Feeling a little bit sick in the morning. Nothing major, just glands up and feeling a tad gross. First thing this morning, made some compost tea. After that me and Keely took some soil samples from the Poinsettias on the west walkway of the main conservatory. A large portion of the 'Orion Red' cultivar have started to crash. The biggest symptom being wilting, even when the soil media is still moist. The most likely culprit is Pythium root rot. The samples that we took will be sent to the University of Delaware for confirmation (though Mike seemed pretty confident...). Without having the resources of a university, a good way to diagnose a root rot (admittedly unspecific...) is to gently pull the roots. If the outer layer slides back then a root rot (of some form) is present. When we arrived back at the lab I read a little about Pythium in the excellent book Diseases of herbaceous perennials. Pythium, like Phytophtheras, used to be classified as a fungus. They have recently been reclassified and are now in a completely different kingdom, the Chomalvolata. But are still thought of as being fungus-like organisms. Plant diseases are an area I feel I could learn a lot more.
After lunch me and Carolyn scouted Joyce's 14 house and the Palm house. I found more of the unidentified scale, this time a slightly larger colony. I still have to get Mike to have a look at it. I also found some more parasitised brown soft scale. The scale are parasitised by a tiny wasp that lays an egg directly into the scale. The grub then proceeds to eat the scale from the inside out. Last week I found a parasitised specimen, and accidentally squashed it while trying to dissect it under the microscope. Today though, I was a little more successful! I found a parasitised scale (not hard, theres a few of them. You can tell them apart from normal scale as they're a darker colour and slightly swollen). I then gently pulled the scale casing away under the microscope using a scalpel. A bit of prising, and there was a kinda startled looking wasp. Which then started to run off (I guess its wings weren't developed fully)... So I put it in a petri dish with some alcohol. Sorry wasp. Felt a bit bad killing beneficials... But now I have to ID it.... It is most likely a species of Aphytis, Coccophagus, Encarsia or Metaphycus (from http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html).
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