ANTHRACNOSE

Causal organism: Colletotrichum gloeosporioides
Sub-division: Deuteromycotina

Symptoms

• On Leaves:
  • Circular, light yellow-brown spots that enlarge with dark brown to black margins.
  • Severe infection leads to coalescence of spots, twisting of foliage, and premature defoliation.
• On Fruits:
  • Spots appear near the stem end as small brown areas that rapidly enlarge and turn black.
  • Affected fruit pulp becomes hard, leading to cracking and decay as the fruit ripens.

Etiology

• Pathogen: Colletotrichum gloeosporioides is a fungus producing conidia (asexual spores) responsible for secondary spread.
• Survival and Spread:
  • Survives on infected plant debris, defoliated branches, mummified flowers, and flower brackets.
  • Spreads through rain splash and wind-driven rainwater.

Disease Cycle

• Primary Infection: Occurs mainly through infected leaves, defoliated branches, mummified flowers, and flower brackets from the previous season.
• Secondary Infection: Conidia are dispersed mainly by rain splash or wind-driven rainwater, infecting healthy leaves, flowers, and fruits.
• Overwintering: The fungus survives in plant debris and infected twigs.

Favourable Conditions

• Temperature around 25°C.
• Relative Humidity 95-97%.
• Moist and humid conditions.
• Rainy and windy weather facilitates spore dispersal.

Management

• Cultural Practices:
  • Avoid overcrowding in orchards to ensure good air circulation.
  • Tree sanitation is crucial; prune and burn diseased twigs along with fallen leaves.
• Chemical Control:
  • Spray Carbendazim (0.1%) or Chlorothalonil (0.2%) at 14-day intervals until harvest.
  • Before storage, treat the fruits with hot water at 50-55°C for 15 minutes or dip in Carbendazim solution (0.1%).
• Post-Harvest Management: Hot water treatment or chemical dip before storage to minimize post-harvest decay.

MANGO MALFORMATION

Causal organism: Fusarium moniliformae sub sp. subglutinans
Sub-division: Deuteromycotina

Symptoms

Vegetative Malformation:

• Excessive Vegetative Branching: Plants develop abnormal vegetative branches with limited growth, swollen appearance, and short internodes.
• Bunchy Top Appearance: Branches exhibit a compact bunch of leaves at the apex or in the leaf axil, giving a “bunchy top” look.

Floral Malformation:

• Abnormal Panicles: Flowering panicles appear as compact bunches of hard flowers instead of normal inflorescences.
• Enlarged Flowers: Individual flowers are enlarged with a prominent disc. The inflorescence becomes hypertrophied.
• Reduced Bisexual Flowers: A significant reduction in the percentage of bisexual flowers in malformed panicles.
• Persistent Black Masses: Malformed floral heads dry up into black masses and persist on trees for a long duration.

Etiology

• Pathogen: Fusarium moniliformae sub sp. subglutinans produces conidia responsible for secondary spread.
• Survival and Spread:
  • Survives in malformed inflorescences.
  • Spread occurs via conidia dispersed by air or carried by the eriophid mite (Aceria mangiferae).

Disease Cycle

• Primary Infection: Initiated through malformed inflorescences present on infected trees.
• Secondary Infection: Spread by air-borne conidia or conidia carried by the eriophid mite (Aceria mangiferae).
• Overwintering: The pathogen survives in malformed floral parts on trees.

Favourable Conditions

• Younger plants are more susceptible.
• Vegetative malformation reduces as the plant ages.
• Mild temperature (8 – 27°C) and high relative humidity (>85%) are conducive to disease development.

Management

• Cultural Practices:
  • Avoid using scion sticks from trees bearing malformed inflorescences for propagation.
  • Use only certified saplings for propagation.
• Chemical Control:
  • Spray Carbendazim (0.1%) in healthy orchards located in disease-prone areas.
  • 200 ppm NAA (Naphthalene Acetic Acid) spray before blossoming helps reduce floral malformation.
• Integrated Disease Management (IDM): Combine cultural practices, chemical sprays, and resistant varieties (if available) for effective control.

Powdery Mildew

• Causal Organism: Oidium mangiferae
• Sub-division: Deuteromycotina

Symptoms

• Whitish or grayish powdery growth on inflorescences and tender leaves.
• Twisting, curling, and defoliation of leaves.
• Damaged floral parts drop off prematurely.
• Fruits, if set, fail to grow and drop off before reaching pea size.

Disease Cycle

• Primary Infection: Through infected plant debris by conidia.
• Secondary Infection: Spread by wind-borne conidia.

Favorable Conditions Warm, humid weather with cool nights favors disease development.

Management

• Preventive Sprays:
  • Apply wettable sulfur (0.3%) before flowers open and again after fruit set.
  • Spray Karathane (0.1%) before flowering and after fruit set (peanut stage).

Mango Bacterial Canker

• Causal Organism: Xanthomonas campestris pv. mangiferae indica

Symptoms

• Minute, water-soaked lesions towards the leaf tip, increasing in size (1-4 mm), raised and turning brown to black.
• Spots may be surrounded by chlorotic halos.
• Cankerous lesions appear on petioles, twigs, and young fruits.

Mode of Spread and Survival

• Primary Source: Infected nursery trees introduce disease into new orchards.
• Entry and Survival:
  • Enters leaves through stomata, fruits, and twigs through lenticels.
  • Pathogen survives up to 8 months in infected leaves.
  • Cankers on twigs are the primary source of infection on fruits.
• Spread: Rapid during rainy days and through infected planting material.

Management

• Chemical Control:
  • Three sprays of Streptocycline (0.01%) + Copper Oxychloride (0.3%) after the first visual symptom at 10-day intervals.
  • Monthly sprays of Copper Oxychloride (0.3%) effectively control the disease.