Some sort of insect is attacking my black-eyed susans. The leaves are full of...

Asked June 9, 2014, 10:59 AM EDT

Some sort of insect is attacking my black-eyed susans. The leaves are full of holes and puckered. Can you tell me which insect is the likely culprit and the best treatment to use?

Montgomery County Maryland flowers black eyed susan possible septoria

1 Response

This does not look like insect damage. Black-eyed Susan can be susceptible to a leaf spot disease called Septoria. The disease shows up as irregular black spots on the leaves. This can disfigure the plant significantly if the weather is favorable, wet, hot and humid. Once established, it is difficult to control.
Try managing the bed culturally. Alleviate poor air circulation, crowded conditions, or standing water to help lessen humidity levels. Inspect new foliage and older foliage regularly for signs of infection to catch infections early.
Removing infected leaves if there are only a few helps. A general purpose garden fungicide may also help reduce the spread of the disease, but these chemicals are protectants and do not cure infected leaves (check label for instructions on spray). At the end of the season really clean up the area well, discard the infected plant material, don’t put in your compost pile.
Monitor throughout the season and if disease pressure is heavy, you may want to consider growing something else.
mh