How much did you water your orange tree? Sounds a bit like fungus gnats in your soil from too much moisture. Pictures would be very helpful

Post pictures of the entire tree and the pot it is growing in.

Before any signs of problems...

Pictures before 1 year- stage black jumping bags in the soil:

Pictures: today

looks like you watered too much and the tree is dying

Thank you Susanne amd Sunshine for helping me out !

Maybe it is too much watered, and i will stop with watering.

Root of the orange looks healthy but it stucks in clay (looks like a clay)

The tree is also very deficient in iron. The leaf symptoms for iron deficiency is yellow leaves with green veins. What fertilizer do you use, does it contain all the required micronutrients, and what is your fertilizer schedule for this tree?

Clay pot with saucer and soil that looks like it retains too much water will result in soil that holds too much water and will result in root rot. I cannot be certain, but the "clay" to which you refer is most likely fungus and that is due to soil that is damp for long periods. I would stop watering until the top 2 inches of the soil feels dry. When the tree shows new growth in the spring, repot it into a less water retentive mix like the 5:1:1 mix.

I use fertiliser for citrus, iron is in conc. 0,06%, approximately 1-2 times per month.

Orange is not in a clay pot, she is in the plastic pot. When i de-pot this orange last year, i was not remove the old soil, i think that old soil is been clay soil and now the root is stuck in the clay and is verry hard to remove.

I will bay a fungicide... And glass magnifier...

Thank you all for help!

Can you show the bottom of your orange tree cotainer, having lots of holes is important, your soil looks heavy.

If you didn't change out the soil it was in, very likely the soil is the problem especially if you say the clay soil is very hard to remove. Best thing would be to put your tree into new soil mix that is more fluffy and give it a micronutrient supplement through foliar spray.

There is no need to buy fungicide because the fungus, if it is a fungus, is not affecting the tree.

Put the tree into a new soil mix.
Many people on this forum use the 5:1:1 mix.

My version of 5-1-1 Mix

· 5 parts pine bark mulch (remove ½” pieces through 1/2 inch screen)

(Some people use Repti Bark instead of
mulch. They do not screen it.) Be sure to soak the bark overnight.

· 1 part sphagnum peat

· 1 part perlite (coarse, if you can get it)

· 1 Tb garden lime /gal 5-1-1 mix (measure the 5-1-1 mix)

· Osmocote plus (follow manufacturer’s instructions). This is optional.

· Moisten well and wait at 2 days before using, if possible.

Remove all of the old soil mix by dunking the root ball in and out of water. You may have to use a garden hose to gently force the old soil off. Or, use something like a screwdriver: stick it into the root ball and pull down to loosen the soil. Dunk and repeat.

Update:

I was repot orange today, it's been verry hard to remove the old soil (clay). Works great with a screwdriver and water ( my bathroom looks like a hell).

In the old soil i was find: rooks, clay, normal soil,...

Is the orange root ok?

It looks ok to me. Your tree has a really nice bushy root system, much bigger and fuller than my tree! If it worries you that much, you can take off the tips of the orange roots just as long as the roots aren't mushy then I think your tree will be ok

Good root system, plant it in fresh good draining soil with lots of holes in the container, keep it in shade for a week but bright, keep away from wind and don't fertilize until the tree gets established.