The global food security crisis is partly caused by significant crop losses due to pests and pathogens, leading to economic burdens. Phytophthora palmivora, an oomycete pathogen, affects many plantation crops and costs over USD 1 billion each year. Unfortunately, there is currently no prevention plan in place, highlighting the urgent need for an effective solution. P. palmivora produces motile zoospores that respond to weak electric fields. Here, we show that external electric fields can be used to reduce root infection in two plant species. We developed two original essays to study the effects of weak electric fields on the interaction between P. palmivora’s zoospores and roots of Arabidopsis thaliana and Medicago truncatula. In the first configuration, a global artificial electric field is set up to induce ionic currents engulfing the plant roots while, in the second configuration, ionic currents are induced only locally and at a distance from the roots. In both cases, we found that weak ionic currents (250–550 μA) are sufficient to reduce zoospore attachment to Arabidopsis and Medicago roots, without affecting plant health. Moreover, we show that the same configurations decrease P. palmivora mycelial growth in Medicago roots after 24 h. We conclude that ionic currents can reduce more than one stage of P. palmivora root infection in hydroponics. Overall, our findings suggest that weak external electric fields can be used as a sustainable strategy for preventing P. palmivora infection, providing innovative prospects for agricultural crop protection.