** Below are disease often found in tropical countries with ambient temperature 25-30 Celsius.
**Below diseases can be minimized if your land have perfect condition (good water flow), less raining/ less humid at planting location, seed treatment and good management practice.
** Always remember wear goggles, mask, gloves and apron when spraying the fungicides. Please ask supplier MSDS for fungicides and read the labeling before use. Wash your hand and body after use it.
Castor Blight/ Wilt/ Damping off --- for seedling and young stage
- Majority occurred at young castor plant before flowering stage or quantity of leave have less than 19.
- Types of the blight/ wilt/ damping off
a) Physical root damage
b) No infection types
c) Infection types
A) Physical root damage
Normally farmer like to transfer the young bud（ 2 leaves）together with root to replace the location (fail to germinate), and make the stems damping off for next day during sunlight period and it become normal during dark period. The leaves stay like normal and greenish, only castor seedling want to re-adjust back and take 1-2 day to recover. However farmer would face the risk of castor seedling grow slowly and affect harvesting in future after transfer.
You can plant the castor seeds in the poly bag as a backup to replace the ingeminated seeds location.
No need take further action because it is a normal case.
For farmer like watering castor seedling in garden every day and it sure will make castor seedling damping off/ wilt after few days. Daily watering make the root system choke/ stifle and damage thus influence the leaves grow then become yellow and finally wilt and damping off. Some more the imperfect garden location, dark & less sunlight place, too humid and bad drained system will damage the castor root system. Also in location with frequent raining season, do avoid to plant castor during raining season.
C) Infection types
Normally pathogen (fungus) likes to attack root system during castor in young stage. They are normally found in high humid and bad water flow land. Farmers are advised to dig the soil in an initial stage to prevent the fungus breed in the soil due to bad drained fields. Below are fungus disease normally found in tropical climate and they attack the root system of castor seedling (young stage) and also other type of crop.
· It generally appears during rainy season, i.e., Terengganu & Kelantan, Malaysia certain area with have raining season on November to January.
** (Only for young stage castor trees!!)
** (for old/ flowering stage is another case and its solution!!)
· 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 or less than. (**Exclude for big cut harvesting method and its height around 6-8 inches)
· 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 and destroys the growing point or collapse the whole stem.
· The leaf spots turn yellow and then brown with concentric zones of lighter and darker brown colour.
· These spots coalesce at a later stage and cover almost the entire leaf.
· The affected leaves shed prematurely. 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 localized on the leaf blade.
· The causal organism, Phytophthora colocasiae., consists of inter and intra-cellular mycelium which develops inside the host tissue.
B) Other infection types of blight disease (young stage+ mature stage)
i) Wilt by Fusarium oxysporum镰刀菌
· 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.
· Avoid water logging
· Burning of crop debris
· Green manuring and intercropping with Red gram
· Choose non-thorn genotype of castor trees.
· Treat the seed with Thiram or carbendiazim
· Seed treatment with Trichoderma virirdae (biofungicides) 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.
ii) Castor Rhizoctonia Blight by Rhizoctonia Solani (pathogen)立枯絲核菌
iii) Castor Pythium Blight 腐霉菌
IV) Sclerotinia Sclerotium by Sclerotinia ricini (pathogen) 蓖麻菌核病
V) Wilt caused by Fusarium pallidoroseum
VI) Castor Blight caused by Sclerotium rolfsii
VII) Bacteria Wilt caused by Xanthomonas ricinicola
Castor Inflorescence/ Capsules/ Stem/ Root/leaves Disease --- Mature Stage/ Flowering Stage
A) Alternaria Blight 蓖麻黑斑病 by Alternaria ricini 蓖麻链格孢
· All the aerial parts of the plant, i.e., stem, leaves, inflorescence and capsules are liable to be attacked by this serious disease.
· Symptom first appears on the cotyledons in the form of light brown spots and if the infection is extensive, the plants become stunted and ultimately die.
· These may appear on any portion of the leaf and are irregular, scattered, and have concentric rings.
· These are brown and later become covered with bluish-green or sooty growth.
· When the attack is severe the spots coalesce and form big patches resulting in premature defoliation of the plant which gradually wilts away.
· The inflorescence and the capsules are also attacked and get covered partially or fully with a similar sooty growth.
· 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 vigor of seedlings are 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.
B) Rust 蓖麻锈病 by Melampsora ricini 蓖麻锈病菌
· Rusty pustules appear on the under surface of the leaves which may coalesce to form bigger patches.
· At later stages the pustules burst and exposing the powdery mass of orange-yellow uredospores.
· The under-surface of the leaf is marked by the corresponding small roundish yellow spots.
· Under severe infestation leaves may get dried up and wither prematurely.
C) Cercospora Leaf Spot 蓖麻斑点病 by Cercospora ricinella 蓖麻尾孢菌
Minute black or brown spots with green margin seen on both surfaces of leaves which later turns to pale brown and then greyish-white surrounded by a deep brown band which may be narrow and sharp or broad and diffused.
· Tiny black dots found in the white centre.
· The diseased spots often occur in great numbers scattered over the leaf and are roundish when young but may become irregularly angular when mature.
· When the spots are close together, the intervening leaf tissue withers and large brown patches of dried leaf may result.
D) Powdery Mildew 白粉病 by Leveillula taurica.
· Whitish powdery growth seen on the under-surface of the leaf.
· When the infection is severe the upper-surface is also covered by the whitish growth of the fungus.
· Light green patches, corresponding to the diseased areas on the under surface, are visible on the upper side especially when the leaves are held against light.
· The infection is wind borne.
E) Root rot / Die back 灰莖枯病/炭腐病 by Macrophomina phaseolina
· Small brown depressed lesions on and around nodes.
· Increase in size on both directions causing 2 to 20 cm necrotic area
· Lesions often coalesce and girdle the stem causing leaf drop.
· Entire branch and top of the plant withers.
· Drying and death starts from apex and progresses.
· Infected capsules discolored and drop easily.
· Sudden wilting of plants in patches under high moisture stress coupled with high soil temperature.
· Plant exhibit symptoms of drought and drooping of leaves.
· At ground level black lesions are formed on the stem.
· Young leaves curl inwards with black margins and drop off later, such branches Die-back.
F) Gray rot 蓖麻灰霉病 by Botrytis ricini
· Small blackish spots on inflorescence from which drops of yellow liquid may exude.
· Fungal threads which grow from there spots, spread the infection and produce characteristic appearance of affected raceme.
· Withering of total plant parts like leaves, stem, flower and capsules.
· The affected flowers rot and are covered by grey coloured fungus.
· The disease spreads upwards infecting all flowers and capsules.
G) Bacterial Leaf Spot 蓖麻斑点病细菌 by Xanthomonas campestris pv.ricini
· Small, round, water-soaked spots which later become angular and dark brown to jet black in colour.
· The spots are generally aggregated towards the tip. At a later stage the spots become irregular in shape particularly when they coalesce and areas around such spots turn pale-brown and brittle.
· Bacterial ooze is observed on both the sides of the leaf which is in the form of small shining beads or fine scales.