My satsuma and gold nugget mandarin branches are yellowing. Please see the pictures below.
They have been like this for last 2 months. It looks like some disease or infestation. I tried neem oil, copper based fungicides, hydrogen peroxide. But not much improvement. I used well balanced citrus and avocado fertilizer. I checked the soil moisture, which seems fine as well (not dry or too wet). Please advise how to recover these trees. Thanks a lot for your help.
Do not apply hydrogen peroxide to Citrus. Also, do not apply neem oil unless you are using it in small quantities as a surfactant with a viable pesticide.
Thanks for your response, Richard.
I’ll skip those for citrus. What do you recommend for the current condition?
This is true for all plants:
Do not apply neem oil unless you are using it in small quantities as a surfactant with a viable pesticide.
The roots are under severe stress. Nitrogen is not being delivered to the stems and leaves in suitable quantity. This is sometimes due to a combination of soil, fertilizer, and water. Macroscopic soil pests that feed on roots are sometimes to blame. The most common cause are soil-borne Phytophthora species. This requires a fungicide that is labeled for both (1) soil drench and (2) phytophthora. The only one I’m aware of that I would use on food crops is Kocide 3000.
Why not? Do you mean as a soil drench, spray or both?
As a pesticide, I use a 2% neem oil (cold pressed) emulsion with Safer’s Insecticidal soap (emulsifier) diluted 1:400 (no added pesticide). Would you consider that to be a “small quantity”?
Superstition ain’t the way.
No. I consider it a waste of money and a contribution to more vigorous pest colonies.
Please explain.
Please explain what you mean by this statement.
Soil type and pH? Location?
Looks like severe lack of fertilizer to me.Neem is more of a fungicide than an insecticide. Dormant oil will kill most citrus pests.
As I’ve posted elsewhere on GrowingFruit, neem oil (including the concentrate) is a surfactant with no viable insect toxins. It will kill some weaker individuals of some species and also kill weak larval stages of a few species (e.g. aphid larvae) by entanglement. In agricultural studies it has been shown that when used alone over a few years the surviving members of the target insects (e.g. spider mites) breed to produce races of extra-strong individuals. It has also been shown that when used with a viable insect toxin (e.g. piperonyl butoxide) it increases the effectiveness of the PB by causing the target pests to struggle while ingesting the toxin. It has also been shown to be an effective surfactant when used (e.g. 1 ml per gallon) with pesticide sprays that require one.
Show me a container of H.p.O. labeled for pesticide use.
It is neither.
Apparently you don’t have the array of Citrus pests we have in California. Dormant oil won’t hold a candle to them.
I think we have all the bad citrus pests in Texas you do in California like leaf miners, spider mites, various scales,etc. Discovered some cottony cushion scale today. I use spinosad to control leaf miners and abemectin to control spider mites. I always add dormant oil to my sprays to kill various scale insects. BTW also add miner elements Scott STEM to keep the leaves nice and green. I bought 25 lbs of STEM once upon a time and still have a few pounds left.
Have never used neem oil myself what with very good chemicals available to keep the citrus looking nice. On various Facebook groups I get the impression that neem oil is some kind of do-it-all “natural” pesticide.
You are correct, dormant oil won’t kill most citrus pests. But it will get rid of scale.
Soil type clay and alkaline pH. Location: San Jose, CA zone: 9b.
I used well balanced citrus and avocado fertilizer once a month. It might be due to Phytophthora, which Richard mentioned above.
Most likely wet feet due to planting in clay soil. Better for raised bed. Alkaline pH not good either.
I was also thinking about that too. I’ll try to raise them by at least a feet before next spring.
