Serpentine leaf miner, from the genus Liriomyza, is one of the most economically important pests responsible for severe yield reductions in numerous vegetables crops worldwide including potato. Potato plays a significant role in the Indian economy. Potato production is being affected by several existing and new biotic stresses; correct and timely identification of new stresses is the key for their effective management. The Nilgiri hills located in Southern India is one of the oldest potato-growing areas of the country and is a prime centre in south India for potato production and supply. During the summer and autumn seasons of the year 2020, a leaf miner outbreak was observed in the potato-growing areas of the Nilgiri hills of Southern India. Here, we surveyed the potato fields to determine the species, damage severity, distribution, and possible alternate weed hosts of leaf miner. Based on the morpho-molecular characterization of the adult fly, the pest was identified as Liriomyza huidobrensis. During the outbreak, the incidence of this pest was 90–100%, with a damage severity ranging from 20 to 100% on the potato crop. The larval population varied from 1.2 to 14.83 larvae leaflet−1. It was also observed that the damage incidence and severity of L. huidobrensis infestation was influenced by the crop age and foliar injury increased with the advancement of crop age. In addition to potato, L. huidobrensis incidence was also recorded on six cultivated crops such as carrot, beetroot, garlic, beans, double beans, and broccoli. The incidence of the pest was also noticed on one cover crop, lupine and seven weed species (Amaranthus spp., Bidens pilosa, Chenopodium spp., Solanum nigrum, Galinsoga parviflora, Hypochaeris glabra, and Sonchus oleraceus) commonly observed in the Nilgiri hills. Field experiments for the management of L. huidobrensis with two potato cultivars (Kufri Swarna and Kufri Sahyadri) were also conducted to have an immediate option against this pest. These studies recommend the application of abamectin for the management of L. huidobrensis. The polyphagous nature of the pest coupled with increasing trade, transport, and changing climatic scenario possesses the risk of its spread in new geographical areas along with the possibility to attain the status of a major pest of potato and other crops in near future. Additionally, the Nilgiri hills are identified as one of the world’s biodiversity hotspots. Therefore in future, the studies should focus on the exploration and conservation of biological control agents and evaluation of safer chemical molecules to minimize the crop losses and to avert its further spread in new localities.