Model Answer
0 min readIntroduction
Mango malformation is a devastating and complex disorder affecting mango trees globally, leading to significant economic losses, sometimes up to 100% in severe cases. First reported in India in 1891, it manifests as abnormal growth of vegetative shoots or floral panicles. While both vegetative and floral malformation are observed, floral malformation is more virulent and directly impacts fruit production by deforming the inflorescences, rendering them sterile. This physiological disorder is a major constraint to mango cultivation in tropical and subtropical regions, necessitating effective identification and management strategies.
What is Mango Malformation?
Mango malformation is a serious disorder characterized by the abnormal development of vegetative shoots or floral panicles. It significantly reduces plant growth and fruit yield. It is broadly classified into two types:
- Vegetative Malformation: Affects young seedlings and nursery plants, causing stunted growth with small, bushy leaf clusters at the shoot apex, often termed "bunchy top."
- Floral Malformation: The more detrimental form, directly affecting the flowering and fruit-setting process in mature trees.
Symptoms of Floral Mango Malformation
Floral malformation leads to characteristic deformities in the inflorescence, which include:
- Compact and Crowded Panicles: Instead of normal, loose panicles, the flowers become dense, highly branched, and often appear as compact green bouquets or "witches' brooms."
- Enlarged and Sterile Flowers: The individual flowers within the malformed panicles are often larger than normal, possess scanty pollen, and are typically sterile, failing to set fruit.
- Reduced Bisexual Flowers: The percentage of hermaphrodite (bisexual) flowers, crucial for fruit development, is significantly reduced in affected panicles.
- Persistent Panicles: Malformed panicles tend to remain on the tree for an extended period, sometimes drying up into a black mass.
- Lack of Fruit Set: The most significant symptom is the failure of these malformed flowers to develop into mature fruits, leading to substantial crop loss.
Causal Organism
The primary causal agent of mango malformation, particularly floral malformation, is attributed to fungal species belonging to the genus Fusarium. The most commonly implicated species include Fusarium mangiferae, Fusarium moniliforme var. subglutinans (also referred to as F. moliliforme), F. mexicanum, and F. sterilihyphosum. These fungi infect the meristematic tissues, disrupting the plant's hormonal balance, particularly the auxin-cytokinin ratio, which is crucial for normal growth and development.
Control Measures for Floral Mango Malformation
An integrated approach combining cultural, chemical, and biological methods is crucial for effective management:
1. Cultural Practices:
- Pruning: Regular removal and destruction of malformed panicles immediately after their appearance, along with 15-20 cm of the apparently healthy basal portion, is vital to reduce inoculum.
- Orchard Sanitation: Maintaining overall orchard hygiene, including proper spacing and disposal of diseased plant material, prevents disease spread.
- Disease-Free Planting Material: Using certified, disease-free seedlings and scion sticks is fundamental for preventing transmission.
- Nutrient Management: Balanced fertilization, with emphasis on appropriate nitrogen, phosphorus, and potassium ratios, can influence disease incidence. Enhanced nitrogen application has been found to reduce malformation in some studies.
2. Chemical Control:
- Fungicides: Systemic fungicides like Carbendazim (0.1%) or Captan (0.1%) can be sprayed at intervals during the flowering stage to control fungal growth.
- Plant Growth Regulators (PGRs): Application of Naphthalene Acetic Acid (NAA) at concentrations of 100-200 ppm during October (before flower bud initiation) can significantly reduce the incidence in the subsequent season.
- Micronutrient Sprays: Spraying with trace elements like Zinc, Boron, and Copper before bloom and after fruit harvesting can help minimize malformation.
3. Biological Control:
- Bioagents: Using beneficial microorganisms such as Trichoderma harzianum or foliar sprays with broth cultures of Bacillus subtilis has shown potential in controlling the pathogen's growth.
- Organic Concoctions: Sprays derived from plant extracts like Datura stramonium, Calotropis gigantea, and neem have demonstrated effectiveness in reducing infection.
Conclusion
Mango malformation, particularly its floral form, poses a significant threat to mango cultivation worldwide, severely impacting yield due to the sterility of affected panicles. The disease, primarily caused by species of the <em>Fusarium</em> fungus, manifests through distinct symptoms like compact, crowded, and sterile inflorescences. Effective management necessitates an integrated strategy encompassing vigilant cultural practices such as pruning and sanitation, timely application of chemical fungicides and plant growth regulators, and exploring biological control agents. Continued research into resistant varieties and physiological aspects like ethylene imbalance will further bolster efforts to mitigate this complex and economically damaging disorder.
Answer Length
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