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Agriculture > Plantation Crops > Rubber (Hevea brasiliensis)

Crop Management

Diseases

Abnormal leaf fall

Causative agent: Phytophthora meadii McRae.

Symptoms: First the fruits rot, later infected leaves fall in large numbers prematurely, either green or after turning coppery red. A black lesion may develop on the petiole with a drop of latex, often coagulated, in the centre. Lesion may develop on the midrib and leaf blades also. Heavy defoliation may lead to considerable loss of crop and die-back of terminal twigs.

Management: Prophylactic spraying of the foliage prior to the onset of south west monsoon with (1) 1% Bordeaux mixture (3000 - 4000 l/ha) using high volume sprayers or (2) Oil-based copper oxychloride dispersed in diluent spray oil employing either low volume airblast sprayers from the ground or through aerial application. For aerial spraying, 6.2 litres of 40% oil based copper oxychloride paste in 37 litres of diluent oil or 8 kg oil dispersible copper oxychloride powder 56% in 40 litres of oil is used per hectare. Spraying should be done as close to the monsoon as possible.

Shoot rot

Causative agent: Phytophthora palmivora (Butl.) Butl and P. meadii Mc Rae

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Symptoms: The tender green shoots rot. This is more damaging for nursery seedlings and the young plants in the field.

Management : For mature plants, prophylactic spraying is given, as in the case of abnormal leaf fall. For young plants in the nursery as well as in the field, spraying with copper fungicides before the onset of south west monsoon coupled with repeated spray rounds during bright breaks protect the plants. For ensuring proper sticking of the spray on tender foliage, sticker (Sandovit, Tenac, Teepol, Triton AE etc) may be added at the rate of 0.5 ml/litre of spray fluid.



Powdery mildew

Causative agent:Oidium heveae Steinm.

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Symptoms: Tender leaves with ashy coating curl, crinkle, and edges roll inwards and fall, leaving the petioles attached to the twigs like a broom-stick. After a few days, the petioles also fall. Die-back of twigs follows. On older leaves, white patches later causing necrotic spots reduce photosynthetic efficiency. Infected flowers and tender fruits are shed, affecting seed production.

Management: For young plants spray carbendazim (0.05%) or wettable sulphur (2g/l) at fortightly interval. Dusting during the refoliation period commencing from bud break in about 10% of the trees, giving 3 to 5 rounds at weekly to fortnightly interval using 11 to 13 kg 325-mesh fine sulphur dust per round per hectare. Sulphur mixed with an inert material like talc (70:30) is commonly used. 0.2% Wettable sulphur (1 kg in 400 litres of water) is also effective in nurseries and for young plants as a spray. Bavistin 0.05% a.i. (1g in 1 litre water) spraying is more effective than sulphur for nurseries and young rubber. Alternate use of bavistin and sulphur is recommended to avoid resistance problem.

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Bird’s eye spot

Causative agent: Drechslera heveae (Petch) M.B. Ellis

Symptoms: Symptoms appear as small necrotic spots with dark/brown margins and pale centre. Severe infection leads to premature defoliation and die back.

Management: Give repeated spraying with Bordeaux mixture 1% or Dithane M-45 0.2% or Bavistin 0.02%. Shading the nursery plants reduces the disease incidence. Maintain seedlings in vigorous condition through adequate balanced nutrition.

Leaf Spot

Causative Agent: Corynespora cassiicola (Berk & Curt)

Symptoms: Large spots, with brown margins and pale centre is the common symptom. The centre may fall off forming shot holes. On mature trees light green leaves during refoliation are more susceptible. Several lesions coalesce to form large blighted area. Disease spreads along the veins leading to a brownish “railway track” or "fish bone" like appearance. Even a localized infection on midrib or base of a leaf causes leaf abscission. Defoliation leads to die-back of branches.

Management: Repeated spraying with Bordeaux mixture 1% or dithane M-45 0.2% or bavistin 0.02% is recommended for nursery. Shading the nursery reduces the disease incidence. Maintain seedlings in vigorous condition through adequate balanced nutrition. High volume spraying with mancozeb (dithane/Indofil M-45) 0.2% or carbendazim (bavistin) 0.05% at 2-3 weeks interval during refoliation is effective in mature plantation. Micron spraying with oil dispersible copper oxychloride 56% (8 kg) or oil dispersible mancozeb 70% (7 kg) dispersed in 40 litre spray oil per ha is also effective.

Pink disease

Causative agent: Corticium salmonicolor Berk & Br.

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Symptoms: It is more damaging for plants in the age group of 2 to 12 years. The main seat of infection is usually the fork region. White or pink coloured cobweb mycelial growth occurs on the bark surface with streaks of latex oozing out from the lesions. Rotting, drying up and cracking of the affected bark will follow. Sprouts develop from below the affected portion. The distal portion of branches dry and dried leaves stick to the dead branches.

