Trump transgender notice, Milton Elm lost

Traces of  Elm bark beetle larvae and Dutch Elm Disease fungus

Today, with three tweets, President Trump, put several thousand transgender military employees on notice that they would not be able to continue to serve. This for a saving of between 0.004% - 0.017% defence spending on health. It achieved the result of deflecting interest from the Russia enquiry and, in part, from the Health care debate. Jeff Sessions still publicly attacked.

Yesterday I noticed tree surgeons working on a large tree next to Milton's All Saints Church. Today they had completed reducing a venerable giant into pieces that would fit into a skip. Curious, I wandered over and asked why the tree had been felled. It was a 100 year old plus Elm that had finally succumbed to Dutch elm disease. It was one of the very few last giant survivors of the Elm in the UK. 

The disease is caused by Ophiostoma species of fungi, which are spread by elm bark beetles. The beetles bore into and under the bark, and the fungus they carry in then spread into the wood underneath. To protect itself, the tree block off the vessels transporting water and nutrients up and down the tree, effectively resulting in a slow death.

One of the tree surgeons picked out a piece of bark and there was a decorative filigree of the channels the bark beetle larvae had carved, some of them lined with white, where the fungus had multiplied.

The battle has possibly been going on for thousands of years. The Elm used to be abundant 6,000 years ago, then less so  3,000 years ago. But it was the spread of a more virulent strain from the 1960's onwards that killed more than 25 million trees in the UK alone, till there were only isolated trees like the one in Milton left. 

There are still 17,000 elms in Brighton & Hove, as a result of a strict program of sanitation felling, pruning, girdling (to prevent infection getting to the roots - this also kills infected trees) and root trenches, to prevent the fungus spreading through touching root systems. It is a radical disease control that works locally.

Elms have not disappeared from the rest of the UK -  they are present in hedges. As long as they are kept below 20 ft (6 m), they will not be infected. 

The reason is that above this height, the tree begins to produce future flowering twigs. These attract the female Elm bark beetles who chew the bark. The flowering hormones in the bark stimulate the beetles to become sexually mature, to go out and find a mate and produce eggs. At this stage the female returns and chews deeper into the elm bark to create a brood chamber. It carries with it the fungus, which actually acts as a food source for the larvae that hatch. As the larvae carve out chambers under the bark, the fungus spreads, infecting more of the tree and providing more food for the beetle larvae, which then hatch out to boost the beetle population.

Coppicing or hedging stops the elms from maturing to flowering, breaking the cycle.