Recipient Organization
CONNECTICUT AGRICULTURAL EXPERIMENT STATION
PO BOX 1106
NEW HAVEN,CT 06504
Performing Department
Valley Laboratory
Non Technical Summary
Mile-a-minute weed (MAM) is a non-native invasive plant. Its botanical name is Persicaria perfoliata. MAM is a rapidly growing annual vine that can reach lengths up to 8 meters (26 feet) in a year. Sharp barbs occur on its stems. MAM is a serious invasive weed because it spreads aggressively in natural and disturbed sites. Originally from eastern Asia, MAM was introduced accidentally into York County, PA in the 1930s. By 1990, it had become established in eight eastern states. MAM was first identified in Connecticut in 2000 at the southwestern corner of the state. Since then, several MAM patches have been found throughout CT. Massachusetts and Rhode Island also have MAM populations. MAM has been declared a noxious weed or an invasive plant in many states. MAM seeds, which can remain viable in soil for at least 6 years, begin germinating in early spring. The vines grow rapidly over the top of other vegetation and climb tree trunks. Dense prickly mats of MAM can smother native plants, nursery stock and Christmas trees. Dispersal of MAM seeds is facilitated by animals that eat its blue fruits (berries); the hard seeds often remain intact after passing through the digestive system. Seeds can also float in water for several days, then are deposited along river banks downstream. Many MAM sites in Connecticut are along streams or in wetlands where herbicide use may be restricted. Several herbicides are effective in controlling MAM. A viable biological control option for MAM is also available. A small weevil (Rhinoncomimus latipes) native to China has high specificity for MAM as a host plant and has been designated an effective biological control agent. R. latipes weevils are entirely dependent on MAM for all stages of its life cycle. Adult weevils feed on leaves and shoot tips, and larvae bore into MAM stems. After extensive testing, R. latipes was approved by the USDA in 2004, and weevils were released at MAM-infested sites in Delaware and New Jersey. In subsequent years, thousands of weevils have been reared in a laboratory and released in DE, MD, NJ, PA and WV. Significant decreases in MAM populations have occurred where weevils have been released with no damage to other plants. In 2009, Connecticut joined a regional program for the first releases of R. latipes in New England. Since then approximately 20,000 weevils have been released at several MAM sites in CT. Effects on MAM populations have ranged from minor to substantial. No weevil damage has been observed on other plants. Potential impacts of herbicides on R. latipes are unknown. Results from the proposed project will be useful in developing an integrated weed management plan for MAM. In CT, MAM infestations occur in a wide variety of habitats. Biological control is a major component of our MAM management plan. However, where new MAM stands are found, an initial application of herbicide may be appropriate to control MAM before seeds are produced. In such cases, weevils may be exposed to herbicide, either directly or indirectly. Thus, I will study the impacts of several herbicides used to control MAM on weevil survival, feeding and reproduction.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
My objective is to evaluate several herbicides used in invasive plant control for their impacts on Rhinoncomimus latipes, a weevil species that is a biological control agent for mile-a-minute weed (Persicaria perfoliata), a non-native invasive plant. Weevils will be monitored for survival, vigor, feeding and other activities following either direct or indirect exposure to one of five different herbicides applied to mile-a-minute leaves. Results of this study will be valuable in determining which herbicides could be used safely as part of an integrated management program at mile-a-minute sites where R. latipes is present or will be released subsequently. The goal is to develop effective and environmentally sound management practices for mile-a-minute weed. Information gained from this project will be disseminated to a wide range of stakeholders, including federal, state and local government agencies, land trusts and other conservation organizations, ecological researchers, vegetation management specialists, nurserymen and other farmers. Expected outputs will include publication of experimental results in journal articles, oral and/or poster presentations at scientific conferences and land management workshops, and field days.
Project Methods
For Experiment 1, mile-a-minute weed (MAM) grown in containers will be sprayed with different herbicides. Leaves will be collected from treated plants and fed to Rhinoncomimus latipes weevils (indirect exposure). In April 2012, MAM seeds will be planted in potting media in greenhouse cell trays. The most vigorous seedlings will be repotted and grouped into plots, each consisting of three plants. Herbicide treatments will be applied to plots when vines are about 50 cm long. Using small spray bottles, each herbicide will be applied at the dose recommended on its product label. In addition to an untreated control, treatments will consist of 0.25% non-ionic surfactant (NIS), imazapic + NIS, sulfometuron + NIS, aminopyralid + NIS, triclopyr + NIS, and glyphosate + NIS. One hour after spraying MAM plants, several leaves will be clipped off, collected, labeled, then immediately refrigerated, as will leaves from untreated plants. Approximately the same surface area of MAM leaves from each plot will be placed in large Petri dishes (three per plot). Each petiole will be cut, then wrapped in a small cotton ball soaked with water to insure that the leaf will remain hydrated. Six R. latipes adults will be placed in each dish. Weevils will remain in the same dish. After the first 72 h, the remainder of treated MAM leaves will be removed from dishes and replaced with fresh untreated leaves, which will remain for 1 wk. Then these leaves will be replaced with fresh untreated leaves for 1 wk. This process will be repeated until weevils have spent 31 d in dishes. Each time MAM leaves are removed, the leaves will be scanned using a flatbed scanner to document the holes created by weevil feeding. A leaf area software program will determine the total area of missing leaf tissue. Data for weevil survival and activity over time, leaf tissue consumed, egg laying and egg hatching will be collected. Experiment 1 will be repeated in 2013 with a new set of MAM plants. For Experiment 2, potted MAM plants will be enclosed within separate cages. After introducing weevils, herbicide treatments will be sprayed onto the plants (direct exposure). In May 2012, MAM seeds will be planted and vigorous seedlings selected as before. Each potted MAM will be enclosed within a netted cage to keep weevils from exiting or entering. When vines are an average of 50 cm long, 12 R. latipes adults will be introduced into each cage. A herbicide treatment (same as in Experiment 1) will then be sprayed onto each plant. Cages will be monitored twice a day for 3 d, and data will be collected on weevil survival and activity, feeding damage on leaves, and herbicidal activity on MAM. Surviving weevils will be transferred to large Petri dishes and provided with untreated MAM foliage (for four 1-wk intervals as before). Data will be collected as in Experiment 1. Experiment 2 will be repeated in 2013. Statistical analyses will consist of ANOVA with means separation for herbicide treatment effects on MAM. Weevil survival and activity data will be analyzed using non-parametric ANOVA. Data will be analyzed, reports written, and a manuscript submitted in 2014.