Gummy stem blight is a cucurbit-rot disease caused by the fungal plant pathogen Didymella bryoniae (anamorph Phoma cucurbitacearum).
[2] Gummy stem blight reduces yields of edible cucurbits by devastating the vines and leaves and rotting the fruits.
[3] There are various methods to control gummy stem blight, including use of treated seed, crop rotation, using preventative fungicides, eradication of diseased material, and deep plowing previous debris.
[4] Gummy stem blight affects many cucurbits including watermelon, cantaloupe, cucumber, pumpkin, and some squash.
[6] When older plants become infected, their leaves may appear water soaked and begin to develop dark tan lesions.
[2] Wounds to the plant, especially those left by feeding insects such as the striped cucumber beetle or aphids, are important passageways for the pathogen to enter in older hosts.
[1] The pathogen is transferred from infected hosts to healthy plants via ascospores carried in the wind and by conidia that are released from pycnidia by water splash and in gummy exude.
Once the primary infection takes place, as long as it remains wet, the pathogen will spread to the stem where cankers form and ooze a gummy substance full of conidia.
[6] A rotation (of at least 2 years) of cucurbit and non-cucurbit crops should be performed to greatly reduce the incidence of gummy stem blight.
[3] Keeping fields pruned and weed-free will help to control gummy stem blight as overgrowth promotes poor air circulation and moisture from humidity, which support D. bryoniae germination and growth.
[3] If chemical control is needed in important cucurbit production regions, there are a variety of preventative fungicides commercially available that can be applied during the early stages of plant growth.
Yield losses due to D. bryoniae exceeding 30% can occur in early season crops facilitated by wet weather conditions.