Invasive Alien Species

Species Name: Asystasia gangetica

Family Name:
Acanthaceae
Synonym:
Asystasia coromandeliana Nees var. micrantha Nees
A. intrusa (Forssk.) Nees in DC
Ruellia intrusa Forssk.
Origin:
Africa
Description:
A strangling perennial herb. Stem weak, erect or ascending up to about 1 m tall.  Leaves opposite, usually in equal pairs, elliptical,  tip sharply pointed, based rounded, variable in size, from 64.5 mm x 25.5 mm or less, leaf stalk slender up to about 50.8 mm long. Flowers terminal, racemes, 25.4 to 50.8 long, single flower with small, narrow free sepal, creamy white, an indigo-blue patch on keel petal; corolla tube narrow cylindrical, expanded above; stamen four in equal pairs from corolla tube. Capsule about 19.1 mm long, club shaped, with 4 seeds in the upper part, the stalk solid.
Invaded Habitat:
It has extremely widespread in oil palm, rubber, pineapple and cocoa plantations and also at the waste places. It has reported recently as important weeds in oil palm plantations in North Sumatra, the large number of seedlings and vigorous growth of this plant has caused the necessity of extra labour to carry out weeding.
Distribution:
West Java and Sumatra
Ecology:
A. gangetica subsp. micrantha  can be found in areas up to 500 m above sea level.  It grows well under shaded areas as well as in the open space. Under shaded areas such as in the oil palm and rubber plantations the plant increases its leaf area by producing more vegetative organs. It is a prolific and competitive weeds and has a high demand for nutrient particularly N and P. The production of seeds is good with 85% viability, which can last up to 8 months in soil. Under natural conditions the seed can germinated within 30 days after sowing, and 10 weeks after germination the plant grows vigorously, continues producing pods and seeds for 8 months or more.
References:
  1. Chan, H.H.  1984.  Masalah Asystasia di negeri Johore.  Seminar Masalah dan Pengaruh Asystasia di Projek Johore Barat. IADP, Johore Barat, Johore.
  2. Chung, G.F., K.R. Pillai and S. Thiagarajan.  1984.  Asystasia in plantation crops.  Proc. on the Problem of Asystasia in West Johore Project. IADP West Johore, Johore. 
  3. Kiew, R & K. Vollesen.  1997.  Asystasia (Acantaceae) in Malaysia.  Kew Bulltetin Vol 52 (4) : 965-971. 
  4. Koo, S.J., Y. W. Kwon  and Chin D.V. 2005. Common Weeds in Vietnam. Second Edition. Saigon Plant Protection State Limited Company. 
  5.  Lee, S.A.  1984.  Control of A. intrusa Bl. Proc. on the problems of Asystasia in West Johore Project.  IADP West Johore, Johore. 
  6. Lee, S.A. , A.B. Yunus and C.H. Tong. 1984.  Survey on the distribution and control of A intrusa Bl. In pinrapple  farms of West Johore. Proc. On the Problems of Asystasia in West Johore’s Project. IADP West Johore, Johore. 
  7. Othman, S.  1993.  Asystasia intrusa (Bl.).  Weed Info Sheet.  SEAWIC, SEAMEO BIOTROP.  
  8. Othman, S. and M.K. Musa.  1992.  The ecology of A. intrusa Bl. Proc. Persidangan Ekologi Malaysia, 1: 91-96.  UPM, Serdang, Serdang, Selangor, Malaysia.
  9. Rajaratman, J.A., K. W. Chan and H.T. Chong. 1977.  Asystasia in oil palm plantations.  In : Int. Dev. in Oil  Palm ed. By Earp and Newel, Kuala Lumpur, Malaysia.