UF/IFAS Okeechobee County Extension Service

458 Highway 98 North

Okeechobee, FL 34972-2578

Phone: (863) 763-6469

March 17, 2005

Feature Article - for release the week of March 20, 2005

Dan Culbert - Extension Horticulture Agent

WASP + WEED – Cricket = Good Grass

Do you know what the number one grass is in our area? Most would recognize it as Bahiagrass. And what is its most serious insect pest? Ranchers and a few homeowners may recognize that Mole crickets are the hungriest Bahia busters in this area. And the conventional wisdom has been that insecticides are the management tool of choice to keep this little hopper at bay.

Researchers have found that Mother Nature can now be used to keep these critters out of our pastures, sod farms and lawns. And a lowly little wildflower seems to be the missing ingredient in the quest to attract a Mole cricket parasite. The Larra Wasp and the False Shrubby Buttonweed are the subject of this weeks feature article

Three non-native species of mole crickets have entered Florida and have become significant pests of many plants, including Bahiagrass. Early control measures involved using chemical insecticides to kill these pests, but these products damaged nontarget animals and good bugs or were too persistent in the environment.

The most commonly used method of managing mole crickets is to use insecticidal sprays or baits. To be successful, they must be perfectly timed with the appearance of mole cricket nymphs. In our area, this will be in May.

Efforts at finding biological control measures have been underway in Florida since the 1970s. Some success in using parasitic nematodes against mole crickets has occurred, but their use has sometimes proved difficult. More success has been found with the introduction of the Brazilian red-eyed fly, and another predatory insect being looked is the Bombardier Beetle.

Mole cricket infected with the nematode, Steinernema scapterisci Photo by E. Buss, UF/IFAS

Brazilian Red Eyed Fly. Photo by E. Buss, UF/IFAS

Bombardier Beetle. Photo by J. Castner, UF/IFAS

Mole cricket management research has also looked at parasitic wasps known as “digger wasps." Females of these insects dig holes in the ground and deposit eggs on their paralyzed hosts. One Florida digger wasp works on native mole cricket species, but it is not able to attack the imported mole crickets which are primary Bahiagrass pests.

UF Entomologist Dr. J. Howard Frank has been working with a Brazilian Digger wasp known as the Larra Wasp, Larra bicolor. He has successfully introduced of this insect into Florida. It’s mode of attack is quite gruesome, and it is detailed, complete with photos, in a UF Featured Creatures article.

The native Larra analis Digger wasp does not parasitize our imported Mole cricket species. Photo by PM. Choate, UF/IFAS.

Adult Larra bicolor wasp preparing to lay egg on a mole cricket. Photo by: A. Sourakov, USDA.

A developing larva of Larra bicolor Fabricius feeding on a mole cricket. Photo by: A. Sourakov, USDA.

The successful establishment of this mole cricket hunter into our area, and its ability to attack mole cricket pests is limited by a lack of nectar sources. In order for the Larra wasp to find a mole cricket, scare it out of the ground, sting it, and lay an egg, it needs nectar from wildflowers as an energy source.

A wildflower known as the false shrubby buttonweed, Spermacoce verticillata, may be the answer to a year-round nectar source for this wasp. UF Entomologists suggest that it might better be named the Southern Larraflower because it has the right size and shape flower for the Larra wasp. It blooms throughout the year and can supply needed nectar to the Larra wasp. Providing patches of this plant can bridge the gap and encourage the Larra wasp.

Closeup of Foliage & Flower of Larraweed. Photo by Dan Culbert, UF/IFAS

Clump of Larraweed at Riverwoods Field Lab, Lorida. Photo by Dan Culbert, UF/IFAS

Patch of Larraweed on Brevard county golf course. Photo by Sally Scalera, Brevard County Extension Service

Larraflower’s status as a native plant is unclear, and it has been brought from Puerto Rico to Florida. It is now found in southern Florida, including Martin and Highlands counties, but has not yet been noted in Okeechobee. Take a look at the pictures on our website or stop by our office to get an idea of what this plant looks like.

On a recent Master Gardener field trip to the Riverwoods Field Lab in Lorida, I noticed a patch of Larraflower had been planted at their site. A few weeks later, I had difficulty finding it, as the frost had leveled this plant to the ground. It will re-grow from the roots when warm temperatures return.

Last fall I received a couple of the Larraflower plants and have been nurturing them along, looking for the right place to plant them: a location that will use few pesticides, that has lots of Bahiagrass with a known mole cricket problem and a property owner willing to keep an eye out for the Larra Wasps. If you have such a site, I can consider your property as a place to plant this little wildflower, which brings the wasp that kills the cricket that eats the grass that keeps Okeechobee Green!

Hope you had a great Palm Sunday, and have a very happy Easter. I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu. If you need additional information on Bahiagrass, Mole Crickets, or Larra wasps, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469. Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners on Tuesday afternoons from 1 to 5 PM on Tuesday afternoons.

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Trade names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. Florida Cooperative Extension Service / IFAS / University of Florida. Larry A. Arrington, Dean Last update: 10/10/2006 . This page is maintained by Dan Culbert Hit Counter

NEW! Download a Larraflower Poster:

Weed, Aaron S. and Frank, J. H. This is a plot of the Southern Larraflower. Gainesville: UF/IFAS IPM Program, October 2006. http://ipm.ifas.ufl.edu/extension-resources/publications/Spermacoce%20poster.pdf

References

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Frank, J.H and Sourakov, Andrei.. Larra Wasps - Featured Creatures EENY-268. Gainesville: UF/IFAS, Florida Cooperative Extension Service, March 2002. http://creatures.ifas.ufl.edu/beneficial/Larra_wasps.htm

Frank, J. Howard, Fasulo, Thomas R., Short, Donald E., and Weed, Aaron S. Larra Wasp Tutorial - What the Larra Wasp is and How to Attract it. Gainesville: UF/IFAS Department of Entomology & Nematology, 2005. http://molecrickets.ifas.ufl.edu/mcri0300.htm.

ibid. Biological Control of Mole Crickets by Sphecid Wasps. Gainesville: UF/IFAS Department of Entomology, 2005. http://molecrickets.ifas.ufl.edu/mcri0007.htm

Leppla, Norm. "Mole Cricket Control in Florida and the Southeastern U.S." in Southern Region IPM Newsletter page 3, June 2004. http://www.sripmc.org/newsalerts/newsletter/June04.pdf

Woods, Chuck. UF Researchers Declare Victory In 25-Year Battle Against Invasive Mole Cricket Pests. Gainesville: UF/IFAS News Release, 06.15.2005. http://pestalert.ifas.ufl.edu/mole_cricket_victory.htm