Trees/Big Hackberry Tree
I live in the Dallas area and have a huge old Hackberry in the back yard; 2 joined together at the trunk. About 2 years ago I had a tree trimmer inspect and cut the left smaller tree at its trunk, as he said it could fall. Then we had an extremely wet spring this year. For two years I have had a problem with the galls (cicada) bugs, not this year. Now I have the soot issue, as you previously addressed. The tree has black leaves and they have been falling for 6 months. Also the tree is thinning badly. Plus it has two huge squirrel nests (which I wish were not there). Was too wet, then two hot to spray before. Does this sound like if I use the pesticides you mentioned before, it will solve all these issues? And should I get rid of the squirrel nests (and how) It is old and give much shade, but does have issues. Thanks so much.
Sound like aphids or scale insects. Both will suck the plant juices from the leaves and twigs and excerete a substance called honeydews. Honeydew is high in sugar content and is sticky to the touch. Usually a black sooty mild will grow on the honeydew making everything black and sticky.
You can either spray the tree's foliage or use a systemic insecticide on the soil beneath and the tree will absorb the insecticide through the roots and take the insecticide to the leaves and twigs. Spraying a large tree can be difficult.
Chemical Control - Contact Insecticides Numerous contact insecticides are registered for aphid control. Since aphids are often placed under considerable pesticide pressure in field crops and greenhouses, they may be resistant to certain categories of insecticides. Therefore, if you do not obtain reasonable control, consider rotation to another insecticide. Contact insecticides currently registered for aphid control include: acephate (Orthene), bifenthrin (Talstar), chlorpyrifos (Dursban), diazinon, malathion, nicotine sulfate, pyrethrum, rotenone, resmethrin, and tetramethrin + sumithrin.
Chemical Control - Systemic Insecticides Several systemic insecticides are useful in aphid control. Aphids have sucking mouthparts and are thus very susceptible to pesticides located in the plant vascular system. Some of the systemic insecticides also have contact activity. Systemics injected or applied to the ground are less harmful to beneficial insects. Systemic insecticides include: acephate (Orthene)
Certain persistent insecticides that move systemically in the plant may provide control through the fall. Imidacloprid (Bayer Advanced Garden Tree and Shrub Insect Control) is a newly available systemic insecticide that can provide aphid control on trees for several months following application to the soil.
Since it is a large tree I would use the Bayer product. Check with your local garden type store. However since it is Fall now I would wait until the spring and treat with the soil applied insecticide then. This will be picked up by the roots in the spring and carry the insecticide to the foliage and limbs killing the insects as they feed. I would also fertilize the tree. Fertilize now with 10-10-10 fertilizer at the rate of 1 lb. per inch of trunk diameter scattered around the tree and watered in good. Apply the fertilizer just before a rain event and you will not need to water. Do not use a Weed and Feed product this contains a herbicide that will kill the tree. Fertilize now and again in the spring. This will increase the root and foliage health.
as far as the squirrels I would try trapping them. When they are gone the nest will break apart on their own. Here in Alabama I would use a ground live trap and move the squirrels to another location. I do not know the laws there so you may want to contact the local Wildlife agency about trapping nuisance squirrels.