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Biological Control of Mile-a-Minute Weed
(Last updated April 10, 2008)
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WORKSHOP AUGUST 25, 2008
All are invited to a workshop sponsored by the USDA Forest Service and University of Delaware to be held on August 25, 2008, at Longwood Gardens (Kennett Square, PA). Talks and discussion updating current information on biological control of mile-a-minute weed will be presented from 10 AM – noon, followed by a box lunch and field trip to research and release sites. Registration is free, and includes entry into Longwood Gardens, box lunch, and transportation to and from field sites. You must register by August 15, 2008.
Follow this link for more information and the registration form.
See Also: Mile-a-Minute Weed Monitoring Protocol (PDF)
Project Background and Initial University of Delaware Research
 Mile-a-minute weed (Persicaria perfoliata (L.) H. Gross, formerly Polygonum perfoliatum L.) is an annual Asian vine that invades a variety of habitats in the northeastern U.S. , including forested floodplains, streamside herbaceous wetlands, and upland forests. A biological control program targeting mile-a-minute weed was initiated by the Forest Service in 1996, with field surveys and laboratory host specificity tests conducted in China and subsequent testing continuing under quarantine conditions in Delaware. A stem-boring weevil, Rhinoncomimus latipes Korotyaev, was determined to be host-specific to mile-a-minute weed (Price et al. 2003, Colpetzer et al. 2004a), and a permit application for field release was approved in July 2004. Additional work on the feeding behavior of this weevil (Colpetzer et al. 2004b) and development of a rapid germination protocol for the plant (Colpetzer and Hough-Goldstein 2004) set the stage for mass-rearing of this insect, which is currently underway at the Phillip Alampi Beneficial Insects Laboratory, Trenton, N.J.
About Mile-a-minute Weed
 Mile-a-minute weed is a prickly, branching, viney annual plant that germinates in early spring, usually in April or May in the mid-Atlantic region. Vines grow rapidly, climbing over other plants, and attain lengths of 6 meters or more. Flowers are inconspicuous, and iridescent blue berry-like achenes are produced beginning in mid-summer and continuing until the plants are killed by frost in the fall. Seeds require a cold period before germinating. Many will germinate within established mile-a-minute patches the following year, while others are spread by birds, mammals, and water. Mile-a-minute seeds can survive for up to seven years in the seed bank.
Rhinocominus latipes Korotyaev, the mile-a-minute weevil
Adult R. latipes are about 2 mm long, and are black, but may be covered by an orange film derived from plant exudates once they start feeding. Adult weevils eat small holes in young leaves of P. perfoliata and lay eggs on leaves and stems. After hatching, larvae bore into the stem where they complete development, then exit the stem and drop to the soil for pupation. Development from egg to adult takes about 26 days under laboratory conditions. Weevils are very small, but can be observed directly in the field, especially at the ends of terminals (Fig. 1). The pale yellow eggs have a characteristic peanut shape and are covered by a thin strip of fecal material (Fig. 2); however they are difficult to spot in the field due to their very small size. Characteristic adult feeding holes ("shot holes" in leaves) are relatively easy to see (Fig. 3). Larval emergence holes at plant nodes (near where ocreae encircle stems or where stems diverge) can sometimes be seen in the field (Fig. 4).
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Fig. 1. Adult weevil |
Fig.2. Eggs (with penny) |
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Fig. 3. Adult feeding damage |
Fig. 4. Larval node damage |
Photos by Ellen Lake
Weevil Releases
Most releases have been conducted in New Jersey, where the weevil is being mass-reared. Between 2004 and 2007, more than 64,000 weevils were released in 37 different mile-a-minute infested sites in NJ. The insects have established populations nearly everywhere that they have been released. In some sites where large numbers were released, the weevils have reduced mile-a-minute to the point wehre it is no longer the dominant plant in the ecosystem. Releases of weevils have also occurred in Delaware, Pennsylvania, West Virginia, and Maryland.
University of Delaware Post-Release Research
Weevil Dispersal
To study the dispersal and life history of the weevil, graduate student Ellen Lake released 450 weevils at each of three sites in Chester County, PA, on 9 June 2005. Weevils reproduced and dispersed up to 200 m from these sites, but most remained within 25 m of the release site during the first year. Four complete generations occurred in a cage study conducted at the same time. Adult weevils were present on foliage in the field until vines were killed by frost. Overall, weevil numbers at all three sites increased, with multiple generations apparent throughout the summer and fall. Weevil populations continued to increase in 2006 and 2007. Maximum dispersal from release sites was at least 800 m in 2006; in 2007 isolated weevils were found as much as 5 miles from the nearest release site. The weevils found not only large patches of mile-a-minute but also small isolated plants (Lake 2007, Lake et al. in preparation).
