Preventing Mealybug Infestation

mealybug prevention

Regular observation and timely corrective actions are the keys to preventing mealybug infestation that unchecked can kill your affected plants. A staff member’s Desert Rose appeared pest-free during May’s dry weather, but in June quickly became heavily infested with multiple stages of the mealybug life cycle. Silky cocoons appeared at the base of stems and flower buds as adult females scurried about and immature crawlers (nymphs) settled into gelatinous protected coverings littering the leaf surfaces with ants on patrol protecting and farming them. While feeding with their piercing mouthparts mealybugs excrete toxins into the plant and dump their honeydew waste on leaf surfaces that attract ants and fungus that in turn reducing sunlight and required photosynthesis for the plant.

What do mealybugs look like?
Mealybugs in their immature nymph stages look like scale and are closely related to them and aphids. Over 275 species of mealybugs are distributed everywhere in the world except Antarctica. Mealybug adult females are oval, white, and mobile, while mouthless winged adult males are rarely seen during their one or two-day life span that’s spent focused strictly on mating.

Where do mealybugs live?
Mealybug occurrences are common in the garden and on houseplants with the mobile females scurrying about under leaves, around their silky cocoons, stems, even plant roots with mealies readily moving from one plant to another. Mealies feed on many ornamental plant varieties, citrus, lawn turf and threaten greenhouse horticultural operations. They also have a highly specialized commensal relationship that ecologists find fascinating. “In this study, the fire ant Solenopsis invicta was found to take advantage of the shelters constructed by the leaf roller Sylepta derogata to protect mealybugs (Phenacoccus solenopsis) against their natural enemies,” according to scientists at the South China Agricultural University, Guangzhou, People’s Republic of China. “This protective effect of fire ant tending on the survival of mealybugs in shelters was observed when enemies and leaf rollers were simultaneously present. Specifically, fire ants moved the mealybugs inside the shelters produced by S. derogata on enemy-infested plants.”

How do I get rid of mealybugs?
Regular observation and having an action plan for dealing with threats before they get out of hand is the best approach to preventing mealybug infestation and resulting damage. Mealybugs can be removed manually and sprayed into a bucket for removal to avoid the same individuals returning to re-infest plants. Besides strictly using water Insecticidal soap and horticultural oil provide the next lowest environmental impact in mealybug management having no residual toxicity after dry that as a result protects other beneficial insects and pollinators. Neem tree seed extract is commercially available as neem oil containing azadirachtin that kills mealies, but is indiscriminate also killing beneficial insects and is moderately toxic to fish and amphibians, requiring overspray protection for water bodies and other potentially impacted areas.

Insecticide treatment options include Bonide systemic insecticide containing dinotefuran available in granules and spray. Additionally, Ferti-lome Tree & Shrub drench, is an effective foliar treatment for mealybugs, which is taken up by the roots and provides protection internally throughout the year. “Cover-spray applications of broad-spectrum insecticides often lead to secondary pest outbreaks,” according to the University of Florida. “Scale insects and mealybugs are secondary pests that may increase following such disturbances to the ecosystem balances in a landscape. For this reason, we often see more scale insect and mealybug outbreaks in landscapes that have been exposed to intensive broad-spectrum insecticide applications.” Biological controls include Cryptolaemus montrouzieri, a brown lady beetle common name ‘Mealybug Destroyer.’ Their young are able to feed on the mealies without being attacked by the ants guarding them. As with introducing any variety of beneficial insects to the garden, there can be predation of them by other animals and suitable amounts of prey must be available for them to stay.

Neem oil dilution

There are two varieties known varieties of mealybugs that affect turfgrass in Florida. Rhodesgrass mealybugs attack Bermuda and St. Augustine grass. Tuttle mealybugs are believed to mostly impact zoysia grass. “Systemic products like neonicotinoids are preferred because they have longer residual activity inside plant tissue,” according to the University of Florida. “Several combination products that contain pyrethroids and neonicotinoids (e.g. bifenthrin + imidacloprid) may provide initial high knock-down rates followed by longer systemic control.”
Thus, while we cannot expect to permanently rid our lawns and gardens of mealybugs, we can manage their numbers and reduce the damage threat by preventing mealybug infestation. In the case of the staff member’s Desert Rose due to the extent of its infestation neem oil was applied (two tablespoons of neem oil per gallon of water) to leaves, stems, and trunk, which will be repeated in seven to 10 days until satisfactorily under control. Garden Center Manager Matt Barlow recommendation for long-term control is use of the Bonide systemic insecticide as he does with his desert roses, which he’s found has been quite successful.

Mealybugs are a threat to a variety of plants in our Florida gardens. Soft stemmed perennial foliage plants are particularly susceptible to mealybugs such as this clients’ coleus.

For comprehensive solutions to your specific lawn, garden and landscaping need contact Earth Works of Jacksonville online and at 904-996-0712. Happy Gardening!

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