Honeysuckle ascochyta leaf spot

The disease is caused by the fungus Neoascochyta desmazieri, a plant pathogen known for causing distinct leaf lesions on various host species. It acts as a parasite that colonizes foliar tissue, disrupting the plant's physiological functions and reducing its overall vigor by damaging the chlorophyll-containing parts of the leaf.

The primary host for this pathogen is the honeysuckle (Lonicera spp.). The fungus often targets bushes in residential gardens and nursery settings, particularly where environmental conditions are stagnant or where the plants are already stressed due to suboptimal soil or drought conditions.

Symptoms of the infection typically appear as small, scattered spots on the leaves. Over time, these spots enlarge, often showing a light-colored center surrounded by a darker brown or reddish margin. Tiny black dots, known as pycnidia, eventually emerge within these spots, which are the reproductive structures of the fungus used to spread spores.

Development and spread of Neoascochyta desmazieri are highly dependent on humidity and moisture. Rain splash and high winds are primary drivers for spore dispersal between branches and neighboring plants. Mild temperatures combined with high atmospheric humidity create the perfect window for the infection cycle to repeat throughout the growing season.

The damage caused by this disease is mainly linked to premature leaf drop and potential branch dieback in severe cases. To prevent and manage the infection, follow these best practices:

• Prune to improve airflow and reduce humidity levels within the canopy
• Remove and dispose of fallen infected leaves to lower the inoculum source
• Keep foliage dry by utilizing drip irrigation instead of overhead watering
• Apply appropriate fungicides as a preventive measure if the disease history is present