Monday, 20 November 2017

 

 

Farmers Advisory


Weekly Status Report on Insects Pests & Diseases of Crops


Water logging due to the heavy monsoon prevailing for the past one month in some states of the country is congenial for occurrence and spread diseases like foot rot in black pepper, capsule rot in cardamom, soft rot in ginger, rhizome rot in turmeric, leaf fall and fruit shedding in nutmeg, Farmers are advised to take the following precautionary plant protection measures immediately to minimize the disease incidences and spread.

Black pepper (Foot rot disease)

The symptom appears on the leaves as characteristic black spots with fimbriate margins which enlarge and the leaves fall off.

Management in the nursery

  • Spraying Bordeaux mixture 1% on leaves and drenching soil with COC (0.2%) at monthly intervals prevents the disease.
  • Alternately, systemic fungicides such as Metalaxyl Mancozeb (1.25 g/L) or potassium phosphonate (3ml/L) which are compatible with Trichoderma harzianum may be used if biocontrol agent used in the nursery.

Management in the field

Phytosanitation

  • Removal and destruction of dead vines along with root system from the garden is essential as this reduces the buildup of inoculum (fungal population).

Cultural practices

  • Adequate drainage should be provided to reduce water stagnation.
  • Injury to the root system due to cultural practices such as digging should be avoided.
  • The freshly emerging runner shoots should not be allowed to trial on the ground. They must either be tied back to the standard or pruned off.
  • The branches of support trees must be pruned at the onset of monsoon to avoid build up of humidity and for better penetration of sunlight. Reduced humidity and presence of sunlight reduces the intensity of leaf infection.

Chemical control

Any of the following chemical control measures can be adopted.

  • A foliar spray with Bordeaux mixture 1% is also to be given. Drenching and spraying are to be repeated once again during August-September. A third round of drenching may be given during October if the monsoon is prolonged.
  • Spraying & drenching with 0.3% potassium phosphonate @ 5-8litres may be done.
  • After the receipt of a few monsoon showers, all the vines are to be drenched with 0.125% metalaxyl mancozeb @ 5-8 litres/vine. May be done.

Nematode infestation

Nursery

The damage caused to roots by nematode infestations result in poor growth, foliar yellowing and sometimes interveinal chlorosis of leaves in black pepper plants.

  • A prophylactic application of nematicide is necessary to check the nematode infestation. For this, make three equidistant holes of 2-3 cm depth in the bag around the cuttings and place phorate * 10 G @ 1g/bag or carbofuran* 3 G @ 3g/bag in these holes and cover with soil.(* banned in Kerala).
  • Also carbosulphan 0.1%@ 50 ml/bag can be applied to control nematodes.

Slow decline (Slow wilt) : Management in the field

  • Foliar yellowing, defoliation and dieback are the aerial symptoms of this disease. The affected vines exhibit varying degrees of root degeneration due to infestation by plant parasitic nematodes. There is no spatial segregation of plant parasitic nematodes and P. capsici in the soil under field conditions. Hence, it is necessary to adopt a combination of fungicide and nematicide application for the management of the disease.
  • Severely affected vines recovery should be removed from the plantation and destroyed, as it is impossible to record them whenever high population of nematodes are noticed.
  • Phorate* 10 G @30 g or carbofuran* 3 G @100 g/vine should be applied during May/June (with the onset of south west monsoon) and September/October. Along with nematicides the basins should be drenched with either copper oxychloride (0.2%) or potassium phosphonate (0.3%) or metalaxyl-mancozeb (0.125%). (*banned in Kerala.
  • In areas severely infested with root knot nematodes, cuttings of the resistant variety ‘Pournami’ may be planted. Biocontrol agents like Pochonia chlamydosporia or Trichoderma harzianum can be applied @ 50 g/vine twice a year (during April- May and September October). The fungus load in the substrate should be 108 cfu/g.
  • While applying nematicides, the soil should be raked in the basin of the vine lightly without causing damage to the root system and the nematicide should be spread uniformly in the basin and covered with soil immediately. Sufficient soil moisture should be ensured at the time of nematicide application.

Cardamom (Capsule rot)

On the infected leaves, water soaked lesions appear first and rotting and shedding of leaves along the veins occur thereafter. The infected capsules become dull greenish brown and decay. This emits a foul smell and subsequently shed. Infection spreads to the panicles also.

  • Remove mulch, regulate shade and provide drainage channels in plantations.
  • Spray with 1% Bordeaux mixture or 0.3% fosetyl – aluminium or 0.125% metalaxyl- mancozeb and drench the plant basins with 0.25% copper oxychloride.

Ginger / Turmeric

In the case of soft rot of ginger and rhizome rot of turmeric foliar symptoms appear as yellowing of lower leaves which gradually spreads to all the leaves. This is followed by drooping, withering and drying of pseudo stems.

  • Remove and destroy infected plants along with soil from beds.
  • Provide good drainage channels to avoid water stagnation.
  • Drench the beds with 0.25% Copper oxychloride or 0.125% Metalaxyl-Mz @ 5-10 liter /bed (3 m x 1 m size).

Nutmeg

In the case of leaf fall and fruit shedding, the infection starts from the pedicel as dark lesions and gradually spreads to the fruit, causing brown discolouration of the rind resulting in rotting. In advanced stages, the mace also rots emitting a foul smell.

  • Spray the plants with 1% Bordeaux mixture and drench the plant basins with 0.25% copper oxychloride @ 5-10 lit/plant.