The idea to use the SSHWT to control the fruit fly infestation was conceived during the EU/TRTA II/UNIDO sponsored training of researchers from the Mango Research Station (MRS) and Citrus Research Institute (CRI) on Postharvest Technology Management and Extension (Mango and Citrus) at the Post Harvest Training and Research Centre, University of the Philippines from 6-15 April 2014. There, the researchers observed and discussed the use of HWT in the mango farming communities of Philippines and were impressed by the adaptation of this simple technology by the local growers.


MRS prepared a model SSHWT unit which could be replicated. The researchers of MRS modified the SSHWT unit according to the requirements of Pakistani mango.


Pakistan with the production of 2 million tons of juicy, sweet and fragrant mango fruit and is the sixth largest producer of mango in the world. In the year 2013 the country exported 98,920 tons of mangoes valued at US$ 57,200,164. Every year Pakistan exports only around 5% of its production. Almost 40% of the produce is wasted.

Every year Pakistan exports more than US $13,980,305 worth of mango to the UK AND EU countries. Recently, the EU regulatory authority, DG SANCO, informed the Pakistani counterparts (the Department of Plant Protection, and the Ministry of National Food Security and Research) about the increasing incidents of fruit fly infestation in the mangoes imported from Pakistan and requested to take concrete actions to control the fruit fly infestation of mangoes exported to EU markets.

As a member of the WTO – and therefore in order to meet its commitment to comply with the Sanitary and Phytosanitary Agreement – and in order to protect its exports, Pakistan is expected to demonstrate its best efforts in managing and controlling  the fruit fly.


The Extended Hot Water Treatment (HWT), Vapour Heat Treatment (VHT) and Irradiation are the three effective techniques most commonly used in mango producing and exporting countries in order to kill fruit fly eggs in the mango fruit. These treatments effectively remove the fruit fly infestation from the harvested fruit and as a result increase the fruit’s shelf life.

Presently there are only three HWT plants in Pakistan, two are private and one is a public-private joint venture. These plants are internationally approved and meet all standard quarantine requirements. There is a small scale VHT plant installed at Karachi Airport but it is not being used commercially. Similarly, an irradiation facility has been established in Lahore but it is not operational.

VHT, Irradiation and large-scale HWT plants are very expensive and therefore Pakistani farmers cannot afford to install any of them. On the other hand most of the importing countries have made HWT mandatory for the mangoes to be imported from Pakistan. The table below reflects some of the current phytosanitary requirements for mangoes from the importing countries:


Phytosanitary requirements

China, Jordan. Lebanon, South Korea, Mauritius

Hot water treatment (48°C for 60 minutes) against fruit fly infestation applied at the facilities duly approved by the importing country’s National Plant Protection Organization (NPPO)


Irradiation or hot water treatment at 48°C for 60 minutes at the facilities duly approved by the Australia Biosecurity Organization


Vapour Heat treatment (47°C for 25 minutes) – facility duly approved by Japan Plant Protection Authorities


Hot Water Treatment (45°C for 75 minutes) to control fruit fly infestation duly approved by importing country National Plant Protection Organization (NPPO)


Irradiation at approved irradiation facility

Most of the importing countries demand hot water treated mangoes. Therefore, Pakistan has to take both short and medium-term measures to tackle the rising menace of fruit flies and other diseases. An advantage of the HWT over VHT and Irradiation is that it also effectively controls post-harvest diseases such as Stem End Rot and Anthracnose, which are also an issue for mango exports.

The commercial facilities for the HWT are located in Karachi, far from growers in Punjab and Sindh. Duplicating similar facilities is not a prudent approach due the huge cost this would incur. Most of the growers have small land holdings, so they cannot afford to establish and maintain the commercial facilities for the HWT.  In this situation the small-scale extended HWT being used by most farms in the Philippines is a very useful alternative.

TRTA II provided the schematic diagram of the SSHWT unit (below) along with the specifications to MRS, MoC & MNFS&R for their consideration in terms of provision of funds (MoC through TDAP/EDF & MNFS&R through PARC and MRS for the manufacturing of this unit and the SOPs for its operations.



Most mango farmers in Pakistan do not do any treatment to increase the shelf life of mangoes. This is the reason that over 40% of mangoes go to waste. In the Philippines, the “Extended Hot Water Treatment” of mango fruit is carried out at most farms. The equipment being used is very simple, valuable and cost effective. Interestingly, mango farmers in the Philippines also use this facility for the mangoes sold in local market.

