves a symbiotic relationship with bacteria, primarily Xenorhabdus nematophila. The infective juvenile (IJ) stage of the nematode is the non-feeding, free-living form that actively seeks out insect hosts in the soil. These IJs are typically between 0.4 to 1.5 mm in length.
Upon locating a suitable insect, the nematode penetrates the host’s body, usually through natural openings such as the mouth, anus, or spiracles, or sometimes through thin areas of the cuticle. Once inside the insect’s body cavity, the nematode releases its symbiotic Xenorhabdus nematophila bacteria. These bacteria multiply rapidly within the insect’s hemolymph, causing septicemia and leading to the host’s death, typically within 24 to 48 hours.
The nematodes then feed on the multiplying bacteria and the liquefied host tissues. They develop through several juvenile stages to adult males and females, which reproduce within the insect cadaver. After consuming the host, hundreds of thousands of new infective juveniles emerge from the insect’s remains, ready to seek out new hosts and continue the cycle.
Target Pests and Application Methods
Steinernema carpocapsae is effective against a variety of insect pests, particularly many lepidopterous larvae. These include surface-dwelling insects such as cutworms, armyworms, sod webworms, and various webworms. It also controls some below-ground insects like certain weevils, wood-borers, and billbug larvae. This nematode’s “ambush” foraging strategy, where it stands upright and attaches to passing hosts, makes it particularly effective against mobile surface-adapted insects.
For successful application, specific environmental conditions are important. Steinernema carpocapsae is most effective at temperatures ranging from 22 to 28°C (72 to 82°F), though it can be active between 14 to 34°C (57 to 93°F). Temperatures below 5°C (41°F) or above 35°C (95°F) can be lethal to the nematodes.
Nematodes should be applied in the early morning or late evening to minimize exposure to ultraviolet (UV) light from direct sunlight, which can harm them. High soil moisture is also important, with irrigation recommended before and immediately after application to ensure the nematodes can move effectively through the soil. Maintaining soil moisture for several days post-application helps the nematodes establish. For foliar applications, relative humidity should exceed 75% for several hours after treatment. Nematodes are typically mixed with water and applied using various sprayers or irrigation systems, and continuous agitation of the solution is recommended to prevent settling.
Advantages as a Biological Control
Using Steinernema carpocapsae as a biological control agent offers several environmental benefits. This method reduces reliance on chemical pesticides, potentially decreasing their use by up to 70%. This minimizes the risk of soil and water contamination, contributing to a healthier ecosystem.
Steinernema carpocapsae is considered safe for humans, pets, and beneficial insects, such as bees and ladybugs, as it specifically targets insect pests. Pests do not develop resistance to these nematodes, which is a common issue with chemical insecticides. This makes Steinernema carpocapsae a sustainable option for long-term pest management.