Invasiveness Ranking System for Non-Native Plants of Alaska

Anthemis cotula L.common names: stinking chamomile, dog fennel,mayweedRanking SummaryEcoregion known or expected to occur inSouth CoastalInterior BorealArctic AlpineYesYesNoPotential Max. ScoreEcological Impact 40 8Biological Characteristics and Dispersal 25 12Amplitude and Distribution 25 14Feasibility of Control 10 7Relative Maximum 41Climatic ComparisonCollected inAlaska regions?CLIMEXsimilarity?South Coastal Yes –Interior Boreal Yes –Arctic Alpine No NoAnthemis cotula has been collected in south coastal and interiorboreal ecogeographic regions of Alaska (Hultén 1968, Welsh1974, AKEPIC 2004, UAM 2004). Using the CLIMEXmatching program, climatic similarity between Nome and areaswhere the species is documented is high. Species range includesRøros, Norway (Lid and Lid 1994), which has a 76% climaticmatch with Nome. However, mayweed chamomile is knownmostly from areas with July mean temperatures above 60 °F(Kay 1971). These conditions are unlikely to occur in the arcticalpine ecogeographic region (WRCC 2005). Thus establishmentof Anthemis cotula in arctic alpine Alaska is predicted to not bepossible.Ecological ImpactScoreImpact on Ecosystem Processes (0–10) 1Though mayweed chamomile has not been reported fromundisturbed areas (Kay 1971, Roberts and Neilson 1981, UAM2004, Whitson et al. 2000), it may retard succession after siteshave been invaded.Impact on Natural Community Structure (0–10) 1Mayweed chamomile typically grows in large numbers and canchange the density of the layer on cultivated fields or ruderal sites.It is not known from undisturbed plant communities (Kay 1971).Impact on Natural Community Composition (0–10) 1Mayweed chamomile has not been observed in undisturbedareas in Alaska (Hultén 1968, AKEPIC 2004) and no impact onnative populations has been documented (Kay 1971, Roberts andNeilson 1981, Whitson et al. 2000).Impact on Higher Trophic Levels (0–10) 5Mayweed chamomile is unpalatable to grazing animals. Theflowers are visited and pollinated mainly by syrphid fliesand other Diptera. Hybrids with Tripleurospermum perforataand Anthemis tinctoria have been recorded. Weevils, aphids,spittlebugs, bugs, moths, slugs, and snails have been reportedto feed on mayweeds, causing serious damage to achenes andvegetative parts of plants (Erneberg 1999). This plant can beseriously infected by fungi (Kay 1971). Mayweed chamomile ispotentially allelopathic to certain forage species (Smith 1990).Total for Ecological Impact 8/40Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3The number of seeds produced by a plant varies widelydepending on the soil fertility and the intensity of competition.Plants of average size are capable of producing from 550 to12,000 achenes. The largest plant observed at the experimentalsite in Britain had a reproductive capacity of 27,000 achenes (Kay1971).Long-distance dispersal (0–3) 0The achenes of mayweed chamomile lack any structuraladaptations for dispersal (Kay 1971).Spread by humans (0–3) 3Mayweed chamomile seed can easily contaminate grass seeds.Achenes remaining on the plant may be dispersed some distancewith hay. They may also be dispersed on footwear and clothes, inmud and soil adhering to agricultural equipment, and the feet offarm animals (Kay 1958, USDA ARS 2005).Allelopathic (0–2) 2Mayweed chamomile is potentially allelopathic to certain foragespecies (Smith 1990). Mayweed chamomile leaf-tissue extractresulted in 50% reduction in Italian ryegrass and alfalfa seedgermination. Tissue extracts also influenced Italian ryegrass andalfalfa seedlings growth (Smith 1999).Competitive Ability (0–3) 1Mayweed chamomile is able to compete with crop species (cf.Kay 1971, Matthews 1972, Ogg et a. 1993). It is suggested to bedeclining in abundance following its introduction in Denmark500 years previously, due in part to reduced competitive ability(Erneberg 1999). It is a serious weed problem in nonirrigatedfields in the Pacific Northwest (Kells 1989) and it can formmonocultures to the exclusion of pasture species (Matthews1972). Ogg et al. (1993) describe the species as having only aslight impact on pea yield when comprising less than 50% of thetotal plants.Thicket-forming/Smothering growth form (0–2) 0Mayweed chamomile typically grows in large numbers and canchange the density of the layer on cultivated fields or ruderal sites.It does not form thickets and does not have a climbing growthhabit (Smith 1987, Douglas et al. 1998, Whitson 2000).Germination requirements (0–3) 0Mayweed chamomile is a weed of cultivated fields and is knownonly germinating on disturbed soils (Gealy et al. 1985, Gealy etal. 1994, Kay 1971, Roberts and Neilson 1981).Other invasive species in the genus (0–3) 3Anthemis arvensis L. considered a weed in Colorado (USDA2002)Aquatic, wetland or riparian species (0–3) 0Mayweed chamomile is commonly found in cereal crops, wasteareas, farm yards, overgrazed pastures, and along roadsides (Kay1971, Roberts and Neilson 1981, Whitson et al. 2000)Total for Biological Characteristics and Dispersal 12/25B-5