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  • Root Knot Nematode (RKN) symptoms and treatment

    One of my little trees broke bud in late January, but last week I noticed that the little leaves and terminal bud has shriveled up. I suspected either over or under watering at this critical stage. I pulled the rootball from the pot and took a look -- the soil looked neither over or under watered, and there were nice, healthy-looking roots visible. This tree was purchased as a bare-rooted little yearling tree in early 2014. It had great looking roots, a bit of growth, and seem to have survived the winter OK (other than breaking dormancy early.)
    I happened to look at the underside of the container and noticed a little misshapen root near one of the draining holes. It looked like it had what could be some RKN galls on it.

    I haven't pulled the soil away from the roots yet to see if it really is RKN and how extensive it is.

    Would even a mild case of RKN be enough to cause the leaf/bud shriveling I noted?
    Now I'm worrying that the RKN came in on a batch of composted pine bark fines or something....in which case other trees can be infected.

    I've read about successful treatment by bare-rooting, submerging in hot water, and re-potting --- but I can't imagine doing that to all my trees.

    Has anyone had success with other treatments. I could certainly envision watering all my trees with beneficial SF predatory nematodes.

    I'm reading up on other treatment approaches, but I thought I'd kick off an RKN thread on this new forum ;-)

    I'll also have to look at the roots more closely. Has anyone ever seen misshapen roots that weren't caused by RKN?

    Jim -- Central NJ, Zone 6b

  • #2
    RKN usually thrive in dry sandy locations, they don't like soils with high organic content or moisture.
    I've seen lots of enlarged and deformed roots that were not caused by RKN.
    A picture would help to ID. Good luck.
    Pete R - Hudson Valley, NY - zone 5b


    • #3
      I ended up crushing the 2 or 3 galls apart with my thumbnail after I plucked it off the end of the root it was growing on. Later today when I pull it from the pot and loo through the bottom roots more closely, I'll keep my camera handy. ;-)
      Jim -- Central NJ, Zone 6b


      • #4
        Just a few galls would not harm the plant at all and would certainly not cause any symptoms on the plant.
        Cutting sales will start Tuesday Nov 1 at 9:00 eastern


        • #5
          I had a break out of RKN last year and lost some good ones..... my head wasn't working well and I automatically thought they would be dead this winter when dormant. Well I dumped 3 trees in the trash container. (I got a few cuttings out of them) I should of just waited and tried to get an air layer out of it. The main thing I noticed is that it didn't kill the tree, it restricted the water as WillsC said.


          • #6
            Armando, do you know where yours came from? It seems it was an isolated incident
            USDA z 10a, SoCal. WL: Boysenberry Blush


            • #7
              OK, I had a busier weekend than expected, but I got a couple of pictures. Better late than never. I didn't get a chance to dissect the whole rootball. However, I pulled it apart just a little bit and checked out the roots on the sides and bottom. Many of the roots I can see look nice and healthy, and there are clear signs of active root growth. There are a fair amount of smaller roots that are dead. Maybe these dried out over the winter. It could be that the tree broke bud and wasn't getting enough water, so the leaves and bud dried out...but then since I watered it, it started putting out new root growth.
              The only signs I see of what looks anything like RKN galls were at the very bottom of the pot. There were no signs of deformed roots anywhere else (i.e. not up the sides.) Again, I haven't ripped it all the way apart to look in the center yet. The malformed roots all seemed to be around the areas of the pot where the drain holes were. On this particular pot, the bottom is "castellated"where each drain hole lies. (i.e. it isn't just a flat surface with holes.)
              Here are some pictures showing the overall rootball and some close ups of the roots that caught my eye.

              Does it look like a mild case of RKN just starting? Or is this somewhat typical of roots at the bottom of containers?
              You may only view thumbnails in this gallery. This gallery has 7 photos.
              Jim -- Central NJ, Zone 6b


              • #8
                Here are a couple of photos. Root system was badly affected. Plant was stunted, leaves and fruits dropped. No choice but to get some cuttings before throwing the tree away. Sayonara Red Khurtmani
                You may only view thumbnails in this gallery. This gallery has 2 photos.


