Wednesday, January 26, 2011

Pests and diseases: Mealy Bugs

Mealy Bug | Photo Courtesy of

The philodendron you’ve patiently been watching uncurl and stretch new vining tendrils upwards, sideways, and downwards around your windowsills all spring, summer, and fall now looks like it’s been attacked by the local kindergarten class covered in marshmallow fluff. The fluffy white masses you’re seeing stuck all over the plant in front of you are actually eggs laid by a female mealy bug.

Life Cycle: The mealy bug of the Pseudococcidae family, are soft bodied insects, covered with a fine whitish wax. Many species of mealy bugs produce noticeable egg sacks enclosed in a cottony wax, resembling white “fluff”. It’s these white masses that are most often noticed in terminal growth, cracks, and crotches of plants and can contain up to 600 eggs. In greenhouses, females have been observed to lay eggs on non-plant surfaces, and can live more than 2 weeks off the plant. The eggs hatch after 7 to 10 days. The yellowish nymphs, known as crawlers, move about the plant until a desirable site is found for feeding. As in the above picture, mealy bugs are generally oval shaped, having 17 to 18 pairs of short wax filaments (legs) along the side of the body. The body is distinctly segmented, averaging about an eighth of an inch when in last adult stage. Females undergo two molts before becoming fully grown. The rarely observed males undergo an additional developmental stage which occurs in a small cocoon of loose wax. Males are much smaller than the females, have wings, and do not feed. One generation of mealy bug can run full cycle in about a month under ideal conditions indoors.

Plants Affected: Many greenhouse plants are susceptible to these fuzzy little beasts. Some common house plants, such as philodendron, ficus, coleus, fuschia, gardenia, and dracaena are also susceptible. They can be a large nuisance pest in citrus orchards in warmer climates.

Symptoms: Mealy bugs damage the plant in a couple of different ways. They are sap suckers, actually feeding off the sap in the living plant. The saliva secreted into feeding wounds by the mealy bug causes systemic damage as well, particularly in new growth. Like spider mites, mealy bug damage can cause distorted growth and premature leaf drop. Honeydew excreted by feeding nymphs and adults further degrades the plant's appearance and supports the growth of a sooty mold fungus.

Control: There are several means of control for mealy bug infestations. A quick look at household plants when watering is a very effective preventative control measure. In larger greenhouse settings, placement of “sticky” cards among plantings can be a quick and efficient preventative monitoring control. The sticky cards come in colors found attractive to particular nuisance pests and are coated in a VERY sticky glue. Basically the crawlers find themselves stuck to the cards as they move from one host plant to another. The cards are checked when conducting usual scouting practices. Here at Johnny’s we’ve made sticky cards available to our customers, but they can be found in garden centers or purchased from biocontrol vendors. If you are able to spot the start of a mealy bug infestation by eye when watering your plants, control can be achieved by squishing the pests in between your fingers.  Should you not catch the pest problem while the threshold is low and minor, there are other routes to solve this problem.

Beneficial Insect releases are by far one of the safest, non-chemical impact courses of action. Green Methods in NH has the “Mealy Bug Predator” or Cryptolaemus montrouzieri available as an effective biocontrol for mealy bugs. With their dull orange head and thorax, and shiny black body, these “friendly” bugs prefer to feed on mealy bugs. When using a biocontrol, make sure to follow the vendor’s enclosed release instructions thoroughly for optimal performance.

Should you be looking for a chemical method of making a mealy bug infestation obsolete, Safer® Insect Soap is a product we have available here at Johnny’s Selected Seeds. The active ingredient being potassium salts derived from fatty acids, Safer® Insect Soap is a safe, organic sprayable concentrate that’s easy to use. This can be applied to household plants with very little to no risk to household occupants, and is not a long residual pesticide. Be sure to follow label instructions thoroughly when handling, mixing, and applying any type of pesticide.


Article by Sonya Reynolds, Greenhouse Coordinator, Johnny’s Selected Seeds

1 comment:

tj said...

...Very helpful! Thank you.

...Blessings... :o)