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St. Louis, Missouri
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Each monthly issue of the Henry Shaw Cactus Digest includes club updates, columns and articles by members on their favorite aspects of cactus and succulent culture. Follow the link below this item to read select Digest articles -- or join HSCS to receive every article in the print version of the Digest.
By Joe Merkelbach
Mealybugs are probably not the most injurious pests to afflict cacti and succulent collections, but they can be among the most frustrating and irritating.
Mealies are members of the Hemiptera order of "true" bugs, which is characterized by gradual development without major form changes, as opposed to orders such as butterflies that have major body form changes from caterpillar to adult. All forms of mealies, from just born through adult, have a covering of waxy, threadlike projections instead of the harder coverings of other scale insects. The males spend little time as juveniles before developing wings to aid in the business of fertilization and do not do much feeding. The females are termed neonatal in that they retain the form of juveniles all through their life cycle, although they do become less mobile as they grow.
Mealie mouth parts are modified to allow the insects to take in the copious volumes of juices that are needed to provide proteins. The sticky, sweet excretions left behind are the result of this need to process lots of plant juice.
Plants summering outside can gather large groups of ants that use these secretions as a food source, and black molds can also grow on these areas. Although mealies usually do not do enough damage to kill plants, they are unsightly and can stunt healthy growth.
Recesses and crevices are very attractive to the pests, so they can be difficult to eradicate. Single insects caught in the open can be easily crushed, and a Q-Tip loaded with an equal blend of water and isopropanol is a good weapon to dispatch the critters.
Vigilance is a good approach for warding off mealies, as they are easier to deal with in small numbers. A big population hidden beneath a thick coat of cactus spines is a daunting task to remove. Root mealies can be dealt with by shaking off soil, washing the roots to remove the bugs and using a Q-Tip to polish off the bitter-enders.
There are some systemic chemicals that can be used on really serious mealybug infestations, but I would advise consultation with experienced members of HSCS or garden supply personnel for direction on their proper use.
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