The whitefly is not an accessory of a suit but a widespread plant pest. This seemingly appears out of nowhere and damages useful and ornamental plants. In order for control measures to be successful, it makes sense to take a look at your lifestyle.
Fighting whiteflies with home remedies
If you want to combat whitefly, you should spray your plants with a hard jet of water. This measure works on sclerophyll or succulent plants. Soft-leafed plants should be wiped off with a damp cloth. It is then necessary to treat the plants with home remedies.
Fighting whitefly: rapeseed oil
Rapeseed oil only harms whiteflies, it is harmless to beneficial insects, people and pets
Rapeseed oil preparations are suitable for use indoors and outdoors because they are gentle on beneficial insects and harmless to people and pets. Mix a rapeseed oil preparation with water and spray the product regularly onto the affected leaves. The pests are trapped under the oil film and suffocate. Since spraying can clog the stomata of the leaves, you should rinse the plants after a period of exposure. This is especially true for houseplants where the oil film does not dissolve due to natural weather influences.
soft soap
The product is made from rapeseed oil and potassium hydroxide and burns the skin of soft-skinned insects such as whiteflies. Since it is classified as a pesticide, you are not allowed to make soft soap yourself. You can buy soft soap commercially and prepare an aqueous solution to use as a spray:
- Dissolve a tablespoon of soap in a liter of rainwater
- spray directly on the pests so that leaves are dripping wet
- Insects die in their sucking sitting position and remain on the leaves after death
When using it, you should make sure that the fine mist does not get into your eyes. The mucous membranes become irritated and burn easily. If soft soap is dissolved in hard water, a type of lime soap is created. It is less suitable for pest control and easily clogs the nozzles of spray bottles. Dishwashing liquid and curd soap are not alternatives to soft soap because they are based on caustic soda. This is considered less compatible with plants.
Plants as anti-fly agents
The plant kingdom has developed natural substances that automatically keep pests away. Although planting such plants does not completely protect against insect infestation, they still greatly reduce populations. Beneficial insects and insectivorous predators can kill off the remaining whiteflies.
Plants with special ingredients:
- Zinnia: Zinnias contain nicotine and attract predatory insects that eat whiteflies
- Nicandra: Blue physalis contains alkaloids and withanolides that reduce pest infestation
- Monarda: Indian mint, golden balm, wild bergamot or peppermint contain frightening essential oils
- Tanacetum: Dalmatian insect flower produces pyrethrins that paralyze the nerve center
Repel and keep away whiteflies
To prevent annoying pests from appearing, you should make your garden as diverse as possible. There are some plants that have a repellent effect on whiteflies due to their natural ingredients. These are either suitable for planting in the greenhouse and garden, or can be used to produce sprays.
Essential oils
Whiteflies can be repelled using essential oils from intensely scented herbs. Since the fragrances are quickly volatile, you should repeat the measures regularly and renew the herb. Fresh plant parts are more effective than dried herbs. To extract the essential fragrances, you can brew a decoction from the herb. Essential oils are the basis for spray agents:
- Add mint essential oil to water
- Mix a liter of rainwater with a drop of dish soap and ten drops of lavender oil
- finely chop two cloves of garlic and pour hot water over them
- Pour 100 grams of tansy with one liter of boiling water
Mixed cultures against whiteflies
If you combine them cleverly, you don't have to worry about pests
Some plants have proven to be a natural defense against pests when planted in appropriate mixed crops. The vitality of the plants plays an important role. In order for such anti-pest plants to develop their full effect, they must be properly cared for. If they suffer stress from drought, waterlogging or a lack or excess of nutrients, the plants themselves develop into fly magnets. Basil makes an excellent underplant to keep whiteflies away.
| Anti-whitefly mixed culture | Bad Neighbors | |
|---|---|---|
| cabbage | Thyme, peppermint, rosemary, pineapple sage | Strawberries, garlic, mustard, onions |
| Tomatoes | Garlic, lavender, nasturtium | Fennel |
| Cucumbers | Dill, celery, leek, caraway | Radish, tomatoes |
| Strawberries | Lettuce, Indian spinach, thyme | cabbage |
Parasitic wasps
You can biologically combat the most common whiteflies with beneficial insects such as the parasitic wasp Encarsia formosa (EF parasitic wasp for short). Identify the pest beforehand to find the right parasitic wasp. The insects are 0.5 millimeters long.
Females have an ovipositor with which they pierce the whitefly larvae and lay their eggs. The larvae that hatch from this eat the host from the inside, so that the larvae turn black. After a week the parasitic wasps hatch. One insect can kill up to 300 whiteflies.
