Parasitic Pediobius foveolatus are black colored small wasps that are known to parasitize larvae of Mexican bean beetles, Epilachna varivestis as well as larvae of squash beetles, Epilachna borealis. Since these parasitic wasps are originally from tropical climates, they do not survive under freezing temperatures and therefore, they cannot overwinter as adults or larvae in the areas where temperature is very cold or below freezing point. Since these wasps cannot survive during winter, they need to be always cultured under laboratory conditions for their continuous supply and release in the field for the successful control of Mexican bean beetles. These laboratory cultured wasps are generally sold as "mummies" and/or adults that can be easily released in the field for the control of Mexican bean beetles.
- - Parasitic Wasp, Pediobius foveolatus effective against following species of Mexican beetle
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- Mexican beetle, Epilachna varivestis
- + What are Mexican beetles?
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Mexican beetle is one of the noxious insect pests of many bean crops and scientifically it is known as Epilachna varivestis. This insect is responsible for causing a significant damage to many different kinds of bean crops including Cowpea (Vigna unguiculata), Lima beans (Phaseolus lunatus), Green/Snap beans (Phaseolus vulgaris), Soybeans (Glycine max) etc. Adults of Mexican beetles look like ladybird beetles except that they have copper to cream to yellowish colored wings with 8 black spots on each forewing whereas adults of ladybird beetles are orange to red in color with 7 black spots on each forewing. The males of Mexican bean beetles are slightly smaller than their females. These beetles overwinter as adults and they become active early in the spring. In the spring, females lay yellow colored eggs on the underside of bean leaves. Eggs hatch within 7-10 days into yellow colored larvae with spines on their bodies. Immediately after hatching from eggs larvae starts feeding on the bean leaves by scraping their surface. The second generation adults are generally noticed in the field in mid-June.
- + How Mexican bean beetles cause damage to bean crops?
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- Both larvae and adults of Mexican bean beetle directly feed on leaves of different kinds of beans including Lima beans, Snap beans, soybeans etc.
- Mexican bean beetle larvae feed on leaves by scrapping their upper surface.
- Whereas adults of Mexican bean beetle feed by completely chewing the leaves of beans.
- + How Mexican bean beetles can be controlled organically?
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- Crop rotation with non-host crops can reduce bean damage in the next season.
- If population of Mexican bean beetle is very low, hand-picking and killing of their adults and larvae can help to reduce damage to future crop and suppress their future outbreaks.
- If population of Mexican bean beetle is very high, it is recommended to use beneficial insects including Parasitic Wasp, Pediobius foveolatus to control Mexican bean beetles.
- + How Parasitic Pediobius foveolatus kills Mexican bean beetles and squash beetles?
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- Parasitic wasps, Pediobius foveolatus that are shipped as adults that would be ready to lay eggs inside the Mexican bean beetle larvae.
- Also, parasitic Pediobius foveolatus wasp that are shipped as mummies will be ready to emerge as adults when they are placed in the field and after mating, their females will be ready to parasitize the young larvae of Mexican bean beetles or squash beetles by laying eggs inside the larval bodies.
- Each female of Pediobius foveolatus wasp lays over 20 eggs inside the body of each Mexican bean beetle larva or squash beetle larva.
- These wasp eggs hatch inside the body of Mexican bean beetle larvae that turns into mummy meaning outer skin (cuticle) of parasitized larvae becomes hard and dark in color but remains intact.
- Then inside the mummy, the hatched larvae immediately begins feeding on the tissues of organs of Mexican bean beetle larvae, which eventually dies.
- While feeding internally on the tissues of Mexican beetle larvae, wasp larva matures and then pupates inside the mummy.
- From these pupae adult wasps emerges out by making a small hole in the mummy.
- These Pediobius foveolatus wasp adults then fly off, mate, mated females starts parasitizing Mexican beetle larvae by laying eggs inside larval host body and life cycle of wasp continues.
- + How many Pediobius foveolatus wasps should be released?
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Pediobius foveolatus wasps are commercially available as mummies or adults.
- These wasps are easy to apply in the greenhouses or fields.
- One Mummy can produce over 25 adults of Pediobius foveolatus wasps.
- Generally rate of Pediobius foveolatus wasps depends on the numbers of Mexican bean beetle larvae present in the infested areas to be treated.
- Higher the density of larvae of Mexican bean beetles larger the numbers of adults or mummies of Pediobius foveolatus wasps are required to treat the infested area.
