Phoenix theophrasti - Leaf Spot disease

[kinzyjr]

I've been noticing that some of my small Phoenix theophrasti are not growing at their normal speed.  Most Phoenix species have issues with graphiola leaf spot here in Florida, but it is usually a minor cosmetic issue.  The leaf spot on my Phoenix theophrasti seem different than the leaf spot on my Phoenix dactylifera.  I did some research and found that a leaf spot disease was attacking some Phoenix theophrasti in Greece:

First Report of Leaf Spot of Phoenix theophrasti Caused by Paraconiothyrium variabile in Greece

vs.

Graphiola Leaf Spot - UF

Graphiola Fact Sheet

From what I see online and in my garden, it would appear the disease affecting my Phoenix theophrasti is the disease described in the research first article; with the ovoid brown spots matching the description.  I'm assuming that since it is a fungal disease as well, fungicide would be a method of disease control either way.  Anyone else that grows these have any experience fighting with this?

Phoenix theophrasti:

Phoenix dactylifera with graphiola:

[Steve in Florida]

I had the same leaf spotting on seedlings grown from Greek locality seeds while three crops from Cretan seeds had none. 

[kinzyjr]

Oddly enough, this batch came from Greece and my former batches predominantly were sourced from Crete or Turkey.  I hadn't thought about that until you mentioned it.  I've had a few in this batch decline to the point of death due to the spotting.

Did you have any luck treating the disease?  toss out the diseased plants?

[Fusca]

That's a bummer - the graphiola is bad enough but this leaf spot looks to be much worse.  My theo. has perhaps a moderate infestation of the graphiola but still looks terrible to me.  I hope you can treat it and save them.

[Steve in Florida]

50 minutes ago, kinzyjr said:

Oddly enough, this batch came from Greece and my former batches predominantly were sourced from Crete or Turkey.  I hadn't thought about that until you mentioned it.  I've had a few in this batch decline to the point of death due to the spotting.

Did you have any luck treating the disease?  toss out the diseased plants?

I don't believe they had graphiola leaf spot.  They developed dark leaf spots, with no edge staining or discoloration,  during cool wet nights.  I would get warm and dry periods and the spotting would stop spreading until the next period of cool and wet would affect the new growth.  I tried three systemic fungicides that had no affect.  The Cretan seed source is the only source that has been 100% free of the spotting.  Now I think it may be a form of phytophthora and  a product containing 45%  mono- and di- potassium salts of phosphorous acid may be used to control it.  

Edited June 4, 2019 by Steve in Florida

[Merlyn]

Per my comments on the other thread, I had a Canariensis with the same leaf spots caused (I think) by growing in a heavily shaded corner of a local nursery.  With full sun from 10am-3pm all year and a single soil drench of Banrot, all the new fronds are growing out clean.  After ~14 months of growth I'm probably going to cut off the last infected frond soon.

[kinzyjr]

1 hour ago, Merlyn2220 said:

Per my comments on the other thread, I had a Canariensis with the same leaf spots caused (I think) by growing in a heavily shaded corner of a local nursery.  With full sun from 10am-3pm all year and a single soil drench of Banrot, all the new fronds are growing out clean.  After ~14 months of growth I'm probably going to cut off the last infected frond soon.

I'll give a soil drench of Banrot a try.  I have them growing in areas that are sunny and partially shaded.  Ironically, the one with the least spotting out of the bunch is in the shadiest corner. 

[NC_Palms]

@kinzyjr I've noticed the same leaf spots on my P. Theoprasti that I got from you last December. Not a concern for me though; the seedlings are starting to grow pinnated leaves now instead of the strap leaves that young palms are known for. Hopefully soon I will plant them in the ground. 

[UK_Palms]

57 minutes ago, NC_Palms said:

@kinzyjr I've noticed the same leaf spots on my P. Theoprasti that I got from you last December. Not a concern for me though; the seedlings are starting to grow pinnated leaves now instead of the strap leaves that young palms are known for. Hopefully soon I will plant them in the ground. 

