If you see needles that look like this: 

Your first thought might be, needlecast! And you might be right. 

Unless, on the reverse (I flipped these needles over), there’s this: scale insect! 

Scale insect often prefers the inside of a needle bundle, on the flat side of a needle. So the causal view from the outside of the needle bundle is that this is a fungus, needlecast. Whereas opening up the needles a bit reveals it to be an insect. 

Not only might we get the identification wrong, we might also reach for a fungicide instead of insecticide.