Pest problem with Meyer Lemon plant - Ask Extension
I have a Meyer Lemon plant for 5+ years. Each winter, there is an infestation that is getting worse. It appears to be powdery mildew but also might ...
Knowledgebase
Pest problem with Meyer Lemon plant #862959
Asked March 31, 2024, 9:30 PM EDT
I have a Meyer Lemon plant for 5+ years. Each winter, there is an infestation that is getting worse. It appears to be powdery mildew but also might be another problem too with black and yellow spots. In November, I bring the plant inside. Starting in ~December, leaves start to fall. By April, almost all leaves have fallen. I bring the plant outside, and the leaves return, but all buds drop. And I get no fruit (last year) or just 1-2 lemons in other years. It now has very few leaves, and most of the leaves appear damaged.
What can I do? I tried weekly spraying with Captain Jack's Copper fungicide and Immunox.
It seems hopeless. I am wondering if I should just get rid of the plant.
Please advise.
Howard County Maryland
Expert Response
We don't see any indication of powdery mildew in the photos, but the white flecks visible do look like mealybug, which are very common indoor plant pests. Some brown soft scale might also be present; we can't see enough detail to be sure, but think we see one scale insect in one of the close-up photos. Scale insects are a very common pest of indoor citrus.
Information in each of those linked pages provides management options. Scale and mealybugs are fairly easy to rub off the leaves with fingers or a fingernail, though admittedly it can be tedious if an infestation is heavy. Putting the plant in a shower or large sink to spray the foliage can help not only rinse the insects off (more so the mealybug than the scale) but also rinse any honeydew off, which is the sugary secretion each can produce as a result of feeding. (The black spots pictured look like sooty mold, which is explained on the linked page; it grows on honeydew residue but does not infect the plant itself.)
Sometimes pest populations boom on plants that were stressed prior to the insect's appearance. When indoors during winter, citrus prefer bright light, moderate levels of humidity, and cool temperatures. The soil should become fairly dry between waterings to a depth of at least an inch below the surface; they do not like staying consistently moist. Make sure the container has at least one drain hole in the base to allow excess water to leave the pot. If a pot sits on a saucer, make sure the saucer is drained promptly of any water it collects after watering so the roots don't get over-saturated (since it might otherwise seep back up into the drain holes and keep the potting mix too wet). Our Growing Dwarf Citrus page has more cultivation information.
A fungicide is not needed in this situation, but for any pesticide used, make sure the product is labeled for indoor use; few are, especially among fungicides. The insecticide you mention might only be legal to use outdoors for safety reasons, depending on its ingredient contents; the label details will always say where it is intended for use.
You probably cannot use a systemic type of insecticide for the scale or mealybug if you intend to eat the fruits, since these chemicals are absorbed by the roots and moved into plant tissues. As the pests ingest the poisoned sap, they die off. The product label will include information for treating fruit trees, though, if it is permitted based on that specific product's formulation. Otherwise, only a topical treatment like horticultural oil or insecticidal soap (that must directly contact the insects to work) will help to smother them. Do not substitute a home remedy version of either spray, but you do not need to apply both; pick one. Repeat treatments, spaced as far apart as the label directions instruct (often every 1-2 weeks for several rounds), may be needed to fully suppress the pests.
Miri
Information in each of those linked pages provides management options. Scale and mealybugs are fairly easy to rub off the leaves with fingers or a fingernail, though admittedly it can be tedious if an infestation is heavy. Putting the plant in a shower or large sink to spray the foliage can help not only rinse the insects off (more so the mealybug than the scale) but also rinse any honeydew off, which is the sugary secretion each can produce as a result of feeding. (The black spots pictured look like sooty mold, which is explained on the linked page; it grows on honeydew residue but does not infect the plant itself.)
Sometimes pest populations boom on plants that were stressed prior to the insect's appearance. When indoors during winter, citrus prefer bright light, moderate levels of humidity, and cool temperatures. The soil should become fairly dry between waterings to a depth of at least an inch below the surface; they do not like staying consistently moist. Make sure the container has at least one drain hole in the base to allow excess water to leave the pot. If a pot sits on a saucer, make sure the saucer is drained promptly of any water it collects after watering so the roots don't get over-saturated (since it might otherwise seep back up into the drain holes and keep the potting mix too wet). Our Growing Dwarf Citrus page has more cultivation information.
A fungicide is not needed in this situation, but for any pesticide used, make sure the product is labeled for indoor use; few are, especially among fungicides. The insecticide you mention might only be legal to use outdoors for safety reasons, depending on its ingredient contents; the label details will always say where it is intended for use.
You probably cannot use a systemic type of insecticide for the scale or mealybug if you intend to eat the fruits, since these chemicals are absorbed by the roots and moved into plant tissues. As the pests ingest the poisoned sap, they die off. The product label will include information for treating fruit trees, though, if it is permitted based on that specific product's formulation. Otherwise, only a topical treatment like horticultural oil or insecticidal soap (that must directly contact the insects to work) will help to smother them. Do not substitute a home remedy version of either spray, but you do not need to apply both; pick one. Repeat treatments, spaced as far apart as the label directions instruct (often every 1-2 weeks for several rounds), may be needed to fully suppress the pests.
Miri
