Main pests of the peach tree, bio defense and prevention

The peach tree is one of the most beloved among gardeners. At the same time, however, it is one of the most challenging to cultivate organically. One of the main problems is the numerous pests that attack its vegetation and fruits. Today, we’ll take a look at an overview of the insects to keep under control when cultivating peaches. Additionally, we’ll see what kind of damage these insects cause and understand how to prevent infestations using organic defense techniques. We will address other issues, such as the common peach leaf curl, in more detail later.

Now let’s explore the main pests of the peach tree.

Main Pests of the Peach Tree

Let’s start with this photographic overview of the main pests of the peach tree.

Cydia Molesta Moths

Cydia molesta, also known as the oriental peach moth, is a Lepidopteran insect that, as the name suggests, originates from eastern Asia. This moth is capable of completing 4-5 generations per year, overwintering as mature larvae in the peach tree’s bark. Its activity resumes in April, with the first flight.
The damage is caused by the larvae’s activity, which in May ruins young shoots. Later, they begin to damage the fruits.
Biological defense is complicated due to the overlapping generations. Continuous monitoring is therefore necessary, to be carried out with chromotropic traps which can be obtained here.
To these, pheromone traps should be added, as seen against the tomato leafminer. Pheromones should be specific, so it’s advisable to purchase them from specialized retailers. These remedies limit the populations of adult moths.
Against the larvae, which cause most of the damage, the best organic remedy is Bacillus thuringiensis var kurstaki, which you can find here.

Anarsia Lineatella

Another highly damaging Lepidopteran for the peach tree is the Anarsia lineatella, or the peach twig borer.
It undergoes three generations per year and overwinters as young larvae beneath the bark of branches and twigs. The first emergence occurs around mid-May for the overwintering generation. For the subsequent generations, it occurs from July onwards.
It causes damage to both fruits and young shoots.
In peach tree cultivation, its presence is often associated with Cydia molesta. They are quite similar and both are phytophagous, making them difficult to distinguish.
In any case, the biological defense is the same for both species. Therefore, what is described for the oriental peach moth applies here.

Aphids

Aphids are a superfamily of insects commonly known as plant lice. The most damaging ones for the peach tree are:

Myzus persicae, the green peach aphid
Myzus varians, the peach-potato aphid
Brachycaudus schwartzi, the brown peach aphid
Hyalopterus amygdali, the almond aphid

: Myzus persicae

: Myzus varians

: Brachycaudus schwartzi

: Hyalopterus amygdali

The biological cycle, damage, agronomic prevention, and organic remedies are similar for all species. Let’s see how to proceed, starting from the first point.

Biological Cycle

These aphids complete their entire biological cycle on the peach tree. They spend the winter as eggs, on old wood or inside the flower buds of pruning spurs.
In spring, coinciding with the vegetative growth, their damaging activity resumes. Often, the species we have listed form mixed colonies.

Damages

The damages caused by aphids on the peach tree are concentrated on the vegetation. These include discoloration, leaf drop or curling, cessation of vegetative growth, production of honeydew, and sooty mold on the fruits.

Agronomic Prevention

To prevent major infestations, it’s advisable to implement a series of agronomic measures such as:

Balanced pruning
Regular and not excessive irrigation
Reduced nitrogenous organic fertilization to avoid excessive vegetative growth

The preservation of biodiversity in the agroecosystem can also facilitate aphid control. For example, maintaining ground cover under the trees and creating hedges where antagonistic insects like ladybugs can find refuge.

Biological Remedies

Due to the rapid reproduction of aphids, which is often faster than that of antagonist insects, the use of organic remedies is often necessary. In such cases, the use of natural macerates such as those from nettle and garlic is recommended.
In case of severe infestations, you can intervene with potassium soft soap, available in a formulation specific for organic agriculture here, or with neem oil, which is also available online here.

Scale Insects

Regarding scale insects, two species are most damaging to the peach tree.
The first is the white scale insect, Pseudaulacaspis pentagona, and the second is the Comstockaspis perniciosa.

The White Scale Insect, Pseudaulacaspis pentagona

Pseudaulacaspis pentagona

The white scale insect is a concerning parasite for many fruit trees. It completes its biological cycle on the tree’s wood and overwinters as a mated adult female. In May, the first migration of nymphs occurs. The second migration takes place in July and extends into the following month. Damages are caused by sap withdrawal, which can lead to the withering of twigs and branches. The second generation can also damage the fruits.
Let’s explore the agronomic prevention and biological defense to safeguard our peach trees.

Agronomic Prevention

Agronomically, to combat the white scale insect, various factors can be addressed to prevent and limit infestations. During summer, direct exposure of colonies to sunlight can be encouraged through green pruning. Moreover, colonies are also vulnerable to winter cold. Thus, manual brushing and pruning can be performed to eliminate infested branches during colder periods.

Biological Defense

For effective biological treatment against the white scale insect, target the overwintering forms during vegetative growth. In this case, use white oil, a (permitted organic product available here).
In summer, oil is not recommended as it can cause plant burns. Instead, clean the vegetation and use pure Marseille soap. Note that this is not the typical soap found in supermarkets but a pure product suitable for organic farming. This soap can be found in specialized stores.

Comstockaspis perniciosa Scale Insect

The species Comstockaspis perniciosa, commonly known as the San Jose scale insect, undergoes three generations a year and overwinters as a nymph of the first or second generation. These stages are the most susceptible to biological treatments.
The nymphs appear in the months of May, July-August, September, October. Infestations occur as the nymphs migrate to new branches to colonize. They settle on branches and fruits, protecting themselves with their gray-slate shield.
Damages to the peach tree are caused by attacks on the trunk and branches, leading to withering and vegetative decline.
Attacks on fruits manifest as chlorotic areas surrounded by a reddish halo, with the scale insect’s shield in the center.
Agronomic prevention and biological defense are similar to those outlined for the white scale insect.

Leafhopper

Empoasca decedens

Another parasitic insect capable of damaging the peach tree is the leafhopper Empoasca decedens, belonging to the order Hemiptera. This species is also known as the green citrus leafhopper. It’s highly mobile and overwinters as an adult on evergreen plants, including citrus trees. It undergoes several generations a year and moves to the peach tree during mid-summer. Females lay eggs on leaf veins, and later, adults feed on the sap from these veins.
The damage caused by their trophic action results in necrosis of peripheral leaf tissue, leading to reduced shoot development.

Prevention and Biological Defense

Prevention for leafhoppers is complex due to their high mobility. However, their damages are generally occasional.
For potential organic treatment in case of heavy infestations, the use of neem oil is recommended.

Thrips

Taeniothrips meridionalis

Among the peach tree’s parasites, thrips are among the most problematic due to the difficulty in biological defense.
The species that affect the cultivar include the peach tree thrips, Taeniothrips meridionalis, and the Thrips major.
Thrips overwinter as mated female adults directly in the tree’s wood. During spring months, the tiny insects move to the flowers, where oviposition occurs.
The resulting nymphs develop and cause damage to flower organs and small fruits.
Agronomic prevention is quite complex. In areas with high infestation risk, it’s even recommended to avoid new planting.
To detect the presence of thrips, you can use blue chromotropic traps, which you can find here.
This type of trap serves for monitoring, not mass capture.
For biological defense, the most effective product is azadirachtin, the active ingredient of neem tree.

Key pests of peach trees, organic protection, and preventive measures

The peach tree holds a cherished place among favorites, yet cultivating it organically proves to be one of the more challenging endeavors. Let's delve into the reasons why.