Master Gardener: What is this white substance on my houseplant?
Master Gardener Laura Simpson writes about gardening in Southern California each week.
Q. I’ve noticed this white substance on my majesty palm, which is an indoor plant. I wipe them off, but they keep coming back. What is it and how can I get rid of it?
Cottony cushion scale is a common houseplant pest. It also appears on outdoor plants, particularly citrus. It is a soft-bodied sucking insect that likes to hang out near the base of leaf petioles or, in the case of palms, in the nooks and crannies of the growing tips. The body of the insect is orange-brown, but the large white egg sac is the recognizable part. It can contain up to 800 eggs which hatch into crawlers within a few days during warm weather. These crawlers migrate to leaf veins and begin to grow their own egg sacs. Females do not need a mate to reproduce, so their population can grow quickly.
A cottony cushion scale infestation can cause a plant to lose vigor, especially when the infestation is severe. They also produce honeydew, a sticky substance that attracts ants. Outdoor plants tend to have limited problems with these insects since there are many natural predators that will readily feast on them. An indoor infestation can be more difficult to eradicate.
If there are only a few scales, use a Q-tip soaked with rubbing alcohol and simply wipe away any visible insects. This process may need to be repeated every few days as new insects emerge. Horticultural oil or insecticidal soap may be effective, but spraying may not reach the culprits. A severe infestation may not be treatable, so you may have to discard the plant and start over.
Q I have an orange tree that was in the backyard when I bought my house 10 years ago. It’s a naval orange but I’m not sure of the age. It was not very well cared for, but I was able to bring it back to life through the years. It has given us very sweet oranges and makes wonderful juice.
In the past 3 seasons, it has gone through different changes. One year it had nice thick green leaves but only grew fruit on one side. Last season’s leaves were sparse and yellow and the fruit was small. This season we had the most flowers on it I ever seen but it’s the sickest I’ve ever seen it. It lost a lot of the tiny oranges but the ones that stayed on look healthy. The tree keeps losing leaves and getting yellow. I fertilize it twice a year and water it with 10 gal of water every weekend.
I haven’t seen any kinds of pest on or around it.
During the summer, a citrus tree could require 40-60 gallons of water per day, depending on the size of the tree and how well the soil drains. Drip irrigation with 2 or 4 micro sprinklers placed along the dripline (where the tree canopy ends) is the most effective way to water citrus. I think your tree may be a bit thirsty.
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