In 1988, USDA scientists released just 88 flea beetles in North Dakota; their descendants multiplied into hundreds of millions across North America

In 1988, USDA and North Dakota State University scientists released just 88 flea beetles in the Valley City, North Dakota, area as part of an effort to control leafy spurge, an invasive weed affecting rangeland. The USDA Agricultural Research Service's 2001 article, Sheep and Beetles Control Leafy Spurge, records that hundreds of millions of flea beetles were subsequently collected and redistributed throughout North America from the Valley City site. A separate USDA Forest Service research paper, Efficacy of Flea Beetle Control of Leafy Spurge in Montana and South Dakota, published in 2006, examined later flea beetle releases in Montana and South Dakota. The two sources concern different field histories, so the later experiment should not be presented as a study of the original 88 insects.

Leafy spurge, or Euphorbia esula, is a perennial plant that can be difficult to control once established. The 2006 research paper describes it as an exotic plant introduced to North America in the late 1800s and now widely established across the western United States and Canadian provinces. Its ability to persist across a range of habitats has contributed to its spread, while the USDA account notes that the plant's milky latex makes it unpalatable to many grazing animals.

Flea beetles became useful against the weed because they feed directly on leafy spurge. The USDA describes a division of labour between the insects and other control methods: adult beetles feed on the plant's leaves, while their larvae damage its roots. The Forest Service paper identifies black flea beetles as Aphthona lacertosa and Aphthona czwalinae, and the brown flea beetle as Aphthona nigriscutis. Root feeding is particularly relevant to a perennial weed because it targets the underground parts of the plant rather than only its visible foliage.


How 88 beetles became a much larger resource

The remarkable figure in the Valley City story comes from what happened after the original introduction. The USDA's 2001 account states that, following the 1988 release, hundreds of millions of flea beetles were collected and redistributed from the Valley City site across North America. It does not say that hundreds of millions of insects were released there in 1988, nor does it identify every insect subsequently redistributed as belonging to a particular species. The safest reading is that the established Valley City population became a major source for further biological control releases.

The North Dakota programme involved several Aphthona species over time. Records cited in the earlier draft about releases and establishment in the state should not be used to infer that every later population was directly descended from the original 88 insects. That distinction matters because the existence of additional releases does not, by itself, establish the ancestry of every beetle later collected from the wider programme.

The USDA account also shows that flea beetle performance was not uniform across all landscapes. It notes that the insects did not thrive in sandy or wet areas and that researchers were looking for other biological control agents for those environments. The lesson is straightforward: establishing a useful flea beetle population depended on local conditions, rather than simply on releasing a particular number of insects.

The later Forest Service research provides a much more controlled look at what happened after new releases. In Efficacy of Flea Beetle Control of Leafy Spurge in Montana and South Dakota, Jack L. Butler, Matthew S. Parker and John T. Murphy studied black and brown flea beetles in north-western South Dakota and south-eastern Montana. In late June 1998, they released about 3,000 insects of each species into permanently marked plots and monitored beetle abundance, leafy spurge and resident vegetation from 1998 through 2004.

What happened after the later releases

The black flea beetles, A. lacertosa and A. czwalinae, increased rapidly after release and dominated the release plots throughout the study. Their population growth was highly variable between sites, but the researchers found fairly consistent patterns of reduced leafy spurge dominance where the black beetles established. By 2004, leafy spurge foliar cover on both release and non-release plots had declined significantly compared with prerelease measurements. Grass and grass-like plant cover increased alongside the reduction in leafy spurge, while forb cover remained below the levels recorded at non-infested sites.

Those results are important, but they do not support saying that flea beetles simply eliminated leafy spurge or restored the original plant community. The researchers specifically found substantial variation in beetle population growth between locations. The brown flea beetle was also an infrequent component of most plots and appeared to be restricted to particular locations. The study's conclusions therefore point to successful establishment of black flea beetles across a range of grassland and shrubland sites, but also show that the response was influenced by conditions at individual locations.

The vegetation results also call for some caution. Although grasses and grass-like plants increased as leafy spurge dominance fell, forb cover did not return to the levels found in non-infested areas during the study period. That means a decline in the target weed should not automatically be described as complete ecological recovery. The research instead documents a measurable shift in vegetation alongside the reduction in leafy spurge.

The 1998 Montana and South Dakota experiment is therefore useful context for the 1988 North Dakota story, but it should remain separate from it. The Valley City record demonstrates the extraordinary scale that a biological control programme could reach after a very small initial release, with the USDA reporting hundreds of millions of flea beetles collected and redistributed from the site. The later Forest Service study shows what researchers observed when flea beetles were deliberately released and monitored at separate sites over six years.

Taken together, the evidence supports a more precise version of the story. The 88 beetles released near Valley City in 1988 became the starting point for a population that the USDA later described as a source of hundreds of millions of beetles for redistribution. The available source does not require us to trace every later insect back to those original 88, so the article should not make that stronger ancestry claim. What can be said is that the Valley City population became an important source within a much wider biological control effort.

The later research shows why that approach attracted interest while also illustrating its limits. Black flea beetles established successfully in the Montana and South Dakota study and were associated with reduced leafy spurge dominance, but their population growth varied between sites and the surrounding vegetation did not simply return to its non-infested state. The story is therefore not one of a single release solving an invasive-plant problem. It is a case of a small biological control introduction becoming part of a much larger management effort, with results shaped by species, location and the ability of the insects to establish.