Leaf spot

[susanapics]

Hi, I have a question regarding the best approach with regard to two lilacs that are already covered with leaf spot. These bushes are on either side of my garden shed within ten feet of a pear tree that looks like it might have a touch of fire blight. All of the lilac leaves are thin, brown and yellow at this point. There are no fresh green leaves to save and both look very sickly. They're about five feet tall. There doesn't appear to be any buds on the plants waiting for next spring so I'm wondering if I should spray an organic fungicide on and around them now or simply cut them way back, then spray and hope they return. I'm planning to mulch around them this fall for the first time (I've only just acquired the property) but thought I would give the whole area a spray (again, organic) before I do that. Any suggestions would be appreciated. Thanks.

[luis_pr]

This information is late so treat it as a f.y.i.... I usually prefer to send samples of affected leaves to someone who can diagnose the problem because applying a fungicide will only work if you apply the fungicide that affects the causal agent. For example,

* some brown dots are usually caused by fungal agents for which there is not treatment so the best one can do is dispose of the affected leaves in the trash, water the plants early in the morning by watering the soil, not the leaves, control soil moisture if the soil is very wet. If not controlled, the brown dots enlarge into brownish or yellowish areas that can cover the whole leaves.

* a bacterial infection commonly attacks white flowering lilacs via lesions in the tree, leaves, etc. the dots start yellow or brown and then turn black eventually causing the leaves (and blooms sometimes) to wilt. Improved air flow and more sun seems to help. Soil defficient in minerals or soil with very high nitrogen levels weakens the plant so make a soil test and take appropriate action. Some people will remove (prune) the affected area by cutting about a foot below it. Being a bacterial infection, I suggest you use alcohol on the pruners after pruning. Water the soil as mentioned above.

[susanapics]

Thanks for the help