1. George Momanyi-KEPHIS
EFFECT OF PHOSPHINE FUMIGANT ON FALSE CODLING MOTH (FCM) LARVAE IN CAPSICUM
Presentation during the 2nd Phytosanitary Conference, 4th-8th June 2018
George Momanyi-KEPHIS

2. Outline Introduction Materials and Methods Results Conclusion
Recommendations

3. Introduction…/1
Fumigation is the act of releasing and dispersing a toxic chemical so it reaches the target organism in a gaseous state.
Chemicals applied as aerosols, smokes, mists, and fogs are suspensions of particulate matter in air and are not fumigants.
The ideal fumigant would have the following characteristics:
 Highly toxic to the target pest 

4. Introduction…/2 Easily and cheaply generated
 Harmless to foods and commodities
 Inexpensive;  Nonexplosive;  Nonflammable;  Insoluble in water
 Nonpersistent;  Easily diffuses and rapidly penetrates commodity
 Stable in the gaseous state (will not condense to a liquid);  Easily detected by human senses

5. Introduction…/3
The toxicity of a fumigant depends on the respiration rate of the target organism. Generally, the lower the temperature, the lower the respiration rate of the organism which tends to make the pest less susceptible.
Fumigation at lower temperatures requires a higher dosage rate for a longer exposure period than fumigation at higher temperatures.

6. Introduction…/4
MB is an effective fumigant for treating a wide variety of plant pests associated with a wide variety of commodities. MB is the most frequently used fumigant in quarantine fumigations. MB may also be used to devitalize plant material.
MB is effective in treating the following pests:
 Insects (all life stages);  Mites and ticks (all life stages);  Nematodes (including cysts) ;  Snails and slugs;  Fungi (such as oak wilt fungus)

7. Introduction/…..5
Although MB is an effective pesticide, when fumigating products, it has two main drawbacks;
highly phytotoxic and causes browning of the plant,
it is effective at temperatures that are higher than storage temperature for most products.
Therefore, to achieve a successful fumigation, the products must be first heated to 21°C and then cooled again resulting in significant reduction of products' shelf life.

8. Introduction/…..6
Furthermore, since the phase-out of MB most of the product export destinations countries demand a minimal use of MB and implementation of alternative technologies
Phosphine was first applied commercially as a fumigant for fresh fruit 7 years ago (Horn and Horn, 2004; Klementz et al., 2005).

9. Introduction/…..7 Phosphine, unlike MB is not phytotoxic;
can be applied during cold storage
does not have an undesirable environmental effect because it is transformed into harmless amounts of phosphoric acid and phosphates by sunlight after its release into the atmosphere (Brash et al., 2009).

10. Introduction/…..8
Horn et al. (2004) determined that the technology can be successful if the fumigation is carried out at a temperature between -1.5 and 15ºC, concentration between 700 and 3,500ppm (1-5g /m3) and with exposure time of between 36 and 72 hours.
that the best treatment conditions for fresh fruit fumigation are 1,500ppm for 48 hours at 0°C.

11. Introduction/…..9
No damage to the fruit has been detected and the shelf life of the fruit after this treatment was found to be similar to non treated fruit
The results of the work by Horn has paved the way for potential use of phosphine fumigation for fresh products.

12. Introduction/…..10
False Codling Moth (FCM) is an important pest in capsicum production and has been rated as a quarantine pest in the European Union (EU) since 2017.
This has significantly affected export of capsicums from Africa and other countries where FCM has been reported to occur. Export of Capsicum from countries where FCM occurs should be from pest free places of production or are treated using appropriate post-harvest treatment.

13. Introduction/…..11
Cold treatment has been recommended as a treatment option which is not suitable for Capsicum due to injury hence need for alternative treatment option.
Fumigation using phosphine gas has been viewed as an alternative treatment method for fresh produce although data of it efficacy on FCM in Capsicum is lacking.
A study was commissioned to evaluate the efficacy of commercial phosphine formulation in Kenya.

14. Introduction/…..12
Phosphine generated from aluminum phosphide, formulated as DETIA GAS Ex-B Fumigation Bags has been commercially available for several years as a fumigant for insect pests of grain and other stored products in Kenya.
The current registration of the product covers stored grain and tobacco pests by fumigation of raw agricultural commodities, processed foods and animal feeds.

15. Introduction/…..13
The product has not been used to control insect pests of fresh fruit and vegetables because pre-shipment fumigation has not been a requirement for most fresh export markets.
The current trial therefore sought to determine the potential for extension of the scope of registration in Kenya to include fresh capsicums.