Mango Hot Water Treatment Unit
MRS Researchers and TRTA II Expert examining a Small Scale Hot Water Treatment Unit being used at the farm level in the Philippines

This simple Hot Water Treatment unit has the ability to control the fruit fly infestation by killing its eggs and maggots if they are present inside the fruit. It is a very simple unit with a heating source, fruit holding tank and water circulation unit. It eradicates the fruit fly infestation and as a result the post-harvest losses are minimised. This small-scale Hot Water Treatment unit is very simple and could be easily produced in Pakistan. The diverse benefits of this small scale HWT unit are summarised in the following table:

Impact factors and Benefits of small-scale HWT unit

Impact factors



Exporters are able to sustain the export market in the UK through compliance with SPS requirements regarding fruit fly infestation


Reduction in losses along the supply chain. Losses are estimated to be more than 40%. This could be brought down to roughly 15%

Social benefits

Increased awareness of post-harvest treatment of fruits at mass level

Employment generation (direct and indirect)

This approach will also create more employment as at least 2 persons are required to effectively operate the proposed HWT unit

Environmental impact

The alternative approach of using Plant Protection Products in managing the fruit fly will leave excessive pesticide residue in the product and in the farm environment, besides being an ineffective approach to managing the pest


The design of the Small HWT Units is based on simple concepts of heating water in a tank and submersion of the fruit in water for the required temperature and duration. Water is heated by portable Liquefied Petroleum Gas (LPG) cylinders and circulated by a manual or simple motor. Any further and elaborate configuration of the equipment design could be added and this would be left to the imagination of the ‘grower-users’ and their evaluation of the practice.

TRTA II programme with the help of MRS and University of the Philippines prepared the design for the small scale HWT unit and prepared a technical proposal for the introduction of this small scale HWT unit at farm level.


The TRTA II experts held meetings with MoC, MNFS&R, Trade Development Authority of Pakistan (TDAP), Pakistan Agriculture Research Council (PARC) and National Agriculture Research Centre (NARC) to present and promote the proposal for the introduction of small scale HWT unit.

Subsequently the MoC and MNFS&R agreed on the initiative as a means to address the on-going issue of fruit flies in mangoes.

MoC through TDAP/EDF has mobilized the funds for the manufacturing of the 10 units to be placed at the 10 farm clusters receiving TRTA II support.

MRS conducts FFSs regularly at the selected farm clusters recieveing TRTA II support. Farmer Field Schools (FFSs), conducted by MRS researchers have become a regular feature of mango farms. The number of farmers attending the FFSs is increasing.

The FFS is attended by farmers from the participating Cluster Group and is open to anybody who wants to share their experiences with others and learn from them. FFSs have become a resource development pool. In each session, farmers gather to discuss and share their experiences and knowledge. Facilitators from the MRS manage these meetings through controlled dialogues, where urgent and specific cultivation issues are discussed and resolved. Through these discussions, knowledge and technical skills are conveyed to the farmers and are internalised by them. Trials and demonstrations are carried out; hence this approach is one of “learning by doing”.


The SSHWT units shall be provided to the farmers on cost sharing basis. The grower shall bear the cost of building the isolation room, where the fruit is dried, kept to cool down and packed, after the hot water treatment and the equipment should be provided to them by the Government of Pakistan.

The operating cost of the small HWT unit, for heating and portable use is estimated to be about Rs 2/Kg. Maintenance costs involves any repairs for leakage and rust.


The experts of MRS shall develop the SOPs for different export varieties of mango to be processed through the small scale HWT unit. The MRS experts shall also monitor the use of SSHWT unit installed at the selected farm clusters recieveing TRTA II support


The extended HWT is an effective fruit fly infestation treatment that is recognised by SPS regulators all around the world. This extended HWT treatment will provide assurance to the Pakistani SPS authorities that the mango being exported to the EU/UK is free of live fruit fly pests (larvae or eggs). In addition, extended HWT also provides protection against post harvest diseases like Stem End Rot and Anthracnose and as a result the shelf life of mango is also increased. So, this shall minimize the chances of rejection of export consignments of Pakistani mango, and also reduce the post harvest losses along the domestic supply chain which are more than 40%.