Potato late blight remains the most significant disease threat of potato cultivation globally, often requiring expensive, time-consuming and environmentally unfriendly approaches to disease management. The goal of this research was to evaluate whether an estimation of potato late blight risk based on environmental factors can be reliably used to adjust the standard potato late blight management practices and the role of cultivar resistance under growing conditions and contemporary Phytophthora infestans populations in the Republic of Ireland. Using the modified Irish Rules model, it was possible to reduce fungicide usage by 58.7% on average, compared to current standard practices used by growers and without adversely compromising disease control and yield, with similar results achieved by the half dose programme. Host resistance levels were found to be correlated with a delay in the initiation of the epidemics, final foliar disease levels and reduction of fungicide usage. Disease levels on the highly resistant cultivars remained low and a clear selection pattern towards the P. infestans genotypes EU_13_A2 and EU_6_A1 was observed. An increase in the frequency of strains belonging to genotypes EU_13_A2 and EU_6_A1 was also observed to occur in the latter part of the trial growing seasons. Due to the increasingly dynamic nature of the population structure, associated with the continued evolution of the P. infestans population and the arrival of EU_36_A2 in the Republic of Ireland, routine population monitoring is required to ensure that potato late blight control strategies remain effective.
Opportunities for an improved potato late blight management in the Republic of Ireland: Field evaluation of the modified Irish Rules crop disease risk prediction model