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The whitefly is an annoying pest that is unfortunately difficult to control. An infestation can occur in garden, balcony or house plants. Once the flying insect has settled in, countermeasures should be started immediately, as the pest spreads quickly and does not stop at plants that are not actually on its menu. However, biological home remedies and natural predators will help you in the fight against the whitefly.
Biological assignment
Biologically, the whitefly is not a fly, but comes from the superfamily of whitefly (Aleyrodoidea) of the suborder plant lice (Sternorrhyncha). There are around 1,100 known species worldwide. About 17 of them live in Central Europe. Various species of whitefly are referred to as whiteflies, such as the ash whitefly or the greenhouse whitefly.
Look
The flying insects are between one and three millimeters in size. Their wings are covered with a flour-like waxy dust, which probably led to the name whitefly. Larvae hatch from the eggs of the animals, which are initially mobile. In the following stages, the larva is immobile and sits on the underside of the leaf. In the course of pupation, the larva is then transformed into the whitefly.
life cycle
The females of the whitefly lay one or two eggs per day. In their four-week life, they lay up to 500 eggs in total. After the larvae hatch, it takes about two to four weeks for them to develop into full insects. Up to ten generations can develop in one year.
eating behavior
Whitefly insects feed on the sap of plants. They suck the leaves of the plants to get the amino acids they value. The sugar contained in the plant sap is excreted by the insects and forms a sticky film on the plant, the so-called honeydew. Whitefly insects live according to the motto "they always eat", i.e. even the immobile larvae continue to suck on the leaves.
damage picture
The tiny animals are difficult to see with the naked eye. In most cases, you will recognize an infestation by touching the plant. Then the insects “fly away”. Unfortunately, they don't run away, but usually settle down on the plant again as soon as the danger is over.
On the plant itself, the whitefly leaves the following traces:
- white dots on the underside of the leaf
- Leaves become yellow-spotted
- Leaves dry up and fall off
- Larvae form a thick layer of wax on the underside of the leaf
- Leaves and stems are coated with honeydew
The sugary honeydew can subsequently lead to an infestation with black mold or sooty mold. However, it also attracts beneficial insects such as bees. These absorb the honeydew and turn it into real bee honey. Therefore, combating whitefly is a mixed bag.
threatened plants
When choosing plants, the whitefly is not very picky. She likes garden and balcony plants just as much as indoor plants. It also makes no distinction between useful and ornamental plants. On the menu of the whitefly are, for example, geraniums, primroses, fuchsias, hibiscus, the hard-working Lizzie, azaleas, rhododendrons, flower mallow, purple bells or the poinsettia. Tomato, cucumber plants, pumpkins, peppers or zucchini are also among the whitefly's favorite foods.
Tip: Since the whitefly comes from tropical and subtropical regions, all plants that prefer a similar climate to the whitefly should be checked regularly for a possible infestation.
countermeasures
To stop a whitefly infestation, two strategies must be combined.
- Control of adult animals - prevention of egg laying
- Fighting larvae - stopping reproduction
To combat the plague in a targeted manner, cut off the leaves and stems that have larvae and eggs on them. However, it is better not to dispose of the cut leaves or plant parts in the compost or in any other unprotected garbage. The larvae of the whitefly continue to suck on parts of the plant that have been cut off and can thus also transform into adult animals.
Tip: Put the cut leaves and plant parts in a plastic bag with soapy water. In this way, the larvae are softened and no longer develop. The reproduction of the pests is thus interrupted and the offspring no longer has a chance.
If you don't want to resort to biological or even chemical agents right away, you can drive the whitefly away or stop its reproduction.
This includes:
- yellow boards
- Change in climatic conditions
- natural predators
Yellow boards or yellow stickers
One of the simplest countermeasures is to put up yellow boards, usually coated with glue. The whitefly literally flies onto the boards, which are provided with an attractant, and sticks to them. So it cannot multiply and the plague is contained. To speed up success, shake the plant vigorously several times a day. In this way, the frightened flying insects stick to the yellow boards more quickly.
Change in climatic conditions
To drive away the whitefly, change the location of the plant in house or balcony plants for a short time. It is best to drive away the pest with a cool, airy location. The flying insects do not like these conditions.
Tip: Hardy plants are freed from the whitefly at the latest when the first frost arrives. Because the animals do not survive temperatures below zero degrees Celsius for very long.
Natural predators
Natural predators are the best help against the larvae, which are much more harmful to the plant than the fly itself. These include assassin bug species and various species of parasitic wasps. These natural predators are available in specialist shops. Ichneumon wasps especially like to eat the larvae of the white fly. You don't have to be afraid of a wasp plague either, the beneficial insects move on as soon as there is no more food available.
Other natural predators are spiders, ladybugs, lacewing larvae and hoverflies. These natural predators are not suitable for indoor plants, as you don't necessarily want to bring insects into your home.
