Mar 03, 2021 10:41 am
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What are Aphids?

Aphids (Aphidoidea) are the most common plant pests alongside slugs and, together with scale insects, scaly bugs, mealy bugs and whiteflies, belong to the group of plant lice. The scientifically correct name of the group of insects is actually Aphididae — with around 650 native species, it is the largest among the plant lice.

How to identify Aphids?

Aphids are only a fraction of an inch in size. Depending on the species they are green, red-brown or black-brown in color. The soft-skinned, partly winged insects live either in large colonies or in small groups on their host plants, mainly on the young leaves and soft shoot tips. They use their proboscis to puncture the plant cells and suck out the sugary plant sap. However, they excrete a large part of the sugar sap again because they primarily need the very low protein content to survive. The Honeydew so to say, covers the host plant with a sticky coating and is a reliable sign of a pest infestation.

This sooty-mold fungi often settle on older deposits. Although they do not damage the plant directly, they do form an unsightly, black-felted mold. In addition, the fresh honeydew attracts ants — they literally milk the aphids and even defend them against ladybirds, and other predators. Another problem with aphid infestation is that winged aphids contribute to the spread of viral diseases in the garden when they colonize new plants, for example in fruit trees or shrub. In dry, warm early summer, aphids can multiply en masse.

Aphids ants
Ants milk Aphids and protect them against their natural predators

The most common representatives in our gardens include the great rose aphid (Macrosiphum rosae, among others on roses, apples, pears, strawberries), Black bean aphid (Aphis fabae, among other things on beans, potatoes, beets, snowball and European spindle), apple aphid (Eriosoma lanigerum, on apple, pear and quince), green peach aphid (Myzus persicae, on peach, plum and mirabelle plum, among other things, as well as various types of vegetables and weeds), green apple aphid (Aphidula pomi, on apple and pear) and the sitka spruce louse (Liosomaphis abietinum, on certain species of spruce and fir).

How do the aphids survive?

Almost all aphid species overwinter in the egg stage on the host plants and initially reproduce asexually after hatching in spring. In this way, numerous offspring are formed within a short period of time — it usually only takes a week until the formation of a new, sexually mature generation is complete. After several generations, the first airborne offspring emerge, which colonize new plants of the same species or - as in the case of the black bean louse, which changes host - only move to their winter hosts, the common snowball (Viburnum opulus) and European spindle euonymus europaeus) at the end of the season. The winged aphids typically reproduces only sexually.

How to prevent aphid infestation?
Aphids Ladybird
Aphids and your No. 1 predator: The Ladybird

The best prevention against aphids is to cultivate your garden close to nature and avoid large groups of similar plants. Combine, for example, your roses with different shrubs and add to your vegetable garden as mixed cultivation. In general: A healthy plant with adequate supply of nutrients, water and light is less vulnerable. On the other hand, a plant that is over-fertilized, planted in the wrong location or ailing, is often colonized by aphids. You should therefore generally avoid over-fertilizing with nitrogen, because the aphids also benefit from the rich sap. Refrain from planting ornamental shrubs that are often attacked by lice, such as Honeysuckle (Lonicera) or the Sweet Mock Orange.

Make sure that the natural enemies of aphids such as Green lacewings, Ladybirds, hoverflies and other have enough nesting opportunities in your garden, for example by creating dead wood hedges and installing lacewing boxes or an insect hotel... If the aphid hunters feel comfortable in your garden, the aphid infestation usually subsides noticeably after an initial invasion in late spring or early summer. Reason: Because of the availability of good food, the beneficial insects also multiply quickly. A balance establishes in summer, something that a hobby gardener can live with.

In order to prevent aphid infestation, the flushing of fruit trees and other woody plants also helps. As soon as the buds swell and the first leaf tips can be seen, the plants are treated thoroughly with a spray that is gentle on beneficial insects such as Promanal. The active ingredient rapeseed oil penetrates into the smallest crevices of the bark and coats aphid eggs and hibernating pests with a fine film of oil so that they die.

How to combat an aphid infestation?

If possible, you should avoid chemical insecticides when combating aphids, as they will end up killing the lice along with several other beneficial insects. Lice colonies on individual plants such as fruit bushes or roses can be sprayed off with a strong jet of water. Flightless aphids are relatively immobile and can barely cover distances of 7.87 to 11.8 inches on the ground. The possibility of it infesting the plants again is therefore extremely low. If the shoot tips are already badly damaged, you should cut them off along with the aphids and dispose of them.

Special plasters with insecticidal properties - once applied - work against aphids for two months (e.g. aphid-free plasters or rose plasters from Celaflor). They are placed around the stems of the plants and release their active ingredient into the sap, which in turn is absorbed by the aphids.

Spray washing plants
Spray washing the plants has proven to be an effective method against aphid infestation

If the aphids multiply excessively, neem preparations that are gentle on beneficial insects (e.g. pest-free neem) or agents based on rapeseed oil or potash soap (e.g. Neudosan aphid-free) can be used. The preparations clog the aphids' respiratory organs, the trachea, so that the insects suffocate over time. In order to target as many pests as possible, it is important that the plants are thoroughly sprayed from all sides. Homemade soap solution also works as a home remedy for aphids. A nettle broth stinging nettle broth is also frequently recommended. To do this, one kilogram of nettle leaves is left to soak in five to ten liters of water for 24 hours. Tests by the Federal Biological Institute have shown, however, that the solution is only 30 percent efficient — and that corresponds exactly to that of pure water.

Nasturtium under apple tree
Nasturtiums and other summer flowers under an apple tree: Unfortunately, this hardly helps against aphids

To keep aphids away from fruit trees, it is often recommended that the tree disc be planted with Nasturtiums, which is intended to lure the insects away from the trees. This is a common misconception: There are two different species of aphids that do not change their host plants. You don’t need to act immediately if aphids appear on the plants. Usually enough beneficial insects appear a short time later so that a natural balance is established. Most plants can cope with a mild infestation.

Aphids on pot plants and house plants

If there are only a few aphids on thepotted plantthey can often be easily wiped off using fingers or combated with soapy solution. If spraying agents are used in case of a stronger infestation, spraying should be carried out several times at intervals of a few days so that hatching insects can also be detected later. Alternatively, granules are sprinkled on the surface of the soil and whose active ingredients the plants absorb through the water. The aphids then ingest it along with their food and perish. The spraying agents are available in normal garden shops. However, you should not use them on flowering plants visited by beneficial insects, as they can get poisoned. Fighting aphids with plant protection sticks has also proven successful (for example Lizetan, Careo or Axoris). You simply put them in the potting soil and there they release their active ingredient to the plant roots over a longer period of time. The sucking insects are poisoned with the plant sap, similar to the rose plaster. Important: Use systemic products that pass through the roots only for ornamental plants, because fruits and vegetables will no longer be edible after such a treatment.