Pg. 15-23 Survey on litchi fruit to determine the incidence of moth damage and the presence of larvae and pupae in the fruit

The South African litchi industry would like to expand their markets and applied to the National Department of Agriculture, Forestry and Fisheries for the export of litchi to the United States of America. The United States Department of Agriculture (USDA) conducted the pest risk analysis, identifying the quarantine pests of concern as litchi moth, Cryptophlebia pelstastica (Meyrick) (Lepidoptera: Tortricidae); false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae); Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae); Natal fruit fly, Ceratitis rosa Karsch (Diptera: Tephritidae); pink wax scale, Ceroplastes rubens Maskell (Hemiptera: Coccidae); fig wax scale, Ceroplastes rusci (Linnaeus) (Hemiptera: Coccidae); coffee green scale, Coccus viridus (Green) (Hemiptera: Coccidae) and Karoo thorn mealy bug, Nipaecoccus viridis (Newstead) (Hemiptera: Pseudococcidae). Mitigation measures were also suggested and the only method which requires no research on the efficacy of controlling regulatory pests is gamma irradiation. The South African litchi industry accepted the proposed use of gamma irradiation as a mitigation treatment, with provision that a cold treatment be used if efficacy is proven. Irradiation of fruit and vegetables with a minimum absorbed dose of 400 Gy is a treatment approved by the USDA-APHIS for mitigating risk for all insects except for adults and pupae of the order Lepidoptera. Both the quarantine pests T. leucotreta and C. peltastica are Lepidopteran pests. In the case of C. peltastica there is evidence that the larvae occasionally pupate in the fruit and therefore, a survey was conducted to determine the presence and abundance of pupae in the fruit at harvest. A total of 64,089 fruit were inspected during the four seasons and no pupae were found in the fruit.

Summary:

• The South African litchi industry seeks to expand its export markets to the USA, facing quarantine pests like litchi moth (Cryptophlebia peltastica) and false codling moth (Thaumatotibia leucotreta) identified in a USDA pest risk analysis.
• A large-scale survey over four seasons inspected 64,089 litchi fruits mainly from Mpumalanga and Limpopo provinces for the presence of moth eggs, larvae, and pupae to assess infestation and pest risk.
• Results showed variable fruit infestation with eggs (up to 27.9%) and larvae (up to 12.3%) depending on season and farm, but importantly, no pupae were found inside any fruit across all samples.
• The absence of pupae inside fruit supports the use of gamma irradiation (minimum dose 400 Gy), already approved by USDA for other insects, as an effective quarantine treatment targeting eggs and larvae stages of these moth pests.
• Findings suggest that although moth larval infestation occurs, the risk of pupae in fruit is negligible at harvest time, supporting irradiation plus possible cold treatment as mitigation measures for export quarantine compliance.
• The survey also covered various cultivars and commercial as well as experimental farms, noting that high infestation on experimental farms may relate to cultivar diversity offering continuous fruit supply.