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.

No abstract

Conservation agriculture practices such as eliminating tillage and planting high residue cover crops are becoming increasingly important in field crop systems in the US Mid-Atlantic. However, these practices have sometimes been associated with an increase in moderate to severe damage to field crops by slugs. Conserving natural enemy populations is a desirable way to manage slug infestations because remedial control measures are limited. Here, we tested the effects of conservation practices, weather, and natural enemies on slug activity-density measured by tile traps placed among 41 corn and soybean fields during the spring of 2018 and 2019 in the Northern Shenandoah Valley, Virginia, USA. We found that a positive effect of cover crops on slug activity-density was reduced by tillage and that slug activity-density declined with increasing ground beetle activity-density. Slug activity-density also declined with decreasing rainfall and increasing average temperature. Weather was the only significant predictor of ground beetle activity-density, which was reduced in sites and weeks that were relatively hot and dry or that were cool and wet. However, we also found a marginally significant negative effect of pre-plant insecticides on ground beetles. We suggest that the observed interacting effects of cover crops and tillage reflect favorable conditions for slugs provided by increased small grain crop residue that can be mitigated to some extent by even low levels of tillage. More broadly, our study suggests that implementation of practices known to promote recruitment of ground beetles in crop fields can improve natural suppression of slugs in corn and soybean that are being increasingly cultivated according to conservation agriculture practices.

Although agriculture is crucial to economic growth in South Africa, the industry faces several challenges, including the effects of pests and diseases that contribute to crop loss. Such losses severely affect the maintenance of food security. Therefore, a major challenge is finding effective, environmental-friendly control measures for insect pests. Potatoes are among the four most widely consumed vegetable crops worldwide. However, a potato crop can be infested by various pests, like the devastating leaf miner, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). The leaf miner species has, since the early 2000s, become an important pest of various vegetable crops in South Africa. The species is highly invasive, causing up to 70 % damage of solanaceous crops. The damage that is caused by the leaf miner is direct, resulting from the female flies feeding on the leaf mesophyll during oviposition, and the larvae mining the leaves. Indirect damage is induced through pathogens entering through perforations that act as vectors of plant diseases. Biocontrol agents, e.g.  entomopathogenic nematodes (EPNs), entomopathogenic fungi (EPF), and parasitoids have shown potential against L. huidobrensis. This review investigates the biology and morphological identification of L. huidobrensis, its host range in the Western Cape, and the potential of associated biocontrol agents, like EPNs, EPF and parasitoids, as future control options.