• Although castor plant (Ricinus communis) serves as an important source of raw material for many industries and is reported to suffer severe losses due to many diseases caused by fungi and bacteria.
• Some of the diseases are.

• The disease is known to exist in India since 1909 when it was reported from Pusa, Bihar.
• It generally appears during rainy season, i.e., about the end of June and continues up to September.
• The disease is severe in low lying and badly drained fields and it is in such areas that it destroys nearly 30-40 per cent seedlings particularly those which are 6-8 inches high.
• The disease has also been reported from Uttar Pradesh in1948 and from Hyderabad in 1947.

• The disease first makes its appearance on both the surfaces of the cotyledonary leaves in the form of roundish patch of dull green colour which soon spreads to the point of attachment causing the leaf to rot and hand down.

• The infection further spreads to the stem with the result that the seedling is killed either due to the destruction of growing point or by the collapse of stem.
• The true leaves of seedlings and the very young leaves of older plants may also be affected; but ordinarily not much injury is caused.
• The leaf spots turn yellow and then brown and concentric zones of lighter and darker brown colour are formed.
• The outer border is not well defined and is greenish above and brownish-grey below.
• The disease spots coalesce at a later stage and cover almost the entire leaf.
• The presence of veins, even in the mature leaves, does not obstruct the spread of the disease.
• The affected leaves shed prematurely. Under moist conditions, a very fine whitish haze is found on the under-surface of the leaf spots.
• In case of mature plants also the disease may spread from young leaves to the stem through the petiole.
• When the older leaves are attacked the pathogen however remains localised on the leaf blade.
• Direct attack of stem is not very common and if it is attacked, the disease does not cause much damage.
• This has been considered to be due to the presence of cuticularised epidermis in older stem which resists penetration.
• Infection of flowers and green fruits in nature has not been reported though under laboratory conditions these parts get infected.

• The causal organism, Phytophthora colocasiae., consists of inter and intra-cellular mycelium which develops inside the host tissue.
• After a few days growth numerous branches emerge from the lower epidermis of the leaf generally through stomata as sporophores either singly or in twos or threes.
• A single colourless ovoid or roundish sporangium is borne at the tip of sporophore.
• A ripe sporangium liberates zoospores when put in water.
• The number of zoospores varies from 5 to 45 in each sporangium. The zoospores germinate readily by one or rarely two germ tubes.
• These are formed freely during hot and dry months when sporangia are scanty and retain the power of germination for many months.
• Oospores have also been produced on artificial cultural media.
• The oospores remain viable for a long period and it is considered possible that these might serve as a source of carrying the parasite over from one crop to the next.
• Secondary infection spreads rapidly through sporangia provided the weather conditions are favourable.
• The sporangia are easily disseminated by the wind and germinate readily on the leaves producing zoospores which penetrate by means of germ tubes either through stomata or directly and produce diseased spots within 24 hours and the next crop of sporangia appear in about two days.
• The fungus also causes infection on young potato, tomato and brinjal plants and seedlings of several garden annuals.
• It also produces infection on the leaf of Sesamum.
• These plants might serve as collateral or alternative hosts of the fungus and help in the perpetuation of the disease.

• Ill drained, damp and low lying localities should be avoided for sowing castor.
• Seed dressing with 4gms g Trichoderma viride formulation and 3g metalaxyl per kg seed can reduce disease incidence. Soil drenching with copper oxychloride @3g /lit or metalaxyl 2g/lit is also useful.

• The disease has been reported from different parts of the country from time to time and is assuming serious proportions in the recent years particularly in Bombay areas.
• In some other countries also, Alternaria leaf spot is considered to be one of the serious diseases of castor.
• In humid years extensive fructification of the fungus takes place on the capsules of castor plant giving black, sooty appearance which on shaking gives rise to black clouds of conidia.
• In some fields about 70 per cent of the plants are reported to be affected with the disease causing serious losses in yield and oil content.
• When the infection takes place in early stages of flower development the buds are killed and the inflorescence turns black.
• If the disease appears at a late stage, the flowers shed without capsule formation and in mild attack only individual flowers dry up.
• The height and general vigour of seedlings were reduced due to the disease which affected the yield to a considerable extent

• In one case the capsules, when half mature, wilt suddenly,turn brown and due to collapse of the pedicel the capsules fall or hand down.
• They are smaller in size and have under-developed and wrinkled seeds with little oil content.
• The germination of the affected seeds is also adversely affected.
• In other case, the attack is generally on the fully developed capsules resulting in the appearance of sunken spots on one side of the capsule which gradually enlarge to cover the whole pod with characteristic growth of the fungus.
• The pathogen may infect the seed if the capsule cracks.
• Stem of the castor plant has also been reported to show symptoms of the disease in some of the exotic varieties.