                • #9
                  The problem with generalizing RKN is there are so many varieties. Most of what we talk about is Southern RKN which is susceptible to both heat (kills it) and cold (slows it down considerably). The Northern RKN are not so affected by cold. I do not think that RKN care in what kind of soil they are growing as they are found worldwide. Soils rich in nutrients, however, attract other bugs which are predatory to RKN.

                  While I wouldn't necessarily plant a fig tree in a whole that is known to be infected with RKN, I, also, wouldn't necessarily dig one out. In the ground the roots of the fig tree will generally outpace the RKN. All other things being ok, the tree will generally survive (and sometimes thrive). This is because RKN has extrememly slow mobility on its own. It is through other interventions (human, rain, wind, tools, machinery, etc.) that RKN travels more than a fraction of an inch per year. In a container, RKN is an eventual death sentence for the trees. The roots are constricted in area and just cannot escape the infestation. If you only see a handful of gals, I do not think it would enough to cause problems, Without removing the growing mix, it is difficult to know the extent of the problem. Also, it is possible to have an infestation and not necessarily see a lot of gals.

                  The problem with other methods to removing RKN is they might kill the nematodes in the soil (the juveniles looking for a host root) but do not penetrate the roots to kill the nematodes which is where the mature female lays the eggs (either fully or partially enclosed in the roots). So your method would need to continually disrupt the life cycle of RKN. A bathtub can hold a lot of plants. A simpler option might be to enclose the root ball of a tree in a clear (1st choice) or black (2nd choice) garbage bag after watering and leave exposed to the summer sun for a day or two. I'd keep them quarantined then bare root a few trees to make sure the treatment worked before considering it a success.
                  Littleton, CO (zone 5b) - In Containers
                  N.E. of Austin, TX (zone 8b)- In Ground.


                  • #10
                    Thanks for your reply. I was hoping you'd post. I'd followed some of your heat-treatment threads, and I considered that to be something I might eventually have to do. I thought I'd have to bare-root it and submerge the roots in hot water to do that. Hopefully the tree will make it to the point where I can expose the rootball to the hot summer sun. (That feels like a LONG WAY OFF given the snow and temperatures up here in the northeast lately!) This tree is being grown in a pot...
                    If I tried the predatory SF beneficial nematodes, I realize that I'd have to make a couple of applications to get them. And maybe I'd have to do some root pruning of the galls to improve my odds.
                    Jim -- Central NJ, Zone 6b


                    • #11
                      RKN are tough here in our sandy fl soils, I have read that french marigolds have the ability to kill RKN you can plant them in your pots with the fig trees. From your pictures that doesn't seem like a bad case to me, You can send soil samples to find out for sure if you have RKN .I sent my samples to UF for analisis found out I have RKN, Sting and stubby nematodes in some of my soil. Im working on adding lots of organic matter and mulch to my trees and plant some marigolds.


                      • #12
                        Very interesting. I learned something....that there is Northern RKN. I thought it was just a Floridian problem.

                        Question: Will Nematicides be effective for both containerized and grounded trees? I just read about an organic/natural Nematicide called 'NEMASTOP' made by American Natural Products. Can these products be used to prevent, and cure infestations? Just asking. Why? I don't want them living in the roots of my trees. Also, since I asked....will systemic granules like BONIDE also effectively kill Nematodes?



                        • #13
                          This doesn't mean there's a Northern RKN. The tree in question was purchased as a bare-root plant in Jan 2014. My notes say that it had great roots in good condition, but that doesn't mean there wasn't some RKN. I'll have to look up the address of the seller and see if they were from the south. If not, it is still possible they picked up RKN before I got them.
                          It is also possible there was some cross-contamination from one container to another once I got them. My notes on two other trees I received about a week later say that they had mild RKN. (They did not survive to break dormancy: I believe that I over-watered the soil they came in, which was not well-draining, and the roots rotted.)
                          Jim -- Central NJ, Zone 6b