Gardening

Aphid


Aphids


Aphids are a large family of plant pathogenic insects. There are about 4000 species classified in 10 families. Of these, around 250 species are considered harmful to agricultural and forestry crops. They are 1 to 10 mm long.
Aphids are one of the most widespread and feared pests in agriculture. They live and feed on a large number of vegetables, undermining their growth, their ability to flourish and to bear fruit. In the event of serious infestations there is also an abundant production of honeydew which, in addition to aesthetic damage, can lead to the onset of dangerous cryptogams. Sucking the lymph, they can also become vectors of even incurable diseases (such as some virosis). For all these reasons it is important to know how to recognize and intervene appropriately, especially considering the extent of the attacks and the possible direct or collateral damage.

Aphids



Also called plant lice, these insects belong to the family of recklessness, and there are about twenty species, often distinguishable by color; the small body, 1-3 mm long, is oval, with short legs, there are both winged forms, which can be moved for tens of kilometers, and forms without wings. They have a stinging-sucking mouthparts, through which they pierce the surface of leaves, small branches and shoots, to suck the sap of the plants. Generally they develop on most of the cultivated plants, from vegetables to ornamental plants; are very common aphids of roses and aphids of tobacco.
Aphids generally nest in the most tender parts of plants, but there are species that prefer the lower side of the leaves and also semi-woody stems. The damage caused to the plants is often considerable, since the aphid colonies have many specimens; generally there are two or three generations a year, produced by non-fertilized females, due to parthenogenesis, which give rise to female specimens; before winter there is a generation of males, which mate with females, which will produce suitable eggs to spend the entire winter holed up in sheltered places.
While sucking the lymph, these insects emit a sugary liquid, called honeydew, which falls on leaves and stems, becoming a breeding ground for numerous mushrooms, especially dark-colored mushrooms called fumaggini, which disfigure the aesthetics of the plants, as well as causing damage functional. The honeydew also attracts other insects, such as bees and ants; with the latter, aphids often live in a sort of symbiosis, so the ants protect aphids and move them to other plants, using honeydew in return, as if they "raised" them.
In addition to this damage, aphids often inoculate plants of various types through saliva, some of which can cause very serious damage.
Aphid infestations are fought with specific or broad-spectrum insecticides, generally when the infestation is already manifest; the most used active ingredients are: Imidacloprid, Pirimicarb, Quinalphos, Fenitrothion, Malathion, Triclorfon, Diflubenzuron, Endosulfan.
In organic farming aphids are fought very effectively by introducing natural predators: ladybirds, especially those of the species Adalia bipunctata, which feed on adult aphids, or small wasps, of the Chrysoperla carnea species; these hymenopterans lay their eggs in the larvae and in the aphid adults, of which they feed.
The most easily found species of aphid are: Myzus persicae, aphid peach and tobacco green; Toxoptera aurantii, black aphid of orange; Brachycolus heraclei, celery aphid; Aphis fabae, pea aphid; Macrosiphum rosae, aphids of roses; Cinara cedars and Cedrobium laportei, found on coniferous trees of the genus Cedrus; Cinara cupressi, present on various species of cypresses.

Types of aphids


Those we call "aphids" or, popularly, plant lice in reality they constitute a very broad category of insects, in turn divided into even ten families and more than 4000 different species. Please note that of these "only" 250 are considered harmful to crops and have attracted the attention of plant pathologists. To the eye of a layman they all look the same since at most we notice the variation of their livery.
For our purposes we can distinguish between aphids and migratory ones.
The steady aphids: they have a marked predilection for a certain type of plant (apple, rosaceae ...). The eggs, already on that type of vegetable, hatch when spring arrives. A "founder" individual is born, without wings that begins to feed on the sap and multiplies giving life to other asexual and wingless aphids. Depending on the particular species and climate, up to 16 times can reproduce by parthenogenesis during the year. If the host plant were no longer sufficient to feed them, individuals will be produced with wings, able to move and colonize another (always of the same species). At the arrival of the cold season there is the appearance of sexed aphids, females and males: the first produce eggs (much more resistant to the cold than the adult insect) which will be deputed to the overcoming of winter. Around March-April the cycle will start again
The migratory aphids compared to the previous ones they are only substantially more polyphagous: they grow on a certain type of plant (for example on the apple tree) until they develop winged individuals that move on a secondary host (for example the plane tree). In autumn there will then be a return to a plant of the first type on which the eggs will be laid.

Symptoms and damage


They feed on the sap of the plants by pricking the fine veins of the leaves or near the flower buttons with the beak. The punctures and the removal of the lymph involve leaf deformations and in the long run make the plant weaker, in addition to transmitting virosis. In addition to producing a sugary secretion, the honeydew is deposited on the leaves and on the branches, favoring the development of the fumaggine (a black cryptogam).

