Answer: Your unmarked fertilizer is a real quandry. You really should use it up according to label directions, but without a label, that's hard to do. On the other hand, if you just dump it out, that would be wasteful. I'd do a little detective work at the local garden center. See if you can match what's left of the label on your product with one on the shelves. If you know it is Miracle-Gro, then you can use it at the regular dilution rate (usually 1TBS. per gallon of water) and fertilize your plants. It won't hurt any of your plants, whether they are acid-loving or not.
As for fruit tree spraying, there are specific products for specific insect pests. For instance, Bt (Bacillus thuringiensis) will take care of caterpillars and the larvae of codling moths and leaf rollers but they must be applied when you first see the pests; rotonone can work against apple maggots, but since insects emerge sporadically through a long period, Pyrethrum and Rotenone do not last long enough to do a good job - you must keep spraying. People with small numbers of trees can prevent some damage using red ball sphere traps with apple essence dispensers hung in the trees in July and treated with Tangletrap. Six to 10 balls/tree hung on the outside is very visible locations will trap many flies before they lay their eggs.
Picking up and destroying all fallen apples will reduce native populations but not prevent fly-in damage.
Hope this information helps!
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