As a farmer, you may have experienced the joy of seeing countless flowers and fruits on your trees, only to be sorely disappointed when most of them end up on the ground the next day. Although this is a common problem faced by many others, the losses (and heartache) incurred are still very real. 

Join us this month as we take a closer look into why trees experience fruit drop and how we can manage it! 

Understanding the problem:

The scientific term for fruit dropping is “fruit abscission”. Abscission in general refers to the separation of a plant organ, such as leaves, flowers or fruits, from the main plant. It is (1.) a plant’s natural response to dealing with harsh environmental conditions, and (2) a measure to ensure it can reproduce successfully. 

For example, trees will shed their leaves, flowers and fruits in periods of drought to minimize transpiration and conserve energy for survival. Trees will also remove less productive fruits so that more energy can be used to develop viable seeds in remaining fruits. 

Taking a deeper look:

At a cellular level, fruits separate from the plant at an area called the abscission zone (AZ). The AZ consists of cells which have no cell walls and therefore will easily break off, and it is usually located in single or multiple locations on the fruit pedicel, depending on the type of crop. The formation of the AZ relies on chemical signals such as hormones, saccharides, and polyamines. For instance, two of the main hormones controlling abscission are auxin (prevents) and ethylene (induces). 

What fruit dropping leads to:

Lower crop yield 

From an agricultural perspective, fruit dropping is almost synonymous with reduced yield and crop losses, since the available fruits for harvest are directly reduced. In apples, yield loss up to 30% in the start of the harvest season is not uncommon. Excessive fruit dropping not only reduces the fruits available for harvest, but also leads to economic losses since income is reduced but costs remain the same. 

Disruption of harvest times 

If fruit dropping is too excessive, farmers may have to induce flowering and fruiting again, so that drastic yield losses can be offset by new crop yields. This can cause them to be unable to meet consumer demands on time, especially for seasonal fruits such as durians and pineapples. 

Reasons for fruit dropping

Fruit dropping can be separated into three types: normal fruit drop, physiological fruit drop, and stress-induced fruit drop. 

Normal 

Normal fruit dropping refers to ripe fruits which are released from trees as a natural part of reproduction. This is a normal part of the plant growth stage. 

Physiological 

This refers to natural dropping caused by physiological reasons. Some examples are incomplete pollination, malformed fruits and overbearing. Incomplete pollination and malformed fruits mean less production of viable seeds. Overbearing trees will drop fruits due to stress and competition of nutrients between the fruits and the tree itself. 

Using a biostimulant high in calcium and boron can help in strengthening the pollination process, helping to avoid incomplete pollination. WUXAL Ascofol CaB contains 21% CaO and 1.26%B, with seaweed suspension rich in naturally occurring growth regulators, helping you prevent fruit drops caused by physiological reasons. 

Stress-induced

The natural response of trees to external stresses is to undergo abscission to conserve nutrients for its own survival. Below are a few causes of stress:

Water stress

Water plays an important part in plant physiology, aiding in nutrient transport, structure and transpiration. During periods of drought, heavy rain, or high salinity, plants experience water stress, leading to them removing organs such as leaves or fruits to maintain the balance of water in their body. 

In order to minimize transpiration and reduce the growth of new leaves, AgroBridge recommends using potassium-rich fertilizers such as WUXAL K40 for the tree to focus growth onto the fruits. For waterlogged soils, fulvic acid should be used to improve the root conditions. WUXAL Fulvic contains 18.7% fulvic acid, suitable to help plant roots continue to absorb nutrients in flooded conditions. 

Light stress

Light plays a crucial role in plants: photosynthesis. It directly contributes to the level of carbohydrates in plants. In periods of low light, lower carbohydrates are produced, causing plants to have less energy to produce amino acids that aid in fruit development, leading to fruit dropping in order to reduce fruit load. 

AgroBridge recommends using WUXAL Unlock to supplement the amino acids that could not be produced due to a shortage in carbohydrates. WUXAL Unlock contains 14.2% of total amino acids, suitable for supplying amino acids that the plant requires. 

Nutrient stress

Nutrient stress can come in the form of deficiencies or toxicities. Nutrient deficiency means that the nutrients available to the tree are not enough for fruit development. On the other hand, nutrient toxicity refers to an excess of nutrients leading to toxic levels. Some commonly deficient nutrients are potassium, calcium, boron, and zinc. 

These nutrient deficiencies can be alleviated through the use of targeted fertilizers. Agrobridge offers a few series of products, such as AgroBridge Complex Special, Innotec and WUXAL: granular and foliar fertilizers which are nutrient-specific, effective, and easy to use. Some popular choices for the fruiting stage are WUXAL K40 to supply potassium, and Complex Purple Special for a chloride-free, well-balanced nutrient supply for the fruiting stage. 

Temperature stress

Excessively high or low temperatures can lead to male and female flowers developing at different times, causing incomplete pollination and resulting in fruit dropping. Long periods of hot weather or rainy days can lead to temperature stress.

WUXAL Ascofol is effective in relieving the effects of drastic temperature changes such as hot weather. Containing natural seaweed extract and 3.8% of boron, it improves pollination and helps to reduce weather stress. 

Mechanical stress

Mechanical stress refers to physical forces that lead to fruit dropping. Strong, dusty winds and human activity such as spraying practices can lead to fruitlets dropping from the tree due to excessive force. 

One of the ways this can be prevented is by strengthening the pedicel of the fruit. WUXAL Ascofol CaB supplies calcium and boron to the tree, helping to strengthen cell walls and prevent accidental breakage from winds and human activity. Pruning can also be done to reduce the volume of fruits on the tree.

Pests and diseases

The invasion of pests and diseases leads to stress and triggers the defence response in trees. As a result, trees shed fruits to remove infected plant parts and to conserve energy for protecting themselves. 

AgroBridge suggests using WUXAL Ascofol Zn and WUXAL Ascofol Cu to strengthen cell walls against invasion of diseases and prevent infections. However, standard pest management practices should still be continued to reduce pest and disease incidence. 

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