- To achieve optimum level of Mexican bean beetle control, it is recommended to release a minimum of 3000 Pediobius foveolatus adult wasps per acre during growing season of beans.
- If you are applying mummies of Pediobius foveolatus, it is recommended to apply them at the rate of 150 (3750 adult wasps) and 300 (7500 adult wasps) mummies per acre for low and heavy infestations of Mexican bean beetle, respectively.
- Also, about 20 mummies (over 500 adult wasps) of Pediobius foveolatus wasp would be enough to treat a small vegetable garden infested with Mexican bean beetle.
- + When Pediobius foveolatus wasps should be released for effective control of Mexican bean beetles?
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Pediobius foveolatus wasps are commercially available as mummies or adults and are easy to apply in the greenhouses or fields.
- As we know that the overwintering adults of Mexican bean beetles generally appear early in the spring in the field where they mate, then their females lay yellow colored egg masses on the lower surface of leaves and when the temperature is favorable these eggs can hatch into first generation larvae within a week.
- It is a well-known fact that the Pediobius foveolatus wasps are very effective against younger larvae of Mexican beetles than their older larvae. This means timing of ordering and releasing of Pediobius foveolatus wasps should be coincided with the hatching of eggs and the presence of young larvae of Mexican bean beetles on the leaves of beans.
- Since the first generation larvae of Mexican bean beetles occur in field, Pediobius foveolatus wasps should be released in the late spring to kill first generation larvae of Mexican bean beetles. This application of Pediobius foveolatus wasps in the field can also reduce the emergence of the second generation adults of the Mexican bean beetles that generally starts appearing in late June to early July the field.
- Also, Pediobius foveolatus wasps released in the spring should multiply and produce second generation adults that can parasitize the overlapping and future generations of Mexican bean beetle larvae.
- + How Pediobius foveolatus wasps should be released for effective control of Mexican bean beetles?
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Pediobius foveolatus wasps are generally shipped as mummies or adults.
- If you have ordered Pediobius foveolatus wasps but still not ready to release them in the field or in the greenhouse then the packages containing mummies or adult wasps should be stored in a cool place until you are ready to release them in the bean fields infested with Mexican bean beetles.
- When you are ready, adult Pediobius foveolatus wasps are released by opening the containers under bean bushes allow them to fly away in the field.
- When you are releasing Pediobius foveolatus wasp mummies, place the open containers on the ground under the bean bushes so that they can be protected from predators.
- Adult wasps will then fly out of the containers or they will emerge from mummies and start searching for Mexican bean beetle larvae.
- Once they locate appropriate stage of Mexican bean beetle larvae, they will parasitize them.
- While releasing these wasps, make sure that there is no heavy rain that may affect their survival.
- + Why you need Pediobius foveolatus wasps
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- they can reduce the crop damage by feeding on larvae of Mexican bean beetles and squash beetles
- they can parasitize young larvae of Mexican beetles
- they are able to actively search for their host larvae and parasitize and feed on them
- they can reproduce and continue their life cycle in the garden after first application
- they are commercially available and easy to apply in the greenhouses or fields
- + Why predatory Pediobius foveolatus wasps are safer than traditional pesticides
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- they do not damage plants
- do not cause any harm to the personnel involved in their production and application
- food products are safe to handle and eat when they are treated with wasps
- they do not harm humans, animals and pollute the environment
- + Research Papers
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- Barrows, E.M. and Hooker, M.E. 1981. Parasitization of the Mexican bean beetle (Coleoptera, Coccinellidae) by Pediobius- foveolatus (Hymenoptera, Eulophidae) in urban vegetable gardens. Environmental Entomology 10: 782-786.
- Own, O.S. and Brooks, W.M. 1986. Interactions of the parasite Pediobius- foveolatus (hymenoptera, eulophidae) with 2 Nosema spp (Microsporida, Nosematidae) of the Mexican bean beetle (Coleoptera, Coccinellidae). Environmental Entomology 15: 32-39.
- Schaefer, P.W., Dysart, R.J., Flanders, R.V., Burger, T.L. and Ikebe, K. 1983. Mexican bean beetle (Coleoptera, Coccinellidae) larval parasite Pediobius- foveolatus (Hymenoptera, Eulophidae) from Japan - field release in the United-States. Environmental Entomology 12: 852-854.
