Seedlings dying off

[SelectOrchids]

A bit busy as of now... But for the seedlings, the problem is to keep the conditions even. If they dry out/get wet in cycles, it eventually damages the base, and result in rot. However there is more to that, and the symptoms are typical of an infection.

For the seedlings death on the photos, the only treatment is an anti-pythium/phytophthora such as mefenofam, fosetyl-al and similar as a drench. It will stop overnight. Afterwards, it is worth to check the EC of the potting mix and its pH. A lot of problems are related to those two parameter, though oomycete death can occur even if all the paramteres are fine. Simply because it is an infection...

Regarding the copper/Kocide that is copper hydroxide, it is still use by some large nurseries, and it is definitely not damaging to Paphiopedilum. It is especially efficient for wet rots types. But in that compot case, it will not help.

 

[swamprad]

For the seedlings death on the photos, the only treatment is an anti-pythium/phytophthora such as mefenofam, fosetyl-al and similar as a drench. It will stop overnight.

Regarding the copper/Kocide that is copper hydroxide, it is still use by some large nurseries, and it is definitely not damaging to Paphiopedilum. It is especially efficient for wet rots types.

Xavier, thanks for your input. As I looked at the photos, I thought it was erwinia. Please tell me how to distinguish pythium/phytophthora from erwinia.

 

[SelectOrchids]

Xavier, thanks for your input. As I looked at the photos, I thought it was erwinia. Please tell me how to distinguish pythium/phytophthora from erwinia.

Erwinia is a great rarity in Paphiopedilum. In fact pretty much all pictures of 'erwinia' or 'pseudomonas' I have seen on Paphiopedilum turned out to be oomycetes, not bacteria. I have to know because we had to run diagnosis by PCR and earlier cultures, and erwinia turned out to be very rare. There is one strain of wetter brown rot that induces a chlorosis in the plants, this is the true erwinia cypripedii, very rare. And another one that makes slow progress as soon as the plants are watered/humid enough, to stop until next time. That's pretty much all about erwinia and Paphiopedilum.

You will find out as well that mefenoxam would stop those 'bacterial rots' absolutely overnight... which is an indirect confirmation of the PCR tests...

That's one of the common problems in the orchid world, wrong information passed from generation to generation. Some of the pythium/phytophthora can induce overnight collapse with watery tissues. They are actually oomycetes, in their own family as of now, they proliferate very quickly.