NUTMEG

NUTMEG

1. LEAF SPOT AND SHOT HOLE
Symptoms:
  • The initial symptoms of the disease appear as sunken spots surrounded by a yellow halo.
  • Later, the central portion of the necrotic region drops off resulting in shot hole symptoms.
  • Die back symptoms are also observed in some of the matured branches.
  • On young seedlings, drying of the leaves and subsequent defoliation are observed.
Pathogen:
  • The disease is caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc.
  • Pathogen, disease cycle and epidemiology have been described under Large Cardemom.
Management:

i) Collect and destroy the infected plant debris.
ii) Apply prophylactic sprays of Bordeaux mixture (5:5:50) and repeat 2 or 3 times at 14 days interval

2. THREAD BLIGHT
The disease manifests in two types:

a. White thread blight:
  • The first is a white thread blight wherein fine white hyphae aggregate to form fungal threads that traverse along the stem underneath the leaves in a fan shaped or irregular manner causing blight in the affected portion.
b. Horse hair blight:
  • The symptoms of this disease appear as fine black silky thread of the fungus form an irregular, loose network on the stems and leaves.
  • These strands caused blight of leaves and stems.
  • However, these strands hold up the detached, dried leaves on the tree, giving the appearance of a bird’s nest, when viewed from a distance.
Pathogen:
  • White thread blight is caused by Marasmius pulcherima while horse hair blight is caused by Marasmius equicrinus.
Disease cycle and epidemiology:
  • These fungi perennate as mycelium in dried up leaves.
  • These diseases are severe under heavy shade.
Management:

i) Follow phytosanitation and shade regulation practices.
ii) With the initiation of the disease spray the crop with Bordeaux mixture (5:5:50).


3. FRUIT ROT
Symptoms:
  • On immature fruits, the symptoms of the disease appear as splitting and rotting of fruits which ultimately drop prematurely.
  • In case of fruit rot, the infection starts from the pedicel as dark lesions and gradually spreads to the fruits, causing brown discolouration of the rind resulting in the rotting.
  • In advanced stages, the mace also rots emitting a foul smell.
Pathogen:
  • The disease can be due to both physiological and pathological regions.
  • The fungi associated with this disease are Phytophthora spp. and Diplodia natalensis Pole-Evans.
Management:

i) Spray the crop with Bordeaux mixture (5:5:50) when the fruits are half mature.

Other diseases of importance are:
  • Die-back (Diplodia spp.)
  • Dry rot (Stigmina myristicae)
  • Root rot (Fomes noxius and F. lamaoensis)
Last modified: Friday, 2 March 2012, 5:49 AM