Title: Ambrosia artemisiifolia L.

Scientific Name:

Ambrosia artemisiifolia L.

Common Name:

annual ragweed



Source & more images (via ALA)

Habitat: Native of North America, most prevalent in eastern and north central States. First recorded as naturalised at Murwillumbah, NSW. Now common along north coast of NSW. Primarily plant of disturbed open areas, occurs as weed of cultivated lands, stubble fields, old pastures, wastelands, roadsides, railway reserves and vacant lots (Parsons & Cuthbertson 2001).

Distribution:

 
Present Distribution - Australia (source: ALA)   Present Distribution - USA (source: USDA)


present, no further details = Present, no further details widespread = Widespread localised = Localised
Present Distribuion - World (source: CABI)




Invasiveness Assessment

ESTABLISHMENT




1. Germination requirements? Germination is combination of light and temperature and although usually germinates in spring, can germinate at other times of year if conditions are suitable (Parsons & Cuthbertson 2001, DNRM 2005).

2. Establishment requirements? Prefers dry, sunny grassy plains, along riverbanks, roadsides, disturbed soils, vacant lots and ruderal sites (Parsons & Cuthbertson 2001). Limited growth in shade.

3. How much disturbance is required? "Primarily a plant of disturbed open areas" occurs as weed of cultivated lands, stubble fields, old pastures, wastelands" (Parsons & Cuthbertson 2001).

GROWTH / COMPETITIVE




4. Life form? Annual herb (Parsons & Cuthbertson 2001) – life form –other

5. Allelopathic properties? Annual ragweed ‘produces allelopathic responses in several other weed and crop species .. strongly inhibit germination of onion, oats, Lolium spp. (Parsons & Cuthbertson 2001).

6. Tolerates herb pressure? Cattle eat annual ragweed in early stages. A variegated leaf beetle and stem-galling moth are used in biological control in Queensland with the moth ‘reducing ragweed populations and seed production in warmer areas’ (Parsons & Cuthbertson 2001).

7. Normal growth rate? Serious competitor with cereal crops and vegetables in early growth stage but poor competitor in well managed pastures and legume crops. Growth rate rapid depending on environment (Parsons & Cuthbertson 2001). Most often occurs in wasteland areas so score as Medium High.

8. Stress tolerance to frost, drought, w/logg, sal. etc? Due to the locations it can be found, it appears to have saline tolerance. Susceptible to frost and fire. Drought tolerant. Can be found in flood plains but no mention of ability to withstand waterlogging (Parsons & Cuthbertson 2001).

REPRODUCTION




9. Reproductive system? Wind pollinated. A ‘self-compatible species’ (Bassett & Crompton 1975 (cited in Genton, Shykoff & Giraud). Cross and self-pollination but cannot vegetatively reproduce (Parsons & Cuthbertson 2001).

10. Number of propagules produced? Annual ragweed produces an average of 3000 seeds per year (Parsons & Cuthbertson 2001).

11. Propagule longevity? Annual ragweed seeds can be viable for more than 40 years (Parsons & Cuthbertson 2001).

12. Reproductive period? Annual plant (Parsons & Cuthbertson 2001).

13. Time to reproductive maturity? Reaches maturity in 4-5 months (Parsons & Cuthbertson 2001).

DISPERSAL




14. Number of mechanisms? Clings to sheep, furred animals, bags, clothing, water, contaminated gravel and soil (Parsons & Cuthbertson 2001).

15. How far do they disperse? Spreads ‘readily over long distances’. Hull provides buoyancy (Parsons & Cuthbertson 2001). Seems likely that some of the propagules will disperse greater than 1 km.


Impact Assessment

RECREATION




1. Restrict human access? Grows to 350 cm but usual height is between 50 and 200 cm. A much branched, hairy herb (Parsons & Cuthbertson 2001). The height may impede individual access – low nuisance value.

2. Reduce tourism? Most species are ‘so ordinary in appearance that they are rarely noticed despite their abundance’. However, as they are serious contributors to hay fever in US, some places advertise as ‘ragweed free’ (Parsons & Cuthbertson 2001). At certain times of the year, ragweed has the potential to have a major impact on recreation

3. Injurious to people? ‘Most important hay-fever producing plant in North America’. Also associated with asthma and can cause contact dermatitis (Parsons & Cuthbertson 2001). Serious problem in autumn and as an annual herb dies off after flowering.

