Lemon Tree Problem

Hello,

I got two lemon trees in pots at the start of winter. The pots seem small compared to the size of the trees, but I decided to wait until I put them outside in spring to pot them up.

They curled and dropped some leaves shortly after I got them, so I added some small grow-lights and watered a little more.

The trees flowered nicely last month and have set a whole bunch of small lemons. I have been fertilizing them with citrus fertilizer once per month (7-3-5) since then. They are watered twice a week (maybe 300ml) once I notice that the top of the soil looks dry.

Recently they developed discoloration on their leaves. It is worst at the top. I included some pictures below.

All suggestions appreciated.

BRS,

- Danny

 

Is that webbing on the leaves.

 

There is a bit of webbing on the plant, but not on most leaves.

The leaves feel a little rough, but the discoloration is of the leaves themselves not something on them.

 

I think it could be red spider mite.
Look closely on the underside of the leaves for very tiny insects, not easy to see unless you have good eyesight.

 

I think you are right (had to blow them up with my phone, but there are some dark red, slightly raised dots.). I just treated with bio insecticide.

 

Be very careful with other indoor plants as they spread really quickly. Whatever you've sprayed with will probably have to be repeated in the next couple of weeks as the half life of them is pretty short and they soon start to multiply.

 

On it. They will rue the day...

 

I've always found them to be very difficult to get rid of entirely, hpefully if you can keep them under control for a couple of month you can then put the plant outside which helps to slow them down.

 

I agree @pete I'd rather my citrus pick up scale insects as they're easier to treat. But it's part and parcel of having them behind glass...they get affected by something in between of outdoor breaks.

 

Red spider mite like white fly are resistant to a lot of pesticides.

 

And frankly I would advise not to use anything more radical than neem oil. Some thorough cleaning of the leaves and some abrasive action will remove them to improve the immediate state of the plant but one has to keep a beady eye for their inevitable return and keep suppressing them.

 

I would suggest cleaning the leaves and stems, re-potting in John Inees no 3 type compost and then sanding the pots on a tray of pebbles you can keep wet. Red spirder mite thrives in dry conditions so if you can't do the pebbles, mist daily.

Make sure you water with rain water if your tap water is hard as they don't do well with too much calcium. You can also correct that with a liquid feed for ericaceous plants.

 

I've used SB Plant Invigorator to control spider mites on an indoor (conservatory) crop of chillies in the past. it sort of glues them in place until they die. However, I'd go with @Obelix-Vendée 's method, as that will be quicker for just one plant. They spread easily and quickly though!

 

Do be a bit wary of standing a citrus tree in or on anything that impedes good drainage. The quickest way to kill off citrus is to leave the pot in standing water If it's possible to put the tree outside somewhere sheltered, cooler temperatures and natural humidity will help to control pests too.