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Mealy bugs are destroying my young citrus! What do I do?

Cheri Abraham, PhD
Entomologist & Operations Manager,
US Citrus, LLC

 

Mealybugs are one of the most common pests on indoor plants in general and even on citrus plants grown indoors or in greenhouses. They look like white fluffy substances that mostly congregate on tender leaves.

Mealybugs actually are tiny soft-bodied insects. Females lay eggs in a yellow pouch out of which the young ones (crawlers) emerge. This is the stage when these insects are most susceptible to any chemical control measure. As times goes by, they secret a white fluffy outer covering, which essentially acts like a jacket, preventing chemicals to penetrate and kill them. This is simply why mealybug control becomes a difficult task in many situations. Often attracted to lush green and soft plants, mealybugs use their piercing and sucking mouthparts to feed on plant fluids. The feeding itself can cause defoliation and stunted growth. Further, they secrete honeydew which causes fungus to grow as a secondary infection and also have ants grow into a symbiotic relationship with the mealy bugs.

If you miss the white fluffy congregation on the plant, you will definitely catch the black coating on leaves, and that observation by itself could throw off the control measure. Since the black color is a fungus, often times, people apply fungicides, but as long as the root cause remains, the secondary infection cannot be controlled completely.

When Ants get into a symbiotic relationship with the mealybugs, they protect the mealy bugs in exchange for the honeydew (sugary solution) that is secreted by the mealybugs. This often times also defeat natural or augmented biocontrol.

More often than not, on plants grown outdoors, mealybug populations do not increase to an extent that warrants active control measures unless there is a factor working against. A prime example would be pesticide sprays that kill existing populations of natural enemies.

How to rid your plants of mealybugs.

Oftentimes, a healthy plant is a first step and the best defence against mealybugs. In situations where plants are crowded and overly moist, a humid pocket does build up and favor mealybug populations as well.

If you already have mealy bugs, there are different ways to go about getting rid of them.

  1. Mechanical: by spraying water with some pressure, you will be able to dislodge the mealy bugs off the leaves. This would have to be repeated as often as you check and find mealybugs on the plant.
  2. Biocontrol/ Natural control:
    1. Ladybeetles,
    2. parasitic wasps,
    3. lacewings

All three mentioned above are natural enemies of mealybugs. They can be purchased and released in your greenhouses. They will be less suited for an indoor (inside the house) growing situation. Something to be cautious about: the presence of ants protects the mealy bugs from these natural enemies. So the Ants need to be controlled before releasing natural enemies.

4. Entomopathogenic fungus like Beauveria bassiana: is applied like an insecticide but contains the fungus that would control mealy bugs.

  1. Chemical:
    1. Organic:
      1. Soaps: 1 tsp of hand soap or detergent soap in a gallon of water. Avoid any additives or fancy ingredients.
      2. Botanical Oils: Neem oil derivatives sprayed at the label rates can keep the plant clean and free from mealybugs. Also available are oils extracted from other plants like Rosemary and other herbs.
      3. Homemade sprays: Various homemade concoctions using vinegar, hot sauce and garlic are effective to control mealybugs and other pests.
      4. Pesticides: Spinosad is an organic option for chemical control. Follow label rates.
    2. Inorganic:
      1. Pesticides: Systemic pesticides (like Imidacloprid, which is the chemical name) that move inside the plant are your best bet. Once the white fluffy substance covers the mealy bugs, it is difficult to get control using chemicals. This warrant sprays every week in an effort to hit the newly emerged crawlers, which are most susceptible to insecticides.

If there are just a few mealybugs here and there, you can just pinch the plant portion containing the mealybugs and trash them in a ziploc bag. If you are more of a bug enthusiast, you could watch them a little closer and marvel at the intricacies of their life cycle!

Suggested readings:

Integrated pest management of mealybugs

Managing mealybugs in greenhouses

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