Subhrajyoti Mishra Fruit thinning agent only acts on the weaker part of fruit. Those excessive fruit which is unnecessarily taking the nutrient from the mother and still have a loose connection to by forming abscission layer in the attachment; only those fruit will abscess. However sometime good and solitary fruit may drop due to the loose attachment and the densely bunch still attached to the mother plant because of strong auxin flow.
There are many factors which affect the thinning capability of a thinner chemical. Particularly, fruits size and leaf/fruit ratio is more important. The competition among fruits decide the thinning efficacy of chemicals. If the leaf/fruit ratio is high, resulting bigger size fruit and strong attachment. Lower photosynthates weaker the fruits and such fruits have strong competition and distribution of food material is greater and are more sensitive to thinning. If the competition is more, efficacy of thinning is also more.
First, you need to understand how chemical fruit thinner works. Application of the chemical thinner results in a significant reduction in fruit growth during the first week following its application. This means that chemical thinners can have a rapid negative effect on the level of nutrients or carbohydrates available for fruit growth. Generally, the chemical thinner creates carbohydrate stress in fruit. The smaller fruits are more sensitive to the carbohydrate deficit and respond by showing a more pronounced decrease in growth rate compared to the larger fruit and eventually drop from the plant. Environmental conditions that reduce the carbon status of the plant, i.e. low light levels, high night temperatures, etc. and chemical thinners, may have a common primary mode of action.
Now coming to your question, many factors affect a tree response to chemical fruit thinner i.e. carbohydrate status of the tree, weather conditions, water rates, spray coverage, droplet size, drying time, the inclusion of wetting agent, uptake and metabolism of leaf, etc. However, the carbohydrate status of plants and weather conditions have a more pronounced effect on fruit thinning. If the plant has high carbon status then application of chemical thinner does not induce required stress in fruit and results in nil or minimum fruit thinning. If the plant is in moderate carbon status then chemical thinner induces stress in slow growing fruit and consequently results in adequate thinning. If the plant has a low carbon status then chemical thinner causes stress in most fruits and contributes to extreme thinning of the fruit. In addition, environmental conditions such as dark, cloudy with a period of more than 1-2 days reduces carbohydrate supply and contribute to greater chemical thinning. High night temperatures increase carbohydrates demand and improve the response to chemical thinning. Very high temperatures in the daytime increase carbohydrate demand and cause excessive thinning. Low temperatures reduce fruit demand and result in a poor thinning response Subhrajyoti Mishra
Thank you Kumawat's sir for your elaborate description and clearing my doubts.
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