Pests: Most Feared By Plants
In this period our gardens begin to take shape and all the work we have done in the past months is transformed into shapes, colours, scents.
This is the period, however, in which the enemies of our plants also show up and undermine every single plant. From April to October, more or less, we will have to defend them from many forms of parasites of which we will analyze the most harmful and infesting.
The green plant bug arrives with the first sunny days and infests the gardens and green areas until November. In September, after a short break in August, it returns with the harvest and only with the end of it and the first cold nights, the bug disappears. We must not, however, generalize the danger of bugs: many species, in fact, are perfectly harmless both for plants and for man. Those from which we must protect ourselves, instead, are the green bugs of the plants, which feed on the sap of the shrubs and therefore of azaleas, rhododendrons, brooms and all the shrubs that enrich our green spaces. If we notice even a single green bug on a plant, it is necessary to intervene immediately to cut down any families or eggs. There are, of course, many chemicals to spray on the area, but if we do not wait for the eggs to hatch, we can intervene with natural methods. One trick that works against bugs is to plant garlic in the garden; bugs have a strong repulsion for its smell and will keep away from the garden.
The Monilia is a fungus that affects fruit plants such as apple, pear, medlar, cherry, peach. Monilia tends to attack fruits that rot when they are still on the branch; the first symptom that tells us that a plant is infested with Monilia is the whitish-grey mould that forms on the outer surface of the fruit. If we do not take action against Monilia, it will soon attack the branches and trunk of the plant as well, creating blackish fissures similar to wounds from which dense substances that may look almost like resin come out. In order to prevent Monilia, we must prune the branches that show cracks or that contain rotten fruit immediately. It is also important to always maintain good soil drainage because Monilia is afraid of humidity and stagnation. If a plant has previously been affected by Monilia, it is best to carry out a general disinfestation in early spring to prevent any residue of Monilia from developing.
Plant aphids are a family of lice that includes about 4000 different species. Aphids are parasites specific to some plants: rose, cypress, cherry, cedar and many others. The symptoms that aphids have affected a plant are: spotted, yellowed, crumpled, withered leaves until, if the aphid attack persists, the plant dies. The aphids can be winged or not. Usually the first generation is not, but since the succession of generations is very fast, the aphids soon adapt to the territory and, if they have to leave the plant because it is no longer nutritious enough, they develop wings. There are powerful chemical remedies against aphids on the market, but it is better to act on prevention, so that the aphids do not hit our crops. The preventive remedies against aphids are:
- eliminate weeds, because aphids tend to lay eggs in them;
- protect crops, especially young ones, with insect nets;
- avoid leaving piles of cut grass or leftovers from the crop.
Oidium, also known as White Mal, and which our grandparents called Albugine, is a plant disease caused by Ascomyocota fungi. The characteristic of these fungi to which powdery mildew belongs is that of producing hyphae (single or multi-cellular filaments). Powdery mildew tends to occur when temperatures are still moderate, in late spring and early summer. It develops more easily on plants with intense vegetative activity. Accomplice of the Oidium is the wind, which spreads the spores, while its natural enemy is the rain, especially if abundant, which cleans the leaves from mycelia.
The symptoms of powdery mildew are: a loss of colour of fruits, shoots and leaves, followed by the formation of a whitish patina, which looks almost like dust. Among the cultivations most affected by powdery mildew is the vine, which first tends to weaken until it cracks into the trunks; at this point other pathogens are introduced from the cracks produced by powdery mildew into the sap and kill the plant. Apart from chemical remedies, to prevent the spread of powdery mildew, it is advisable to avoid thermal shocks to the plant, for example by watering during the middle hours of the day. If we keep the plants away from these shocks it will be more difficult for the powdery mildew to attack our crops.
The Cochineals belong to the family of the Aphids. Characteristic of the Cochineal is to pierce the external lamina of the leaves and enter inside. It feeds on the sugary sap inside the leaves. The term “Cochineal” actually means dozens of species very different in size, which can range from a few millimeters to half a centimeter. Some species of Scale Cochineal are introduced into the roots of plants, feeding on the inner lymph. The Cochineals develop mainly on succulent or succulent plants, conifers, citrus fruits and vines. If the infestation is at the beginning we can remove the Cochineal manually, being careful not to hurt the branches from which other parasites could enter. We must then avoid nitrogen-rich fertilizers, in which the Cochineal thrives, and be careful to water and ventilate the plants because aridity, lack of ventilation and scarcity of light are excellent living conditions for the Cochineal. The whole moderate and warm period is ideal for the propagation of the Cochineal.
