Recognize and diagnose common plant pests

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Recognize and diagnose common plant pests: damage

They leave traces of food, feces, saliva, eggs, nests and at worst a sight of devastation in pots or beds. But then it's usually way too late. To be able to recognize an infestation with plant pests in time and to determine them is therefore anything but useless knowledge. Especially when you hate to use the chemical club against the pests. Who is eating there? From the snail to the aphid, every pest leaves its own traces.
An overview of the most common plant pests, their appearance, their habits and their traces help to initiate the right prevention and control strategies. Already the classification of the appropriate class and order in the animal or insect world can give valuable information for the resistance. Certain plants are susceptible to certain pests. There are plant pests that are barely visible to the naked eye. Then there is the vole, for example, relatively large, but also extremely active, but hidden. A snail rarely gets to the palm and spider mites drift away from the harsh nature of green lily and ficus.
The main suspects by size:

  • voles
  • snails
  • Beetles / larvae
  • fly
  • lice
  • mites


The damage caused by voles can be significant. Many hobby gardeners only discover the damage when the plants die or the turf is completely destroyed. Often there are doubts, were they moles or voles? A distinction is important, because while the fight against vole is allowed, the mole is under protection. Mole mounds may disturb some in the optics, while the hills of the voles are rather small and inconspicuous therefore. The damage, because the latter cause, however, is much larger.
AppearanceVole mice, also called Schermäuse, are somewhat similar to the beaver. They have a rounded whiskers and they can grow up to 24 cm, depending on the species. Her coat is light brown to dark brown. But what good is the whole description, they do it in secret and you rarely see them. It is more important to identify them in time on the basis of their traces and damage.
damageVoles feed on juicy tubers, onions, rhizomes and roots underground. The damage to the plants can only be determined clearly late. Identification of the vole are:
  • The raised piles of earth point in one direction (as opposed to a molehill). Often the troughs on the surface can be seen. To be sure, just dig up a pile. If the hole goes sideways along the surface, it is a vole.
  • On the plants themselves, the feeding damage is late to see. They can easily be pulled out of the ground or simply enter.


A tiresome subject for every gardener, especially in rainy summers. The biggest damage is probably caused by the Spanish slugs, which flock in droves over young leaves in the garden.
AppearanceThe most common type of nudibranch is the Spanish slug (Arion lusitanicus). It is so dangerous because it hits us with plenty of food and hardly natural enemies. The color of this different long snail ranges from dark brown to light orange.
damageThis snail is after almost everything that is fresh, young and green. The huge damage is immediately recognizable. In addition, they usually caught in the act.


Mostly it is the voracious larvae of the beetles that add to the plants. But even some beetles are aiming for the fresh green. In addition to potato beetles and wild beetles, it is primarily species of the weevil family that can cause considerable damage in the garden.
Black-backed weevil (Otiorhynchus)The weevils are among the weevils. The species of this beetle genus are around ten millimeters in size and are usually black to brown in color, with lighter dots on a fluted surface. They are nocturnal and can not fly. With their biting tools they work on leaves, buds and young shoots. Their distinguishing features are:
  • U-shaped feeding damage (Buchtelfraß) on the leaf margins or needles
  • Sudden wilting of the plant parts or the whole plant
The larvae damage the roots of the plants with their feeding. Therefore, it is important to determine a damage by the weevil early enough, and then best to proceed against him in the larval stage. In May, June the finished beetles hatch. Fighting the larvae in March, April is therefore the most effective.


Among the lice, the aphids (Aphidoidea) are among the most widespread plant pests.


Aphids are a plague for both indoor and outdoor plants. In the garden they come, with proper plant care, often on their natural enemies, such as the ladybugs. But even with indoor plants, if they are examined regularly, they can quickly identify and combat the following characteristics and damage:
  • They are 1 to 5 millimeters in size
  • Green, black or gray
  • Sitting close to the shoot tips and undersides of the leaves
  • Sticky plant parts
  • Rolled and curled leaves
  • Black plaque on the leaves


Mites belong to the class of arachnids. The smallest of them are just 0.5 millimeters in size. The red spider (Panonychus ulmi) causes widespread and great damage to plants.
Spider mites (red spider)It is equally annoying in both indoor and outdoor plants. Especially if the plants grow under unfavorable conditions (over-fertilization, dryness).
The spider mites are half a millimeter small. Mostly reddish or brownish yellow. They preferably stick to the leaf undersides. The damage picture:
  • Leaves turn yellow and wither
  • Leaves with light speckles
  • White webs on the leaves

White fly

Mainly in rooms and greenhouses one finds the white fly (Trialeurodes vaporariorum). It belongs to the family of moth sign lice (Aleyrodidae) and is therefore not a fly. This becomes clear when you take a closer look at the tiny flying insects:
  • They are about 1.5 millimeters in size
  • Wings lie roof-shaped over the small yellowish body
  • Wings are white and have a wingspan of 5 millimeters
  • Hind legs strongly pronounced
The white fly sucks on the leaves. If you go near the infested plant, they fly or jump in all directions. An infestation of the plant can be recognized:
  • Yellowed, withered leaves
  • Sticky plant parts
  • Black mushroom topping


Thrips are also airworthy and frequently encountered plant pests. Thrips belong to the flying insects, to the order of the fringed wing (Thysanoptera). In heated rooms they suck with relish on the leaves of houseplants and multiply rapidly. The thrips can be recognized by:
  • long stretched body up to 3 millimeters long
  • sometimes with two pairs of wings (not very active in flight)
  • black and white horizontal stripes on the wings
  • Saw-like drill on the head
Due to their rapidly increasing population, they can be quite dangerous house plants. To make matters worse, that you can make them only bad, because they are usually well camouflaged in the wells of the leaf structures. They suck the juice from the bottom of the leaves. The damage picture:
  • Leaves appear silvery due to many small white dots
  • Black stains on the undersides of the leaves
  • Leaves are drying
ConclusionThe plant pests described here are so annoying and common because they have not specialized in particular plants. Most like crisp roots or fresh greens, almost no matter which plant. If you know what the most common pests look like and recognize their damage pattern early, you can usually do more harm to your plants. Often it is also worth taking a look at the order, class or family of the respective pests, in order to be able to sensitively disturb them with this knowledge in their reproductive and living habits.

Video Board: Plant Health & Disease Troubleshooting Guide.

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