Effect of climate change on the incidence and severity of Phytophthora disease and evaluation of sustainable management strategies in vegetable production in Tanzania

Abstract Climate change is driving increased incidence and severity of Phytophthora diseases in Tanzanian vegetable production systems, threatening food security and smallholder livelihoods. Field assessments were conducted over four cropping seasons (2022–2024) across five major vegetable-producing regions (Arusha, Morogoro, Kilimanjaro, Iringa, and Tanga). Disease incidence and severity were recorded in tomatoes (Solanum lycopersicum), peppers (Capsicum spp.), and cucurbits, alongside climatic variables (temperature, rainfall, humidity), and evaluated under management strategies, including resistant varieties, nursery hygiene, raised beds with mulching, crop rotation, and integrated disease management. Regression analyses revealed that temperature (p < 0.01) and relative humidity (p < 0.05) significantly increased disease severity, while rainfall had no significant effect (p > 0.05). Management strategies significantly reduced disease severity (p < 0.0001), with integrated disease management outperforming standalone interventions. Resistant varieties reduced disease incidence by 40%, nursery hygiene by 30%, and crop rotation by 25%, while integrated strategies achieved the greatest overall efficacy. These results highlight the urgency of scaling climate-resilient integrated practices. We recommend targeted policy support, farmer training, promotion of resilient cultivars, and development of localized early warning systems to enhance adaptation and sustainability in climate-vulnerable vegetable farming systems in Sub-Saharan Africa.