Tip: If there is a spider web in the corner of the room, you should not remove it immediately. It serves as an additional defensive measure, because the whitefly can also get caught in the spider web.
home remedies
If yellow boards or natural enemies do not help against the whitefly, then you should first use home remedies in the event of an infestation. Apply the biological remedies early in the morning, at this time the animals are still a bit sluggish.
- Shower the leaves with cold water from below (against larvae)
- Basil as a spray
- Spray made from stinging nettles
- Garlic broth as a spray
- Canola oil spray (animal suffocation)
- soft soap solution
For the sprays made from basil and nettles, soak a few handfuls of leaves in water for several days. After filling into a spray bottle, the treatment can begin.
garlic broth
For the garlic broth, cut one or two cloves of garlic into small pieces and put them in a pot with a liter of water. Bring to a boil and then leave to simmer for an hour. Remove the garlic pieces and pour the cold brew into a spray bottle. Depending on the success, the plant can be sprayed again after a few days.
soft soap solution
You can spray the plants with a soft soap solution or wipe the leaves with a damp cloth, the latter only getting the larvae. Alternatively, you can also paint the affected parts of the plant. For the soft soap solution, 30 grams of soft soap are dissolved in one liter of warm water. Cut or grate the soft soap and shake the bottle vigorously. This speeds up the resolution. Then pour the solution into a spray bottle. The prepared solution can be stored for a long period of time.
Tip: Only use tough soft soap for the solution, liquid soft soap is unsuitable for combating whiteflies. Cover the substrate well so that the lye does not contaminate it.
Water-rapeseed oil emulsion
For the water and rapeseed oil emulsion, mix 70 percent water with 30 percent oil. Always mix only as much as you need, as the emulsion only lasts for a short time. Spray the plant carefully with the mixture so that the film spreads evenly over the plant and the pests. Enveloped in this way, animals and larvae suffocate. If necessary, repeat the application every few days.
Tip: You can use regular edible rapeseed oil from the supermarket for the emulsion.
With all sprays, make sure that the underside of the leaves in particular is sprayed well. This is how you destroy the larvae, i.e. the offspring of the whitefly.
Tip: Isolate affected plants if possible. This will prevent the flying insect from “moving”. The whitefly also lays its eggs on plants that are not on its menu.
Chemicals
Chemical agents should only be used in exceptional cases. On the one hand, you may also poison beneficial insects such as bees or natural predators of whiteflies, and on the other hand, some whitefly species are resistant to chemical agents. Whitefly, for example, has already developed a high level of resistance to pyrethrum, a harmless active ingredient. Bemista tabaci (tobacco whitefly) become even more instead of less through pesticides.
Those who resort to chemical agents should be aware that they are considered systemic. These include sticks that are stuck into the ground. The active ingredient is absorbed through the roots and distributed through the plant sap in the plant. With systemic plant sprays, the active ingredient is absorbed through the leaves. Agents based on pyrethrum or fatty acids are considered unthinkable active ingredients.
Tip: If crops are infested with whiteflies, you should avoid using chemical agents to protect yourself.
Replace substrate
If you have successfully fought the whitefly on the plant, the danger is unfortunately still not over. Because there can be stunned larvae, adult animals or eggs in the substrate. Eggs or larvae in particular can lead to a new infestation after a few weeks. In any case, to avoid this, you must replace the substrate.
- Carefully lift the plant out of the pot
- Rinse root ball thoroughly
- Thoroughly clean the planter
- Put the plant in a new substrate (and pot).
With garden plants, you should remove the top layer of soil, because larvae can also hide here.
Personal experience of the author:
Whitefly larvae can even survive the cold season in the substrate with the plant in its winter quarters. As soon as the plant gets used to the sun again, the infestation begins. Therefore, the substrate must be changed before moving to the winter quarters.
preventive measures
To prevent the whitefly from settling in in the first place, you can protect your plants from infestation with the right environment. So-called defense plants are not on the menu of the white fly. They drive away the flying insects with their smell or attract natural predators.
- Basil and thyme have an unpleasant odor
- Lavender protects roses
- Savory protects beans
- Nasturtium
- Wild herbs, marigolds, marigolds and cornflowers attract parasitic wasps
- Celery protects squash, cucumber and zucchini
Also, the whitefly does not like certain climatic conditions. Since the whitefly originally comes from tropical regions, it prefers warmth (over 23 degrees Celsius) and high humidity (70 percent and more). An airy location and low humidity protect the plants from the pests. If the houseplant allows, temporarily place it in a place with drafts.
Tip: Cool winter quarters that are adequately ventilated protect your plants from whiteflies during the cold season.
In order to detect an infestation early, regularly examine all plants that may be on the whitefly's menu. It is best to check the underside of the leaves when watering.