Bug Word of the Day: Entomopathogenic
Entomopathogenic is a long adjective that simply means, “capable of causing disease in insects.”
Most commonly, the term refers to nematodes, fungi or bacteria that cause potentially fatal diseases in insects. Entomopathogenic organisms play an important role in Integrated Pest Management, or IPM (see this week’s Bug Word of the Day selections) and biological control programs, because they are a non-toxic, environmentally friendly way to eliminate pests.
Even better, many entomopathogenic organisms are host-specific and can be easily distributed without concerns about unwanted side effects on other beneficial insects, like bees and ladybugs. The entomopathogenic organisms most commonly used in Florida include fungi, nematodes and bacteria.
Let’s look at entomopathogenic nematodes as an example:
The nematodes used for biological control have an unusual trait – symbiotic bacteria live in their intestines. As juveniles, these nematodes enter an insect host, and then transfer bacteria from their intestines to the host. The bacteria then multiply inside the host, causing death within 24 to 48 hours. After the host dies, the nematodes feed on the host and continue to reproduce.
There are two nematode families that include entomopathogenic species used commercially, Heterorhabditidae and Steinernematidae.
These nematodes can be classified, informally, based on their feeding behavior – they are either ambushers or cruisers. Ambushers, such as Steinernema carpocapsae, conserve their energy and wait in the upper soil to attack more energetic insects that might pass by. Cruisers, on the other hand, take the opposite approach, moving across long distances to seek out their hosts.
Large quantities of entomopathogenic nematodes can be produced for commercial use as biological insecticides. Production is accomplished in two ways. For in vivo production, nematodes are cultured inside a live insect host, usually the larvae of the wax moth species Galleria mellonella, and the juveniles are captured for distribution. This method is best for small-scale production or studies done in a lab. On the other hand, experts say that in vitro culturing, without the use of live hosts, is best for producing large numbers of nematodes.
Entomopathogenic nematodes must be handled properly because the nematodes are sensitive to stressors such as extreme temperatures and UV light. When it’s time to distribute them, however, farmers and technicians can use common horticultural equipment with large diameter nozzles, including pressurized sprayers, mist blowers, and electrostatic sprayers.
You can read more about entomopathogenic nematodes in this “Featured Creatures” document from the UF/IFAS Entomology and Nematology Department. http://entnemdept.ufl.edu/creatures/nematode/entomopathogenic_nematode.htm
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Photo by Bonsak Hammeraas, NIBIO – The Norwegian Institute of Bioeconomy Research, Bugwood.org