Wednesday, 19 July 2017

Summer update

Once again, it feels like absolutely forever since I updated my blog (because it has). I have been tremendously busy with one thing or another, but I continue to buy (rather too many), grow, and bloom (rather too few) orchids.

I learned a rather hard lesson in June when I went on holiday for a week to Scotland (very nice, thank you for asking). Usually in the UK June is quite wet and not usually hot. This year has been rather different and June was very hot indeed (at least by UK standards) and very dry indeed (at least in my area, not so across the country as a whole). Usually when I go away, I close the growroom window and door to keep some humidity in and give the plants a good watering before I go away. Normally I find the plants have dried down quite nicely over the course of a week and need watering again upon my return. Not so this time. I came back to find the plants till far too wet (you can see what's coming, can't you?). At first glance the damage didn't seem too bad but as any grower will tell you it can take ages for orchids to respond to anything and it is only now, a month later, that I am finding less black rot in my plants and new growths are starting to open out properly. Notable deaths include Cochleanthes discolor and Coelogyne Orchideengarten Joaquim. Both of these rotted very fast and my efforts to cut out the rotted parts were unsuccessful, sadly. Coelogyne velutina rotted out two new growths and it is still touch and go for some of the others, though the rot hasn't spread into the pseudobulbs and the plant has started to put out more new growths to replace the ones lost. Dendrochilum magnum has almost completely defoliated, though this years new leaves and all pseudobulbs are undamaged. Many other Dendrochilum have ugly spotting on their leaves now, and I think I am going to lose D. coccineum altogether, though I haven't binned it yet. Lesson learned. Next time I shall leave the growroom door open to keep the air moving.

I think I have tracked down the source of the ugly spotting and blotching on many of my Phalaenopsis leaves - mites. I thought I was familiar with red spider mite attacks, and I can usually just about see the little blighters with the naked eye, but it appears that there is a new mite in town that I can't see with the naked eye, and it has been wreaking havoc among my Phalaenopsis (but only my Phalaenopsis, so far as I can see). I had assumed that the damage must be fungal (the visible damage almost certainly is a secondary fungal attack), but having seen the classic silvery appearance of the foliage and flower spikes, I am almost certain it is a mite problem I have. They seem to like P. mannii and amboinensis and their hybrids the best, and seem to leave P. violacea and its hybrids alone altogether. Very odd. I have sprayed with an insecticide to which I have added some soft soap to help with leaf coverage and soap has anti pest properties of its own, as I have discussed in earlier posts. I will spray again at the next watering cycle to catch any eggs hatching, and will continue to spray until I am certain that subsequent generations have been killed.

It all seems doom and gloom, doesn't it? Not so, I'm pleased to say. I am now much less concerned about virus being present in my collection, as I am almost convinced that most problems are environmental and fungal. I have fitted a fine net curtain at the growroom window so I can leave it open without fear of letting lots of pests in, and the result is that I have had no aphids at all this season, so that is a definite improvement on previous years.

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