Application:
- Spread cards with parasitic wasp larvae between the plants
- at temperatures of at least 16 degrees Celsius and a humidity of 60 percent
- not suitable for winter months due to lack of light
- After fighting whiteflies, parasitic wasps die
If home remedies don't help
Whiteflies prefer moist, warm locations
Whiteflies prefer high humidity and temperatures above 23 degrees Celsius. They don't like drafts, but look for windless and protected areas in dense stands of plants. Plants in very dry or cool places are avoided. If your plants are suffering from pests despite numerous control measures, environmental conditions could be a cause.
Increased infestation after spraying
The infestation often seems to increase after the control measure. This is because the environmental conditions change as a result of spraying and the pests produce more eggs. Therefore, repeat sprayings with rapeseed oil or soft soap solutions at intervals of ten to 14 days.
Constantly recurring infestation on houseplants
It is not uncommon for the pests to be very stubborn and no control measure brings the desired success. Individual eggs often survive in the leaf axils or in the folds of rolled leaf edges. Place the affected plants on the balcony or terrace during the summer months and let beneficial insects work for you. Remember to use sun protection to prevent the leaves from burning.
If whiteflies keep coming back, consider changing location.
Whiteflies on basil
Pests often appear on herbs in the greenhouse, even though the infected plants actually have a deterrent effect. Basil is a good example of this dichotomy. When he althy and with optimal care, the culinary herb grows vigorously and proves to be an effective deterrent. Weakened and sickly plants or specimens that are in suboptimal locations are more likely to suffer from whiteflies. The two species found in the greenhouse are the greenhouse scale insect and the cotton or tobacco whitefly.
Getting basil pest-free:
- With at least six hours of sunshine, the frightening aroma develops optimally
- A cooler location with temperatures below 18 degrees reduces the number of flies
- changing the location to a well-ventilated area will drive away the pests
Rapeseed oil is ineffective
Commercial rapeseed oil does not dissolve in water without an emulsifier, so a few drops of oil in water do not make a suitable spray. Rapeseed oil preparations contain soy lecithin, which acts as an emulsifier and dissolves the oil in water. Dishwashing liquid has a similar effect, although the exact mixing ratio and speed of mixing are crucial. An oily film does trap the insects. Oil droplets still tend to roll off, so an ecological adhesive such as Break-Thru should be mixed in.
Preparation of an oil-water solution:
- Mix ten milliliters of rapeseed oil with half a shot glass of dish soap
- add a small sip of water
- slowly add a liter of water while constantly mixing
Fighting whiteflies – with chemicals
There are numerous chemical remedies against whiteflies. Many are based on potassium s alts and have the same effect as an aqueous soft soap solution. Other products contain rapeseed oil and are expensive compared to homemade rapeseed oil sprays. To make the products work better than home remedies, various neurotoxins are added.
Common neurotoxins in injections:
- Acetamiprid: nicotine-like active ingredient, approved for potted, ornamental and vegetable plants
- Deltamethrin: Pyrethroid, approved for grain, meadows, potatoes, rapeseed and beets
- Methiocarb: no longer approved as an insecticide due to high toxicity
- Thiacloprid: nicotine-like active ingredient to combat crop and fruit pests
- Pyrethrins: natural substance with insecticidal effects
Such neurotoxins, however, are not gentle on beneficial organisms. They not only kill pests, but also wild bees, bumblebees or important pollinators and endanger birds or aquatic life. When used in your own garden or house, they affect the he alth of pets and humans. Therefore, avoid using chemical agents and resort to effective home remedies or use mechanical measures.
Species of commonly affected plants
The greenhouse scale insect is just one of around 80 species of whitefly
Whiteflies are not picky when it comes to food. They are polyphagous and occur in species from more than 80 different families. The term whitefly refers to the whitefly family and includes more than 1,500 species. Many of them prefer certain plants, which is reflected in their common German name. The cabbage moth scale insect is a common whitefly on cabbage.
Tip
You should fight the whitefly in the morning when the weather is cool. At lower temperatures the insects are less active.
Background
Detecting an infestation
Whiteflies are plant lice and have four wings. They leave a sticky secretion on the leaf surfaces, which is an ideal breeding ground for sooty mold fungi. The sucking activities weaken the plant. If whiteflies occur in large numbers, yellow spots appear on the leaves. These increasingly wilt and fall off if the insects are not controlled.
