A review of integrated control of Phytophthora root rot in oak rangeland ecosystems

Abstract: The root rot caused by Phytophthora cinnamomi is the most devastating disease affecting cork and holm oak trees in the southern Iberian Peninsula. Every year thousands of trees are killed, with severe ecological and economic consequences. Over the last 10 years, different control strategies have been developed, and they can be integrated for disease management. Firstly, cultural actions may be applied in healthy areas to minimize pathogen arrival, but also in infected areas to reduce its spreading, such as soil drainage, livestock load and soil tillage limitation, as well as reducing movement of farm machinery and other vehicles. Other cultural methods are focused on reducing the viable inoculum density in the soil, including the soil application of calcium amendments, especially CaSO4 and CaCO3, which are able to reduce the infectivity of P. cinnamomi. In the same way, the cultivation of susceptible species (Lupinus luteus) that favour the multiplication of the pathogen (production of zoospores and chlamydospores) should be avoided. Biofumigation using Brassica spp. with high content in Sinigrin, like B. juncea or B. carinata, shows a suppressive effect on P. cinnamomi resistance spores survival. The use of oak morphotypes resistant to the pathogen appears very limited; however, hybridization with some species could be used in breeding programs as showed for natural hybrid Q. ilex-Q. faginea, which exhibit low levels of root symptoms and only in artificial inoculations. Finally, chemical control actions based on inducing resistance, such as the application of systemic phosphonate fungicides by trunk injection or the increase of Ca2+ content in the tree, could be also applied.