• The disease is caused by Alternaria ricini. The conidia are produced abundantly on the diseased portion under moist conditions and borne in chains on the conidiophores.
• The conidiophores are straight, erect or irregularly bent, sollitary, sometime in fascicles and are olivaceous in colour.
• The conidia are obclavate, light olive in colour but become darker in mass.
• They are segmented into 5-16 cells with transverse and longitudinal septa with and without beak.
• The beak is narrow, colourless, long and unbranched.
• The conidia formed in culture are usually smaller in size than those formed on the host.
• The disease is carried over through the seed both externally and internally.
• It is reported that the disease causes pre and post-emergence damping off and a seedling and foliage blight when the diseased seeds are sown.
• Some of the conditions which govern the severity of the disease are reported to be the presence of a susceptible variety, high atmospheric humidity and low temperature (16-20⁰ C).

• Seed treatment may be useful in combating the initial phase of the disease.
• Use of healthy seed and treat the seed with Captan or Thiram @ 3g/kg seed or spray Mancozab at 2.5g/lit concentration at an interval of 15days commencing from 90days of crop growth.

• The disease occurs in Bombay, Deccan districts, Coimbatore and Nagpur.
• It usually appears in Bombay between November and February on castor sown in June.
• The damage caused by this disease was very severe in moist localities and at places where the disease appeared quite early.
• In Hyderabad the disease appears only in December when the capsule formation has already started so that little damage is done to the crop.

• The under-surface of the leaf is marked by the corresponding small roundish yellow spots.
• In severe attacks practically every leaf is densely covered with rust pustules with the result that leaves may get dried up and wither prematurely.

• The hyphae of the causal organism (Melampsora ricini) collect beneath the epidermis of the leaf and form a minute cushion.
• The uredospores arise beneath the epidermis on the tips of branched hyphae.
• Stout club-shaped paraphyses are also formed in the sorus.
• At maturity the epidermis ruptures releasing clouds of spores.
• The uredospores are round or elliptic, warty and orange in colour and measure 25-29 X 19-25u.
• They germinate by germ tube which comes out from the pores and infects fresh leaves of castor.
• 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.
• Melampsora ricini is pathogenic to Euphorbia obtusifolia, E.ipecacuanha, E. giniculata and E.marginata besides 24 strains and varieties of R.communis.
• Isolates of M. euphorbiae from 5 species of Euphorbia including E.peplus failed to infect castor.

• 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.

• The disease has been reported from Bihar, Uttar Pradesh and Hyderabad and is probably present in many other parts of the country.
• It causes considerable injury to the leaves and is the source of loss of food for the Eri-silkworm which is maintained on castor plant.

• The disease is caused by Cercospora ricinella. The hyphae of the causal organism collect beneath the epidermis and form very small stomata.
• Clusters of conidiophores usually in groups of 10-20 emerge through any part of the leaf tissue and form the fructification of the fungus.
• The conidiophores are brown below and lighter towards the tip and are septate, unbranched and measure from 24 to 70 by 3 to 6.5u. The upper part of the conidiophores is characteristically knobby or flexed.
• The conidia are elongated, colourless, tapering above and truncated below, straight or slightly curved, multiseptate (upto 7 transverse septa).

• Spraying with Bordeaux mixture or other copper fungicides may help to bring the disease under check; but where the cultures of Eri-silk worm are maintained on castor plants, spraying would not be desirable.
• Use of resistant varieties would be the most effective method for combating the disease.
• Spraying twice with mancozeb 2.5g/lit or Carbendazim 1g/lit at 10-15 day interval reduces the disease incidence.
• Treat the seed with Thiram or Captan 3gm/kg seed.