Management

Prophylactic: Spraying two rounds of 1% Bordeaux mixture (during May and August) on to the fork and branches reduces disease incidence. For 2-year-old plants, the topmost brown portion has to be applied with Bordeaux paste in a 30 cm wide band all around. The forking region also has to be applied with the paste. In leaning plants, in addition, a 30 cm wide band on the convex side of the bend has to be applied. In 3 years old plants, application has to be made on all major forking regions except the lowermost one and also on all the leaders of the topmost brown regions.

Curative: Follow frequent tree inspection during June to October for detecting infection and application of Bordeaux paste in early stage on infected part and up to 30 cm above and below. In advanced cases, Bordeaux paste may be initially applied and then the affected portion scraped to remove mycelium and decayed bark, followed by a second Bordeaux paste application. Dried branches should be pruned after disinfection. Thiride (TMTD) (10 g in 1 kg) incorporated in a wound dressing compound like rubberkote, sopkote etc or tridemorph (calixin) 2% in 1% ammoniated field latex or thiride 0.75% or tridemorph 1% or propiconazole (tilt) 0.1% in pidyvyl, china clay and water (1:2:4 by volume) is also effective as rainwash is prevented. Tridemorph (2 per cent) incorporated in 1 per cent ammoniated field latex is also effective.

Patch canker or bark canker

Causative agent: Phytophthora palmivora, Phytophthora meadii, Pythium vexans

Symptoms: On the tapping panel region or anywhere on the stem including the collar region, and occasionally on the roots, swelling and bark burst occur with amber-coloured liquid oozing out. This may not be evident in all cases. In most cases oozing of latex is observed. The bark rots, and a coagulated rubber pad, emanating a foul smell is seen in between the wood and the rotting bark. When this is removed slight discolouration of the wood in this region is also noticed.

Management: The affected region may be scraped to remove all the rotting bark and the coagulated rubber and the wound washed well with Dithane (Indofil) M45, 0.75% (10 g per litre of water). When the fungicide dries up, apply wound dressing compound.

Black stripe, black thread or black rot

Causative agent: Phytophthora palmivora, P. meadii

Symptoms: In the renewed bark region, small depressions are formed due to localized rotting and drying of bark, which gets pressed to the wood. When scraped, deep vertical black lines running downward into the tapping bark and upwards into the renewed bark are noticed. Bark rot often reduces yield. The renewed bark becomes highly uneven.

Management: If tapping is regularly done during rainy season, the tapping panel should be disinfected at weekly intervals by brushing with Dithane (Indofil) M45, 0.375% a.i. (5 g per litre of water). Phosphorous acid 0.08% at weekly intervals is also effective. In the infected cases, scrape off the affected tissues and apply the fungicide. When the fungicide dries up, a wound-dressing compound may be applied.

Dry rot, stump rot, collar rot or charcoal rot

Causative agent: Ustulina deusta (Hoffm.ex Fr) Lind.

Symptoms: It affects roots, collar, trunk and branches with copious exudation of latex from the lesions. Affected bark and wood become soft and powdery with double black lines in the wood. Grey, crust-like flat fructifications, which later coalesce and turn black are seen on the bark. Affected trees or branches are killed or blown over. Ustulina root infections are also noticed.

Management: Scrape off the fructifications, affected bark and wood showing black lines. Apply a wound dressing compound in which Thiride 0.75% a.i is incorporated. Hexaconazole 0.02% a.i (Contaf) is also effective. Avoid accumulation of rubber at the base of the tree. For root infection, see the treatment for brown root disease.

Brown root disease

Causative agent: Phellinus noxius Corner G.H. Cunn

Symptoms: Retardation in growth and a general yellowish discolouration of the foliage occur. Affected roots when examined show a thick encrustation of soil, sand and fungal hyphae cemented to the root and brown lines in the affected roots. In advanced cases, the plants dry up.

Management: Completely killed and dried roots may be traced, pruned off and burnt along with any rotting stump in the immediate vicinity and partially affected and healthy roots washed with calixin 1% or tilt 1% solution (provisional recommendation). When the fungicide dries up, a thin coating with a wound dressing compound may be given. Refill the soil and drench the base with fungicide solution. The dried up plants may be uprooted, root traced, collected and destroyed. As prophylactic measure the bases of trees neighbouring the affected trees may also be drenched with calixin 1% or tilt 1% solution. Drench the nursery beds having affected plants with any of the above mentioned fungicide solution.

Poria root disease

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Causative agent: Poria vincta (Berk.) Cooke

Symptoms: Yellow discolouration of leaves is the only external symptom. The affected root shows soil encrustation as in the case of brown root disease but to a limited extent. Around the root, fungus forms a complete mat, pale white in colour intermingled with brick red and black tinges.

Management: Completely killed and dried roots may be traced, pruned off and burnt along with any rotting stump in the immediate vicinity and partially affected and healthy roots washed with calixin 1% or tilt 1% solution (provisional recommendation). When the fungicide dried up, a thin coating with a wound dressing compound may be given. Refill the soil and drench the base with fungicide solution. The dried up plants may be uprooted, root traced, collected and destroyed. As prophylactic measure, the bases of trees neighbouring the affected trees may also be drenched with calixin 1% or tilt 1% solution. Drench the nursery beds having affected plants with any of the above mentioned fungicide solution.

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