From the Case Files: Scale Insect

What are Scale Insects?

Scale LCIf you’re noticing small white bumps or film on your cactus, chances are it’s a scale insect. There are roughly 8,000 known species of scale insects. Though scale insects can be found on many species of plants, they are particularly fond of cacti. The most prevalent species of scale insect found in the desert southwest are those in the Diaspididae family, commonly referred to as the “armored scale.” This nickname is derived from the scale-like protective covering the insects hide under. The most common scale insect found in Arizona is the Cochineal Scale.

Scale insects attach themselves to plant tissue and suck the juices from the cactus. Their attachment is surprisingly strong and when they are removed, they typically leave a scar behind. Though a single scale insect will do very little damage to a mature cactus, they multiply rapidly and could potentially cover the surface of an entire cactus in just a few days. It’s easy to recognize the infestation by the frosty, white appearance of your plants.

How to Treat Scale

The first step in treating a scale infestation is to physically remove the scale insects from your cactus. DLC’s experts recommend simply using a hose with a pressured spray nozzle. A high pressure setting can remove the insects with ease. However, you’ll want to be careful to avoid damaging the cactus. When spraying the cactus, be sure to to get down in the cracks and under the spines to ensure all insects are removed. After removing the insects, remain vigilant of any additional signs of scale insects as they sometimes find their way back to your cactus. To prevent repeated infestations, treat your plant with a systemic insecticide. Systemic means the insecticide is absorbed through the plant’s roots, therefore entering the plant tissue and making it poisonous to any scale insect that dare take a bite. For best results, DLC’s experts recommend applying the insecticide once at the beginning of the growing season.

Until the systemic insecticide has taken effect, you’ll want to continue to monitor your cactus and remove any scale insects. Some products we’ve found available at local home improvement stores labeled for scale insect include:

  • Bayer Advanced Tree & Shrub Protect & Feed Dual Action Formula
  • Bayer Advanced Insect, Disease & Mite Control

As always, DLC recommends that you follow the directions provided on the insecticide label prior to application.

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