Citrus leaf problem

[BSJ]

Hi folks, we have been told a solution to the leaf curl problem but after 2 weeks and 2 sprays with copper fungiside the problem still exists.

How long does it take to get the plant healthy?

We are getting plenty of new growth but the trees won't develop fully until we get this leaf problem sorted.

[drtreelove]

BSJ, this is most likely an insect pest problem, aphids, psyllids or thrips can distort foliage like this in citrus. Look closely at the affected leaves, upper and undersides and inside the curled portions. You may need a magnifying glass to see the pest. And the pest life cycle may have come and gone and you won't see the insect now at all. Some leaf curl conditions are fungal, as in peach leaf curl, but fungal leaf curl is not common inn citrus from my experience. Copper solutions are for preventive barrier to fungal infections, this will do nothing to correct leaf curl from pests or prevent arthropod pest problems.

It is curious to me that a portion of the plant in your photo appears darker green and has less leaf curl, and the portion with leaf curl is also chlorotic (yellowed). There may be a structural deformity at the base of the branch that is inhibiting circulation to this branch/leader and therefore weakening uptake of water and nutrients and making it susceptible to the pest. Just a hunch.

And there is a dire possibility to consider:

Worst case scenario is that you have an infestation of Asian citrus psyllid and beginnings of citrus greening disease or HLB. This is a serious and fatal bacterial disease, spread by the psyllid vector when it feeds on the trees and flies to other citrus trees.

Where in Thailand are you located? The chances of HLB are greater if you are in the north where HLB is rampant, or if you are in an area with large commercial citrus growing operations this would be a factor.

There is no know cure for HLB, but prevention is possible for unaffected trees.

If this is one tree in a small home garden it is worth attempting pest control with natural/botanical pesticides (pyrethrins, neem oil extract solution), weekly spraying would be required until you are out of the woods. You are not posting in the organic forum, so you may be interested in using harder chemistry for pest control. Just don't use systemics or the insecticide can end up in the fruit. If you are a commercial grower and you have other trees that are currently unaffected, then I would make an immediate attempt to identify the pest causing the leaf distortion. Get a university entomologist or pomology expert to help if needed. If identified as the psyllid vector and HLB, cull the infested tree and institute a serious pest control program to prevent further spread of the disease in your grove.

Edited August 27, 2015 by drtreelove

[BSJ]

Thanks for the reply DrTreeLover. We are in Wang Plong, Amphur Noen Mapruang, Phitsanulok. No other commercial citrus growers for many miles.

It's a one rai class room for the wife to learn citrus growing before we commit to larger orchard. I guess we are learning all the bad sh1t early in the learning experience.

The trees get sprayed every 7 days with insecticide. It's a never ending battle with insects. Will be doing it every 5 days for a while and spraying copper fungacide in between. We can see what looks like a film on the leaves that has been identified as a fungal growth by the wife cousin who grows citrus over past Wang Phup.

"Asian citrus psyllid and beginnings of citrus greening disease or HLB" Not sure if she is aware of those problems. I'll have to look it up in English on the web and Google translate and compare pictures with those on her chemmie bottles.

Half the trees came from the cousins stock but the other half came from a commercial supplier, but not sure where he is located.

Always willing to look at organic solutions to problems so I will have a closer look at the Neem oil.

[drtreelove]

It's worth looking into HLB and ruling it out. I've attached some information from the state of Florida USA, where there is a huge citrus industry and devastating HLB. There is much more info available on the net.

Even without citrus orchards in your area, the commercial grower source of your trees could be suspect. I don't want to alarm you and discourage your beautiful project, but you need to protect your obvious considerable investment and get on top of this issue.

Chiang Mai U has a PhD plant pathologist specialist in HLB, and an active program for the citrus industry in the north. She ran DNA PCR tests for samples sent to me by another forum member, when I was in CM. They turned out negative for HLB for a property in Issan. But DNA is the only available positive identification. Look at your trees and signs and relate to the photos and descriptions in the articles. If you think it could be ACP and HLB, then get on top of it.

Your weekly insecticide spraying will certainly do a lot to suppress the psyllids from feeding on your trees and infecting them. What are you using as a pesticide? If it's hard synthetic chemistry, that's a lot of environmental impact. Try to take it to a stage where you know exactly what you are dealing with and use the IPM approach and "bio-rational", reduced risk pesticides.

PM me if you post or want to discuss options. I don't follow the forum every day.

AsianCitrusPsyllid.pdf

APSnet Feature Citrus Huanglongbing The Pathogen and Its Impact.pdf

BIO-RATIONAL PEST CONTROL.pdf

[BSJ]

Hi there, thanks for the info. I'll pass it on to the wife.

[drtreelove]

CMU had a website in Thai for the orange and tangerine HLB management project a few years ago. I don't know current status but you may be able to find it.

Some additional thoughts, as I grew a few manao, som and som-O trees in Chiang Mai; I noticed in the photo that in your wife's project, the trees have all been planted in concrete rings/containers. If this is a sample one rai project as you indicated, with anticipation of planting more area, that's an expensive and labor intensive way to go; There are advantages and disadvantages in this method. She must have reasons for not planting in the native soil, flooding, poor soil quality, etc But if there are no substantial horticultural reasons, she may consider planting in the ground for a larger project; with soil testing and improvements.

By planting in containers, the soil volume is restricted, and therefore root growth is restricted. This prevents roots from ranging far and wide in the soil to gather as much moisture and nutrients as possible. It becomes a very intensive operation, requiring very attentive irrigation, soil moisture monitoring and fertilization. Eventually the concrete containers, by limiting root growth, will limit foliar canopy growth and fruiting capacity.

Is the bottom of the ring open to the native soil, or is there a solid bottom with drainage ports? If there is a bottom concrete slab, then depending on soil texture in the containers and drainage, overwatering will be a primary concern for the issue of root and crown rot, common in citrus. The trees eventually can get root bound in the container. If the bottom is open, then the roots will soon be down and out into the native soil, so she will need to recognize that reality, water and amend the native soil as needed. I see people growing in containers who continue to water and fertilize within the container only and don't provide support for the absorbing root systems that have developed outside the container. That can make a difference in plant health and susceptibility to pest and disease problems.

Something to consider. She has big spacing between trees and lots of soil where she could grow something else while the trees are young like this, if she has irrigation. Plant between the containers with green manure crops to enrich the soil. Then when the trees have outgrown their containers, bust out the concrete and let them grow into the improved native soil of the full field.

I mentioned the pesticide issue. If she is using hard chemistry like chlorpyrifos, an organophosphate insecticide, a favorite in Thai farm shops because it kills everything and has substantial residual action, then weekly may be too much. The primary risk is to the applicator, with frequent exposure like that. A less toxic alternative would be a pyrethroid like cypermethrin, which also has considerable residual action, usually once a month application is adequate. If she has budgeted for weekly spraying, then she could use botanical, organic program compatible products. The main drawback for botanicals and most farm budgets, labor and materials costs, is that it takes weekly applications during the period of time when pests are active. So my point is, if you are spraying weekly anyway and can afford it, then why not use the least toxic alternative.

[drtreelove]

Circling roots in container plantings vs unrestricted expansive root systems