Occurrence of the potato leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae), and parasitoids in potato fields and natural vegetation of the Western Cape province, South Africa

The leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae) is a polyphagous fly, which infests a wide range of vegetables and ornamental plants. However, scant knowledge exists of the biology and ecology of the pest in the Western Cape province of South Africa, both of which are essential components in developing an effective management programme. Several aspects of its biology and ecology were studied in two potato [Solanum tuberosum L. (Solanales: Solanaceae)] fields in the Sandveld region during both winter and summer months. The population densities of adult L. huidobrensis were monitored using yellow sticky traps, which were retrieved and counted once every two weeks (June 2019 to January 2020). The number of leaf miner adults caught throughout the summer and winter monitoring periods was significantly different. In addition, 50 randomly selected plants were assessed for leaf damage (in the form of punctures and mines) using presence/absence sampling. Leaf miner persistence within the soil was confirmed through one-time soil sampling of the two fields, one month after harvesting. Leaf miner pupae were detected in the soil samples after the potatoes were harvested. However, no adult emergence was recorded among the collected pupae under laboratory conditions. The observed trend was that the traps, in both fields, caught an increasing number of leaf miners as the crops matured. Damage occurred in both the monitored fields as early as week four, after plant emergence. Of the five parasitoid species collected, Diglyphus isaea (Hymenoptera: Eulophidae) was the most abundant.