White Bumps & Yellow Spots On Your Plants? This Invasive Pest Could Be To Blame

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If you spend a lot of time caring for the ornamental plants in your garden, it can be heartbreaking to see them not looking their best. Not only do you have to work out what's wrong, but you also have to determine how to fix the problem. One issue you might come across on your leaves is the proliferation of white bumps accompanied by yellow spots. This rather unpleasant-looking problem is caused by an invasive pest from China known as false oleander scale, or FOS (Pseudaulacaspis cockerelli), and it doesn't just attack oleanders. It's probably one of the worst garden pests you'll want to banish as quickly as you can.

False oleander scale is similar to many other types of scale in that the adults, both males and females, have an armored shell covering, and that's what you see as the white bumps. These pests also don't exude honeydew as other sap-sucking insects do. The yellow spots on the leaves are the result of the nymphs sucking the sap and goodness from the plant tissue. Older leaves are more likely to be infested, and the leaves will eventually die and drop off. A heavy infestation of these pests on your plants will result in stunted growth. 

Plants that are most likely to be affected include southern magnolia, camellias, gardenias, sago palms, English ivy, boxwood, banana shrub, and oleander, though there are more than 100 possible host plants. It's also quite a problem in nurseries in the warmer states, as the pest prefers warm temperatures and is most commonly seen in summer.

If only a small part of your plant looks like it's been infected, the best thing you can do is just cut off the affected portions and dispose of them in the trash. This is also the most environmentally friendly solution and one of the best ways to get rid of scale on plants.

Contact insecticides like pyrethrum aren't going to be very effective because they can't get through the armored coating of the adult scale insects. They're really only able to kill the crawlers, which are the nymphs that first emerge from the eggs. Plus, these products are going to harm any beneficial insects that may well prey on the scale, such as parasitic wasps. You can attract these good insects into your garden by having plenty of plant diversity and reducing your use of insecticides.

Horticultural oils have been shown to be quite effective in treating FOS during all stages of their life cycle because the oil suffocates the pests. These products also have a very short residual, so they have less chance of harming those predatory insects you want to protect and attract more of to your yard; Monterey's horticultural oil spray from Amazon should do the trick. The only thing to be aware of is that you may have to spray your plant multiple times to get rid of all of the scale infestation. Be aware that dead scales will tend to cling to the leaves, which are already lost to infection. Spring will bring scale-free new growth, though.

As a last resort, you can use a systemic insecticide that contains dinotefuran, like Valent Safari insecticide. This is applied to the soil around the base of the plant and taken up by the roots to then be transported to the foliage. Insects that feed on the leaves will die after they ingest the materials.