Question
Good morning.  Our Red Oak has been diagnosed with tree aphids.  The honeydew is coating everything,and there are more acorns than I have ever recalled.  I learned that we could spray the tree with systemic to kill the aphids. When is the best time to do this when the leaves are on, or as my husband thinks, one the tree is without leaves.  We would also like to perform a significant amount of trimming, and we believe we will have to hire an arborist to do this.  Can we do this at the same time we spray for the tree aphids?  Thanks so much for your response.  I look forward to learning your comments.

Answer
Aphids are controlled during the growing season not usually during the dormant season. Scale insects are controlled during the dormant season OR during the growing season. Both of these insects suck the plant juices and secrete honeydew. Aphids can move around and scales look like little turtle shells and are attached to the twigs. Spraying large trees is difficult since all limbs (for scales) and all foliage (for aphids) will need to be covered with the insecticide.

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  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.  

IF it is aphids and the tree is small and can be sprayed I would go ahead and spray the tree -foliage and branches with Orthene. IF the tree is large I would wait since it is late in the year and the tree will start to shut down soon. Next spring I would treat the soil around the tree with Bayer Advanced Tree and Shrub Insect control and the roots will carry the insecticide to the foliage and twigs killing the insects as they feed on the plant juices. This will protect the tree for the season. Treating the soil now may do no good since the roots will soon stop moving water and nutrients up to the foliage.

IF the problem is scales You can treat the tree if it is not too large with Insecticidal oils. Many scale species on deciduous trees can be effectively controlled with a dormant spray of a refined horticultural, superior-type oil. Oils and insecticidal soaps work by smothering the insect, both adults and crawlers. If the tree is too large to spray all the limbs you could try the Boyer product but you may not get much effect until the spring when the roots move the product to the leaves.

In any case I would prune the limbs before you treat especially if you use a spray. Cut the unwanted limbs back to about 1/4 of an inch from the trunk this will leave a branch collar and the wound will heal better.

In summary--if the tree is large and you can not spray all the tree--treat the soil around the tree with the Bayer product next spring. Go ahead and prune the limbs before you treat. IF the problem is aphids and you can spray go ahead and do this with the leaves on. IF scales spray the oil after the leaves have fallen off. Prune before you spray the oil. I hope this answers what you wanted.

Here is a web link to the Bayer product.  http://www.bayeradvanced.com/insects-pests/products/12-month-tree-shrub-insect-c...