| scientific | colloquial | favorite plants | parasitic Encarsia species | |
|---|---|---|---|---|
| Mothscalefly | Siphoninus phillyreae | Ash Whitefly | Ash trees, apple, pear and quince trees, citrus plants | E. inaron |
| Greenhouse scale insect | Trialeurodes vaporariorum | Greenhouse Whitefly | Ornamental and useful plants, houseplants | E. formosa, E. lutea |
| Silverfly | Bemisia tabaci | Tobacco Whitefly | Vegetables and fruits of various plants, e.g. tobacco, tomatoes, poinsettias | E. bimaculata, E. lutea, E. sophia, E. pergandiella, |
| cabbage moth scale insect | Aleyrodes proletella | Whitefly on cabbage | Cruciferous vegetables such as alfalfa, clover or cabbage | E. tricolor |
| Citrus scale insect | Dialeurodes citri | Lemon Whitefly | Citrus plants | E. lahorensis |
Damage to houseplants
The plant pest Trialeurodes vaporariorum occurs primarily on plants in rooms or greenhouses. After the females lay their eggs on the underside of the leaves, the larvae hatch and feed on the plant sap. They secrete honeydew, so that the undersides of the leaves are covered with a sticky film. When the humidity is high, sooty mold fungi can settle here. A short-term change of location to an airy place can help. You should treat sensitive plants such as orchids with a jet of water.
Tip
Do not buy plants that have been treated with Confidor. The plant protection product contains the active ingredient imidacloprid, which drives parasitic wasps away.
Plants in the garden
When combating plant sap suckers, you should not only focus on the affected crops. Broaden your view of the entire plant population. In the garden, vegetable plants are often affected by the pests if the microclimate offers favorable conditions. The insects predominantly attack weakened and ailing plants. Annual herbs and balcony flowers are particularly often affected. Whiteflies don't stop at ornamental plants and woody plants either. Occasionally weeds may become infested.
Commonly affected plants:
- Vegetables: Kohlrabi, cucumbers, broccoli
- Woods: roses, hibiscus, boxwood
- Ornamental plants: Petunias, Rhododendron
- Fruit perennials: Strawberries
Development and Threats
Whiteflies can reproduce both sexually and asexually. The females place their eggs on small stalks on the underside of the leaves, arranging them in a ring. A layer of wax protects the eggs from drying out, while the stem ensures water absorption.
Larval stages
Females hatch from fertilized eggs, while males emerge from unfertilized eggs. The newly hatched larvae are initially freely mobile so that the offspring can spread. Only the following three stages are immobile. During these phases, the larvae sit firmly in one spot and protect themselves with a thick layer of wax. After the fourth larval instar, the organisms pupate.
Natural enemy in the ground
A globally widespread fungus that occurs naturally in the soil poses a danger to the whitefly. The spores of the Beauveria bassiana species adhere to the outer skin of the plant pest, allowing the fungal hyphae to grow into the insect after germination. They spread and deprive the insect of nutrients and water. Larvae are particularly susceptible to the fungus, which also affects eggs and adult whitefly insects. This makes this fungus a useful weapon against the pest.
Frequently asked questions
How do I recognize a whitefly infestation
The whitefly is small, but can be seen with the naked eye
If you notice yellow spots on the leaves, you should inspect the undersides of the leaves. The adult flies quickly flee when the leaves are moved. Females lay their eggs in characteristic rings. The larvae are freely mobile in the early stages and can be recognized by their whitish color with yellow, greenish or brownish nuances. In the later larval stage they attach themselves to the underside of the leaves and are reminiscent of smallpox. You can often see different stages of development on the underside of the leaves.
Typical signs of an infestation:
- Leaves yellow and eventually fall off
- Plant suffers from stunted growth
- Fruits are deformed
What helps against whitefly?
You can fight whitefly with simple methods. Home remedies should be the first choice because they often make chemical agents unnecessary. An aqueous solution of soft soap has proven to be an effective remedy. Essential oils have a deterrent effect and keep insects away from your plants.
If the infestation is so severe that even home remedies no longer help, you should use beneficial insects. Parasitic wasps are among the most effective control agents against whiteflies. They lay their eggs in their larvae and kill countless offspring within a short period of time. It is important that you use the correct parasitic wasp species. Each species prefers different host insects.
Whiteflies on kale – still edible?
Basically, cabbage is edible because neither the pest nor its secretions are poisonous. Eggs and larvae usually cannot be washed off completely. They provide an additional source of protein, but may cause feelings of disgust in sensitive people. The honeydew disappears when cooked. Increased humidity can cause the film to be colonized by sooty mold fungi. Check the kale for rotten spots or black discoloration. If mushrooms have settled, the vegetables should no longer be consumed.
What are those whiteflies in the potting soil?
If you notice white insects in the potting soil that crawl out of the substrate after watering, these are springtails. These insects are one to three millimeters long and wingless. They break down dead plant material and are not harmful to your houseplants. The insects were probably introduced into the planter with the compost because they prefer to live in the compost heap. Here they prove to be useful organisms involved in humus production.
