Knowledgebase

What is hurting my lilacs? #923615

Asked January 14, 2026, 11:39 AM EST

I have well-established lilac bushes that have been blooming beautifully for years. For the last two years, they have budded and grown leaves in the spring, but I've had few to no flowers. The leaves begin to turn whitish-gray, seeming to start toward the bottom of the bush and working up. They eventually all fall off. I have tried treating with a fungicide spray and even tried sour milk, which I read was a possible natural solution. I want to be preemptive and avoid this happening again this year. Any help would be greatly appreciated!

Hillsborough County New Hampshire

Expert Response

Hello Pattie,

Thank you for reaching out to the UNH Extension Infoline.  The following website at Purdue offers a few suggestions for combating powdery mildew: https://www.purdue.edu/hla/sites/yardandgarden/decrease-powdery-mildew-through-prevention/#:~:text=Lilacs%20are%20quite%20susceptible%20to,method%20of%20control%20is%20prevention.

UNH has a site that suggests raking up the debris at the end of the season around the lilacs so that it won't happen in the next year: UNH Extension

The following UMaine site suggests from photos that were sent in that it could be insects. They have two photos of what the insects look like that may help you: https://extension.umaine.edu/gardening/2024/08/02/what-is-the-grayish-white-growth-on-my-lilac-trees/

I hope this information is helpful! Please feel free to reach out with any further questions!

Thank you for contacting the Infoline, a service of the UNH Cooperative Extension. Replied January 15, 2026, 11:56 AM EST

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