Mealybug Damage: Signs to Look Out for

Mealybugs and other insects with piercing-sucking mouthparts, like aphids, feed directly from the host plant vascular system. Feeding from this pest can lead to wilted, yellowed chlorotic leaves, premature leaf drop, stunted growth, and even death!! The sugary honeydew secreted from mealybugs as a byproduct of their feeding habit can cause sooty mold to grow on plant surfaces, hindering photosynthetic capability. The honeydew can also attract ants to the situation which can lead to distribution of the mealy pest.

 Options for Control:

For small infestations, a light isopropyl alcohol solution spray can help kill some of these pests on contact without damaging your plants. Mechanical removal by washing plants with water can help significantly as well. These pests are great at getting down into plant crevices and hidden points in new growth that will help keep the covered from sprays and washes, not to mention their waxy coating can also act as a barrier to sprays. Another defensive behavior that has been observed is the egg laying, adult female Mealybug covering stage 1 and 2 instars when sprays are being conducted.

Commercially, we can offer an entomopathogenic fungi such as Beauveria bassiana to help with mealybug outbreaks. Some of the products that we offer including this fungi are Velifer, Botanigard MAXX, Mycotrol, and BioCeres. Another successful biopesticide that we offer is the beneficial fungus product NoFly. This contains the fungal organism Isaria fumosorosea and works wonders for mealybug control. Long Shadow does include mealybug on its label but comes with caveat that cinnamon oil can be highly phytotoxic, so use caution and do a test before spraying everything.

Cryptolaemus montrouzieri are the best biocontrol option. These adults and their larvae are both predacious and a single Cryptolaemus can eat up to 250 small mealybugs over its lifetime. Their larvae do look oddly similar to the mealybug, although they appear a bit “harrier”, are much larger, and eventually turn into an adult Ladybird Cryptolaemus. They spend about 2-3 weeks as larvae and can live over a month as an adult. This gives them close to 50 days of life, which is pretty long compared to other beneficial predators. They may be more effective against citrus mealybug because they are known to lay eggs in cottony masses. The long tailed mealybug is still a good prey option for the Cryptolaemus but are not known to lay eggs which is an easy target for the predator. The predators will likely go after younger mealybugs first. The Cryptolaemus is a specialized predator so its’ main focus will be the Mealybug.

Chrysoperla rufilabris, or the Green Lacewing is a generalist predator that will eat just about anything (including its own kind!). These predators have shown success in controlling mealybugs and can be a cheap option for coverage of multiple pest issues.

Mealybugs can reproduce without mating, like aphids and each female can lay up to 350-600 eggs. The mealybugs can each live for around a month and will do damage the entire time. Some mealybugs can also be found colonizing in soil so scouting root masses can be an integral part of monitoring and control.

Sources of this information are:

-New Zealand Landcare Research

-NC State Extension

-University of California IPM

-University of Florida Entomology Department 

Cryptolaemus montrouzieri is the most commonly used biological control for mealybugs. Cryptolaemus is used to control mealybugs mainly in interior plantscapes. They can be used outdoors, but will not survive sub-freezing temperatures. To keep mealybug populations down to acceptable levels in greenhouses, several releases of Cryptolaemus may be necessary, particularly during winter months. They are less effective on longtailed mealybug (Pseudococcus longispinus) because this species lacks the cottony masses Cryptolaemus requires for egg laying.