Many organisms eat the leaves, fruit and nuts of trees. When using systemic by Bayer, who claim their products are plant food as well, the good guys get a dose as well as the so-called, yet to be proven, bad guys. I believe in predisposition. When energy reserves are low or lacking secondary organisms will move in. Product pushers tend to have the secondaries as the target. Its like hunting and aiming at shadows. Its very upsetting to hear that they have teamed up with Arbor Day Foundation. Their add claiming they can sell you products that feed trees mentions their connection with Arbor Day. I did not know Arbor Day teamed up with product pushers.
BTW for the record. Food is a substance that provides and energy source, mostly. Nutrient is a substance that provides an energy source, elements, and other substances essential for life, in types and amounts that can provide a healthy life. Fertilizer is a substance that provides elements, as salts mostly, or in bonded forms, that require microorganisms to alter to forms that can be absorbed by plants. Trees do not get food from the soil. They manufacture their own food. Why lie to people and mislead them? You get your joys that way? Trees cannot absorb a nutrient or food. They do absorb essential elements. There are 17 essential elements - 14 From The Soil. Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Potassium, Calcium, Sulfur, Magnesium, Manganese, Iron, Copper, Boron, Molybdenum, Chlorine, Zinc, Nickel [Sodium, Cobalt, Selinium?]. They are elements. Elements are single atoms or groups of atoms of similar type. They are not food or are they nutrients. A list of elements can be found here:
I suggest these articles for a better understanding of tree chemistry.