What is killing my lemon tree, and how to cure?
June 20, 2012 10:35 PM Subscribe
Help me save my lemon tree. It's got tiny black spots on both sides of its leaves, and small beige bumps on the undersides. It's been spreading for about a month, but I'm finally noticing that it's actually harming the plant and killing the leaves.
Badly damaged leaf: top, bottom, top close, bottom close. Early-stage leaf: top, bottom. Barely-affected leaf: top, bottom, bottom close.
There's no discharge or slime, everything is dry to the touch. The plant lives in a dry climate in front of the window. We water it frequently, and it's had a history of being the healthiest of our plants.
This doesn't completely match up with any of the plant problems I googled up, so I'm wondering if it's something I haven't thought of.
Once the affliction is identified, how do I keep the plant from dying? I've removed every affected leaf that didn't fall off on its own (most were barely attached anyway), and one portion of branch that was showing spots. I also removed the one fruit that had been growing. Now there's only 8 leaves on the whole bush, it's pretty Charlie-Brown.
There's no discharge or slime, everything is dry to the touch. The plant lives in a dry climate in front of the window. We water it frequently, and it's had a history of being the healthiest of our plants.
This doesn't completely match up with any of the plant problems I googled up, so I'm wondering if it's something I haven't thought of.
Once the affliction is identified, how do I keep the plant from dying? I've removed every affected leaf that didn't fall off on its own (most were barely attached anyway), and one portion of branch that was showing spots. I also removed the one fruit that had been growing. Now there's only 8 leaves on the whole bush, it's pretty Charlie-Brown.
Yeah, definitely looks fungal. If you like you can compare your photos to the Citrus Foliar Fungal Diseases Identification Sheet, but the solution for all of them seems to be treatment with a copper fungicide.
posted by purpleclover at 11:28 PM on June 20, 2012
posted by purpleclover at 11:28 PM on June 20, 2012
A picture of the entire tree itself would help. But yeah, if you've removed the infected leaves (depending on the overall health of the tree), it should be fine. Any recent changes in its environment?
posted by trip and a half at 11:30 PM on June 20, 2012
posted by trip and a half at 11:30 PM on June 20, 2012
Response by poster: Good ideas! I'm definitely buying the fungus idea. None of the pictures quite looks like my plant's pattern of tiny specks, though, so who knows which fungus. The specks are really tiny -- none larger than the head of a pin.
No changes in the environment before the spots started showing up, unless you count summer. Here's a picture of the whole plant. I guess I underestimated its remaining leaf count, there's literally dozens! Though it may end up being only 8: I just removed 3 more leaves that I noticed had some patches of black. Those grassy shoots in the pot are, we believe, baby palms that blew in through the window about a year ago. The plant definitely gets a lot of outside air, so maybe a spore blew in?
posted by breath at 11:47 PM on June 20, 2012
No changes in the environment before the spots started showing up, unless you count summer. Here's a picture of the whole plant. I guess I underestimated its remaining leaf count, there's literally dozens! Though it may end up being only 8: I just removed 3 more leaves that I noticed had some patches of black. Those grassy shoots in the pot are, we believe, baby palms that blew in through the window about a year ago. The plant definitely gets a lot of outside air, so maybe a spore blew in?
posted by breath at 11:47 PM on June 20, 2012
Oh, thanks for posting a pic of the whole thing! It needs a bigger pot. A much bigger pot. Citrus plants need room for their roots. Ideally, you wouldn't be growing a citrus this young inside. Put it outside for the summer, or at least pull it out from the wall a bit and re-pot it. Outside, if possible. Pull it inside to a sunny window when it gets cold. Good luck!
posted by trip and a half at 12:47 AM on June 21, 2012
posted by trip and a half at 12:47 AM on June 21, 2012
Immediate steps: just pull it out from the wall and pluck the grassy shoots. Looks like it has a lot of sun so that's okay. Keep the kitty away, and replant in a larger pot as soon as you can.
posted by trip and a half at 1:07 AM on June 21, 2012
posted by trip and a half at 1:07 AM on June 21, 2012
Response by poster: Awesome, thanks for the advice, we've been thinking about repotting for a while but never got to it, didn't realize it was so important. Is it bad to repot while it's suffering from this fungus whatever? Should I maybe wait for a recovery?
Good points about the cats, and the outdoors, will do our best on those fronts.
posted by breath at 1:34 AM on June 21, 2012
Good points about the cats, and the outdoors, will do our best on those fronts.
posted by breath at 1:34 AM on June 21, 2012
Yes, a bigger pot! Also, what's your fertilizer situation? Citrus are heavy feeders, especially in containers.
Finally, I'm guessing you're watering too much too often. Generally watering every 5-7 days, when the plant is dry at root level, not on the surface, is what's recommended. Good luck!
posted by purpleclover at 9:00 AM on June 21, 2012
Finally, I'm guessing you're watering too much too often. Generally watering every 5-7 days, when the plant is dry at root level, not on the surface, is what's recommended. Good luck!
posted by purpleclover at 9:00 AM on June 21, 2012
Response by poster: OK guys, new shit has come to light. Last night I removed every bespotted leaf, and this morning there were new spots on the untouched leaves. Looking more closely, I discovered small insects! Here's a picture. It's hard to see even in person, but they definitely have distinct heads and wings.