• The disease in India is reported to be prevalent during November to March at Coimbatore.

• The disease is caused by Leveillula taurica.
• The pathogen is endophytic and consists of hyphae which are intercellular and occupy the spongy parenchyma of the mesophyll.
• The haustoria penetrate into some of the parenchymatous cells.
• The conidiophores of the fungus are branched and usually emerge through stomata in aggregation.
• The conidia are hyaline, varying in shape, bear minute papilla-like projection at the broad end, and are borne singly at the tip of each branch.
• These germinate readily in water producing a germ tube from one end.
• The fungus is also reported to produce powdery mildew disease on Cyamopsis tetragonoloba, Capsicum annuum, Medicago sativa and Vinca pusilla.

• When weather is comparatively dry spray twice Wettable Sulphur 3g/lit at 15 days interval , starting from 3 months after sowing.
• Spray 1ml Hexaconazole or 2ml Dinocap /litre of water at fortnight intervals. The variety jwala is resistant to this disease.

• Grow tolerant and resistant varieties like Jyothi, Jwala, GCH-4, DCH-30 and SHB-145.
• Avoid water logging.
• Destruction of crop debris.
• Selection of healthy seed.
• Providing irrigation at critical stages of the crop.

• Treat the seed with Thiram @ 3g / Kg or carbendazim @ 2g/ kg seed.
• Seed treatment with Trichoderma viridae formulation at 4g/kg of seed .
• Soil drenching with Carbandazim(1g/1 litre of water) 2-3 times at 15 days interval.

• Seedling to maturity. The disease appears in patches.

• When seedlings are attacked cotyledonary leaves turn to dull green colour, wither and die subsequently.
• Leaves are droop and drop off leaving behind only top leaves.
• Diseased plants are sickly in appearance.
• Wilting of plants, root degeneration, collar rot, drooping of leaves and necrosis of affected tissue and finally leading to death of plants.
• Necrosis of leaves starts from margins spreading to interveinal areas and finally to the whole leaf.
• Spilt open stem shows brownish discolouration and white cottony growth of mycelia much prominently in the pith of the stem.

• Selection of disease free seed.
• Grow tolerant and resistant varieties like Jyothi, Jwala, GCH-4, DCH-30 and SHB 145.
• Avoid water logging
• Burning of crop debris
• Green manuring and intercropping with Red gram

• Treat the seed with Thiram @ 3g/ kg or carbendiazim @ 2g/ kg seed.
• Seed treatment with 4g Trichoderma virirdae formulation.
• Multiplication of 2kg T.Viride formulation by mixing in 50kg F.Y.M, Spinking water and Covering with polythene sheet for 15days and then applying between rows of the crops is helpful in reducing the incidence.

Night temperatures below 22^oC followed by rains highly favourable

• Use of non spiny varieties (48-1)
• Avoid excess irrigation
• Avoid close spacing
• Destruction of crop debris.
• Selection of variety with Non-spiny capsules and less compact inflorescence like JWALA.

• Spray Carbendazim (0.05%) or Thiophanate methyl (0.05%) at 15 days interval.
• Seed treatment with carbendazim at 3g per kg and spraying with carbandazim at 1g/lit depending on weather forecast atleast 6-8 hours before rain.
• Application of 20kg area and 10kg of Muriate of Potash after removal of diseased panicles.

The disease has been reported from Bombay.

• The disease is caused by Xanthomonas ricinicola , which is gram negative, liquefies gelatin, hydrolyses starch, digests casein, peptonises milk, reduces litmus, produces ammonia and hydrogen sulphide and does not reduce nitrates.
• The optimum temperature for the growth of the bacterium and its thermal death point are 31 ⁰C amd 51 ⁰ C respectively.

1.   Field sanitation help in minimising the yield loss as pathogen survives on seed and plant debris.
2.   Hot water treatment of seed at 58^oC to 60^oC for ten minutes.
3.   Grow tolerant varieties.

• Spray Copper oxy Chloride(0.3%) or (500 PPM) Streptocycline 1g in 10 litres of water or Paushamycin (0.025%).