Impact of cactus moth (Lepidoptera: Pyralidae) pest densities on fruit production and quality in cactus pear

The prickly pear cactus, Opuntia ficus-indica (L.) Miller, is the most economically important Cactaceae species worldwide. It thrives in arid and semiarid agricultural lands with minimal inputs, providing benefits such as livestock fodder, fruit, and vegetable production. The South American cactus moth, Cactoblastis cactorum (Berg), represents the most important insect pest of prickly pear crops. This study aimed to evaluate the impact of C. cactorum feeding on O. ficus-indica plants in a plantation in northwestern Argentina. Fruit production, fruit attributes, and plant size were evaluated under increasing C. cactorum pest densities in a manipulative 3-yr-long experiment (2018 to 2020). In the 2019 harvest, the increase in the pest density significantly reduced the number of fruits produced/plant. Plants with the highest pest density produced 60% fewer fruits than pest-free plants. In the 2020 harvest, the reduction was marginal. Fruit and pulp weights significantly declined with increasing C. cactorum densities in both years. No effect occurred on plant size or fruit sweetness. This was the first effort to measure the magnitude of the impact of C. cactorum on a cactus crop species and provides crucial information for prickly pear fruit producers. This information is helpful to implement more effective preventive and control measures to protect producers' investment and ensure a profitable harvest. Further studies in younger plantations and other areas will help develop an economic damage threshold level to support Integrated Pest Management decisions to limit C. cactorum's impact.