Powdery mildew control in pea. A review

Pea powdery mildew is an air-borne disease of worldwide distribution. It is particularly damaging in late sowings or in late maturing varieties. It is caused by Erysiphe pisi, although other fungi such as Erysiphe trifolii and Erysiphe baeumleri have also been reported causing this disease on pea. The disease can cause 25-50% yield losses, reducing total yield biomass, number of pods per plant, number of seeds per pod, plant height and number of nodes. The disease also affects green pea quality. Current powdery mildew control methods include early planting, the use of fungicides and of resistant cultivars. Chemical control is feasible with a choice of protective and systemic fungicides. However, public attitude and environmental concerns towards the use of pesticides as well as the development of powdery mildew strains resistant to different fungicides have reduced the appeal of chemicals and have led to the search of alternative control methods. The present review summarises the current control strategies and highlights future challenges for efficient and sustainable powdery mildew management. Non-fungicide products, such as soluble silicon, oils, salts and plant extracts are under study but are not fully ready yet for commercial application. Attempts have also been made to control powdery mildews with mycolytic bacteria, mycophagous arthropods, fungi, yeasts and other possible non-fungal biological control agents, but more efforts are still needed to prove the efficacy of these methods in agricultural practice. Genetic resistance is acknowledged as the most effective, economic and environmentally friendly method of control. However, only three genes (er1, er2 and Er3) have been described so far in Pisum germplasm and only er1 has been widely used in breeding programmes, what is very risky. Expansion of cultivation areas of pea varieties harbouring the same resistance gene could promote the occurrence of new races of the pathogen that would lead to a breakdown of the resistance. The use of polygenic resistance or combining several major genes could enhance the durability of the resistance.