You'll never get away with planting Theophrasti in the ground in your location. I have just checked and your record low is -20C with an average low of 0C in January. I am at the very edge of the boundary, climate-wise, for growing Theophrasti and even here they are a risk during cold winters. But my record low is only -13C and my average low in January is around 3-4C. And my yearly rainfall is less than half of yours. I wish you the best of luck with it, but I can only see it ending one way. To put it in perspective, I'm sure that Texas Cold Hardy Palms guy has lost a bunch of Theophrasti's during winter in Dallas, TX...?

[Laaz]

I would agtee, mine took quite a bit of damage @ 16F in the freeze of Jan 2018. They recovered quickly, but also have 6 ft of trunk.

[UK_Palms]

30 minutes ago, Laaz said:

I would agtee, mine took quite a bit of damage @ 16F in the freeze of Jan 2018. They recovered quickly, but also have 6 ft of trunk.

And you're 250 miles further south than @NC_Palms and you're also right on the coast, right. Yet you're trunked Theo's took considerable damage. 

Even in my location, I think Theo's would get wiped out every 10 years or so, when it gets cold enough. Snow in the crown especially seems to make them spear pull, or at least for people in the UK. 

[RJ]

I have been told there is a large one in Columbia, SC, although I have yet to get over to it and actually put eyes on it. 

 

Here is where I read it: 

 

 

Edited June 17, 2019 by RJ

[NC_Palms]

@UK_Palms @Laaz Okay I thought these were way hardier. Hearing about these getting damaged in Charleston is making me lose hope on their survival here. 

I have had luck with CIDPs but I keep them protected in the winter. I am convinced that CIDPs are more root hardy than Butia since I’ve seen them survive winters that killed off many of the Butia along the NC coast. 

I guess it never hurts to try P. Theoprasti in my climate, but I think I will keep mine potted for a few more years to allow for more growth and then decide what I will do with them. 

[Steve in Florida]

Phoenix theophrasti from Crete are tough.  I had a bunch from two gallon to 15 gallon that endured at least 7 hours at 14F.  The rootballs froze solid and the bottommost roots died at the ends.  These grew back and the toots were completely replaced in less than three months.

[Laaz]

Our freeze wasn't normal, it started out as rain then freezing rain then pure ice & then about 6 inches of snow. The leaves snapped from the weight of ice on them. Many roads that were in the shade had ice on them for over a week.

[UK_Palms]

12 hours ago, Steve in Florida said:

Phoenix theophrasti from Crete are tough.  I had a bunch from two gallon to 15 gallon that endured at least 7 hours at 14F.  The rootballs froze solid and the bottommost roots died at the ends.  These grew back and the toots were completely replaced in less than three months.

Surely the Cretan sourced ones would be the least cold hardy variety? Crete is an island surrounded by the warm Med and it never drops below freezing, apart from in the most mountainous regions. But the part of Crete where Theophrasti grows never see's temperatures below freezing.

The populations on the Greek & Turkish mainlands would almost certainly be hardier, as they are accustomed to freezing temperatures most winters, when cold fronts hit and make it through, and the ones in those places also experience far higher rainfall, especially during winter. So I fail to see how the Cretan ones could possibly be hardier. 

But none of that is based on fact. Just logic. I guess we would need to phsyically test all 3-4 sub types of Theophrasti alongside one another.  

[Steve in Florida]

12 hours ago, Laaz said:

Our freeze wasn't normal, it started out as rain then freezing rain then pure ice & then about 6 inches of snow. The leaves snapped from the weight of ice on them. Many roads that were in the shade had ice on them for over a week.

I surveyed many of the large Phoenix palms in Panama City and Panama City Beach, FL after a rare freezing rain event where the high was only 33-34F and the low was 19-20F.  All had moderate to heavy leaf damage.  I only found three date palms that were completely unfazed by the ice event. They were surrounded by the dark asphalt of a newly paved parking lot and of sufficient height that the ice may have melted after a much shorter time then other places.