Impact on mile-a-minute weed
Percent cover of mile-a-minute weed was significantly reduced within a 5-meter radius of the weevil release sites between 2005 and subsequent years. Numbers of seed clusters were also reduced; in addition, the number of seeds per cluster were reduced from around 12 to as low as 6 in the most-impacted site (Lake 2007, Lake et al. in preparation).
To gain a better understanding of the impact of R. latipes feeding on P. perfoliata,
experiments were conducted in 2006 and 2007 using single mile-a-minute plants enclosed in weevil-proof cages with various numbers of weevils applied at different times. In a preliminary study in 2005, isolated P. perfoliata plants in field cages were shown to be highly plastic in response to light, producing more than 2200 seeds per plant in full sun but fewer than 400 in the shade (Hough-Goldstein, 2008). Therefore subsequent studies were done mostly in full sun.
In 2006, 20 weevils introduced into cages with single plants in May (when weevils first emerge from overwintering) suppressed seed production for about 9 weeks, while weevils introduced in June (when the first summer generation of adults emerge) did not affect seed phenology. In 2007, plants grown with some competition from other plants within field cages showed substantial mortality, with 63% of plants with 10 or 20 weevils and 75% of plants with 40 weevils per plant dead by mid-August, compared with 12.5% of control plants. Seed production was again delayed, by more than a month in surviving plants with 10 or 20 weevils, and by more than 2 months in the few survivors with 40 weevils (Hough-Goldstein et al. 2008).
Conclusions and Next Steps
This insect has established easily on mile-a-minute weed, producing multiple generations per year, and has been shown to reduce mile-a-minute cover, reduce seed numbers and quality, and in the presence of plant competition, cause mortality of plants. Our hope is that with an integrated program that combines several types of competitive and other stresses, with the ultimate goal of producing a shaded environment at sites currently overrun with mile-a-minute, the weevil will provide the “tipping point” that will allow a sustainable diverse plant community to develop. Our next step will be to test this theory, and also determine whether it is possible to produce weevils in a field nursery rather than depending strictly on laboratory rearing.
Acknowledgments: Ellen Lake, Kimberly Shropshire, Kelsey Paras, Jamie Pool, Matt Frye, and Brian Butterworth have all contributed to mile-a-minute biological control research at the University of Delaware.
NOTE THAT IF YOU WISH TO MOVE THE MILE-A-MINUTE WEEVILS FROM ONE STATE TO ANOTHER (OR GET SOME SHIPPED FROM THE NJ LAB TO ANOTHER STATE) YOU MUST HAVE A PPQ 526 PERMIT. TO APPLY, SEE:
http://www.aphis.usda.gov/plant_health/permits/organism/index.shtml
Our Research is supported by funding from:
References Cited
Colpetzer, K. and J. Hough-Goldstein. 2004 . A rapid germination protocol for mile-a-minute weed, Polygonum perfoliatum L. Seed Sci. Technol. 32: 749-757. Colpetzer, K., J. Hough-Goldstein, J. Ding, and W. Fu. 2004a . Host specificity of the Asian weevil, Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae), a potential biological control agent of mile-a-minute weed, Polygonum perfoliatum L. (Polygonales: Polygonaceae). Biol. Control 30: 511-522.
Colpetzer, K., J. Hough-Goldstein, K. Harkins, and M. Smith. 2004b . Feeding and oviposition behaviour of Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) and its predicted effectiveness as a biological control agent for Polygonum perfoliatum L. (Polygonales: Polygonaceae). Environ. Entomol. 33: 990-996.
Hough-Goldstein, J.A., 2008. Assessing herbivore impact on a highly plastic annual vine. In: Julien, M.H., Sforza, R., Bon, M.C., Evans, H.C, Hatcher, P.E., Hinz, H.L., Rector, B.G. (Eds.). Proceedings of the XII International Symposium on Biological Control of Weeds. CAB International, Wallingford, UK. (in press).
Hough-Goldstein, J., M. Schiff, E. Lake, and B. Butterworth. 2008. Impact of the biological control agent Rhinoncomimus latipes on mile-a-minute weed, Persicaria perfoliata, in field cages. Biological Control (in press). http://dx.doi.org/10.1016/j.biocontrol.2008.04.001
Lake, E.C. 2007. Dispersal, establishment, and impact of the mile-a-minute weevil, Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae): a two-year study in Southeastern Pennsylvania. M.S. Thesis, University of Delaware, Newark.
Price, D. L., J. Hough-Goldstein, and M. T. Smith. 2003 . Biology, rearing, and preliminary evaluation of host range of two potential biological control agents for mile-a-minute weed, Polygonum perfoliatum L. Environ. Entomol. 32: 229-236.
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