4. Damage to cultural sites? Not known to cause structural damage. Little or negligible effect on aesthetics.

ABIOTIC




5. Impact flow? Terrestrial species (Parsons & Cuthbertson 2001).

6. Impact water quality? Terrestrial species (Parsons & Cuthbertson 2001).

7. Increase soil erosion? Plants have a robust taproot system with ‘numerous branching fibrous roots’ (Parsons & Cuthbertson 2001). Unlikely that the species would contribute to large-scale soil erosion.

8. Reduce biomass? Likely that biomass would slightly increase as ‘exhibits a high degree of morphological and reproductive plasticity in response to encroachment by neighbouring plants’ (Sprague 2002).

9. Change fire regime? Herbaceous plant. Unlikely that it would change the frequency or intensity of fires.

COMMUNITY HABITAT




10(a) Impact on composition of high value EVC? EVC= Low rises woodland (BCS =E); CMA=Wimmera; Bioreg=Lowan mallee; CLIMATE potential=VH. Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Minor displacement of some dominant species within the lower stratum.

10(b) Impact on medium value EVC? EVC= Shallow sands woodland (BCS =D); CMA=Wimmera; Bioreg=Lowan mallee; CLIMATE potential=VH. Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Minor displacement of some dominant species within the lower stratum.

10(c) Impact on low value EVC? EVC= Shrubby woodland (BCS =E); CMA=Wimmera; Bioreg=Lowan mallee; CLIMATE potential=VH.
Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Minor displacement of some dominant species within the lower stratum.

11. Impact on structure? Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Likely to have a minor effect on plants in the lower stratum.

12. Effect on threatened flora? No information available.

FAUNA




13. Effect on threatened fauna? No information available.

14. Effect on non-threatened fauna? Annual ragweed is ‘unpalatable to horses’ (digester class) but cattle (fermenter class) can eat it so likely that native fauna (usually fermenters) can also (Parsons & Cuthbertson 2001). Tends to grow in ruderal sites so assume that there is no reduction in food for non threatened fauna.

15. Benefits fauna? In the US the seed ‘provides food for pheasants, quail, dove, grouse, prairie chicken and songbirds..attract insects..provide browse for deer and rabbits’ (Scott 2001). Possible that provides some assistance to desirable species in Victoria e.g. quails, doves, ground-dwelling birds

16. Injurious to fauna? Beaked and spined seed attach to sheep and furred animals but no documented evidence that it impacts upon health of animal (Parsons & Cuthbertson 2001).

PEST ANIMAL




17. Food source to pests? In the US provides browse for rabbits (Parsons & Cuthbertson 2001). Therefore possible that rabbits also browse weed in Victoria.

18. Provides harbor? Not likely that it provides harbour for pest spp.

AGRICULTURE




19. Impact yield? In US, shown to impact upon sweet corn yield. Also serious competitor in ‘cereals, maize, vegetables, sunflowers, soybeans and tobacco’. Competes for nutrients in orchards. ‘Grows densely to detriment of crops and pasture’. ‘Annual ragweed densities in excess of 0.5 plants per metre reduce soybean yields significantly’ (Williams & Masiunas 2004).

20. Impact quality? Shown to effect several quality traits in corn (green ear mass, husked ear mass, ear length and width, kernel mass, depth and kernels per row) (Williams & Masiunas 2004).

21. Affect land values? No information on whether or not the weed affects land value. Numerous studies on effect of annual ragweed on cropping systems but no references made to land values.

22. Change land use? Even though the weed does affect crop yield and quality there is no reference made to a change in priority of land use. Assume that there would be little or no change.

23. Increase harvest costs? Spined seeds difficult to remove from wool so added costs in acid carbonate used for removal (Williams & Masiunas 2004)..

24. Disease host/vector? Acts as an ‘alternate host in the development of sclerotinia rot of cabbages’ (Scott 2001).





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Assessment ratings originally made by the Victorian Department of Primary Industries.
The entry of this assessment was made possible through the generous support of an anonymous donor.








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Date: November 22, 2011; 10:05:04 PM EST
Author Name: David Low
Author ID: admin