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Flower and bud drop in chilli

Flower and bud drop in chilli is a multi-causal physiological disorder rather than a single disease. It results from the interaction of temperature extremes, water stress, micronutrient deficiency (notably boron) and sucking-pest damage, and is a major cause of poor fruit-set in the Indian crop.

Principle

Boron has a documented role in pollen-tube growth, fertilisation and fruit-set. TNAU notes that boron deficiency in chilli produces incomplete pollination, flower abortion and a reduction in fruit size and weight. The other principal drivers are high day-night temperature swings, soil moisture stress and feeding damage from black thrips (Pest Thrips Parvispinus Black Thrips).

Implementation

The standard corrective package combines plant-growth regulator and micronutrient sprays:

  • NAA — alpha-naphthaleneacetic acid at 2-3 ml/10 L (research data show 50-75 ppm gives the best fruit-set), sprayed at 45 and 60 days after transplanting
  • Boron — 0.2% borax foliar spray, integrated into a balanced micronutrient mixture
  • Calcium/magnesium — added at flowering and pod-fill where deficiency-induced blossom-end disorders are suspected

These sprays are placed within the eight-spray IPM schedule (Practice Chilli Spray Schedule) and complement the staged NPK regime (Practice Chilli Fertilizer Schedule).

Adoption context

The disorder is widespread across south Indian rabi chilli, where high midday temperatures and the invasive Thrips parvispinus outbreaks of 2021-22 onwards have made flower retention a central management concern.

Limitations

Once a flush has been lost, NAA sprays cannot recover the dropped flowers; the corrective programme is preventative. Where sucking-pest pressure is high, vector and pest control (Pest Sucking Pests Chilli, Pest Thrips Parvispinus Black Thrips) is more important than the PGR/micronutrient regime.

Practice Chilli Fertilizer Schedule, Chilli Yellow Leaf Pandaku, Pest Thrips Parvispinus Black Thrips, Practice Chilli Spray Schedule

References

  1. Boron in chilli. TNAU Agritech plant nutrition page.
  2. Effect of plant growth regulators on chilli. The Pharma Innovation Journal, 2022.