Gnomonia leptostyla
Ophiognomonia leptostyla on walnut leaf
Ophiognomonia leptostyla (syn. Gnomonia leptostyla ) is a species of fungus in the family Gnomoniaceae. It causes the so-called Marssonina leaf spot disease on walnut and black walnut, named after its addition to fruit shape Mars Soni Ella juglandis.
- 6.1 Notes and references
Features
Macroscopic characteristics
Ophiagnomonia leptostyla can be macroscopically identified primarily on the basis of their attack symptoms. The leaves get first small dark brown spots with lighter center. As a result, whole yellow leaflets, larger leaf parts are brown and Frond and fall leaves in various stages of infestation prematurely. Also, fruits and occasionally shoots are infested. Infested nuts have dark sunken spots and a dark schrumpeliges pulp.
Microscopic characteristics
The perithecia are recessed into the leaves. Their necks are shorter than 250 micrometers. The ascospores are 19-23 microns long and 3.5 microns wide. In addition to fruit shape two-celled, curved conidia on the underside of leaves in acervuli be formed.
Ecology and phenology
Ophiognomonia leptostyla infects different types of walnuts. The species overwinters on fallen leaves and infected from there again in early summer leaves and fruits.
Dissemination
Ophiognomonia leptostyla is found throughout Europe and North America.
Importance
The disease causes especially in wet years, substantial yield losses in the walnut harvest and can cause severe defoliation. Important measures against the disease are removing and destroying the leaves in autumn. Only in exceptional cases a fight with fungicides should be considered. A high fertilization with nitrogen also reduces the extent of disease.
System
Ophiognomonia leptostyla in 1823 first described by Elias Magnus Fries as Sphaeria leptostyla, Vincenzo de Cesati and Giuseppe De Notaris set the style in the genus Gnomonia. In 2008 she was placed in the genus Ophiognomonia due to molecular biological studies.