Aphids are insects that have small dimensions and a stubby shape, where the abdomen is larger than the chest and the head. There are different species, which may differ due to some peculiar characteristics. The profile of these insects is ovoid, with the front that is more tapered. On the head are the ocelli and compound eyes. The ocelli are not able to perceive the images, but they are able to detect the polarized light, a function that serves to detect the position of the sun even when there are conditions of cloudiness. They have biting apparatus of the pungent-sucking type, with rostrum. The antennas are thin, upward and bent backwards, in some species they are as long as the entire 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 the drupaceous: the green peach aphid (Myzus persicae Sulzer), for example, which attacks the peach tree, the almond tree and to a lesser extent the other stone fruits as primary hosts, with the potato, tobacco and chard as secondary. They are noted for the presence of small green animals on the apexes of the young shoots or under the leaves of the affected specimens. The symptoms are: distorted leaves covered with honeydew, which is then covered also with sooty molds. There are strong doubts as to whether this parasite could be the vector of the Peach Mosaic Virus. If the attacks of these parasites occur on varieties such as nectarines, which are much more sensitive, deformation of the fruits is still small and altered coloring. If the attack occurs during flowering it causes the flower drop, a technical term that indicates the premature fall of the flowers.
Aphids on stone fruits
The green peach aphid overwinters among the crevices of the bark as an egg, developing a first generation on the peach tree and another 3-4 generations on the secondary hosts and then returning to the peach tree in the autumn, to lay down the durable egg that will overwinter. Other aphids on the stone fruit and in particular on the peach tree: the peach brown aphid (Brachycaudus schwartzi). Insect, this, which hibernates in the form of a wintering female or as an egg in the interstices of the peach bark, attacks begin again in the early spring. The whole biological cycle takes place on the peach tree, without secondary guests. The aphid attacks leaves and young shoots that shrivel. The congener Brachycaudus persicae attacks the buds, but also the peach roots.
How they act
The powdery peach aphid (Hyalopterus amygdali) attacks peach, almond and apricot. Its name derives from the whitish, powdery waxy secretion, similar to a flour of which both adults and nymphs are covered. This, together with the honeydew, leads to the death of the leaves and shoots by asphyxiation. Contrary to the attacks of other types of aphid, the leaves in this case do not curl up, but bend slightly at the sides. However, fall of the leaves and stunted and deformed growth of the shoots are determined. Secondary guests are reed straw canes. The insect winters as an egg on the primary host, where it gives rise to 4-5 generations, it transfers to the secondary hosts for the summer and returns to primary in autumn, to lay the wintering egg.