Re: Milwaukee, WI Our linden is about 15 years old and 35' high. After a few years we noticed red gall mites on the tree and did not pursue treatment as the nursery told us they were harmless. Now, 12 years later, we are getting leaf yellowing/browning and premature leaf drop on the stipled leaves. An tree specialist firm recommended injecting the tree with "Inject a cide B(?)" to kill mites now. Next spring (2017) they recommend a couple fungicide spray applications (Banner Max) for anthracnose. Does this sound reasonable? We are confused because several websites give conflicting information about trying to "preserve" Linden trees. This tree is close to the street lined Ash trees which were recently injected by our City for the ash borer. Might this be an issue to keep in mind for the Linden treatment too? Additionally, this tree doesn't get the pretty yellow "blooms" - is it a male? Thank you.
Linden tree tend to have a few insect problems (aphids and other sap sucking insects) I would treat the tree yourself (maybe cheaper then the company). There is a systemic insecticde that is applied to the soil around the trree in the sprring after leaf out and the roos take it up to the foliage and when any insect sucks the juicxe they are killed. The name is Bayer Advanced Tree and Shrub Insect control. It runs about 130 per gal. But you can get smaller sizes. The amount that is mixed with water will depend on the trunk size of the tree. (about an ounce per inch of diameter). The mixture is poured around the tree and the roots will carry it to the leaves. It will last the season..
Here is a web site that has this product or Home Depots should have it. http://www.domyownpestcontrol.com/bayer-advanced-12-month-tree-shrub-insect-cont
The leaf spots are not worth trying to control. A fungicide can be appied to the new leaves in the spring BUT will need to be re applied after any rain.
As far as the flowerts--One of your pictures showed fruit of the Linden so if there is fruit there was flowers. To increase the flowering and the overall health of the tree. I would recommedn that you fertiliize in the Spring with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good.If you apply the fertilizer just before a rain storm you will not need to water. This willincrease the helath of the tree and green up the foliage.