Pg. 41-50 Pre-harvest moth control and moth breeding

The South African Litchi Growers’ Association is striving to gain access to more foreign markets. Fruit flies and moth species attacking the fruit are quarantine pests which can deny producers access to these markets. Quarantine treatments are therefore required. The focus is to develop quarantine cold treatments for both fruit fly and moth species and to combine it with preharvest management practices, resulting in an effective systems approach.

One of the objectives of the study was to develop a rearing technique for litchi moth. Infested litchi fruit were collected in different production areas. Alternative host plants were also collected. Fruit were examined and all 5th instar larvae found were placed in containers with a layer of sand for the larvae to pupate in. Male and female pupae were placed in a small container to enhance mating of moths. Litchi fruit were collected, peeled and put in a jar filled with alcohol. As soon as the moths emerged, pips and filter paper were drenched in the jar with fruit and alcohol for egg laying. Eggs were placed on a maize meal medium used for rearing false codling moth with either grounded litchi pips or litchi juice as an additive. Larvae developed successfully in the different mediums and pupated in the cotton wool plugs.  An attempt was made to breed the second generation in a similar way, but this was not successful.

Fruit in different production areas were collected and infestation levels determined. The highest infestation level of 8.2% was found on the ARC-ITSC Nelspruit experimental farm. The litchi moth was the dominant species found. No macadamia nut borers were reared from litchi fruit during the past season. Moths were monitored in the Hazyview, Malelane, Nelspruit and Tzaneen areas.

Fenpropathrin (Meothrin, Philagro South Africa), triflumuron {Alsystin, Bayer CropScience), fenpropathrin in combination with a granulovirus (Cryptogran, River Bioscience) and triflumuron in combination with a granulovirus (Cryptogran, River Bioscience) were tested for controlling the moths. The best results were obtained with triflumuron, triflumuron in combination with a granulovirus and fenpropathrin in combination with a granulovirus.

Summary:

• The South African Litchi Growers’ Association aims to expand access to foreign markets, but fruit flies and moths are quarantine pests that threaten exportability. Quarantine treatments are essential to prevent these pests from restricting market access.
• The study focuses on developing quarantine cold treatments for both fruit fly and moth species, integrated with pre-harvest management practices, to create a comprehensive systems approach for quarantine security.
• One key objective was to develop a rearing technique for the litchi moth (Cryptophlebia petastica). Infested litchi fruits were collected from various production areas, and larvae at the 5th instar stage were pupated in sand-filled containers. Male and female pupae were placed together to encourage mating.
• Emerged moths were provided with litchi pips and filter paper soaked in alcohol and fruit for egg laying. Eggs were placed on maize meal medium (used for rearing false codling moth) with added ground litchi pips or litchi juice. Larvae developed successfully but attempts to breed a second generation in the same way failed.
• Infestation levels were assessed across production areas, with the highest infestation of 8.2% recorded at the ARC-ITSC Nelspruit experimental farm. The litchi moth was the dominant species, while false codling moth was rare, and no macadamia nut borers were reared from litchi fruit.
• Moths were monitored in Hazyview, Malelane, Nelspruit, and Tzaneen areas with pheromone traps. Different synthetic pheromones were evaluated, with effective ones leading to more accurate population monitoring.
• Various chemical and biological control treatments were tested against moths:
  • Fenpropathrin (Meothrin)
  • Triflumuron (Alsystin)
  • Fenpropathrin and triflumuron each combined with a granulovirus (Cryptogran)
• The best results came from triflumuron alone, triflumuron with granulovirus, and fenpropathrin with granulovirus.
• Control trials were conducted on litchi trees (variety HLH Mauritius) with treatments applied to branches.
• Fenpropathrin and triflumuron were applied six weeks before harvest; the granulovirus was applied two weeks before harvest.
• The granulovirus is a biological control agent naturally present in false codling moth populations in South Africa.
• Alternative host plants for the litchi moth were identified, including several native and ornamental species like Pappea capensis, Schotia afra, and Poinciana regia. Some host plants such as flamboyant pods were confirmed as good sources of infestation.
• The study calls for further research on alternative hosts and more control trials to finalize recommendations.
• The research was supported and funded by the South African Litchi Growers’ Association and SA PIP, with acknowledgments to advisers and contributors for rearing techniques and control products.