[1][2][3] There have not been any indications found of cultivar specificity, although hop yards established for a longer time may have a higher risk of Phoma infection [4].
Symptoms of infection typically begin with small chlorotic leaf spots and develop into greyish brown lesions that have a distinct target or concentric ring appearance.
[5] Pycnidia formation begins with hyphae near the epidermis in lesions forming a cavity followed by the production of dark hyphal cells.
[2] Repeatedly growing hops in the same area where Phoma wilt occurred previously increases disease incidence rate, as the pathogen is able to survive in debris and material on the ground.
The simplest cultural method is the removal of plant debris from hop yards which may help reduce the spread of the disease as well as initial infection in new stock.
It is also important to water the hop plants from the ground as opposed to misting or sprinkler type systems which will create or prolong a moist environment where the pathogen can thrive.
[9] The fungicide trifloxystrobin acts by interfering with some aspects of fungal pathogen respiration, resulting in the inhibition of both growth and spore germination.
Fosetyl-Al may therefore help decrease the spread of the Phoma infection in hop plant tissues, but this has yet to be studied more closely.
Copper hydroxide is a widely used foliar applied fungicide which denatures proteins on the plant surface and inhibits pathogen forced entry.