A new threat to an old man

Question

Old man Geppetto was feeling bereft;
It was only a week since young long-nose had left.
He’d be back in a month from his trip to Iraq,
But the old man just missed him and wished he was back.

His Vulgarian penpal had sent him a letter.
He thought to himself “This will make me feel better.”
He opened it up with a smile on his face,
But it was clear from the outset his joy was misplaced.

“My Dearest Geppetto”, the missive had started,
“I have tidings of woe that must now be imparted.
Though the Baron is banished and the children are free,
A new threat has risen for you and for me."

"Our future’s in danger but there’s naught to be done,
For this threat isn’t one that can be overcome.
I’ve have sent you some rhymes that will help you to know,
The name of our most unassailable foe.”

Please help poor Geppetto decipher the clues
To the cause of the Toymaker’s worrying news?
The theme is traditional, but as you will spot
The riddle’s solution is certainly not.

• Two dozen turdus in a spot, a regal treat made them hot
• A construction calamity what can we do? It’ll take bit more than paper and glue.
• The sound of sternutation twice before our ruination.
• A surfeit of kin in an unsuitable place for an overstretched mother with lines on her face.
• Lost by a trio when someone was scared, but these little athletes were already impaired.
• I specialise in horticulture of a kind most strange now can you see how all my beauties were arranged.
• A sedentary location for some self-congratulation

Answer 1

Partial answer:
Each rhyme is a:

nursery rhyme

In order:

- Sing a sing of sixpence (Four-and-twenty blackbirds, baked in a pie)
- Humpty Dumpty London Bridge is falling down (credit to CodeNewbie)
- Ring a ring o' roses (sternutation is sneezing - "atishoo, atishoo, we all fall down" - originally about the black death/bubonic plague)
- There was an old woman who lived in a shoe (I can't remember how this one goes, but I'm fairly sure she had a lot of children)
- 3 blind mice (they all ran after the farmer's wife//who cut off their tails with a carving knife)
- Mary, Mary, Quite Contrary (How does your garden grow?)
- Little Jack Horner (sat in a corner, and said "What a good boy am I!") (credit to dennis deems)

Making use of the highlighted sections:

- The regal treat is a pie
- The construction calamity is London Bridge itself
- The sound of sternutation is, onomatopoeically, atishoo
- The unsuitable place is a shoe
- The thing the trio lost was their tails (cut off with a carving knife)
- Mary's flowers (and pretty maids) were arranged all in a row, row, row
- And little Jack Horner's sedentary location was a corner

Putting these all together, and taking their first letters, we find that the threat to Gepetto is

plastic - modern mass production techniques and quick formation of molded figures are certainly a threat to his slow creation of hand-carved puppets

Answer 2

The last one is

Little Jack Horner
Sedentary place: "Little Jack Horner sat in a corner"
For some self-congratulation: And said 'What a good boy am I!'