Jeffery K. Tomberlin, Assistant Professor & Extension Specialist, Texas A&M AgriLife Extension, Stephenville, TX
Department of Entomology, Texas A&M University
IDENTIFICATION: Like its name suggests, the adult black soldier fly is black in color and measures approximately 5/8 of an inch. Its elongate shape and black body allow for easy identification. It has one pair of wings and two translucent spots located along its midsection, which give it a wasp-like appearance (Figure 1). Black soldier fly larvae are more commonly encountered than adults and can be identified by their large size (as long as the adult), and dark-spined skin (exoskeleton) (Figure 2).
ECONOMIC IMPORTANCE: Black soldier fly larvae will occasionally be found in association with decaying organic matter around faulty plumbing, such as underneath toilets or sinks. Additionally, the black soldier fly will colonize earthworm beds, and the larvae occur at high densities in manure basins in confined animal facilities. In the past, it was thought larvae in confined animal facilities were pests because colonized manure would liquefy and spill outside of the basins. However, more recent evidence has determined that these flies are beneficial, and their presence can result in 95-100% suppression of house fly populations by out-competing house fly larvae for resources in the manure. Additionally, black soldier fly larvae can reduce manure accumulation and associated nutrients by 50%. Moreover, the larvae can be self-harvested and utilized as animal feed.
Figure 2. Black soldier fly larva
(Photograph courtesy of Dr. Craig Sheppard, Department of Entomology, the University of Georgia).
BIOLOGY AND HABITAT: The black soldier fly has a complete life cycle with an egg, larva, pupa, and adult stage. Eggs are often deposited in decaying organic materials, such as fruits, vegetables, animal feces, and even human remains. At 81oF, the egg takes approximately 4 days to hatch, while the larval stage can be completed in 21 to 45 days depending on food quality, as well as temperature. The pupal stage lasts approximately three weeks. Adults do not feed and live approximately 15 days. Adults are often found in vegetation surrounding livestock facilities, and adult males will remain in these areas, find a female, and mate. Mated females return to a larval resource only to deposit their eggs and then die soon thereafter. The black soldier fly has three generations per year in the southeastern United States and is active from April through October depending on prevailing temperatures. Temperatures above 80oF will often result in adult black soldier flies emerging even during the winter. However, once the temperature drops, adult populations will once again be suppressed.
MANAGEMENT: If control is desired, it is suggested that an integrated pest (IPM) management approach be used. IPM relies on three tactics for successful suppression of an insect pest.
- CULTURAL: Cultural methods rely on manipulating the environment to reduce insect pest populations, such as removing black soldier fly breeding sites, such as piled manure, from the vicinity of a confined animal facility. Often in livestock facilities, removal of all manure can be difficult due to the sheer volume being produced. Therefore, it is suggested that the manure be aerated to reduce the moisture content below 40%, which is attractive to females looking for oviposition sites. If the black soldier fly problem is inside a home or building, it is recommended that the larvae be removed by hand, the larval food source, i.e., accumulated feces, removed, and any faulty plumbing from which the resource, such as accumulated feces, is being released fixed.
- BIOLOGICAL: Biological control uses predators, parasites, and pathogens to suppress pest species. Parasitic wasps, which are extremely small, will lay their eggs in immature black soldier flies. The wasp eggs deposited inside the black soldier fly larvae will hatch and resulting offspring will then feed on the black soldier fly and eventually killing it. The immature parasitic wasp will develop into an adult and repeat its life cycle. Many of the wasp parasites used to control house fly and other livestock-fly pests will also parasitize black soldier fly larvae. These parasites are available commercially and can be purchased and used to augment local parasitic wasp populations. However, it is important to realize that although parasitic wasps will offer some measure of control, immediate results will not be observed and they will not completely suppress a fly population. Therefore, biological control should not be used alone, but in concert with other control methods such as sanitation.
- CHEMICAL: If a black soldier fly problem persists, an insecticide can be used. Because the black soldier fly spends a small percentage of its time as an adult in livestock facilities, it, and its larvae, is typically extremely susceptible to standard permethrin insecticides labeled for livestock facilities. Applying these insecticides along the perimeter of the manure basin where female flies will be attempting to lay their eggs should be enough to suppress a black soldier fly population. This tactic will also most likely prevent black soldier flies from colonizing earthworm beds.
The author would like to thank Drs. Carlos Bogran and John Jackman, Texas Cooperative Extension, for their helpful comments on this manuscript.
For more information on insect management, visit our Web site at http://entomology.tamu.edu/.
* Professor and Extension Entomologist, Texas A&M AgriLife Extension, and Professor of Entomology, Texas A&M AgriLife Research, Department of Entomology