Most fungi prefer warm and moist conditions so it’s not surprising that fungal pathogens are harder to find on plants in winter.
A pathogen that is common on campus at the moment is Puccinia malvacearum, the Hollyhock Rust. This occurs on Malva sylvestris, the Common Mallow.
Symptoms are yellow-orange spots on the upperside of leaves with orange pustules underneath.
Under a hand lens you can see the pustules bursting out from beneath the leaf surface. These are full of teliospores which tend to germinate within the pustule. They grow to produce ash-grey basidiospores which are dispersed on air currents to infect new plants.
Some rust species have up to five types of spores forming a complicated life-cycle but this is not the case with Puccinia malvacearum.
The species is a common disease on hollyhocks, rarely killing plants but causing distorted and stunted growth.