There appears to be more than one issue affecting the citrus. We'll consult with our plant pathologist, but in the meantime, additional information would help us make a diagnosis.

Some foliage seems to have either mite or thrips (or both) damage, causing the fine stippling and tiny black specks on the leaf surface. When you have sprayed the plant with neem, what issue were you spraying it for? How long ago was it sprayed, and was the treatment repeated at the time?

Horticultural oil can be used to control mites and thrips (and should work better than neem), though multiple treatments will be needed. Upper and lower leaf surfaces will need to be coated as thoroughly as possible. Follow label directions about how long to wait between sprays. Do not spray when temperatures are above 85 degrees, and make sure the plant is not due to be watered before spraying - both can cause leaf damage ("phytotoxicity") from the spray itself in those circumstances. If you need to treat and it's very hot out, wait until morning or evening when it's cooler.

The distorted young growth is difficult to diagnose. Some plant viruses cause distortion, and more commonly herbicide damage causes disfigurement. Was the plant outside when any weed killer was used in the yard? Was the spray container you used neem in earlier this season one that was used for an herbicide at some point?

Was the plant repotted into fresh soil in the past year or so? Successive years of fertilizer applications can leave "salt" (minerals beyond just sodium) buildup in the soil, which eventually will damage roots and cause them to not function properly or die back. Although this might not explain the leaf deformities, it would contribute to overall plant stress. We see you mention root-pruning every few years, but perhaps the soil itself isn't being replaced.

Was this plant grown from a nursery-purchased plant, or one which you started from seed ten years ago?

If you've harvested fruit in recent years, has it ripened normally?

Miri

When you have sprayed the plant with neem, what issue were you spraying it for? How long ago was it sprayed, and was the treatment repeated at the time?

We were spraying for ‘mites’ that it seems to get over the winter when left indoors. We only sprayed once and did not repeat. This was done sometime in April after we bought it out on our deck.

Was the plant outside when any weed killer was used in the yard? Was the spray container you used neem in earlier this season one that was used for an herbicide at some point?

Use of weed killer is extremely rare in our yard (poison ivy for instance) and we label all spray devices for fertilizer, repellent or herbicide and do not combine use.

Was the plant repotted into fresh soil in the past year or so?

I am pretty sure we used fresh potting soil, although it may have been mixed with some of the older potting soil.

Was this plant grown from a nursery-purchased plant, or one which you started from seed ten years ago?

This was purchased as a small tree from a nursery.

If you've harvested fruit in recent years, has it ripened normally?

Fruit harvest has been excellent in the years past and this is the first time we have seen this type of issue.

Thank you for the additional information.

Treatment for mites tends to take several treatments to be successful, so we recommend trying another round of sprays with horticultural oil (it also may be more effective than neem). Follow label directions for intervals to wait between sprays (it'll probably be a week or two) and treat 2-3 times in total. As mentioned previously, be mindful of the heat when spraying. Some mites are essentially invisible with the naked eye, and their feeding in the nooks and crannies of young growth can distort emerging leaves. We also see what looks like thrips feeding damage, and the oil will control them as well.

Do you know if anything was sprayed for poison ivy or other weeds around the time the plant was set outside? Might a neighbor have sprayed or applied granular herbicide to their yard on a breezy or hot day? Some plants are hyper-sensitive to drifting evaporated herbicide and it would manifest as distorted young growth.

One final educated guess as to damage trigger is cold. You mention this plant was outside starting around April, which is much earlier than our typical last-frost date. Usually indoor plants are best not moved outside until around mid-May. While citrus overall are fairly cold-tolerant, bringing an indoor plant that hasn't been accustomed to near-freezing temperatures outside when we still have quite cold nights risks tissue damage. Although the symptoms here do not look like typical plant cold damage, perhaps a cold snap (of which we experienced several late this spring) disrupted normal leaf development at a critical time. The mottling on older, normally-shaped leaves looks more like mite/thrips feeding damage, but the two factors may have interacted.

Since the malformed uppermost leaves will not heal, we suggest trimming them all off (including the stem tips they are growing from, rather than just the individual leaves themselves). This will not only encourage replacement growth, but will help you monitor for recurrence by removing old damage. Aside from pests that weren't killed-off by a spray, the other suspected cause of returning symptoms would be a virus. Plant viruses are, unfortunately, incurable. If the new growth develops normally, however, virus is much less likely.

Miri

On 06/23/2021 10:00 AM Ask Extension <<personal data hidden>> wrote: