Use only pathogen-free seed produced in arid western locations. Resistant varieties are not currently available.
Gummy stem free#
The optimum conditions for growth of the organism are temperatures from 61 to 75 F and free moisture in the form of dew, fog, or rain.Ĭrop rotation and clean tillage (for example, plowing) help reduce the risk of disease by reducing the amount of primary inoculum (spores) in the immediate area. Cucumbers, muskmelons, cantaloupes and other melons and citrons are infected fre- quently. In Florida, watermelons are infected annually. Infection of fruit commonly occurs throughwounds or through dying flowers. Gummy stem blight (black rot) is caused by the fungus Mycosphaerella citrullina. Following primary infection, secondary spores are released in a gummy substance, which makes them adapted for short-distance spread by splashing water. The pathogen can be seedborne or can survive on plantdebris from previously infected cucurbits or on wild or volunteer cucurbits. Fruit may decay at the site of attachment as a result of the fungus invading the stem. A seminar titled 'Movement of Stagonosporopsis species, causal agents of gummy stem blight on cucurbits, by land, air, and sea ', presented by Dr. Lesions may develop anywhere on the fruit, first as water-soaked areas dotted with fruiting bodies, as described above. Fruit symptoms vary among crops but generally appear as a brown to black rot of the rind, flesh, and seed cavity, accompanied by heavy white and black fungal growth. bryoniae delivered to freshly crushed tissue, followed by 48 h incubation at 20☌ and 100 RH in the dark. Vine infections appear as water-soaked, cracked, brownish cankers that produce a reddish gum. Resistance to gummy stem blight (Didymella bryoniae) was not detected among 1208 cucumber lines of diverse origin when cotyledons of four-day-old seedlings were inoculated with an aqueous suspension of 5000 spores of D. In contrast to bacterial diseases, tiny, black fruiting bodies may be seen (using a hand lens) within leaf lesions caused by the gummy stem blight pathogen. A wide range of foliar symptoms occurs on cucurbits, which can make diagnosis difficult. Lesions begin at leaf margins but rapidly extend back into the leaf blade, causing curling, shriveling, and leaf death. Gummy stem blight refers to the foliar and stem-infecting phase of the disease, black rot to the fruit rot phase (see fact sheet, page 732.10, Fruit Rots of Squash and Pumpkins).
Leaf symptoms appear as dark yellow or reddish brown lesions of various shapes. When the disease occur on fruit, it is called black rot.
Infection of vines and leaves, which is usally associated presence of gum on vines, is referrred to gummy stem blight. Gummy stem blight, or black rot, can occur at any growth stage and on any aboveground plant part. Gummy stem blight, or black rot, caused by the fungus Didymella bryonia, is an important disease of cucurbita, particularly pumpkins and squashes. Gummy Stem Blight or Black Rot of Cucurbits FrequencyĢ (1 = very little damage 5 = plants killed) Hosts
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