I've got probably fourty or fifty citrus trees, varying and unidentified cultivars, and one of them is sucumbing to a mystery disease that looks like fungus. Luckily they're planted fairly far apart, so I don't think it'll spread to the others. I've searched extensively on diseases that citrus could possibly contract here in Ecuador, and nothing matches up to what's happening to my tree. Perhaps the most important thing is that this in not grafted rootstock - it's original. All of my trees are. The thing that puzzles me is that it's only affecting half of the tree; there are two main stems and only the left one is being consumed. The other half is happy and flowering. BUT this is spreading really fast and I don't want it to get into the healthy half. I'm hampered by not knowing whether it's an orange, lime, grapefruit, or what. I'm pretty sure it's not a lemon, as nobody in my biome can get them to grow. I have been waiting for fruits on the trees in order to identify them. Here are some photos of the tree. Any help would be greatly appreciated.
As for identification, here is a link that will help: http://members.aol.com/mmmavocado/MMMspage.html As for the problem, it is difficult to tell from the picture, but it looks to me like it could be scale. Skeet
This book may help. Wish I had a copy of it on hand to look at a few of the diseases we seldom or never see here before I venture out and tell what I think from the bark lesion where the arrow points to in the first photo. Can you show close up photos of the leaves sometime. Is the dieback from the top of the tree downwards or are you seeing localized areas in the middle of the tree and then see the discolored areas move up and down from there. You give the impression these trees are on their own roots, are they seedlings or did they come about from cuttings? Do you know where these trees came from, who grew them and are any of those trees enduring the same type issues as your trees have? Compendium of Citrus Diseases Jim
The images look quite similar to those in the thread Is this the dreaded Mealy??? | UBC Botanical Garden Forums.
Hi Jim; the dieback is localized and it did seem to start in the middle of the tree, and has since spread down to the foot and is spreading upwards. When I go out this afternoon, I'll get some photos of the leaves. As far as I'm aware, these are seedlings, not rooted cuttings. I have no idea where they came from (I just got here, and they were here before me) but none of the other trees I've seen in the valley seem to have this problem... I'm hoping it's something localized and that it won't spread to the other trees, as they're starting to set.
If there is a scale involved then we need to know if there are deposits of honeydew on the leaves and on the branches of these trees. We also need to know is there high amounts of ant activity and then we may be looking at a severe scale infestation, perhaps Snow scale as it does not look like Cottony Cushion Scale to me at this time. I would want to see an online or book photo of Snow scale with this kind of infestation to better know it. Much of the time without a hand lens and without close-up photos of the insects and not seeing evidence of honeydew and no mention of ants then I think we are more likely dealing with a mealybug of some kind. Even still it is not common to see this much mealybug presence on the older wood branches so I am not sure what to say at this point in time. Heavy scale infestation damage is usually seen in the tops of the trees with the leaves succumbing to having much of their "juice" taken away from them. Young shoots are next to show the lack of flow and then the upper branches working on down the tree. I'd use a chemical spray also and it will take several insecticide applications along with horticultural oil, hand or tank mixed, to get a handle on this infestation. An oil spray alone now will only cover over the caps but will not cover up much of the juveniles residing under the caps. You need a spray that will work itself under the caps if it is a scale and will kill on contact and you will probably want to spray again in three weeks and/or every six weeks after that until you see signs that this insect has been knocked down and then in the late Fall and early Spring come back with a horticultural oil as a standalone spray. Not knowing for sure what the insect is may entail not knowing what the correct spray to use is either. In warm weather I think it is risky now to use a heavy horticultural oil unless it is a "light" oil. Another issue of using an insecticide spray along with an oil as a contact spray is that we treat for one insect and another insect such as Red Mite can have their populations increase. I'd rather deal with a scale infestation than a Citrus Red Mite outbreak as then the lower grade malathion and carbaryl sprays may be off the table to use for the Mite unless we know when to time our sprays. I'd go with Diazinon for my spray for this current infestation. To me there is no question that a disease issue exists and from the looks of the bark lesion and it being localized in the middle of the tree then works down and then may move up higher into the tree as the lesion spreads. I will order the book just to see what the guys from Florida are calling this disease, perhaps by another name than what I know it to be named for Fruit and Nut trees and ornamental forms of them. If I am right then this disease will not spread throughout your grove but will remain in the tree it is already in unless you introduce it into a clean tree by pruning from tree to tree. The disease can be passed from the parent tree into its seedling raised and cutting grown offspring and that is likely how you got it in your trees as they came with it already in their systems. Jim
No way would I even consider pruning an infected tree! That's how I lost an apricot tree back when I lived in Canada. At any rate, I sterilise my instruments after each tree or shrub in mentholated alcohol. I'm currently spraying as you suggest. There don't seem to be any ants to speak of, but there is some honeydew happening on the surviving leaves. The critters also seem to be colonising the leaves a bit. I think the lack of ants may have to do with them farming aphids on a large scale in my manioc, which is not too distant from this tree. (however as this only affects the leaves and not the root vigour I'm content to let them have the manioc because it keeps them out of the loquats and the citrus.) I'm glad you think they won't spread. My grove is not a traditional layout; instead my citrus alternates with loquats, guava, huilcos, and a couple of endemic fruits that I don't have names for yet. It seems to me that I've got a better chance at keeping disease isolated this way. (but watering's a bit of a chore. It's 4 ha of plantings...) When I go into the city next, I'll be looking for a big box of ladybugs, as I was always successful with them in Canada; if these are mites then they should take care of that, but good. I'm probably going to order the book, as well. It seems like a handy reference, as I'm quite enjoying the whole citrus growing experience. Below are macro photos of the leaves; I'll see what I can do about extreme macros of the bugs. Apologies for the blur in photo #2; it's been quite windy here.
UPDATE! Yesterday, in desparation and because I hate using commercial pesticides (I'm chemically sensitive and it hurts me just about as bad as the bugs) I went out and sprayed a test branch with a 10% aspirin solution (this has worked very well for me with other nasty bugs in the past) It's receding. I shall repeat daily until it completely goes away. Mr. Shep - this may be a solution for the bug. It doesn't seem to matter what they are, since this is killing them. This way, if they are scale, they go away, and if they're red mites, they go away, and I don't have to put on the hazmat suit to use the Diazion or the Malthion. HTH Lorax
Lorax, I too am chemically sensitive. You mentioned using aspirin so you may already know of these organic 'solutions'. http://www.ghorganics.com/page15.html http://www.ghorganics.com/page9.html Newt
Sensitivities to pesticides does make a big difference but what you may see as a killing mechanism may only be short term relief. High pressure water can do about as much good and I have referenced using it in the past in this forum for both scale and mites. If you are wanting to use a salicylic agent as your main spray ingredient then add in some peppermint oil or wintergreen oil. Capsaicin oil works well also as a contact spray. For the pepper oil you may want to wear protective clothing as the oil is a skin irritant. Jim
