leaf spot disease on ilama

[brian]

My ilama scion seems to have a bacterial or fungal disease causing warty spots on the leaves.  Any idea what this might be and how to treat it?  I would hate to lose this scion and successful graft.  The rootstock trees (cherimoya) have no symptoms, nor any of my other annonas. 

[JCorte]

Hi Brian,

There was a previous discussion regarding this same leaf issue.  Response from member Fleep:
It’s either intumescence or edema or a mixture. It’s a physiological response and not one caused by disease or nutrient deficiencies. Unfortunately there isn’t any definitive solutions to the problem and there are still studies to find out what causes it for other plants such as in some cultivars of tomatoes and sweet potato. In my experience I’ve had happen mostly on cloudy, gloomy and rainy weather. Edema and intumescence are different by the way but because they look similar they are sometimes used interchangeably. Intumescence is light quality specifically lack of enough ultraviolet light while edema is related to too much water uptake through the roots and the leaves aren’t able to output it fast enough and results in the blisters, high humidity and  low temperatures may tie in as well. Grow lights with just the visible light spectrum do not help btw./i]

Link to thread:
https://tropicalfruitforum.com/index.php?topic=47695.msg462585#msg462585

Janet

[brian]

Wow, thank you so much for pointing out this thread.  My experience matches exactly... plants are in a greenhouse (glazing blocks UV entirely), it has been overcast and wet for a week, and only ilama affected not other annonas.

I guess I can try moving the container/grafted one outside the greenhouse during the day.  I can't move the in-ground one, it might end up that it is impossible to grow ilama in a greenhouse because of UV requirements!  That would be unusual, never heard of such a thing

[Fleep]

I would try keeping it outdoors until weather drops no less the 45°f. In general low temperatures don’t favor proper wood development on green branches of some tropicals. I’m not sure what the temps are out your location. But don’t expect fast growth until temps are between 70-100°f. During 50-70° you may not see any growth. I would keep the ilama outside the greenhouse as much as possible. Note that hardened leaves aren’t affected so once the growing season is over and growth has slowed on the ilama most of the leaves will be hardened and you can place it in the greenhouse sacrificing only the tips until the ilama wakes up from its dormancy. If it rains a lot where your at, or you tend to overwater in the spring, you might consider switching to fabric pots. Overwatering affects new growth especially in the winter and spring and it’s just not a great combination with what your going through right now. If the grafts don’t survive. I would give it a shot with seeds when temps are above 60 or 70° outdoors with fabric pots.

[brian]

It has been 8 weeks or so since I first posted, and the affected leaves had fallen off and were replaced by healthy new leaves that do not show the same symptoms.  Meanwhile, the same scion still in my greenhouse shows the symptoms with new leaves!  It looks very much like UV light is the answer.  I wonder if I will need to set up supplemental light for this tree, or give up on it entirely.  Or, maybe it can stay forever in a container as a 3-season tree and defoliate it in winter.

- container ilama scion outside looks great



- in-greenhouse ilama scion looks bad

[Fleep]

This is my second attempt at growing an ilama. Not the best looking sapling, but so far this second attempt is working in my favor. It’s currently going through it’s second year of growth from seed. In my opinion, I would strongly recommend against defoliating it anytime during the winter in your climate. The leaves that have matured are unaffected unlike fresh new leaves. Believe it or not, those mature leaves are what are keeping the tree alive. Ilamas don’t go dormant in the same sense as maple or oak tree. In its native habitat, drought is what keeps a tree semi dormant. In our climate, low temperatures are what keep a tree semi dormant. But their are still proceses in its semi dormancy occurring that are not visible to us. So please let the leaves drop naturally until it warms up for you to see it actively growing again. In my second attempt I chose to use fabric pots. I did this to prolong the life of the leaves and roots. Rotting roots cause premature leaf drop which causes ilamas to flush sometimes in the winter in warm enough weather and I can’t help watering In the winter. I was still able to keep the trees old leaves through most of the winter even with watering. I read somewhere that someone was able to keep ilama alive without watering in the winter in regular plastic pots but I can’t vouch for that. One added benefit of fabric pots is it will help with the Sun and heat not cooking your roots in the summer and keep premature flushing in the winter if it warms up to early before the last frost. I considered investing in lights, but most of what I see in stores nowadays are led based which emit no UV rays. The older bulbs like incandescents and fluorescents emit some but I am not sure if they are worth it. And Most uv lights sold online aren’t meant to be used an entire season or they will roast your plants or be bad for you if exposed too much. Personally, I feel that if you can prolong the health of the mature leaves, then it’s possible to keep the tree alive and healthy an entire winter season.