Plant Pests

The Pelargonium’s Top Terrorist: The Root Mealy Bug

Perhaps nothing is more destructive to the pelargonium as the root mealy bug.  Like a terrorist they hide underground, suck the energy out of a population, and spread slowly but surely throughout a large host range of plants, causing great losses over time.  Adult root mealy bugs are small, oval-shaped white pests that can be found attached to the roots when sedentary, or crawling within the soil, saucers and benches when mobile.  Females crawl to a root where they feed off of the root’s nutrients and eventually lay several eggs, which later hatch, grow, and this cycle repeats on.  This mass of offspring is often seen as a cottony, fine white meshwork. 

On a dark coloured pot, this can be seen as whitish residue on the sides (sometimes there is a tinge of blue), but root mealy bugs may also be hidden deep within the center of the soil/root mass.  When watering, eggs and adults can be flushed out of a pot, where they travel to another to infect, crawling inside the drainage holes to set up residence once again.  More recent evidence has shown that the male root mealy bugs can fly during their mating stage, and some growers have even stated theories that they may also carry eggs to another location.  The eggs can stay dormant for extended periods of time within recycled soil, or attached to the sides of a reused pot.  The bottom line with these bugs is that they are TOUGH to eradicate. 

Whenever dealing with any serious pest for the long run, IPM (Integrated Pest Management) is the best approach, as it incorporates several different techniques to tackle pests of all sorts.  The main categories of IPM are: Cultural, Biological, & Chemical. 

                                                                                                           

Culturally, there are many things we can do to prevent the spread or importation of root mealy bugs.  If you have a serious problem, take many cuttings, and pitch the older plants.  Sterilize the growing area well with bleach & water or rubbing alcohol.  Its best to do this a few times over the summer months when you can empty the area easily.  Throw out the infected pots/soil in a sealed garbage bag.  Make sure you don’t cross-contaminate your new cuttings, and isolating the new growing area as much as possible is recommended.  Be aware that plants in soil from garden centers, or even un-sterilized potting soil can be a source of re-infection.  Get a high quality growing mix, and sterilize it when in doubt.  Investing in brand new pots when sterilizing your collection is also a good idea.  Your new cuttings will have greater vigor without the mealy bugs, and after a few months you will be taking cuttings off of them.  Also, as shameful as you may feel, inform other people that may have received an infected plant from you, as ignorance hurts us all.  Similarly, let any grower know if you find pests lurking on a plant you receive from them.  Even better: Only accept cuttings when acquiring a new specimen!!!  This is the best rule of thumb.  Its an honor to be given plants from somebody, but there should be no shame in requesting cuttings only, or by taking cuttings off of a plant, while throwing out the rest. 

Biologically I am sure some predators eat the soil mealy bug, but trust me, forget about this IPM category.  Chemically, only one is proven to work well: Enstar II.  It’s a concentrated chemical that kills all stages of the soil mealy bug as a drench.  Each pot is submerged into a solution and thoroughly saturated.  Follow the directions carefully, and take all the precautionary measures explained in the accompanying pamphlet. You will notice improvements fairly quickly, and once repeated again you should have your collection clean.  Good luck!