Sunday, October 30, 2011

A new invasive species: Asian kudzu bug Megacopta cribraria attacks legumes in US

Megacopta cribraria Stone Mountain Park, Dekalb County, Georgia, USA
June 25, 2011Photo#565670 copyright © 2003-2011 Iowa State University

             Soybean aphid, corn earworms, soybean rust, soybean cyst nematode, Sclerotina stem rot and the exotic pathogen, red leaf blotch and now the Kudzu bug are threatening the US soy bean crop. Soy beans, Glycine max (L.) Merr.,  are harvested and processed into animal feed and vegetable oil.  The oil component of crushed soybeans is bound for human consumption or biofuel production.  Food uses include tofu, soymilk and soy-based yogurts to name a few.  In addition soy ingredients, according to the Soy Facts  web page provided by Soyatech, "...have become staples in the food manufacturing industry.  Soy protein ingredients play functional roles in baked foods, processed meats and other products. Soybeans are also processed into many industrial products.  The primary one at this time is biodiesel, or soy methyl esters, which may be used in any diesel engine."

            Finding a suitable legume for agricultural production in the south eastern US was a major focus of USDA in the early years of the 20th century. Gibson and Barren (2005) write that "The soybean was first introduced into the American Colonies in 1765 as "Chinese vetches."  According to their web page, "an 1879 report from the Rutgers Agri­cultural College in New Jersey is the first reference that soybeans had been tested in a scientific agri­cultural school in the United States."[1]  In the preface to a 1908 report by Charles V. Piper, agrostologist in charge of forage crop investigations of the Bureau Of Plant Industry for the United States Department of Agriculture lays out the importance of new plant species for agriculture:
"Leguminous crops play so important a part in agriculture that unusual interest attaches to any new ones, especially if adapted to sections of our country where a satisfactory legume is still a desideratum. The need of satisfactory legumes is greatest at present in our semiarid regions, though a good perennial species adapted to the Cotton Belt would be of incalculable value. If it be true that no system of agriculture can anywhere be permanent without the use of a leguminous plant in rotation, this makes imperative the search for such a crop for every part of our country where agriculture is possible"[2]
Among the many species that were tested for potential as a food, feed or forage crops was a close relative of soybean, kudzu, Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & S. Almeida.

            It should come as no surprise then that an invasive species, insect native to the same regions of Asia from which came soybean and kudzu might feed on both species. And given the general lack of concern on the part of the public and the lack of much support for invasive species programs such as EDRR (early detection and rapid response), it was only a matter of time before this new invgasive species reach the US.  Megacopta cribraria (Fabricius) was found invading homes in large numbers in northern Georgia in late October 2009. The good news is that this pest of numerous legumes in Asia, has the potential to provide biological control of kudzu, Pueraria montana var. lobata (Willd.) Ohwi, (Fabaceae); the bad news is that it islikely to continue to be a household pest in the vicinity of kudzu fields as well as become a pest of North American legume crops such as soybean.[3]

            To be very clear, USDA APHIS reports that in China  this recent invasive species, the kudzu bug, "...has caused springtime crop losses of up to 50 percent and summertime losses of up to 30 percent. Severe infestations on some host plants result in seed yield losses, improperly developed pods, and undersized seeds. The bean plataspid is also listed as a harmful pest of Chinese fruit trees. If it moves to other host plants in the United States, the pest has the potential to cause significant agricultural damage."[4]

            The continual drumbeat of those who claim there is no problem from invasive species seems at odds with the facts. Part of the problem is the artificial division of invasive species issues into environmental and agricultural camps. The very term invasive species was created by naturalists to address the destructive nature of introduced species on ecosystem services as if there were no existing category of investigation. At the same time US agriculture has established a century plus dedication to the research, control and management of invading species in both USDA ARS and APHIS dating back in to the late 19th century (and earlier if you take in to account US government efforts surrounding the Hessian fly - but that is another blog) . Instead of working together and pooling resources the two stakeholders view each other warily and lobby their respective federal agencies to adopt policies that occasionally duplicate efforts in research and control strategies.

            As long as we continue to think of managed fields and natural areas as exclusionary ideas we will not address completely the challenges of invasive species. All landscapes are managed to some extent; the tools of horticulture should not be automatically excluded from the needs of ecology. Agriculture must be sympathetic to the problems of invasion biology. The collision of desires is highlighted by the positive control of kudzu and the negative impact on soybean and native legumes. Agricultural pests and ecological invasives are two sides of the same problem. The destruction of our natural areas and our managed fields is growing and in growing adding costs (130 billion Pimentel et al. 2001) which will threaten our collective futures. We must adapt or perish, we cannot hide. 



[1] Lance Gibson and Garren Benson, Revised March 2005. Origin, History, and Uses of Soybean (Glycine max). Iowa State University, Department of Agronomy


[2] USDA Yearbook - Congressional edition, Volume 5481. 1909

[3] J. E. Eger, Jr., L. M. Ames, D. R. Suiter, T. M. Jenkins, D. A. Rider, and S. E. Halbert. April 2. 2010. Occurrence of the Old World bug Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae) in Georgia: a serious home invader and potential legume pest.  Insecta Mundi 0121: 1-11

[4]  USDA APHIS Fact Sheet. October 2010. Invasive Insect (Bean Plataspid) Poses Risk to Soybean Crops and Infests Homes in Southeastern States