nph

These two bananas are standing next to the overflow from the pool and lately we had a lot of rain so it overflowed. So these two bananas are the closest and only ones I can see with the spots. You can see it also on the p-stem for the one that has way more of them.
Could it be a disease instead?
Appreciate any help!!!

zfallon84

Edwmax, a couple of others, and I discussed my pest problem here Sun Burn, or Over-fertilized? . That one large browning spot on the one leaf looks like insect damage. As for all of the black spots, I am unsure. Maybe it's "swamp spot" (I can't remember which fungus causes it). Hopefully someone else has some info.

nph

WEll; that rea was flooded for several days when we got 9 inches of rain over a weekend recently so would make sense. The new leaves seems ok.

edwmax

Chlorine (Cl) and Sodium (Na) both will cause damage to the roots long before becoming visible on the plant leaves. Chlorine causes chlorosis at the leaf tips and margins starting as looking like sunburn. ... So what was the chlorine considerations of the pool water? ... About 1000 ppm or more is known to cause problems.



Sodium blocks uptake of essential elements causing deficiencies.


The black spots are looking more like a fungus or bacterial problem. The black mid rib seems to suggest the fungus is spreading through the sap. ... Try spraying the plants with a Bordeaux mixture (https://www.gardeningknowhow.com/garden-how-to/info/diy-bordeaux-fungicide.htm )

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nph

Well, chlorine level was low due to the rain. I always try to stay away from adding during the rains since it will overflow. So it might then have just been sitting in water and could that have caused the issue?

edwmax

Bananas are known to do Ok when irrigating with chlorine levels up to 600 ppm. ... The recommended chlorine level for swimming pools is 1 ppm (3 ppm for hot tubs). This is far below any danger to banana plants.

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louis14

Those black areas on the pseudostem look like thrip marks to me. We have the same in our fields and treat it with pesticide spraying. If this was my plant, I would encourage upward growth via severe pruning of the lower leaves, then treat, then observe if the new stem is green and not covered in black scars. But then, that is me...

edwmax

Thanks Louis, I have those marks on some of my plants too. But haven't identified them as being cause by thrips. I'm not sure if I know what a thrip looks like. I just see the black marks. ... Anyway I find that copper sulfate (& lime) will also work as a pesticide on these vary small insects/grubs due to copper toxicity and well used by by organic gardeners. ... And it is very economical to mix. ... So copper sulfate can be used as an algaecide, bactericide, fungicide, antimicrobial and molluscicide for host of gardening/Ag problems. ... I believe the Bordeaux mix with copper sulfate was first invented and used on Banana plantations in the early 1800s or late 1700s.

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louis14

Thrips are invisible to the naked eye, the marks on the pstem are not such a big problem but if untreated, they will bore hundreds of holes in the skin of the fruit, lowering the value and a cause of bursting through weakening of the skin. I assume the holes on the leaves could also be caused by thrips. This problem creeps up in the rainy season her, and requires regular treatment as the rain will wash away the coating. Thrips are causing a big problem for organic banana growers in Costa Rica for who have often had to give up the organic label for lack of a working acceptable treatment that works.

edwmax

Same here, it is that time of year for a number of problems from white flies, & thrips to fungus & bacterial problems. Many of the symptoms look the same. ... The rains may wash some of the coatings/treatments off but it go to the ground where many of the problem originate & hibernate. So on the whole that's not as big a problem as it seems other than having to re-spray the plants later. Surfactants does help to keep copper sulfate & lime stuck to the plant and reduce wash-off. I've seen it on my plants after rains.



I think the banana growers in Costa Rica might be using a commercial prepared copper sulfate mix with a pesticide added which would void any organic labeling. ... Copper sulfate is a nutritional supplement for larger animals and humans when used within USDA recommended levels. I used a pinch or 2 in the water buckets and wading pool for the chickens and ducks to control alge. Also, copper sulfate has been noted to control intestinal parasites in barn yard animals so there is no problem for the animals to drink it.

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