CASTOR RUST

Minute,orange-yellow coloured,raised pustules appear with powdery masses on the lower surface and corresponding upper surface yellow colour leaves

1. CC CCA CASTOR RUST OR COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562 Course teacher: Student: Dr. Parthasarathy . S Miss. C. Pon Alagammai . Asst.Professor (Plant Pathology) 2015021095

2. Name of the disease : Castor Rust. Casual organism : Melampsora ricini .

3. Castor oil plant ( Ricinus communis L., Euphorbiaceae ) originates from tropical Africa and has seeds that contain ricin , an extremely toxic protein. The seeds also yield oil, which has industrial and medicinal uses.

4. In Australia, castor oil plant is a weed in all States and, in southern Australia, is grown as an ornamental. One rust, Melampsora ricini E.A. Noronha, has been recorded on castor oil plant, in Africa, Asia and southern Europe ( Punithalingam 1968).

5. 1. M . ricini is known only in its uredinial and telial states. 2. In Australia, M. ricini was first collected (BRIP 25782) in Brisbane in August, 1999. 3. Within weeks the rust was found in Perth.

6. 4. Telia were observed as light brown spots, 0.5- 1.5 mm diameter, on the lower surface of young expanding red leaves. 5. Teliospores are prismatic, 25-65 x 5-13 ym , with walls 1-1.5 mm. 6. Expanding leaves with telia had few uredinia .

7. 7. At least seven other rusts of plants in the Euphorbiaceae are known in Australia (J. Walker, unpublished). 8. Of these, the rust on Euphorbia peplus L., a member of the Melampsora euphorbiae Castagne complex ( Sydow & Sydow 1914), is most similar to M. ricini .

8. Significance : Controlling the rust with hyperparasites has been attempted but not found to be economic importance. It is suggested that at the first sign of infection, diseased leaves should be destroyed

9. Symptoms : 1. Minute, orange-yellow coloured , raised  pustules  appear with powdery masses on the lower surface of the leaves and the corresponding areas on the upper surface of the leaves are yellow. 2. Often the pustules are grouped in concentric rings and coalesce together to for drying of leaves.

10. 3. Pale leaf spots eventually develop into spore-producing structures called pustules. 4. The pustules are found most commonly on the lower leaf surface and produce huge numbers of microscopic spores.

11. 5 . S ome cases there may be dozens of pustules on a single leaf. 6 .Severely affected leaves often turn yellow and fall prematurely.

12. 7. Pustules also sometimes form on leaf stalks (petioles), stems and, rarely, on flowers and fruit. 8. Heavy infection often reduces the vigour of the plant. In extreme cases (e.g. with antirrhinum rust) the plant can be killed.  

13. C astor rust U redospores

14. Etiology : 1 . The hyphae of the causal organism Melampsora ricini collect beneath the epidermis of the leaf and form a minute cushion. 2. The uredospores arise beneath the epidermis on the tips of branched hyphae . 3. Stout club-shaped paraphyses are also formed in the sorus .

15. 4 . At maturity the epidermis ruptures releasing clouds of spores. 5. The uredospores are round or elliptic, warty and orange in colour and measure 25-29 X 19-25µ. 6. They germinate by germ tube which comes out from the pores and infects fresh leaves of castor.

16. 7. It was observed that the rust culture could not be maintained on host plants under Delhi conditions beyond the beginning of April because of rise in temperature. 8. Melampsora ricini is pathogenic to Euphorbia obtusifolia , E . ipecacuanha , E. giniculata and E. marginata besides 24 strains and varieties of R.communis .

17. Systemic position: Kingdom: Fungi Phylum : B asidiomycota Class : U rediniomycetes Order : U redinales Family : M elampsoraceae Genus : M elampsora Species : M.ricini .

18. Spread: 1. Chiefly by urediospores, and sometime by winds. Distribution: 1. The disease occurs in Bombay, Deccan districts, Coimbatore and Nagpur. 2. It usually appears in Bombay between November and February on castor sown in June.

19. 1. The damage caused by this disease was very severe in moist localities and at places where the disease appeared quite early. 2. In Hyderabad the disease appears only in December when the capsule formation has already started so that little damage is done to the crop.

20. Favorable condition : Common in I ndia – N ov- F eb-Annual crops. Geographical distribution: Africa (Algeria, Congo, Egypt, Ethiopia, Kenya, Libya, Malawi, Morocco, Mozambique, Rhodesia, Sudan, Tanzania, Uganda); Asia (Ceylon, Cyprus, India); Europe (Italy, Lusitania, Portugal). (From literature and Herb. IMI)

21. Hosts: On Ricinus communis ; also by inoculation on 1. Euphorbia geniculata , 2. E. ipecacuanha , 3. E. marginata and 4. E. obtusifolia .

22. Management: The disease is reported to be successfully controlled by spraying the crop with fine sulphur powder @20-30kg / hec . Spraying of Tridemorph 1 ml/ litre of water or Mancozeb 2.5 g/ litre of water minimises disease spread.