Magnificently thriving plants are a treat for the eye and sometimes also a prerequisite for a good harvest. It is all the more disturbing when white dots appear on the leaves.

In a nutshell

  • small white dots on the leaves can have different causes
  • most of the time there is no reason to worry
  • Damage can indicate care errors, diseases or pest infestation
  • Recognize the cause as early as possible in order to be able to act effectively

Casting error

Small white spots on the leaves are often the result of improper watering. With the exception of marsh plants, the majority of all plants get by with relatively little water. They fear nothing more than too much moisture. The roots rot and can no longer supply the plants with nutrients. For example, if succulents have stored too much water in their leaves, they sweat it out, leaving white dots.

countermeasures and prevention

  • Transplant affected plants into dry soil as soon as possible
  • do not water in the first few days after transplanting
  • do a finger test before every watering in the future
  • let the top layer of soil dry out
  • Take into account the needs of the respective plant species
  • Use a moisture meter if necessary

Tip: It is best to find out about their special requirements when buying plants.

Diseases

Powdery mildew (Erysiphaceae)

Occasionally powdery mildew can also be behind such discolouration, for example on tomato or rosemary plants. Initially, small white dots or spots can be seen on the leaves, which quickly expand and soon spread over the entire plant. They consist of a white, powdery down and occur mainly in warm and dry weather, hence the name "fair-weather fungus". Too much nitrogen in the soil can promote an infestation because it weakens the plants' defenses.

Powdery mildew on zucchini leaf

combat

  • Combat as early as possible
  • in case of initial infestation with self-made spray solutions
  • One part whole milk and eight parts water
  • Repeat treatment several times
  • If the infestation is advanced, remove affected leaves or shoots
  • incinerate or dispose of with household waste

prevention

  • pay attention to loose, not too dense planting
  • Use fertilisers, especially nitrogen, only in good doses
  • Allow the soil to dry thoroughly before each watering
  • Water only on root area, not on leaves
  • preventive spraying with plant decoctions made from stinging nettle or field horsetail
  • increase the resistance of the plants
  • Never dispose of infested seedlings on compost

Tip: When choosing plants or sowing, you should pay attention to resistant species and varieties.

White spot disease (Mycosphaerella fragariae)

White spots on leaves can also be an indication of vitiligo, for example on strawberries. The spots have a reddish-brown border. The stronger the infestation, the more they run into each other. The associated reduction in leaf area damages the plants. The fungal spores overwinter on infected leaves and infect healthy leaves in spring. Again, too much nitrogen can promote an infestation.

White spot disease on strawberries

Combat/Prevent

  • Control with a suitable fungicide
  • Spray the leaves evenly with it
  • Remove particularly badly infested plants
  • preventively ensure sufficient planting distances
  • This allows plants to dry out faster
  • Regular weed control makes sense
  • do not fertilize with too much nitrogen

Tip: Heavy rainfall can cause a very heavy infestation.

White Rust (Albugo candida)

This fungal disease can affect every known cruciferous vegetable. Root vegetables such as turnips and horseradish are particularly frequently affected. Symptoms are white dots or spots on the upper side of the leaves, which get larger as the infestation progresses. Later, pustules form. Partially affected leaf parts can be deformed and swollen.

White rust (Albugo candida) on mustard plant
Source: Plant pests and diseases, Mustard- White rust, Adapted from Plantopedia, CC0 1.0

combat

  • only promising in the early stages
  • Remove all affected leaves and plant parts
  • also fallen leaves
  • Otherwise spores will get into the soil
  • dispose of with household waste or incinerate
  • Cut back into healthy wood
  • Disinfect cutting tools afterwards
  • if necessary, treat with a suitable fungicide
  • If the infestation is very severe, dig up and dispose of the plant

Tip: Damp and 13-18 degrees cool weather, caused by fog or prolonged thaw, promotes an infestation. The spores can survive for many years in the soil, but also in seeds.

pest infestation

Mealybugs (Pseudococcus)

The tiny pests covered by a white layer of wax can be seen as small white dots. They wear bright, cotton-like threads. In addition to the leaves, they attack all parts of the plant. There is sticky honeydew on the leaves. The plant dies if left untreated. Draft favors an infestation.

Mealybugs on houseplants

Combat/Prevent

  • eliminate the cause to combat it
  • so move to a draught-free location
  • Use spray solutions that are easy to prepare
  • twelve grams of paraffin oil and one liter of water
  • good alternative is alcohol
  • spray it over the pests
  • Repeat treatment several times
  • Chemical control only for stubborn infestation

Tip: These pests make no special demands on plants in order to infect them, making it difficult to identify the cause.

Spider mites (Tetranychus)

The spider mite causes small white spots on the leaves by sucking. The leaves wither and dry up. In addition, fine white webs can be seen that envelop the affected parts of the plant.

Spider mite infestation on hemp plants

control/prevention

  • ensure a humid environment
  • Rinse affected plants vigorously
  • Don't forget the underside of the leaves
  • Put the translucent foil bag over the entire plant
  • finish with stones or the like on the ground
  • Sack should be as airtight as possible
  • leave it like that for three days, then remove the bag
  • repeat again if necessary
  • Optimize site conditions

Woolly scale insect (Pulvinaria regalis)

This pest occurs on trees and shrubs, especially maple, linden and horse chestnut. In the spring, the egg sacs appear on the trunk and branches as white dots five millimeters in size. On top of that are the brown shields of the dead females who die shortly after laying their eggs.

Woolly scale insect (Pulvinaria regalis)
Source: Donald Hobern from Copenhagen, Denmark, Pulvinaria regalis (7439920846), Edited by Plantopedia, CC BY 2.0

Combat/Prevent

  • difficult with large trees
  • treat shrubby plants with insecticide
  • Ideally, remove any ice sacs that appear in the spring
  • by brushing or using a high-pressure cleaner
  • preventively avoid spreading the pests
  • Only transport clippings covered

Planthopper (Edwardsiana rosae)

Infestation is particularly common on climbing roses and in hot, dry weather. It first manifests itself in fine whitish speckles on the leaves. Initially along the leaf veins and later on the whole leaf. If the infestation is severe, the leaves will turn brown and fall off.

Planthopper (Edwardsiana rosae)

Combat/Prevent

  • fight light infestation with stinging nettle broth
  • use biological pesticides
  • for example, neem-based preparations
  • preventively pay attention to a well-ventilated location
  • avoid sunny locations
  • regular pruning to remove overwintered eggs
  • settle natural predators in the garden

frequently asked Questions

Do the damage symptoms of powdery and downy mildew differ?

Powdery mildew occurs in warm and dry weather and initially appears on the upper side of the leaves. Downy mildew requires high humidity and affects the underside of leaves.

What to do with recurring powdery mildew?

Powdery mildew can occur again and again. You can only try to prevent it and pay attention to the correct disposal. The best thing to do when buying plants is resistance to powdery mildew.

How important is it to clearly identify the polluter?

Even if it is not always easy, this is precisely the prerequisite for effective and effective control. Otherwise there is no effect and the infestation may be increased or the plants may be additionally damaged.

Category:

Garden pests