Aphids are insects that are small in size and squat in shape, where the abdomen is larger than the chest and head. There are different species, which may differ in some peculiar characteristics. The profile of these insects is ovoid, with the front part being more tapered. On the head are the ocelli and compound eyes. The ocelli are not able to perceive the images, but are able to detect polarized light, a function that serves to detect the position of the sun even when there are cloud conditions. They have mouthparts of the pungent-sucking type, equipped with rostrum. The antennae are thin, upward and folded back, in some species they are as long as the whole body. The legs are thin, divided into two segments. Only some species have wings.
There are various infections that can result from the attack of aphids on stone fruit: the green peach aphid (Myzus persicae Sulzer), for example, which attacks the peach, the almond and to a lesser extent the other stone fruit as primary hosts, with the potato, tobacco and chard as secondary. They are noted for the presence of green animals on the apices of the young shoots or under the leaves of the affected specimens. The symptoms are: distorted and covered leaves of honeydew, which is subsequently also covered with fumaggine. There are strong doubts that this parasite could be the carrier of the Peach Mosaic Virus. If the attacks of these parasites occur on varieties such as nectarines, which are much more sensitive, the deformation of the fruits is still small and the color is altered. If the attack occurs during flowering it causes the fall of the flowers, a technical term that indicates the premature fall of the flowers.