Bacterial speck is caused by Pseudomonas syringae. Cool, moist environmental conditions contribute to the development of the disease.The foliar symptoms of speck consist of small black lesions, often with a discrete yellow halo. The lesions of bacterial spot are similar, but tend to have a greasy appearance, whereas those of speck do not. Speck seems to curl the leaves more severely than spot. Both diseases affect flowers. Lesions on stems and petioles cannot be distinguished. Bacterial speck and spot are more clearly differentiated by symptom development on the fruit. Bacterial speck lesions are slightly raised, but are generally much smaller than those of bacterial spot. Bacterial speck lesions are very superficial and do not crack or become scaly as in bacterial spot.