The current hypothesis is that the insects cause the black spots by feeding, and after they drain a spot of the leaf they move on to another location, leading to lots of bugless spots, and making the leaf more susceptible to incidental fungus. I wiped all remaining leaves and stems with alcohol and made sure that there were no bugs visible.
Can we identify these bugs? Where do they leave their eggs? How do I keep them from returning?
posted by breath at 1:09 PM on June 21, 2012
The current hypothesis is that the insects cause the black spots by feeding, and after they drain a spot of the leaf they move on to another location, leading to lots of bugless spots, and making the leaf more susceptible to incidental fungus. I wiped all remaining leaves and stems with alcohol and made sure that there were no bugs visible.
Can we identify these bugs? Where do they leave their eggs? How do I keep them from returning?
posted by breath at 1:09 PM on June 21, 2012
Best answer: Yeah, I'm not seeing any signs of fungus, that black stuff is bug poop. You have Citrus thrips. You also have a deficiency of some sort, and your indoor conditions are ripe for bug infestation.
This is what you do: you take it outside and blast off all the thrips with a jet from the hose. (Do not remove any more leaves! You tree needs them to create food for itself., and they are not diseased.) Do this every week. Mist your lemon every day with a sprayer, thrips do not like humidity (or better, get a humidifier). Water your lemon only when the top 2 inches of soil dry out, and make sure you have good drainage. You re-pot in a five gallon container with a good sized saucer for drainage. Do not use any cheap Miracle-Gro crap or "potting soil" from a big-box store, use good soil from a nursery or rockery with no added fertilizer. Mix it 1/3 with damp peat moss to increase the acidity, because citrus won't take up nutrients if the soil pH is above 6.7 or so. Then mix up 2 tablespoons of epsom salts in a gallon of water and water with that this week, and then again in two weeks, because I suspect you have a magnesium deficiency. Soak the whole plant.
Do not fertilize with any nitrogen until the bugs are gone. Nitrogen is crack to pests and pathogens. Use a good quality liquid organic fertilizer that is for citrus or azaleas, and use at 1/3 the strength.
posted by oneirodynia at 2:18 PM on June 21, 2012
This is what you do: you take it outside and blast off all the thrips with a jet from the hose. (Do not remove any more leaves! You tree needs them to create food for itself., and they are not diseased.) Do this every week. Mist your lemon every day with a sprayer, thrips do not like humidity (or better, get a humidifier). Water your lemon only when the top 2 inches of soil dry out, and make sure you have good drainage. You re-pot in a five gallon container with a good sized saucer for drainage. Do not use any cheap Miracle-Gro crap or "potting soil" from a big-box store, use good soil from a nursery or rockery with no added fertilizer. Mix it 1/3 with damp peat moss to increase the acidity, because citrus won't take up nutrients if the soil pH is above 6.7 or so. Then mix up 2 tablespoons of epsom salts in a gallon of water and water with that this week, and then again in two weeks, because I suspect you have a magnesium deficiency. Soak the whole plant.
Do not fertilize with any nitrogen until the bugs are gone. Nitrogen is crack to pests and pathogens. Use a good quality liquid organic fertilizer that is for citrus or azaleas, and use at 1/3 the strength.
posted by oneirodynia at 2:18 PM on June 21, 2012
Best answer: Oops, sorry, they're greenhouse thrips. They fly or get blown in, and they love new growth, especially when nitrogen-induced. If the hose, Neem oil is somewhat effective (thrips are notoriously hard to kill with any pesticide); if you are very good about spraying the undersides of the leaves. The silvery damage will persist for the life of the leaf- it is cellular damage.
posted by oneirodynia at 2:30 PM on June 21, 2012
posted by oneirodynia at 2:30 PM on June 21, 2012
Response by poster: Awesome, greenhouse thrips look very much like the bugs I found. Been reading up on them, they are weird little creatures.
Thanks for the detailed instructions on fixing the plant's situation, I'll do the epsom salt thing this weekend, and be more circumspect about watering. Already sprayed it. It's amusingly appropriate that citrus plants like acidic soil.
posted by breath at 3:18 PM on June 21, 2012
Thanks for the detailed instructions on fixing the plant's situation, I'll do the epsom salt thing this weekend, and be more circumspect about watering. Already sprayed it. It's amusingly appropriate that citrus plants like acidic soil.
posted by breath at 3:18 PM on June 21, 2012
Response by poster: Thanks, guys! After a few weeks of thrips-culling the tree regrew many of its leaves, and it now looks like this. It still had a nutrient deficiency that didn't respond to multiple epsom salt treatments, so i moved on to manganese and zinc supplements before finally repotting in a larger pot. The leaves are still yellowed in places but seem to at least not be getting yellower. I still find the occasional thrips on the underside of a leaf, but that situation is under control now. The plant has been saved, I honestly thought it was a goner.
posted by breath at 1:23 PM on November 28, 2012 [1 favorite]
posted by breath at 1:23 PM on November 28, 2012 [1 favorite]
Response by poster: (the picture is pre-repotting)
posted by breath at 1:23 PM on November 28, 2012 [1 favorite]
posted by breath at 1:23 PM on November 28, 2012 [1 favorite]
Thanks for the update! It looks a lot better, and will thrive even more in its larger pot! You done good!
posted by trip and a half at 10:54 PM on November 28, 2012
posted by trip and a half at 10:54 PM on November 28, 2012
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posted by mleigh at 10:47 PM on June 20, 2012