Browning on Trichocereus peruvianus

[MitchellM]

This was brown and scabby looking when watered with hard alkaline tap water and sometimes Jack's Classic. It added healthy green growth when I put it outside in May. The healthy growth continued since I brought it inside and switched to hard tap water adjusted to pH around 6 and Dyna-Gro at 2 ml per gallon. I've been using gnatrol for all my plants every watering since December. This has some kind of detritivore, I think springtails, on the soil surface, and part of the main column has rotted but then dried. In the past few weeks it has signs of browning on the tip again. I'm about to cut the still pretty healthy top off and root it on it's own and repot the main column to see if it will produce more healthy pups.

Could a buildup of minerals, even though I'm acidifying the water, be causing the new browning? What about the gnatrol? For now I've switched to distilled water for all my South American cacti and using tap water only for North American desert species.

Peruvian.jpg (65.12 KiB) Viewed 619 times

[mikethecactusguy]

Is this a Graft? The lower part looks way undersize in diameter. If it is a graft, are the base roots ok?
Mike M

[esp_imaging]

You may have a mite problem if you are getting brown scabby patches forming.

Otherwise, how close is it to the lights, and how hot and bright are they?
For a point light source, if you halve the distance to the light, the light intensity goes up by 4x; go 10x closer and the intensity goes up by 100x.

The maths is more complex for intensity vs. distance with a set of strip lights, but the top of the plant looks far closer to the lights than anything else you are growing. Maybe it's too bright / hot?

[MitchellM]

Is this a Graft? The lower part looks way undersize in diameter. If it is a graft, are the base roots ok?
Mike M

The narrow part at the bottom is the way it grew on alkaline tap water. My profile picture is that same cactus outdoors getting rain water. I'm going to repot the main column today or tomorrow so I'll see what kind of shape the roots are in.

[MitchellM]

You may have a mite problem if you are getting brown scabby patches forming.

Otherwise, how close is it to the lights, and how hot and bright are they?
For a point light source, if you halve the distance to the light, the light intensity goes up by 4x; go 10x closer and the intensity goes up by 100x.

The maths is more complex for intensity vs. distance with a set of strip lights, but the top of the plant looks far closer to the lights than anything else you are growing. Maybe it's too bright / hot?

I don't think it's the proximity to the lights. I had another of the same genus poking up between the between the T5 tubes before I cut it.