[argonaut]

Each year I plant cucumber plants (various varieties) in bag toppers in grow bags … and once growth starts I get issue with yellowing on the lower leaves. .. …. Top leaves are fine …. Anything I should be doing.

Have been spraying with Epsom salt solution in case its magnesium deficiency  ... although I have also read don't get water on leaves (how do I avoid that)

Have examined with magnifying lass - no mites seen.

[JayG]

Your pictures look very much like the problems I was describing in a recent thread:

I failed two or three years on the trot with all female greenhouse varieties whose older leaves bleached and died almost as quickly as they grew new ones (and then more quickly!  ) I put it down to scorching due to too much sun and maybe too little humidity, but careful positioning and shading didn't improve things much until I added fertiliser to the containers, so I have to conclude their food requirements were greater than my particular compost could provide.

The above doesn't provide the exact answer either to my or your difficulties, but at least gives you a few ideas to try (shade, humidity, extra feed - in your case that would presumably be into the pots rather than the bags.)

[mumofstig]

Google pics of cucumber mosaic virus to see if it looks like your plants.

[argonaut]

The pics seem to be different .. and in the main seems to affect fruit.

It wont be shade as sun not that strong yet .... I'll try feeding a bit

[Trikidiki]

Remember all those droplets of water you have on the leaves will act like little magnifying glasses. I would try to keep the water off the leaves and see if that helps.

[argonaut]

The only time water was on leaves was when the epsom salt solution was sprayed on ........

[BabbyAnn]

The only time water was on leaves was when the epsom salt solution was sprayed on ........

I think you answered your own question (combined with Trikidiki's comments about the droplets) - once the water evaporated, the salts would re-crystallize thereby scorching the leafs.

[argonaut]

So the advice to spray with Epsom salts mix is wrong then ?

Wasn't my idea it was given as a recommended solution to this.

[mumofstig]

It isn't the epsom salt itself that caused the problem IMO - it's just best to apply any spray when there is no strong sun on the plants, so they don't scorch.

[argonaut]

OK ... I read it as the epsom crystals were the issue.   (my fault)

Intersecting though that the first incident of  this was before I had done any spraying, so there is something else causing an issue - at least at the start.