The Red Awl is a beetle native to Asia and is a parasite harmful to many species of plants, including especially palms. The Red Awl is so harmful that some regions, including Tuscany, have adopted real protocols of action against it. In addition to coconut, oil, American, Chinese, juice and dwarf palms, i.e. almost all known types, the Red Awl also attacks aloe and sugar cane. The infestation caused by the Red Awl can be asymptomatic for a long time. The insect fits inside the plant and is often not visible. The first external symptom is the fact that the foliage turns over “open umbrella” and can even go so far as to lose the whole foliage. The remedies against the Red Awl are very complex because it is a fast moving parasite and can infest a huge portion of the total surface of the plant at the same time. Prevention seems to be the best cure to date; it is therefore advisable to monitor the plants and, at the first hint, proceed with pesticide symptoms. The most natural methods considering the Red Awl do not seem to have any success. A technique of attack through specific viruses sprinkled on the plant is being tested but is not yet usable.
The Citrus Serpentine Miner is a lepidopteran widespread everywhere but only recently arrived in Italy. Since 1994 Italy has been fighting against this parasite, which attacks mainly legumes, but also leguminous plants, willows and numerous other plant families. The Serpentine Miner, first identified in Sardinia, in 1995 had already spread in Sicily and Calabria, precisely because it loves to feed on plants that prefer warm climates. The external appearance of the adult specimen is that of a silvery-white butterfly, fringed, with a small black dot at the apex. The larva, on the contrary, is greenish-yellow. The symptoms of the contagion from Serpentine Miner are: swelling of the lower page of the leaves, where the larva develops, and which become brown due to the faeces deposited just by the Serpentine Miner. The affected leaves appear weakened even on the upper page and folded downwards.
The best method to fight the Serpentine Miner is a natural pesticide known as Neem Oil, of which there are several brands on the market. This insecticide has a long life span that allows it to be used as a preventive method at the beginning of the hot season, so as to hit the larvae of the Serpentine Miner.
The Mediterranean fruit fly, more commonly called fruit fly, is a phytophagous insect, i.e. it feeds on vegetables. Its larva develops directly inside many fruits and consumes them from the inside. The fruit fly is considered by agronomists to be one of the most formidable enemies in fruit-growing. It is a vermin that can destroy up to 100% of a crop. In Italy the most attacked species are peach, apricot, fig, fig, persimmon, apple, pear, strawberry, kiwi and medlar from Japan. We can say, therefore, that the fruit fly is really a fierce enemy for the production of fruit in Italy.
The chemical solution is to let the insecticide penetrate into the fruit so as to destroy the fruit fly larvae as soon as they form. If you wait too long, in fact, the fruit will already have been eroded from the inside. Another chemical solution is to attract the adult specimens in chromatic traps, so as to reduce the number of hatching but it is still a costly and poorly functioning solution. The bio-technical fight, on the contrary, foresees to insert in the environment a relevant number of sterile males, in order to slowly reduce the proliferation. This solution is the one with the lowest environmental impact and is increasingly followed but for now the results on the spread of fruit Moscow are not always encouraging.
The Drosophila, or Fruit and Vinegar Gnat, is one of the most studied insects in biology because it is easily preserved in the laboratory and has a very short life cycle, not exceeding two weeks. The Fruit Gnat is about 3 mm long in the adult phase. It mainly attacks fruit in fermentation. Fruit midge eggs hatch 24 hours after laying and grow for five days at the expense of the fruit on which they attack, decomposing the sugars of which it is composed. If we have only one tree or, in any case, a few plants, to eradicate the Fruit Gnat it is better to use biological solutions: the simplest is to put some fruit in a bottle, in which we will have inserted a paper funnel, and let it ferment. The fruit midge will be attracted by the smell and will remain trapped in the bottle. If, on the other hand, we have an orchard, let’s not rely on solutions that are too bland and immediately defeat the Fruit Fly with valid insecticides; only during the maintenance phase will we be able to resort to non-invasive solutions. Once the Fruit Fly is in place, it is difficult to eradicate it.
The Processionary, also known as the Pine Processionary, is widespread in Europe, Asia and Africa. In its adult form, when it becomes a greyish-white triangular butterfly, it is highly destructive because it deprives the pine trees of their leaves and gradually kills them. In the larval phase, on the contrary, the Processionaria presents itself as a hairy caterpillar and releases a highly stinging dust for man. In the adult form, the Processionary is a nocturnal lepidoptera and hardly ever enters houses; in the larval form, instead, it forms tails that resemble a procession, hence its name, and is generally found around the pines or on their branches.
In Italy for about twenty years it has been compulsory to disinfest the Processionary in public areas; the problem remains in private land. The most innocuous method to eradicate it is to destroy the nests containing larvae. To do this it is necessary to cover completely to avoid the itching caused by Processionaria. For large plots of land, chemical fertilizers are usually used, which must be recommended by experts.