I have a meyer lemon tree that has leaves with a white substance on the underside. This tree grows well produces fruit but I can tell something is wrong. there's this substance on the underside of the leaves and a blackish fungal looking stuff on the top of the leaves. There is fruit on the tree but its slow to ripen or turn yellow and some of the fruit has started to spontaneously rupture. The fruit also looks pitted discolored. I have treated it with neem oil in the past hoping for a less toxic insecticide but I think I may have to give up and get something stronger.

Does anyone know what this is?

Maybe Woolly Aphids.

Thank you for your reply, I will be more agressive with the insecticidal soap.

Make sure you spray the bottoms of the leaves as that is were the bugs are.

The soap will work, but you will need to repeat until you kill the following generations. Citrus are an ongoing battle with bugs.

ctcarol said:The soap will work, but you will need to repeat until you kill the following generations. Citrus are an ongoing battle with bugs.

You're right about the ongoing battle :sigh:, it's not for the faint of heart. I have a lemon and a lime tree and every year if its not one thing its another.
I want to try and put up a good fight, when I get fruit its so much juicier than anything I buy at the market.

Same here!