- Knowing that there may be a variety of causes for unfruitfulness, it is vital to take the appropriate remedial actions, which should start at the planning stage and continue through an established orchard.
- Based on the climatic and edaphic characteristics of the orcharding site, the choice of crop and variety should be decided.
- For regions vulnerable to wind damage, provide windbreaks and shelter belts.
- Before establishing an orchard, the soil should be optimized by adding organic matter, additives, and nutrients in accordance with the results of the soil analysis.
- A combination of varieties should be developed through the introduction of efficient pollinizer varieties and pollinators in cases of pollination issues caused by heterostyly, dichogamy incompatibility, sterility, embryo abortion, etc. (Honey bees).
- After standardization in terms of chemical content and application timing, unfruitfulness owing to sluggish pollen tube development, early and delayed pollination, and employment of plant regulators might be impacted.
- Replanting or rejuvenating aged trees might solve the issue caused by ageing.
- Thinning at the proper time can solve problems caused by becoming overpowering.
- In cases of drought and waterlogging, irrigation management would play a crucial role.
- Thinning and crop management should be used to handle the issue caused by the unequal distribution of blooms on the tree.
- By implementing the proper nutritional programme based on plant and soil analysis, it is possible to maintain the critical nutrient status in tree leaves for optimum crop production.
- Standard procedures must be created for crops that require routine pruning based on the crop, the variety, and its phenology.
- Utilizing an integrated strategy, effective plant protection measures should be used to address pathogen-caused unfruitfulness.
- Replacement of normal bearing kinds and crop control should be used to address the issue of unfruitfulness caused by the tendency of alternating bearing.
- Analysis of the issue is crucial, after which potential solutions should be put out. Planning should essentially be done in such a way that there are no problems in the future, and the appropriate set of procedures should then be adopted.
External Factors for Unfruitfulness
1. Nutrient Supply:
It is commonly accepted that applying manures and fertilisers to trees while flowers are emerging will encourage fruit set. However, over-bearing from the previous season exhausts the tree and reduces subsequent flowering, even if intensive nitrogenous manuring would boost vegetative development. Nutritional loss in weak shoots leads them to fall before and after fruit set more slowly.
2. Climate:
The main elements that favour fruit set or prevent it in other cases include light, temperature, rainfall, humidity, and wind.
A high blooming temperature will dry out the stigmatic fluid and stop pollination.
Close spacing, excessive branch growth, or shadow will all frequently restrict blooming.
Because pollen is washed away after heavy rains at blossom time, pollinator activity may be limited and poor fruit set may occur. Mango flowers are very vulnerable to fog, rain, and overcast conditions. The grape vine’s blossoms and newly set grapes are destroyed by cloudy and rainy weather.
Flowers and fruits may be lost due to high wind velocity.
3. Pest and Diseases:
Fruit set is negatively impacted by insect and disease attacks. Mango and Santra flowers lose their petals as a result of mango hopper and citrus psyalla sucking the cell sap from them, respectively.
4. Locality:
A variety that works in one place could not work in another, which could result in unfruitfulness.
5. Disturbed water Relations:
Low fruit set will occur if there is a moisture shortage at a crucial time for blooming and fruit set.
6. Cultural Practices:
Fruits may be lost due to deep ploughing during the blossoming period, excessive irrigation leading to weed growth, etc.
7. Pruning:
In grape, fig, and rose plants, pruning causes the fruit to set.
B. Internal Factors:
Some fruit species generate a large number of blooms but few fruit. On a tree, there could occasionally be nothing to eat. The main causes of infertility might be poor pollination, sterility, or nutritional deficiencies.
The internal factors are:
(1) Impotency, (2) Incompatibility, and (3) embryo abortion. Some other factors are related to flower structure and form.
These are:
1. Dicliny or Uni-sexuality:
Separate blooms contain the stamens and carpels. The same or separate trees can produce male or female blooms.
(a) Monoecious :
Monoecious plants, such as walnut, pecan nut, chestnut, banana, and coconut, are those that have both male and female flowers on the same plant.
(b) Dioecious:
On two distinct plants, the male and female flowers are produced. Therefore, male flowers from male plants are positioned adjacent to female blooms on the other plant, for example, papaya and date palm, to set more fruit.
2. Dichogamy:
The anthers and stigma mature at various times in many bisexual flowers. Dichogamy is the name given to this condition. It prevents self-pollination, which leads to unfruitfulness in such plants. The state of the flower is protogyny when the gynoecium of the same flower matures before the anthers.
Protandry, on the other hand, is a circumstance when the anthers of the same flower develop first and release their pollen before the stigma. Since mango stigma are receptive for just two hours but avocado flowers are protogynous and pollen is readily available for a longer amount of time, protandry is the word used to describe this circumstance. Another such example is coconut.
3. Self-sterility:
Many fruits fail to bear fruit because the pollen in such flowers does not fertilise the ovule of the same flower through the stigma. Incompatibility is another word for this. Both the pollen and the ovule are viable in incompatibility, yet for some reason they cannot mate. Mango, pear, apple, plum, almond, and citrus varieties have all been discovered to be self-sterile. The self-sterilizing bartlett pear. Commercial loquat varieties cannot coexist with one another. Due to self-incompatibility, pollinizer Kala Amritsari has been suggested for cultivars of plum.
4. Heterostyly:
While other flowers on the same tree or species have long styles and short filaments/stamens, the blooms in this condition have small styles and long stamens. Dimorphic heterostyly is the term for this. Similar to trim-orphic heterostyly, trim-orphic heterostyly refers to the presence of stamens and styles with three distinct lengths, as in pomegranate, litchi, sapota, and almond flowers. Therefore, heterostyly may be the cause of poor fruit set.
