Flowers and Fruits drop in Citrus

UNIVERSITY OF MIYAZAKI

PRESENTED BY: GUL NABI KHAN NOORANI

EMPLOOY OF MINISTRY OF AGRICULTURE, IRRIGATION AND LIVESTOCK

Fruit Drop Fruit drop is the detachment or separation of a fruit from a branch of a tree or a plant, caused by the formation of a separation of layer of cells on the fruit stalk due to a series of physiological and biochemical events.

Types of Fruit drops Fruit drops maybe divided into three major periods of time 1. Post bloom drops2. Jun drops 3. Pre-harvest drops Some fruits have two additional periods of drops• Summer drop • Summer-fall drop

Fruit Drops possible causes and solutions

Post-Bloom Fruit Drops (PFD) Post bloom drop occurs during and within a few weeks of bloom, involving the abscission of flowers and small fruits.

Causes 1. Inadequate pollination

2. Water or temperature stress

3. Inadequate nitrogen levels

4. Natural abscission probably by hormone imbalances

Possible solution: Gibberellic acid sprays have been used to reduce post bloom drop by many researchers.

June drop June drops is a common occurrence for many fruit crops. It occurs in Jun when the size of many temperate fruits are 1-3cm in diameter. June is the most severe and troublesome to growers in arid climates where temperature reach to 40C.

Many causes proposed by scientists Water stress, hormone imbalances and competition among fruitless and high temperature.

Possible solution Regular overhead irrigation

Use of growth regulator Gibberllic acid (10-20ppm) and 2-4-D (10-16ppm).

Pre-harvest drop Pre-harvest drop occurs after the fruit have reached legal maturity but prior to harvest.

Causes: abscission of mature fruit due to nature aging and abscission.

It become severe in particular situations

1. Lack of water

2. Over fertilization

3. Excessive cropping

Possible solution: Crop thinning by growth regulators may reduce pre-harvest drop

Summer-drop

Summer drop Occurs during June and July when fruits are 5-6 cm in diameter.

Causes: Physiological disorders

Production of ethylene increases in this stage which leads to fruit abscission.

Summer-fall drop Occurs from September to October as fruit near maturity

Causes Physiological disorders

Splitting (heavy rain or irrigation after dry weather),

Stylar-end decay

Natural abscission

Other fruit drops causes Can be divided into three major categories

A. Insects and Pathogens Purple scale , Mealy bugs cause peel damage and produce ethylene which leads fruit drop. Brown rot

B. Environmental factors Low and High Temperature and water stress at late-season

C. Mechanical causes Movement of equipment

Physiological factors

Pathological and Mechanical factors

Environmental

From (F.S. Davies, Fruit drop Problems of Citrus)

ReferenceF.S. Davies, Fruit drop Problems of Citrus