Treatment for Severe Greasy Spot on Indoor Citrus Lemon Tree

Question

I bought a Corkscrew citrus lemon tree for my flat in December 2010 and within a few months I noticed a greasy substance on the top side of the leaves, which has quickly spread to 90% of the foliage. In addition, I have noticed many small yellow/brownish spots covering the top side under leaves, branches and even the fruit. I have researched the disease and concluded it must be this common disease, greasy spot. Reading many publications on treatment of the disease, I concluded I should use a copper based fungicide. I opted for Bayer Garden’s Fruit and Vegetable Disease Control. Approximately one month ago, I used a spray guy to apply the treatment to every area of the plant. I haven’t seen any change in the disease; in fact, I would actually say the disease has infected a greater area of the plant in comparison with earlier in this year.

I am genuinely in need of advice on how to treat this disease, as I would describe my general gardening knowledge as beginner. I would be keen to share photographs of the infection if it helps in understanding of the scale of the problem. I am considering a second application of the fungicide treatment; however, I am reluctant given the poor results I found after the first application. Any help, advice or similar experience would be helpful. My flat sits on a south/east facing large sunny window and I regularly use a citrus fertilizer when watering (altering the dosage based on the season).

I hope this information is helpful and I really would be keen to engage with a fellow lemon tree grower to help my poor tree out! I really am in desparate need as I fear going into the autumn/winter seasons, my tree my not survive.

Many thanks,

Stephen, 26 from Glasgow.

Answer 1

You need to start treating the plant regularly with a fungicide like neem oil or copper sulphate. I prefer neem oil myself, but either will do and are not harmful to the plant or yourself. Spray the plant every 2-3 weeks until the problem is gone.

Also, remove and destroy any dead leaves ASAP, as these can contribute to reinfestation. If you have had the fungus for awhile, it may take a little time to clear it up completely.

Answer 2

Heather,

Firstly, thank you for taking the time to reply and offering new methods of tackling the fungal problem. I’ve now managed to track down an organic shop near my home in Glasgow which sells neem oil [this stuff is completely new to me, it sounds wonderful – so many properties!]. I intend to spray late this afternoon (I believe that’s an ideal time to attack the fugus). I much prefer the ethics of using a natural soluation to tackle the problem (and I’m sure my lemon tree will too).

I’d read in previous articles that you must remove any dead leaves, but it’s just occured to me, does this apply to dead/dying leaves which are still attatched to a brach or just those which have fallen off?

My plan for a first application of Neem oil treatment is to clean as much of the scabs, grease and visible fungus I can with diluted soapy water and then begin a first spray of neem oil solution [I plan to create a neem oil/water/washing up liquid mix which I found through google].

Thank you again Heather – I’m now looking forward to beginning this treatment!