16. Introduction/…..14
The specific objective of the trial was to determine the commercial efficacy of aluminium phosphide in the post- harvest quarantine treatment of fresh capsicum fruits.

17. MATERIALS AND METHODS…1/
Fresh capsicum fruits naturally infested with FCM larvae sourced from a capsicum field in Thika, Kenya.
Treatment conducted in three replicates in a 20 foot/34.56 M3 container/fumigation chamber between 10th February 2018 and 1st March 2018.

18. MATERIALS AND METHODS…2/
Infested capsicums loaded into a clean fumigation chamber and arranged into units to allow ease of air circulation.
Two sachets of ALP were then suspended at the center of the chamber to allow good circulation of gas at temperature of 25 0c.
Chamber doors tightly closed to allow for gas activation in 6 hours and the treatment was left to run for 72 hours.

19. MATERIALS AND METHODS…3/
After 72 hours, container gas analysis undertaken, chamber opened, the crates offloaded, temperatures recorded (fig 3 & 4) and the treated material analyzed for FCM larvae survival, destructively

20. Infested capsicum fruit
Infested fruit put in perforated polythene
Sachet containing aluminium phosphide
Crates arranged in chamber

21. Destructive sampling
Dead FCM larvae

22. Results 1 72 23 All 7 FCM larvae found on treated material dead 2
Trial No.
Duration (Hrs)
Treatment temperature (oc)
Treatment effect 1 72 23
All 7 FCM larvae found on treated material dead 2
All FCM found on treated material dead 3

23. Discussions…1/ Treatment effective but shelf life compromised.
Based on literature damage had been caused by two reasons mainly:
presence of ammonia in the phosphine that is generated through hydrolysis reaction of metal phosphides
relatively high fumigation temperature, over 15 °C, at which the tests have been carried out.
Need for cold fumigation

24. Discussions…2/
Aluminium phosphide or magnesium phosphide based products have the great disadvantages:
if they are used at low temperature, they produce phosphine very slowly, which forces the application of the product at high temperature.
these metal phosphides always produce ammonia as a by-product and ammonia is known to be very phytotoxic.

25. Discussions…3/
phosphine forms explosive and self- flammable mixtures with air at concentrations over 18,000-ppm, it had not been possible to apply phosphine in its pure state by means of direct dilution with air, even though this would be the best way to apply the gas.
The main challenge then is to manage the dilution of pure phosphine with air into concentrations, below the limit of self-ignition, without producing ignition in the process.

26. Discussions…4/
A solution for the above challenges have been devised by a system that makes it possible to apply pure cylindered phosphine for fumigations (Horn and Horn 2006)--HORN DILUPHOS SYSTEM
Possible to carry out fresh fruit fumigation with pure phosphine free from ammonia, at low temperature and with high gas concentrations
the quality of the fruit is not damaged
Treatment is effective

27. Discussions…5/
Fumigation carried out at between –1,5 and 6 ºC with a concentration of pure phosphine, between 1,000 and 2,000 ppm in a sealed enclosure
Exposure time between 24 and 72 hours, depending on the pest.
It was discovered that when lowering the temperature, it is possible to carry out the fumigation with a very high concentration of phosphine with no damage to the fruit, since at that temperature, the metabolic activity of fruit is slowed down.

28. CONCLUSION
Aluminium phosphide has shown potential as an effective FCM fumigant of fresh capsicum fruits.
However, there were observations that the shelf life of the capsicums is compromised as a result of the treatment.
This commercial trial therefore is in-conclusive in determination of efficacy of phosphine gas in the treatment of FCM in fresh capsicums for export purpose at ambient temperatures.

29. CONCLUSION
Therefore, more data needs to be generated for refinement of a number of test parameters to achieve complete mortality of a large number of test insects.
Further investigation is needed to optimize and validate the treatment protocols

30. RECOMMENDATIONS
Efficacy against a range of life stages of FCM found on exported commodity (time and/or dose response trials) to determine effective treatment parameters and the order of tolerance for each life stage tested.
Demonstration of probit 9 mortality level.
Tolerance of the fresh produce to a range of the treatment parameters that have been demonstrated to cause a high level of pest mortality

31. RECOMMENDATIONS
Acceptability of the treatment in the target market (includes determining if a Maximum Residue Limit (MRL) is required and impact on shelf life of the products).
Identification of the cultivar associated with the lowest mortality
Determination of the phyto- toxicity in fruit after treatment

32. RECOMMENDATIONS Work to be carried out in two stages.
The first stage under laboratory-controlled conditions and
the second a semi-commercial stage conducted in a cool room at the packinghouse.
In both stages test infested commodity of interest. All insect pests to be collected at their adult and larval stages together with the commodities at the field.

33. Thank you