Biology



Depending on the colonized plants the color can go from green, to brown, to black to even red.
They spend the winter in an egg state, but if they are rather mild, even adults can survive. Their presence becomes massive in spring and summer. In fact the females without wings, visible on the back of the leaves, are able to reproduce very quickly by parthenogenesis. In autumn, however, even those with wings appear. At this time sexual reproduction takes place to produce the winter-capable eggs. However, it happens that winged forms are present even earlier, in summer: they allow the colony to be disseminated when the first plant begins to be too haunted and unable to sustain all the subjects. An important goal to prevent the spread of infestation is to prevent these winged forms from moving from one plant to another.

Symbiosis between aphids and ants


As is known among aphids and ants there is an almost unique symbiotic relationship in nature. It could be said that ants literally breed aphids by protecting their eggs during winter and spring by transporting them directly to the branches. This with the precise purpose of feeding them and making them produce the honeydew, a sugary substance of which they are very fond.
It is therefore always necessary to pay the utmost attention when seeing many ants around a plant, be it fruit or ornamental. Almost certainly it is the alarm bell of an infestation in the starting phase or, unfortunately, already advanced.
The relationship between ants and aphids is truly unique and interesting in many respects. It is in fact one of the very rare cases of "breeding" that can be found in nature.
Ants are very guttata di melata, a sugary substance produced by aphids (and also by other insects like cochineals) starting from the sap and deposited on the stems and leaves of host plants. In order to always have plenty of ants, they are committed to protecting the eggs of "lice" during the cold season. As if that were not enough, they also deal with their spread, in the period in which the aphids are not equipped with wings: they carry eggs and asexual individuals from one vegetable to another.
If we notice a strong presence of ants near a plant it is certainly the case to be alarmed by trying to contain them first and then eventually resorting to specific products for phytophages.

Black aphids



Aphids, as we have seen, can be of different species and colors. The black aphids they are a type of aphid that creates problems in different plants and there are many species of black aphid to know for those who practice gardening and horticulture.
The black aphid of the cherry is one of the aphids of this type to know absolutely. Its Latin name is Myzus cerasi and affects the leaves and tips of cherry trees. Like all the other aphids, even the black aphid of the cherry tree attacks the plants by sucking the sap and causing a deterioration of the plant and especially of the affected areas, with a consequent crumpling of buds and leaves. These aphids also produce honeydew and therefore can cause not only decay, but also the development of fumaggini on the leaves.
Another black aphid that often does damage in the garden and the black aphid of legumes. This aphid, like all its similar insects, presents itself in humid vintage and infests rapidly and devastating legume plants such as faiences, green beans and broad beans. Sometimes the reproduction of this black aphid can be so intense that it cannot even reach it because sometimes it is more the cost of the intervention than the actual damage due to the lack of collection.

How do aphids work? What damages do they involve?


Aphids feed on plant sap; they are equipped with a stinging-sucking not very robust buccal apparatus, suitable for penetrating only the thin and tender vegetation: for this reason we see them piled up above all with their tips, new shoots or buds. The plant, due to their massive presence, grows more stunted. Other times there is also the appearance of deformations of the stem and foliage, which are negative both from an aesthetic and functional point of view.
Coming into contact with the sap (and passing from plant to plant), they are also an important vehicle of contagion, especially for some virosis. Unfortunately, many of these cannot be fought: the only "remedy" consists in the felling and destruction of the plant to avoid further spreading. It is therefore worth paying particular attention.

The honeydew



The honeydew is a waste substance that is produced by a large number of phytophagous, most of them classified as "harmful". These include aphids, cochineal, aleirodidae and psyllids. These insects feed on sap, very rich in sugars, but low in amino acids. In order to reach their minimum requirements for these nitrogen compounds, they are forced to swallow a lot of them, producing then highly sugary droppings.
The damage it can cause to crops is not to be underestimated: it is in fact an ideal substrate for the proliferation of the maize. It is a dark-colored fungus which, by impeding photosynthesis, leads to less growth and, in very serious cases, the deterioration of the plant.

Natural fighting methods




If the infestation is of slight entity you can try to intervene by manually removing the insects or pouring a strong jet of water on them. You can also try tobacco-based infusions (these are also very harmful for useful insects!), Chilli, garlic and nettle macerate.
We can also resort, if the problem is more important, to products based on pyrethrins. Let us always remember to distribute them far from the moment of flowering because they damage the phytophagous, but also the bees. They must be sprayed, after having been diluted in non-calcareous or slightly acidified water, on the back of the leaves and on the buds, if possible, in the evening. In this way they will be effective for a longer time: the active principle, in fact, is very sensitive to light and if it is distributed during the central hours of the day it degrades rapidly by acting limitedly. If you wish you can also resort to new preparations that contain toxins of natural origin, such as products based on Spinosad.
Clearly it is always a good idea to encourage the presence of natural predators such as ladybugs and earwigs. The honeydew can be removed using a little Marseille soap dissolved in water or using special plant soaps.

