Science and environment
The Japanese beetle discovery at Dreer’s nursery
Documented discovery · Arrival route uncertain
Two inspectors collected unfamiliar beetles from a nursery near Riverton in 1916. Within a decade, control had become a large state and federal operation stretching toward Moorestown.
A dozen unfamiliar insects
Rutgers’ history of the Japanese beetle quarantine says Weiss and Dickerson collected roughly a dozen beetles while inspecting Henry A. Dreer Inc.’s nursery, described as about two and a half miles east of Riverton. The insects were recognized as unfamiliar to New Jersey but were not identified immediately. In spring 1917, H. S. Barber at the United States National Museum identified them as Popillia japonica. The inspectors returned on August 8, 1917, and found beetles abundant in a small area, particularly on smartweed.
Rutgers says the insects probably arrived as grubs in iris roots imported from Japan five or six years earlier. That is a historical explanation, not a documented shipment-to-beetle chain. The USDA’s historical account also places the first discovery at a nursery near Riverton.
An experiment in containment
Federal and state researchers proposed spraying a belt around the infestation, treating soil, trapping adults and inspecting shipments. Rutgers reports that the beetles flew past treated foliage, rain washed off applications, and funds and labor were insufficient. By 1920 the aim had shifted from eradication to slowing spread; Rutgers estimates about 213 square miles infested in New Jersey by 1921. The same institutional history says the Japanese beetle laboratory moved to Moorestown in 1926.
This episode connects the Delaware River nursery belt with the farms, nurseries and market shipments farther into South Jersey. The Riverton environmental inventory describes Dreer’s nursery as a large operation spanning Riverton and Cinnaminson, so a modern pin on one surviving lot would misrepresent its scale.
Explore the ground carefully
The map marks the East Riverton area as a geographic reference, not the exact 1916 collection site. Much of the nursery landscape has changed and some land is private. To compare historic geography from home, use the 1876 Cinnaminson atlas entry and the Historical Society of Riverton’s Dreer history. Neither establishes the precise beetle plot.
Sources and research limits
- Rutgers Department of Entomology, Japanese Beetle Quarantine — inspectors, identification, control timeline and Moorestown laboratory.
- USDA, Japanese Beetle in United States — federal historical overview.
- Borough of Riverton environmental resource inventory — broad nursery geography.
Rutgers’ distance east of Riverton and the borough inventory’s placement of nursery fields do not identify the same surveyed plot. The map deliberately shows an area, and the hypothesized iris-root introduction remains unproved.