The bugs are coming, the bugs are.....??  GONE???


By:  Michael J. Green


The most common pest that attacks cactus is, unfortunately, humans. Next are the mealy bugs, and those we can treat without incarceration. There are many different families / genera of mealy bug. Some are host specific, others are less discriminating in their tastes. Mealies are a major crop hazard for grapes, citrus, sugarcane, pineapple, coffee trees, ferns, and orchids. Other sources also list rice, coconut, bananas, tapioca, cotton, ornamentals and arecanut amongst the victims. More and more experts are beginning to call mealy bugs another group of “scale”. Mealy bug and scale, as well as aphids, are members of the same order: Homoptera. There are three distinct families of scale insects. These are: (1) Coccidae, which are soft scales; (2) Diaspididae, which are armored scales; and (3) Pseudococcidae, which includes 275 different species of mealybug in the United States alone. With the exception of biological controls, all three families can be treated the same.


Mealy bugs are only 1 to 4 millimeters long and the body is usually covered with a white cottony or mealy wax secretion. The plant appears to have small spots of cotton, particularly when the female is laying eggs and producing an ovisac to cover and protect the eggs. Mealybugs generally have an oval body outline. As immatures, male and female mealybugs look alike, but as adults they are quite different. The adult male looks more like a small two-winged fly. Adult males have no functional mouthparts, live only a day or two, and exist solely to fertilize the females. (xxxxx?)

Mealybug life history does vary depending on the species. The female mealybugs go through four developmental stages or instars and as adults may lay up to 600 eggs, usually in a cottony-like ovisac beneath her body. The eggs hatch in 6 to 14 days and the first instars (or "crawlers", as they are commonly called), spread out to find tasteful feeding sites. They can survive only about a day without feeding, and once they insert their stylets to feed they generally remain anchored permanently. The crawler stage is the most fragile and easily controlled stage in a mealybug's life. Some mealybugs, like the longtailed mealybug (
Pseudococcus longispinus), do not lay eggs, but bear their young as active crawlers. Male mealy bugs go through five instars feeding only in the first two. And all in 48 hours or less.  

For most cactus hobbyists there are three types of mealies: the

spine mealy, root mealy and just plain mealy. The spine mealy is actually Eriococcus coccineus (with a common name of “Cactus mealy bug”), the root mealy is the different Rhizoecus species, and the so called common mealy is either the Obscure mealybug  Pseudococcus affinis, or the Longtailed mealybug Pseudococcus longispinus. 


These are mealy bug remedies found online or in the cactus literature:


Biological control - Introduce Hypoaspis and/or Cryptolaemus (Australian Ladybird)  to the infected plants.  Hypoaspis is a small mite that feeds on small insects, especially mealy bug.

Manual removal - Pick the bugs off manually in plants that are not severely infested or use a strong jet of water (be careful not to damage plants). Or submerge the entire plant, pot and all, in water overnight with 1 oz Safer’s soap per gallon of water.

Manual Removal - Use a 50/50 mix of water and a mixture of ethyl alcohol (95%) and methyl alcohol (%5) to wipe away the bugs. The spirits should kill any remaining pests. Note that in most states you can not purchase ethanol itself or even methanol in some jurisdictions. Methanol is toxic; the 5% is supposed to make it very “unsatisfying”.  Or..

Use a Q-tip with rubbing alcohol (70% iso-propyl alcohol in water).


Systemic (“chemical”) pesticide options:


Malathion : Neem Oil Mix 0ne teaspoon each per gallon of water


Malathion : Volk Oil Spray one tsp each per gallon of water


Dimethoate spray 1 tablespoon per gallon of water. For a root drench use 1 ounce per gallon


Imidacloprid one tablespoon per gallon of water

(Marathon is another trade name for Imidacloprid, it’s also in Bayer Advanced Plant Care, Tree & Shrub).


Magical Mealybug Mix(Terrific Garden Tonics Jerry Baker p327)

Option 1: 1.5 cups of brewed black tea, 1 tsp baking soda, 1 tsp dishwashing liquid, 1.5 cups water and Option 2: 2 tbsp each of corn oil and dishwashing liquid in 1 gal water


A home mealy bug and scale recipe from way back:

16oz 409, 8oz rubbing alcohol, add water to total 1 gallon. Shake up and put into spray bottle. Spray plants thoroughly.


And, of course, the “Those Pesky Mealy Bugs” recipe seemingly distributed at every cactus group: 4 pts 70% rubbing alcohol, 8-12 drops of Ivory dish soap, 8-12 drops Tabasco sauce, fill to  1 gallon with water. Great for those mealy’s with real taste.


For all sprays: Spray until the plant is dripping wet. Repeat weekly for three weeks to take care of the eggs, larvae and adults. Even diluted, Malathion will kill crassula.

      Eriococcus coccineus  
              United States National Collection of Scale Insects Photographs Archive, USDA ARS,
      Rhizoecus cacticans
               United States National Collection of Scale Insects Photographs Archive, USDA ARS,
    Pseudococcus longispinus  

   David Cappaert, Michigan State University,