P hthorimaea absoluta in potato cultivars: tolerance analysis and implications for integrated pest management

Phthorimaea absoluta is an invasive pest that causes substantial damage to Solanaceous crops, such as tomato and potato. This study evaluated the resistance of five commonly cultivated potato varieties to P. absoluta infestation in field conditions across South Africa. Morphological parameters, gas exchange, and nutrient assimilation parameters were analysed in both infested and uninfested plants. Valor exhibited the highest tolerance, showing minimal leaf damage, fewer mines, optimal gas exchange, and greater assimilation of key nutrients (e.g. iron, zinc, and manganese), which may enhance its defensive capacity against pests. Conversely, Sifra was identified as the most susceptible cultivar, with reduced nutrient uptake and significant physiological disruption in response to infestation. Infested plants showed a decrease in photosynthesis, transpiration, and stomatal conductance, along with an increase in intercellular CO₂, highlighting the harmful effects of P. absoluta. These findings support the selection of cultivars in breeding and integrated pest management programmes, especially in African contexts where field data are limited.