Mealybugs Deconstructed

Organic Strategies for Effective Mealybug Control

Mealybugs have made quite a name for themselves. The tough guy on the block. Taking over plants, greenhouses and crops in a single season. Covered in a protective bullet-proof coat. They may seem insurmountable, but here are some tips to help you take down this pernicious pest. Let's deconstruct the mealybug. 

The term 'mealybug' was first used around 1820 to describe a bug covered with a waxy white material resembling cornmeal or flour. This fluffy material protects them from excessive heat and moisture loss. Mealybugs are similar to scale insects, but without the shell and they can move around. The females protect themselves with a waxy cottony coating and are found in ornamental crops indoors and outdoors around the globe. They feed on plant juices and can also vector disease. Male mealybugs resemble tiny flies or gnats with long tails of white wax. Very young nymphs are flat, oval and yellow, acquiring the white waxy coating as they age. They mature in 6-10 weeks, ready to start the life cycle all over again. The females die soon after giving birth. 

Females do not fly and must be transported to new host plants by crawling across the leaves or transported by an animal or human. They tend to feed on stems and can produce copious amounts of honeydew. Honeydew will attract ants and these ants may be your first sign that you have a pest problem. Avoid using excess nitrogen when fertilizing as this can lead to higher egg production. 

Immature mealybugs can travel on the wind outdoors. Mealybugs are easy to overlook when their numbers are small as they prefer to hide out in cracks and crevices and underneath leaf surfaces. But once they start to reproduce, it's a population explosion with one female producing 100-600 eggs which hatch into nymphs which leads to a mealybug infestation.

The Usual Suspects

Citrus mealybug (Planococcus citric) Perhaps the most common species found in ornamental horticulture, often found on succulents, coleus and citrus. Females are oval and covered in the classic white waxy coating. They may have a darker line down their back. Citrus mealybug inject a toxin while feeding, causing deformation of the plant surface. After mating the females lay 200-600 eggs in a fluffy but dense egg sac. They are also found on fuchsia, jade, poinsettia, rosemary, bird of paradise and cactus. 

Longtailed mealybug (Pseudococcus longispinus) This species is commonly found in conservatories. Two distinctive characteristics of this species are the peripheral filaments extending from their body, two long tails and their ability to give birth to live young. Draceana is a favored host plant.

Root mealybug (Rhizoecus spp.) found on the roots or in the soil making them difficult to see and treat. 

Madeira mealybug (Phenacoccus madeirensis) are slightly grey with less noticeable waxy secretions on top. 

See more photos of the different types of mealybugs at this University of Florida website. 

Beneficial Insects for Mealybug

The mealybug destroyer says it all in the name. Cryptolaemus montrouzieri is a  biological control agent that targets mealybugs with both the larvae and adults feeding throughout their life. This tiny lady beetle has a dark brown body and orange head, but the larvae are another story. They actually resemble their prey and are covered with a white waxy coating (bottom right photo). They will go after mealybug as soon as they are released (bottom left photo). 

 

Lacewings, both Green Lacewing Larvae and Brown Lacewings, are generalist predators that will feed on an assortment of pests, including mealybug. 

Anystis baccarum, the Crazee Mite, is another generalist predator that can be used in combination with the above biocontrols and can help knock down a population of mealybug. 

Treatment

The best way to discover mealybugs is to visually inspect susceptible plants. Scout for pests on a weekly basis. Look under leaves, in stem crotches, in leaf folds and other tight locations. Mealybugs prefer nitrogen-rich lush foliage, so avoid over-fertilization. Since mealybugs love Coleus, consider using a red coleus as a trap or early detection plant. 

• Weed management is critical to keep mealybug populations down. Continually remove weeds that may harbor pests.
• Sanitize greenhouse surfaces where mealybug may be hiding out. They can live for up to two weeks without food on metal benches or plastic pots.
• For small areas, wipe off pests with a cotton ball or cloth dipped in rubbing alcohol. 
• A strong spray of water will dislodge many mealybugs. This is especially useful for woody plants. 
• Prune out heavily infested plants and immediately put trimmings in trash.
• Dispose of plants that are over 30% covered in mealybug. 
• Repeat spray with a rotation of the organic insecticides below. Try for thorough coverage and hard to reach places where mealybugs may be hiding. 
• Utilize pheromone lures to trap the male mealybugs and slow down the reproductive rate. Combine with red sticky traps. 

Organic Insecticides 

The cryptic behavior of mealybugs creates a challenge when spraying. It's hard to reach them! Good coverage can be achieved by getting close to the plants and slowing down while spraying. Early instars are the most susceptible stage to insecticides, so know the life cycle of this pest and look for those very small crawlers before spraying. If plants are over infested with mealybug, the best strategy is to dispose of the plant and start over. 

• M-Pede Insecticidal Soap - Provides broad spectrum protection against soft bodied insects, including mealybug. Kills on contact. 
• Suffoil X Spray Oil Emulsion - Suffocates mealybug in all life stages. Odorless and non-toxic.
• Circadian Sunrise - Horticultural spray oil containing corn and peppermint oils. Suffocates pests. 
• Pyganic Botanical Insecticide - Organic contact insecticide with a rapid knockdown. Contains pyrethrins which are derived from Chrysanthemums. 
• NoFly Biological Insecticide - Microbial contact insecticides. OMRI listed. Contains active ingredient Isaria Fumosoroseus, a naturally occurring fungus. 
• Velifer Biological Insecticide - Contains the beneficial fungus Beauveria bassiana and active against all life stages of mealybug. Direct contact necessary. 
• Botanigard Biological Insecticide - Broad spectrum mycoinsecticide containing Beauveria bassiana.  This is a contact insecticide - spores infect directly through insects cuticle. Note! It's critical for temperature and humidity to be optimal for fungal products to be effective. 
• Azaguard Botanical Insecticide - Contains azadirachtin which acts as an insect growth regulator, antifeedant and egg laying deterrent.
• Azatin O Biological Insecticide - Contains azadirachtin. Insect growth regulator used to control larval stages of insect pests, including mealybug. 
• Molt-X Botanical Insecticide - Contains azadirachtin which is highly successful when combined with a mycoinsecticide such as Botanigard. 
• Protection Plus Natural Insecticide - Uses a citric acid base to destroy mealybugs and kills on contact. See video below. 

For further information, see our Mealybug Tech Sheet. 

Mealybug Management in Greenhouses and Interiorscapes, Kansas State University