Scale always seem to attach the older plants first

Hi bromadams,
Like HDD says, plus the possibility that mum could be weaker and more vulnerable because the pup has drawn on her resources during its growth.

I also find that any heat or cold damage usually seems to hit the mum first while the pups stay pretty well undamaged probably for the same reason plus they are partly sheltered by the mum as well.

All the best, Nev.

I don't see why strength or weakness would play much of a role in this. I've had scale on very healthy plants.

New scale insects are going to crawl (or fly?) toward something that they find attractive and pups don't seem to have that. Maybe they are attracted to the rotting of debris in the cups of mature plants. It seems that plants with a lot of debris in the cups tend to attract/hold more scale than others.

For the two plants I got yesterday, the oldest one was full of debris and covered with scale. The very big pup had no scale and no debris. But that doesn't prove a thing.

Hi Nick, I used to get the same thing happening when I grew native Dendrobium orchids. With the "parent" plant being much longer lived post-"pupping" (typically at least several years) compared to most parent broms, a bit of a pattern emerged. I came to the conclusion that the opportunity for the scale to colonise the plant was a relatively rare event, so a plant was more likely to get colonised the older it got simply because it had been around for longer, but it was unlikely to show up on new growth. This seemed to be pretty much the case over quite a few years, except for a couple of exceptions when I didn't notice an infestation developing and it got out of control.

Of course, broms may be different, but there seem to be a lot of similarities. I also think there may well be something in Nev's point about the parent plants being less resistant. They certainly seem to be less resistant to sunburn after pupping. Also, most plants run a constant battle of chemical warfare with insects, fungi and bacteria. It seems quite conceivable that changes in chemical defences could occur after a plant has pupped and is heading into senescence (I haven't looked for any research to support this, but it might be interesting to follow up)

Hope these thoughts help. Cheers, Paul