There are hundreds of insect species known collectively as mealybugs, nearly 300 of which are found in North America. They are small oval sap-sucking insects, 1/10 to 1/4 inch in size, that secrete a powdery wax substance as a protective coating. This coating has a white cottony appearance, making mealybugs easy to identify when they appear on the stems and leaves of plants. Mealybugs are warm-weather insects, so in northern climates they principally a problem with houseplants and in greenhouses and are rarely seen outdoors. In warmer climates, however, they can pose a serious problem for entire crops.
Mealybugs are related to scale insects. They cause damage by sucking the juice from their host plants, and like many pests, mealybugs tend to favor new growth. Over time, their damage causes the leaves to yellow and eventually drop from the plant. They can also cause fruits, vegetables, and flower buds to prematurely drop off. In a bad infestation, their waxy excretions (also known as honeydew) encourages the development of sooty mold fungus.
7 Ways to Get Rid of Mealybugs on Plants
Wash Mealybugs Away
Mealybugs can be dislodged with a steady stream of water. Repeat the treatment as necessary. This is best for light infestations, and some plants do not tolerate this kind of vigorous treatment.
Use Isopropyl Alcohol
Soak a cotton ball with regular rubbing alcohol and wipe it on the mealybugs, which will both kill and remove them. Use a solution consisting of no more than 70 percent isopropyl alcohol, and test it on one leaf before you apply it to the whole plant to make sure the alcohol doesn't burn it.
Spray With Insecticidal Soap
Insecticidal soaps are available on the market (such as Safer's Insecticidal Soap), or you can make your own by using a dish detergent such as Ivory Liquid. Try to find a product free of perfumes and additives that might harm plants. Mix the soap in a weak concentration with water (starting a 1 teaspoon per gallon and increasing as necessary). Spray the soapy solution on plants.
Use Neem Oil
Need oil is a natural substance derived from the neem tree. In addition to its insecticidal properties, neem oil is also a fungicide. When used as directed, it not only kills insects on contact, but serves as a systemic pesticide by being absorbed into the plant. According to the Environmental Protection Agency, neem oil is safe to use on vegetables and other edible plants, as well as ornamentals.
Introduce Predatory Insects
Lacebugs, lacewings, parastic wasps (Leptomastix dactylopii), and a beetle sometimes known as the "mealybug destroyer" (Cryptolaemus montrouzieri), are natural predators of mealybugs. These are more commonly used for outdoor infestations or in greenhouse situations and are available from commercial online retailers.
Use Homemade Insect Spray
To make a batch of homemade insect spray, combine 1 garlic bulb, 1 small onion, and 1 teaspoon of cayenne pepper in a food processor or blender and process into a paste. Mix into 1 quart of water and steep for 1 hour. Strain through a cheesecloth and add 1 tablespoon of liquid dish soap. Mix well. The mixture can be stored for up to 1 week in the refrigerator. Spray the solution on the plant parts where mealybugs are present.
Use Synthetic Chemical Pesticide
A number of stronger insecticides are approved for use against mealybugs, but be cautious when using these chemicals, especially in indoor locations. Stronger pesticides have varying degrees of toxicity to pets and humans.
What Causes Mealybugs?
Mealybugs tend to be drawn to certain plants that are heavy in the juices they prefer to feed on. Citrus trees are particularly susceptible, and mealybugs can pose a serious threat to some commercial crops, such as mango. Mealybugs can infest a number of indoor houseplants, particularly tropical species.
Mealybugs are attracted to plants with high nitrogen levels and soft growth; they may appear if you overwater and over-fertilize your plants.
How to Prevent Mealybugs
Like most pests, the best control for mealybugs is defensive. Healthy, vigorous plants are less susceptible to infestation than weak, underpotted, and stressed plants. As a general rule, make sure your plants are healthy, and you're less likely to attract these pests in the first place.
However, mealybugs can infect even healthy plants. Often, they come in on new plants, because greenhouses are the perfect breeding ground for them. Check any new plant purchases carefully before adding them to your collection.
A number of other strategies can help prevent mealybug infestations on your plants:
- Reducing feeding and watering may sometimes prevent mealybugs since it reduces nitrogen levels and hardens the growth.
- Wiping foliage regularly with a leaf shine solution containing neem oil may prevent mealybugs on susceptible plant species.
- With plants that can tolerate such treatment, regular spraying with hard blasts of water can prevent mealybug infestations from taking hold.
- For indoor plants that can tolerate it, dropping nighttime temperatures to 60 degrees Fahrenheit will discourage mealybugs, which prefer more tropical temperatures.
If an infestation cannot be controlled after two or three weekly applications of insecticide, consider destroying the plant before the mealybugs spread to other plants in your home.
Mealybugs vs. Scale
Mealybugs are closely related to scale insects, but mealybugs are soft-bodied, rather than having the hard protective shells fond on scale insects. Rather than the fluffy, cottony material, scale insects create a hard, barnacle-like coating on the leaves and stems of plants. The methods for getting rid of scale are very much the same as for mealybugs.
How Long Do Mealybugs Live?
Female mealybugs lay from 200 to 600 eggs, which hatch in a few days. Within six to 10 weeks, the hatched insects are ready to lay their own eggs, so an infestation of mealybugs can perpetuate itself almost indefinitely unless they are eradicated.
Do Mealybugs Bite or Sting?
Mealybugs do not pose any danger of biting or stinging humans; they feed only on the juices of plants.
What Plants Are Most Susceptible?
There are so many species of mealybugs that almost any indoor plant can be susceptible to these pests. In particular, tropical plants with softer stems and leaves are very likely to develop mealybugs. Orchids, African violets, begonia, coleus, and amaryllis are among the plants known to be especially susceptible, but in warmer climates, many outdoor plants are likely to experience infestations. Mealybugs thrive at temperatures between 70 and 90 degrees Fahrenheit.