Natural methods against aphids




They are strategies that can be adopted in cases of light infestations, just after their appearance. Generally they require a lot of perseverance and attention because they have to be repeated promptly whenever the problem occurs again.
A very short-term remedy consists of directing a powerful jet of water over the affected areas so as to remove almost all insects.
Garlic macerated
It has a good effectiveness if used promptly, in the initial phase of settlement and reproduction.
The macerated is obtained by chopping a pound of wedges and leaving them in 10 liters of water at least one day. Later, after filtering the mixture using a pantyhose, we will spray it on the leaves and the soil around the plant. If we want we can also add some chilli pepper although its effectiveness is not proven.
If there is need for urgent intervention we can obtain a similar compound, an infusion, leaving a few cloves of minced garlic in boiling water until it has cooled. The use is similar to the previous one
Nettle macerated
The common nettle, a often denigrated weed, can become our good ally. We collect (with gloves) 1 kg of leaves chop coarsely. Let's soak them in 10 liters of water for at least 24 hours, in a shady area. We carefully filter, dilute to 10% with more water and spray on the leaves and on the ground. Fights insects as well as being a good fertilizer.

Other home remedies for aphids



Garlic and tobacco macerated
In half a liter of water we put six finely chopped garlic cloves and the tobacco of five cigarettes. We leave to macerate for about a week then filter and spray.
It has a good effectiveness, but let's remember that the active principle is the same as in the neonicotinoids: the compound is therefore extremely harmful for all pollinating insects!
Soaps and detergents
Foaming agents are effective because it is more difficult for insects to stick to the supports. They are also a valid aid in eliminating honeydew (at least in the early stages of storage). However, we use these agents with the utmost caution because their storage on the ground can, in the long run, become harmful. In agrarian consortia we find for sale special potassic soaps for plants. Alternatively the authentic Marseille soap, consisting mostly of vegetable oils, can be used.

Synthetic insecticides




If you have many plants, they are large or if the infestation is serious you can resort to synthetic insecticides. Generally they are more effective because they are more persistent and sometimes have a cytotropic or even systemic action, ie they penetrate, more or less, into the plant, protecting it for longer.
The most commonly used synthetic products are pyrethroids (for example deltamethrin, cypermethrin, permethrin), and slightly more effective and persistent than natural pyrethrins. They act mainly by contact and ingestion and therefore must be sprayed directly on the animals or on the parts of the vegetable that will be eaten.
We can resort, in the case we live in particularly infested areas, also to systemic insecticides. However, they should be used very sparingly, because they are very harmful to useful insects. It is important, if you choose to use them, distribute them for preventive purposes at least one month before the start of flowering so that they never come into direct contact with pollinators. They can be distributed either by vaporization (on plants in the open ground), or by irrigation (or by spreading the granule formulations) for potted plants.
It is recommended, in the case of treatments on vegetable or fruit plants, to carefully read the instructions of the producers on the recommended doses and above all to scrupulously respect the times of deficiency.

Sale of synthetic and natural assets


The aficides we can find for sale can be divided, for our purposes, into three categories:































GUY

ACTIVE PRINCIPLE

EFFECT DURATION

SELECTIVE

DEFECTIVE TIME
From contact, p. to. natural pyrethrins Short no short
From contact, p.a. of synthesis pyrethroids average no Generally short
Systemic, p.a. of synthesis neonicotinoids Middle-long no long

- Contact and ingestion effects with natural active principle (pyrethrins)
They contain extracts of a particular chrysanthemum (pyrethrum) which is poisonous to all insects. They should be sprayed on the plant, preferably in the morning or in the evening (they are photosensitive and thermosensitive). They have very short waiting times, but they are not selective (and therefore should be used with caution).
- Contact and ingested aphidics with synthetic active ingredient (pyrethroids)They contain substances very similar to the previous ones, but obtained industrially by synthesis. They are much more stable and last longer. Shortage times are generally quite short, but they too are not selective.
- Systemic aids with active synthetic principle (neonicotidoids): the active ingredient is similar in structure to that present in tobacco, but strengthened and synthesized so as to remain stable longer. It acts from the inside, since it is absorbed by the plant and remains in circulation in the sap for a medium period. It spreads in acropetal sense, that is from the roots to the apexes and if administered through irrigation it is able to give an integral protection.
They are not easily found on the market because a use without criteria has made them very dangerous for pollinating insects (api). They should be used only once a year, at the beginning of the season and in any case far from the flowering period. The waiting time is long.

Aphid: Biological fight with aphids



In recent years, a new method has been created to stem the damage caused to crops: relying on antagonistic insects. The most famous is of course the ladybird: especially at the larva stage it is a large aphid eater. They are also effective juvenile stages of many diptera, sirfidi and hymenoptera.
In a system with the right balance it is generally sufficient to resort to insecticides in the early stages of the vegetative period (when the antagonists are still inactive) and then leave the latter with the task of keeping the plantations healthy. Watch the Video