Phal Orchid leaves with patchy green and yellow areas

[sweta]

Hi Orchid Pals,

I have had this grocery store bought phal for about 3 years now. 1st year it rebloomed but after that had scale infection so it went though a setback for a period of time but its been doing good past few months with new leaves and healthy roots. Now I see that now the leaves have suddenly turned patchy and slowly dying off. There are 2 to 3 more of my phals that are showing similar signs that have been close to this one. Is it bacterial or fungal disease and what treatment can I give it so its healed from the disease? I'm attaching pictures. Home temperatures are arounr 70F watered weekly, fertilized biweekly.

[estación seca]

What are the numbers on the fertilizer? How much fertilizer do you mix in how much water? It could be nitrogen or magnesium deficiency. Is there magnesium in your fertilizer?

[sweta]

Originally Posted by estación seca

What are the numbers on the fertilizer? How much fertilizer do you mix in how much water? It could be nitrogen or magnesium deficiency. Is there magnesium in your fertilizer?

Hi es, I use the repot me fertilizer and yes it does have magnesium. I mix in 1.5 tsp in 1/2 gallon of tap water. Our tap water is moderately alkaline so after adding in the fertilizer I try to adjust the pH to be 6.5 with pH down solution that I got with my hydroponics gardening kit. Winter times I try as to use rain water but summer times I just use tap water and adjust the pH I'm attaching pic of the fertilizer ingredients

[Ray]

For that formula, you should be applying your current solution every week, not every two.

Do not bother adjusting the pH, as the solution pH does not affect the rhizosphere pH very much, if at all.

Is the medium getting dry between waterings? If so, water more frequently.

[sweta]

Originally Posted by Ray

For that formula, you should be applying your current solution every week, not every two.

Do not bother adjusting the pH, as the solution pH does not affect the rhizosphere pH very much, if at all.

Is the medium getting dry between waterings? If so, water more frequently.

Oh yes you are right didnt realize I have to increase the fertilize during the summer months hmm so this is probably due to nutrient deficiency.

The medium doesnt get dry between waterings. In fact I have to wait longer to water than the usual watering schedule for my other orchids.

Regarding the pH, I've been reading up online that for nutrients to be absorbed properly phals need slighly acidic medium like 6.5 pH. Wont it make any difference if the water content is alkaline? I dont get a great bloom show thats why wanted to see if this would change anything

---------- Post added at 03:09 PM ---------- Previous post was at 02:56 PM ----------

@es and @ray should I treat my orchids with cal-mag just for few weeks to overcome the deficiency?

[Ray]

Originally Posted by sweta

Regarding the pH, I've been reading up online that for nutrients to be absorbed properly phals need slighly acidic medium like 6.5 pH. Wont it make any difference if the water content is alkaline? I dont get a great bloom show thats why wanted to see if this would change anything

If the water is high in alkalinity - which is not the same as having a pH above 7 - it will eventually shift the rhizosphere pH upward.

As far as pH affecting nutrient availability or the ability of the plant to take it up, that is only true if the pH is toward the extreme ends of the scale. Please read this and this.

Besides, microbes and the plant, itself, affect the pH far more than does the solutions applied. Prove it to yourself by doing a simple pour-through test, described in one of those articles.

@es and @ray should I treat my orchids with cal-mag just for few weeks to overcome the deficiency?

Yellowing - assuming it really is a nutrient deficiency - is caused by a lack of nitrogen and magnesium, not calcium. If you simply go to a more appropriate feeding regimen, it ought to resolve it going forward. The affected leaves may not recover.

[sweta]

Originally Posted by Ray

If the water is high in alkalinity - which is not the same as having a pH above 7 - it will eventually shift the rhizosphere pH upward.

As far as pH affecting nutrient availability or the ability of the plant to take it up, that is only true if the pH is toward the extreme ends of the scale. Please read this and this.

Besides, microbes and the plant, itself, affect the pH far more than does the solutions applied. Prove it to yourself by doing a simple pour-through test, described in one of those articles.

Yellowing - assuming it really is a nutrient deficiency - is caused by a lack of nitrogen and magnesium, not calcium. If you simply go to a more appropriate feeding regimen, it ought to resolve it going forward. The affected leaves may not recover.

Thats very interesting Ray. I will try the pH test suggested in the article.

Yellowing - I will go to an appropriate feeding regimen as suggested.

Thank you Ray!