Whiteflies are tiny insects that love living on indoor or greenhouse plants. You can find them grouped underneath leaves, where they feed on the plant’s sap. But can these parasitic insects kill your plants?
Whiteflies can kill plants if the infestation is severe. This typically happens during summer, when the warm weather helps them to multiply rapidly. If the plant is dehydrated, malnourished, or diseased, whiteflies are more likely to attack it and eventually kill it.
Read further to find out how whiteflies kill plants and discover some useful tips for getting rid of and preventing them.
How Do Whiteflies Kill Plants?
Whiteflies kill plants by damaging them when they feed on the sap. This causes the plant to lose chlorophyll, absorb energy inefficiently, and weaken. Whiteflies also secrete sticky honeydew, which causes sooty mold and attracts other pests, further weakening the plant.
When whiteflies feed on plants, they penetrate the phloem (sugar-rich tissue that moves nutrients from the leaves) and leave toxic substances in the plant tissue. In severe whitefly infestations, the plant tissue weakens and dies rapidly.
How To Get Rid of Whiteflies
Now that you know how whiteflies can damage and kill your plants, how do you eliminate them?
Here are 6 ways to get rid of whiteflies:
- Wipe them off the plant
- Spray your plants with water
- Use an organic insecticide
- Put out sticky yellow traps
- Use citrus fruit rinds
- Introduce firefly predators
Let’s look at each solution in more detail.
1. Wipe Them off the Plant
If you notice tiny, white, and triangular insects underneath your plant’s leaves, they’re probably whiteflies. The easiest way to get rid of them is to wipe them off the plant. Try to gather them into your cloth so you can relocate them far away from the plant.
This removes them temporarily and prevents them from damaging the plant further until you find a more permanent method.
2. Spray Your Plants With Water
Spraying the whiteflies with water dislodges them from the plant and can drown and kill them. It can also help remove eggs or young whiteflies, which depend on the host plant for food.
The best way to do this is with a spray bottle, which offers good accuracy. When watering your plants, make a habit of inspecting your plants for whiteflies, and always remove any that you detect.
3. Use an Organic Insecticide
Chemical insecticides used to be effective against infestations, but whiteflies have developed resistance to them in recent years.
Homemade or shop-bought organic insecticides work well and are suitable for growing vegetables or fruit. There are many options to consider:
- Organic dish soap and water. You can make a homemade insecticide from soap and water by combining equal parts of water and organic dish soap. Allow the soapy solution to sit on the leaves for half an hour. This will suffocate the whiteflies and help remove any honeydew residue from the leaves.
- White vinegar, Castile soap, and water. Fill a spray bottle with two parts water, one part Castile soap, and one part white vinegar, and apply it to the affected areas. Since whiteflies are most active in the early mornings or evenings, try applying it at these times for maximum efficacy.
- Horticultural oil. The most popular horticultural oil is neem oil. Its active ingredient is azadirachtin, a potent insect repellent. You can apply neem oil with a spray bottle or by wiping a saturated cloth onto the plant.
- Essential oil. Essential oils, such as jasmine oil, aren’t toxic to plants, so you can use them as a natural insecticide. The oil will repel the whiteflies and remove any eggs on the leaves.
4. Put Out Sticky Yellow Traps
Whiteflies love yellow flowers and will mistake a sticky, yellow trap for a food source. After flying into the trap, they won’t be able to escape, making it an excellent method for removing whiteflies.
You can buy or make sticky yellow traps. The Gideal Dual-Sided Yellow Sticky Traps from Amazon.com come with twist ties, allowing you to attach them to your plant. They are also non-toxic and waterproof.
Making your own yellow sticky trap is easy:
- Find a yellow, letter-sized piece of cardboard (or paint white cardboard yellow), and punch a hole at the top.
- Cover it with petroleum jelly or honey.
- Thread some string through the punched hole and attach it to the plant.
- Replace it with a new one once it has trapped enough whiteflies.
5. Use Citrus Fruit Rinds
Citrus fruit contains limonene, a powerful whitefly repellent. The highest concentration of limonene is in the rind, so remember to keep the peel after eating an orange or grapefruit.
To get rid of whiteflies, place pieces of citrus rind on top of the soil or hang them from the branches.
An extra benefit of using this method is that your greenhouse or garden will have a subtle citrus fragrance.
6. Introduce Whitefly Predators
If you have a whitefly infestation in your greenhouse, you should consider introducing whitefly predators, which will eat the whiteflies and their eggs. Examples include:
- Pirate bugs
- Parasitic wasps
- Green lacewings
You can buy whitefly predators from natural pest control companies and some nurseries. These insects eat whiteflies rapidly, so you can expect to see results within a day or two.
How To Prevent Whiteflies
You can prevent whiteflies by keeping your plants healthy, controlling ant colonies, and quarantining new plants. Planting alliums or marigolds and using reflective mulch are also effective prevention methods.
Let’s discuss these methods in more detail.
Keep Your Plants Healthy
Whiteflies have an orderly way of consuming a plant’s sap—they will remove the sap from a leaf completely before moving on to the next one.
Whiteflies will feed on the weak leaves if the infestation is new. They’re also attracted to visibly unhealthy plants, which makes reaching the sugar-rich tissue easier.
Keeping your plants healthy by fertilizing them and removing dead leaves can deter whiteflies.
Control Ant Colonies
Controlling ant colonies is an effective whitefly deterrent. Large ant colonies attract other insects, including whiteflies, as it implies that they have a sugar-rich food source.
You can control ant colonies by spraying your plants with peppermint oil or sprinkling black pepper over the soil. Both substances repel ants.
Quarantine New Plants
Many whitefly infestations occur when people introduce new plants to their garden or greenhouse.
When buying new plants, inspect them closely for whiteflies, and quarantine them for a week before placing them in your greenhouse or planting them.
Plant Alliums or Marigolds
You can prevent whiteflies from making a home on your plants by planting marigolds or alliums.
Marigolds contain limonene, a natural whitefly repellent. They thrive in warm and sunny conditions. Consider planting them in your garden during the summer to protect your plants from whiteflies.
Alliums have a potent aroma and can mask the smell of the sap in your plants, confusing and repelling whiteflies. Allium is a genus that includes many kitchen staples, such as:
Use Reflective Mulch
Reflective mulch is usually white or silver and reflects light onto the plant. This confuses whiteflies and causes them to move away from the plant.
Another advantage of using reflective mulch is its ability to improve your plant’s health. Reflective mulch increases the light rays that hit the plant, helping your plant grow and better withstand a whitefly infestation.
Whiteflies can kill plants if the infestation is severe, so eliminating and preventing them is important for any gardener.
You can eliminate them by:
- Wiping them off the plant.
- Spraying them with water.
- Using an organic insecticide.
- Putting out sticky, yellow traps.
- Introducing whitefly predators.
To prevent whiteflies from appearing in the first place, you can keep your plants healthy, control ant colonies, quarantine new plants, plant alliums or marigolds, and use reflective mulch.