Damage from cold, disease or otherwise?

[Stranger]

I've noticed some spots on a few of my plants recently, and given that I've had no experience with pests so far (knocks on wood) I'm not sure what to make of this. Here's a leaf on my N. burbidgeae x robcantleyi, the spots near the edge have appeared in the last two weeks:

The other concern is a glandulifera I got last month, here's a picture of it after potting:

It's been growing without a hitch, but those two leaves look concerning.

Cold damage has crossed my mind (nights have recently hit ~5-8 C) but I didn't think cold damage looked like that. I also have a rafflesiana x ampullaria that's doing just fine with nothing like this at all.

Thoughts on what it is? I may have to hold off on new plants for a while until this gets sorted...

 

[Cthulhu138]

Looks like it could possibly be the Cercospora fungus common to many Nepenthes. You can treat with systemic fungicides, if this turns out to be the case.

 

[Stranger]

Thanks for the pointer, further research brings up similar pictures and seems to say that it's present on most neps but is only really an issue if the plant is stressed. Huh, reminds me a bit of golden staph.

If it is Cercospora then the glandulifera is easily explained since it's probably still acclimatising, time to reevaluate the burbidgeae x robcantleyi's happiness though. Maybe it's just proximity to the glandulifera, although there's a chaniana between them with no symptoms. Systemic fungicide recommendations seem to be something with thiophanate methyl or propiconazole, will go shopping tomorrow to see what's available locally.

 

[Whimgrinder]

Cercospora and Nepenthes have evolved together - for many species of the genus. I see a clear propensity for certain species (and their hybrids) to show some degree of infection much of the time. Its only of concern when/if the plant becomes overwhelmed with the affliction, which indicates something wrong with the conditions the plant is being exposed to. Yes, propiconazole will suppress the fungus, but it won't eliminate it, and eliminating Cercospora shouldn't be the goal anyway; evaluating your growing conditions and fine-tuning for optimal growth is more important.

That said, 5-8C is a temperature range you should avoid exposing highland Nepenthes to as much as possible - that is too cold. Anything more than a few nights in that range can stress the plants and set you up for disease processes. You're exposing rafflesiana X ampullaria to those temps?! That's asking for trouble.

 

[Stranger]

Thanks for the info Whimgrinder, will reevaluate growing conditions further. Those minimums are typically rock bottom minimums for short times (average night temp is more like 10 C) but you're right that they're still low, I've been looking at better insulation recently. More bubble wrap! In the meantime the daytime temps are still reaching 26-27 C, which is hopefully helping to take the edge off things.

The rafflesiana x ampullaria is a curious one though, the supplier said that despite its heritage they've successfully grown it with their highlanders and my experience to date has corroborated that. I don't mean to sound like I'm brushing off your advice (I value it greatly) or sound like I have some sparkly unique plant, but have you heard of any similar cases? I've heard of intermediate/highland ampullarias, but their near-mythical status makes me doubt that it's involved in this particular plant.

 

[theplantman]

Cercospora and Nepenthes have evolved together - for many species of the genus. I see a clear propensity for certain species (and their hybrids) to show some degree of infection much of the time. Its only of concern when/if the plant becomes overwhelmed with the affliction, which indicates something wrong with the conditions the plant is being exposed to. Yes, propiconazole will suppress the fungus, but it won't eliminate it, and eliminating Cercospora shouldn't be the goal anyway; evaluating your growing conditions and fine-tuning for optimal growth is more important.

That said, 5-8C is a temperature range you should avoid exposing highland Nepenthes to as much as possible - that is too cold. Anything more than a few nights in that range can stress the plants and set you up for disease processes. You're exposing rafflesiana X ampullaria to those temps?! That's asking for trouble.

+1 Definitely Cercospora.

 

[RandyS]

That said, 5-8C is a temperature range you should avoid exposing highland Nepenthes to as much as possible - that is too cold. Anything more than a few nights in that range can stress the plants and set you up for disease processes. You're exposing rafflesiana X ampullaria to those temps?! That's asking for trouble.

That would eliminate virtually all of even Coastal Southern California as a place to grow highland species outside. Avoiding 5-8 C (41-46 F) would even be right on the edge for the immediate coast in San Diego. The average at the airport in December is 48 F (9 C). Some other places, average December low: Oceanside (San Diego Country) 44 F (6 C), Laguna Beach (Orange County) 43 F (6 C), Santa Barbara 43 F (6 C), Monterey (Central Coast) 44 F (6 C)...