How to Stop Mealybugs From Destroying Your Fruit Trees, According to Gardening Experts

Fruit trees face their share of pests and diseases, but mealybugs are a particularly troublesome pest. These insects most commonly bother citrus trees or trees grown in greenhouses, but in some tropical or subtropical locations, mealybugs can also damage other types of fruit trees. If mealybugs are wreaking havoc with your fruit trees, here are some expert-approved ways to help.

How to Identify Mealybugs

Protecting your fruit trees from a mealybug infestation starts with recognizing the culprit. "Mealybugs are small insects that feed by sucking plant juices," says horticulturist Carol Allen. "They have a fuzzy, waxy outer cover, and you will often see more than one at a time."

There are different species of mealybugs, and they are usually a few millimeters long, but their size varies depending on the life stage, according to Allen. She adds that long-tailed mealybugs and citrus mealybugs are the types generally seen in the Mid-Atlantic. 

Signs of Mealybug Damage on Fruit Trees 

It is easier to identify mealybug damage when you understand the behavior of this insect. "Mealybugs are a piercing, sucking insect that goes right for the active living tissue in all plants that they are found on, including fruit trees," says certified arborist Eva Monheim.

She explains that the plant becomes depleted of nutrients, resulting in yellowing or discoloration, followed by a slow decline in growth and overall vigor of the tree. "Fruit will drop because the nutrients that are being depleted weaken the tissue in the developing fruit. Leaves will yellow and sometimes exhibit unusual coloration," Monheim says, adding that in the case of severe infestations, leaf drop can also occur.

If you're seeing these signs, it's time to dig deeper. "Mealybugs can be found on the midrib of the underside of the leaf and are usually not mobile when they are feeding," says Monheim. "The insects are usually easy to spot, or they may be the color of the bark, but will be bumpy in appearance en masse. Using a butter knife, you can see if you can scrape them off." She says that another visual effect is a sooty mold that grows on the juices the mealybugs are sucking from the tree and then excreting.

How to Stop Mealybugs From Ruining Fruit Trees 

Thankfully, you don't have to just stand by and watch as the mealybugs continue damaging your trees. Many all-natural options can help stop the infestation and protect your trees from further harm.

Spray With Water

Sometimes it's best to start with something simple. "As an integrated pest management practitioner, for control, I will start with the least toxic and most effective means of control, and that is a strong stream of water," says Allen. "I'll use a little finger pressure to wipe them off as I spray the water over leaves and twigs." Repeat regularly to reduce the overall population, says Monheim.

Scrape Off the Bugs

A few objects in your home can be useful for fighting against mealybugs. "If the infestation is in a small area, you can use a butter knife to scrape off the insects and put them in a brown paper bag," says Monheim. Another surprising object that can dislodge mealybugs is a paintbrush. "I use a child's paintbrush to dislodge the smallest mealybugs in the leaf axils," says Allen. "If you do a good, thorough job, you might be one-and-done."

Use Horticultural Oils

If basic remedies like water and brushing aren't doing the trick, you can try using natural products, like a horticultural oil. "Horticultural oils derived from natural products can be sprayed on, or insecticidal soaps can be used," says Monheim. Reapply these products regularly and after heavy rains to control infestations.

Encourage Birds

Birds are great predators that feed on mealybugs, says Monheim. "I love watching birds going up and down my tree trunks, picking off insects to protect the trees from further infestations." Birdhouses, feeders, and birdbaths can help attract beneficial birds. Wrens, chickadees, and similar songbirds may consume mealybugs without any additional effort on your part.

Invite Predatory Insects

Mealybugs also have insect enemies, and some citrus growers purposely introduce these bugs as part of their mealybug management solution. "In the greenhouse or conservatory, you can release natural enemies like Cryptolaemus montrouzieri, also known as the mealybug destroyer," says Allen. These insects don't survive cold temperatures, so they are reintroduced each year as necessary. The parasitic wasp (Leptomastix dactylopii) is another common mealybug predator used as a biological pest control for some species of mealybug.

Prune Periodically

If less severe methods have proven unsuccessful at eradicating mealybugs, you could also consider pruning the affected branches to remove the infestation.

How to Prevent Mealybugs From Coming Back 

Once you eradicate mealybugs, you can turn your attention towards preventing them from returning.

• Prevent tree stress: The best way to prevent mealybugs is to avoid tree stress and irrigate during periods of drought, and plant cover crops under your trees to provide extra nutrients. "Clover is an excellent cover crop for added nitrogen. The clover will also invite beneficial insects to the scene," says Monheim.
• Conduct regular inspections: "Do a weekly inspection of your trees to discover early outbreaks," says Monheim. She also suggests looking for egg masses in April or May when they are being laid on the leaves and bark of your fruit trees. "They are cottony long structures or rounded structures, depending on the type of mealybug. These cottony masses can house hundreds of yellow eggs," she says. "Destroy these egg masses by manually removing them. The eggs start to hatch in or about June."
• Clean surrounding areas: Clean the area around your fruit trees to keep mealybugs away, including the container or basket your tree is in (if it's potted). "Just soap and water will do, but be thorough. Regular scouting pays off if you are growing a mealybug-prone plant."