The aphids or lice that attack our plants are certainly one of the biggest concerns for indoor and outdoor growers. It is therefore of paramount importance to visually check and monitor all cultivated specimens frequently in order to detect the problem and prevent infestation; however, monitoring for preventive purposes is also extremely important.
In this article we will talk about how to prevent and eliminate aphids, known as plant lice, both with traditional methods (chemical products) and with natural remedies and products, which can be easily made at home or – for those who want practicality – can also be purchased online or in specialized shops.
Aphids or plant lice: what are they and what do they look like?
Among the many parasites that normally attack plants we find aphids, also called plant lice, or small insects – with a soft, pear-shaped body – of which we find hundreds of different species, which therefore have different characteristics, but all have in common the danger for our plants, especially ornamental plants (of all types) and all types of crops. That is why plant lice is a very common problem. The aphids are about 1 to 3 mm long, the body colour varies according to the specific family to which they belong and can range from yellow to green and brown to black, so it is not so trivial to recognise them immediately.
Some of these plant lice have wings and are covered by a layer of woolly wax, which they make themselves through the texture of their secretion.
The main problem with winged aphids is their great ability to turn from one plant to another and thus damage large plantations in a short time. The aphids that have lost their wings, on the other hand (which take the name of attere) focus on reproduction and precisely for this reason are able to generate large colonies of dangerous lice in a short time.
One of the main characteristics of aphids – which allows them to be more easily recognized and distinguished from other parasites – is the presence of a pair of horns present on the back of the abdomen.
How common is this parasite?
Where are the aphids and what do they do to the plant?
Plant aphids – just like many other pests such as the whitefly – tend to colonise the stems and lower part of the leaves; you can notice their presence due to their intense colour which often contrasts sharply with the green colour of the plant. Other families of aphids, on the other hand, tend to camouflage among the leaves and – in this case – it is more difficult to detect them and notice their presence.
But how do these insects behave? What exactly do they do to the plant?
The lice that attack the plants have a mouth equipped with an apparatus that is able to suck the sap from the plants and at the same time to release – in the very tissue of the plant – a particular saliva that induces the plant to form protuberances, which – in turn – protect the colonies of insects by providing them with food. This intense activity set in motion by lice on plants also leads to the production of honeydew, generated as a result of the waste of the sugary sap on which these insects feed, which involves the spread of sugar drops, which progressively invade the whole plant, favoring – consequently – also the formation of dangerous fungi and preventing the proper photosynthesis chlorophyll activity.
But that’s not all, because honeydew also becomes appetizing food for other types of insects potentially dangerous for plants, such as bees and ants, which feed on sugar drops, further weakening the plant.
How do they reproduce?
Plant lice prefer warm and mild climates, with temperatures ranging between 18 and 26 degrees centigrade, and opt – in particular – for dry environments. In order to contain the proliferation of aphids, it is good to remember that these lice fear the rain, the wind and – more generally – the low temperatures; therefore, it will be easier to find them in the warmest places and climates, in particular from spring to summer, and less in periods characterized by cold temperatures.
Aphids are insects as dangerous and harmful as they are resistant and able to reproduce. In particular, plant lice resort to the so-called “canning of generations”, a process that allows the female to keep inside her already formed daughters, which – in turn and even before birth – contain other insects in the embryonic phase. These – once given birth by their mothers – are already able to behave like normal adult aphids, so they will immediately attack the plant to feed themselves, weakening it even more.
Another strength of plant lice lies – as can be expected from their behaviour on plants – in their great ability to adapt to the environment, particularly when the climate is mild. Many families of aphids, in fact, often manage to resist even the action exerted by insecticides, both natural and traditional ones. However, luckily, there are many antagonistic insects that the aphids deeply fear, thanks to which it is possible to resort to them in order to contain the proliferation and then to progressively eradicate these insects.
What does it do to the plant?
Aphids feed on plant juices by piercing the leaves and sucking the sap from the stalks, branches and leaves from the straw mouth. To get enough protein to thrive, the aphids suck in lots of sap, refine the protein and expel a sugar solution called “honeydew”. This refined and concentrated compound attracts ants who ally themselves with the aphids protecting them from predators. The honeydew creates an ideal substrate for the growth of soot, which causes necrosis of parts of the leaf. Plants attacked by aphids have curled leaves, wilting of the plant and a delayed production of flowers and fruits. They carry viruses, bacteria and fungi and can quickly cause an epidemic.
Adiphi or plant lice: prevention
The most important months for prevention against plant lice are April and May, the spring period, when these dangerous insects are particularly strong and resistant.
In order to prevent the presence and spread of aphids, it is good to know that plant lice are transported by air for part of their life cycle, so – in the case of indoor crops for example – a thin filter in the inlet air intake helps to keep them away from your growing area. To make sure you create a hostile environment for them, clean thoroughly before you start indoor growing and check the stems and underside of the leaves periodically.
Always remember that most aphids cause the most damage when temperatures are warm (18-26°C) – i.e. when they find their ideal habitat for reproduction, as we have seen above – and they are very difficult to control because the very large, curly leaves protect them from insecticides or natural enemies.
One way to prevent the onset and spread of aphids is to constantly control your cultivation and your outdoor garden, especially at the edges against the wind, and to predict the presence of natural enemies, such as ladybugs and neuropterans, which effectively and naturally counteract the reproduction of plant lice.
Generally speaking, it can be said that constant control of cultivation and the presence of natural enemies and deterrents can counteract the reproduction and spread of the aphid population, which – in some cases – can be easily reduced without the need for treatment. In indoor cultivation – and for further prevention – a treatment with natural products (without pesticides) such as Agrobacterias Protect Killer, K-Directin or a Biofortifying Spray is recommended.
How to eliminate plant aphids or lice with natural remedies
Natural remedies against aphids can be implemented with great effectiveness especially at the beginning, when the problem is noticed or as a preventive treatment. Before treating aphids it is important to check for the presence of ants, because it is much more difficult to control aphids when they are present, so – before any treatment can be carried out – they must first be eliminated.
The first step to take, as always, is to clean the leaves manually, in order to remove the insects, and cut off the parts of the plant already colonized. When the infestation of aphids is minimal, it is possible to spray the aphids away simply with cold water, this solution is particularly effective in outdoor crops. Secondly, if the infestation is still low, some natural remedies can be used.
For example, one of the most widely used systems against plant lice is nettle macerate (but also that of garlic, chilli or tobacco, which are natural repellents capable of annoying these insects), a technique that is also widely used in the world of organic farming, which offers its advantages, provided it is carried out several times. To facilitate and simplify the treatment, it is possible to use one of the nettle macerates commonly available on the market.