Ecology means what the insects' plant hosts are, where on the apple tree the insects occur, and what type of damage they cause. Many apple pests feed on a variety of host plants, while others are restricted to a few or one host. The species descriptions appearing later in the publication deal primarily with the biology of the species as related to the apple orchard and ignore other host plants. The location of the insect or mite on the apple tree will provide clues to the pest's identity. Recognizing which pest is most likely to be found on each portion of the tree will streamline scouting by reducing the areas to be examined.
Damage caused by each pest species is also indicative of the species.
With a little experience, the scout can easily tell the difference in internal feeding damage caused by the codling moth, plum curculio, and apple maggot. Damage sometimes may not be observed until the pest is no longer present, but it is still important to note for future management decisions. The feeding behavior of a pest is linked to the damage it causes and can help producers immediately identify the pest. For example, the codling moth usually enters the fruit through the side of the calyx end and burrows deeply to feed in the core of the apple. The apple maggot also tunnels through the fruit, but very erratically, leaving smaller brown trails and without the granular frass indicative of the curculio.