Something growing on Meyer lemon branches - Ask Extension
The leaves are drying up and falling off. This plant is outside for 6 months and is inside all winter. I’m in Sparks, MD.
Knowledgebase
Something growing on Meyer lemon branches #819658
Asked February 02, 2023, 2:17 PM EST
The leaves are drying up and falling off. This plant is outside for 6 months and is inside all winter. I’m in Sparks, MD.
Baltimore County Maryland
Expert Response
Unfortunately the lemon appears to be infested with a very high population of scale. These insects feed on plant sap and can stress a plant when numerous; here, they may even kill it eventually since they are so abundant. When they first colonized the plant is hard to determine since scale often go unnoticed when their populations are low, since they themselves are small and blend-in fairly well. Treatment for scale outbreaks takes time and isn't always successful in eradicating them. Given the apparent poor health of this plant, it would be most practical to simply replace it, cleaning the pot if you re-use it so any wandering scale are removed. (Scale tend to glue themselves to the plant, but the miniscule juveniles do wander about from time to time.)
If the plant has sentimental value or you'd prefer to try to salvage it, gently scrub all stem surfaces with a moist, mildly-abrasive material (a spare toothbrush may work) to remove as many scale as possible. Don't scrape off the bark in the process, so use caution. Look over both upper and lower leaf surfaces to remove any scale there too. Then, you can try treating the plant with either horticultural oil or insecticidal soap, as directed by the product label instructions. Normally you'd be spraying foliage, but in this case, just thoroughly coat all branch and leaf surfaces with spray. Repeat treatments will be needed, and make sure edible plants are included on the insecticide label as some houseplant pesticide formulations that use other ingredients are not safe to use on fruits. Recovery make take a while, especially since citrus don't produce much, if any, active leaf growth during winter.
To support the plant's health, make sure it's only being watered when needed. Citrus prefer to get fairly dry between waterings -- more so than most indoor plants -- and if you use a saucer or decorative pot to catch drips, empty it promptly after watering so the roots don't re-absorb the excess through the drain holes and stay too wet. (If its current pot doesn't drain at all, repot the plant into one that does if it starts to recover in spring.) More care information can be found on our Growing Dwarf Citrus page.
Plants under stress are more vulnerable to insect attack, so keeping the plant as stress-free as possible going forward (with either this or a new plant) will reduce the impacts of pests like scale. Spending the summer outdoors is an excellent way to maintain a thriving citrus plant, and usually naturally-occurring beneficial insects that prey on scale will "clean-up" a plant for free in the process, assuming a yard isn't too heavily treated with other pesticides. Scale numbers need to be less abundant for this to be effective, however, so waiting for this plant to go back outside as-is won't be an option. Inspecting plants that summered outdoors before they come back inside for the winter can help catch pests before they reproduce inside, though admittedly finding a few scale on a lush, shrubby citrus can be challenging, which is why a treatment or two a few weeks prior to moving indoors using of one of those low-toxicity pesticides mentioned above can help knock-down any populations that were undetected.
Miri
If the plant has sentimental value or you'd prefer to try to salvage it, gently scrub all stem surfaces with a moist, mildly-abrasive material (a spare toothbrush may work) to remove as many scale as possible. Don't scrape off the bark in the process, so use caution. Look over both upper and lower leaf surfaces to remove any scale there too. Then, you can try treating the plant with either horticultural oil or insecticidal soap, as directed by the product label instructions. Normally you'd be spraying foliage, but in this case, just thoroughly coat all branch and leaf surfaces with spray. Repeat treatments will be needed, and make sure edible plants are included on the insecticide label as some houseplant pesticide formulations that use other ingredients are not safe to use on fruits. Recovery make take a while, especially since citrus don't produce much, if any, active leaf growth during winter.
To support the plant's health, make sure it's only being watered when needed. Citrus prefer to get fairly dry between waterings -- more so than most indoor plants -- and if you use a saucer or decorative pot to catch drips, empty it promptly after watering so the roots don't re-absorb the excess through the drain holes and stay too wet. (If its current pot doesn't drain at all, repot the plant into one that does if it starts to recover in spring.) More care information can be found on our Growing Dwarf Citrus page.
Plants under stress are more vulnerable to insect attack, so keeping the plant as stress-free as possible going forward (with either this or a new plant) will reduce the impacts of pests like scale. Spending the summer outdoors is an excellent way to maintain a thriving citrus plant, and usually naturally-occurring beneficial insects that prey on scale will "clean-up" a plant for free in the process, assuming a yard isn't too heavily treated with other pesticides. Scale numbers need to be less abundant for this to be effective, however, so waiting for this plant to go back outside as-is won't be an option. Inspecting plants that summered outdoors before they come back inside for the winter can help catch pests before they reproduce inside, though admittedly finding a few scale on a lush, shrubby citrus can be challenging, which is why a treatment or two a few weeks prior to moving indoors using of one of those low-toxicity pesticides mentioned above can help knock-down any populations that were undetected.
Miri
