Tropical & Subtropical Fruits

Alternate Bearing

Irregular and alternate bearing in mango is a major problem faced by mango growers. This problem causes great economic loss to the growers with the poor yield or failure of crop during "off year'' and the selling produce at low price during "on year'' due to fruit glut in the market. Though planting of regular bearing varieties like Amrapali are suggested for getting regular fruits, most of the commercially grown varieties in North India, like Dussheri, Safedas, chousa and Langra are alternate bearers. In such trees regularity can be achieved by pruning, flower induction with paclobutrozol, fertilization, irrigation and pest control.
• Mango normally flowers during February-March and is ready for harvest during June-July. Fruits are borne largely on previous years shoots, so pruning should not be very severe. Light pruning limits the vegetative growth and activates the quiescent fruit bearing buds by redistributing the endogenous hormonal substances and favours flowering, fruiting and improves fruit yield. After harvesting the fruits, troop off branches to open the centre. Also remove dead wood, weaker branches and criss- cross branches to allow sunlight to enter the canopy.
• This should be followed by tractor ploughing and fertilizer application. Though recommended doses of fertilizer differ with locality and variety, in general apply 1.5 kg N, 0.75 kg P2 O5 and 1.5 kg K2O (in two split doses) along with 250 kg FYM/tree, in the drip circle.
• Foliar spray of 1 per cent potassium nitrate or 1 per cent potassium dihydrogen phosphate + 1 per cent urea thrice at monthly intervals should also be done to achieve a balance in carbon and nitrogen ratio. During September-October months, treat the soil with paclobutrazol (5g/ plant).
• The field should be irrigated immediately after treatment to increase efficiency. Paclobutrazol checks Gibberelic Acid biosynthesis, increases cytokinin level, Chlophyll content, improves mineral uptake and carbohydrate gradient of the entire plant system. This helps in achieving a balance in C:N ratio which induces flowering normally.
• After flowering, attack by mango hoppers and powdery mildew a fungal disease will completely destroy the inflorescence. Two fortnightly sprays with Carbaryl (0.25 per cent), Diazinon (0.1 per cent) or Endosulfan (0.07 per cent) in the month of February and March, will check attack by mango hoppers.
• Similarly spraying with wettable sulphur (2g/ lt of water) is quite useful to control Powdery mildew. A liquid soap should be mixed along with pesticides for proper retention of the chemical on the plant surface. The trees thus treated will give bumper crops regularly year after year.