Viewing post #1148757 by sooby

Polymerous said:

Just to be clear, does inadequate potassium promote rust?

Thanks so much for your help.

Yes and A couple of snippets from a text on plant nutrition. "As shown in Table 11.2, a high nitrogen supply increases the severity of infection by obligate parasites but has the opposite effect on diseases caused by facultative parasites....."

Rust is an obligate parasite.

"Potassium decreases the susceptibility of host plants to both types of parasites.....Beyond the optimal potassium supply for growth, no further increase in resistance can be achieved by increasing the supply of potassium and its content in plants."

In Table 11.2 the examples of obligate parasites are Puccinia spp. rust diseases and powdery mildew.

This is from Mineral Nutrition of Higher Plants, Second Edition, Marschner, Academic Press.