Oak Tree decemation

[Fungus]

One of the great wonders is that tits time the hatching of their eggs to coincide with the first great flush of caterpillars.

Also the pupae hatch just on budburst as the old leaves contain too much tannin. How do they all do that?

 

Graham,

The birds react to the length of daylight. And the synergy of birds and trees sometimes goes wrong, like this year, when the hatching of the four eggs of the blue tits in my backyard had taken place two weeks before the leaves of the oak trees sprouted and the young birds died because of lack of caterpillers, i.e. food.

The hatching of the pupae of oak tree leaves depended moth on "fresh", not yet containing tannin oak leaves is restricted to some species, like Operophtera brumata. The caterpillers of the Oak Processionary, which by the way are not on the menu of birds, only eat tannin rich leaves.

[janey]

The caterpillers of the Oak Processionary, which by the way are not on the menu of birds, only eat tannin rich leaves.

 

It's my understanding that OPM caterpillars ARE predated upon until they reach their third instar, when they develop the urticating hairs.

[Fungus]

It's my understanding that OPM caterpillars ARE predated upon until they reach their third instar, when they develop the urticating hairs.

 

Janey,

You could be right, provided they have not yet become indigestible (awful taste, mildly poisonous), because of the tannin stored in their bodies without poisening themselves. So that is why they eat fully developed leaves and not just depend on the development of the urticating hairs.

Edited May 8, 2011 by Fungus

[janey]

Janey,

You could be right, provided they have not yet become indigestible (awful taste, mildly poisonous), because of the tannin stored in their bodies without poisening themselves. So that is why they eat fully developed leaves and not just depend on the development of the urticating hairs.

 

The OPM egg plaques time their hatching to coincide with the scales on the buds breaking in the spring. For the first few weeks of their life they actually feed in the buds and the newly emerging leaves which are very low in tannins.

 

It's only when they are larger and into their more advanced instars that they move away from feeding on the very tips of the twigs and start to feed throughout the crown.

 

It'd be interesting to find out if the low levels of ingested tannins play any significant part in their predetor deterant stratagy in their first, more vulnerable, instars

[Fungus]

The OPM egg plaques time their hatching to coincide with the scales on the buds breaking in the spring. For the first few weeks of their life they actually feed in the buds and the newly emerging leaves which are very low in tannins.

It's only when they are larger and into their more advanced instars that they move away from feeding on the very tips of the twigs and start to feed throughout the crown.

It'd be interesting to find out if the low levels of ingested tannins play any significant part in their predetor deterant stratagy in their first, more vulnerable, instars

 

Janey,

In The Netherlands, the appearance of the first hatched eggs of OPM always is preceded (tree species specific succession) by two to three weeks by other caterpillars, such as those of the moth Operophtera brumata, which are intolerant for tannin. These caterpillars alone, or along with OPM as successors, can leave completely leafless branches behind, by which the lammus foliage is triggered to develop, which in its turn often is infected by spores of the anamorph of the oak leave mildew. In this way, up to more then 70-90 + 30 = 100-120 % of the normal yearly energy production by fotosynthesis is lost, which ultimately weakens the energy reserve of the total tree species specific ecosystem, including the ectomycorrhizal macrofungi, dramatically, which in its turn causes the tree roots to be poorly protected against parasites or toxic elements (salt, heavy metals) and drought by (the self produced antibiotics and fungicides of) their symbionts.

In a row or lane of early caterpillar species affected Quercus robur, sometimes an unattacked oak can be found with a completely normally developed first foliage. In my experience and that of the Dutch OPM-taskforce, this always is an oak, which has fully developed its leaves two to three weeks before the surrounding oaks did, so it was no longer "edible" for tannin intolerant species hatching at that time. And peculiar enough, the leaves of this tree also are not "consumed" by their successors, the later hatching OPM and neither is the lammus foliage of the surrouding oaks if covered with the anamorph of the oakleave mildew, which has "stored" its spores in the leave buds to immediately being able to infect and completely colonize the young leaves.

What I did observe last year, was that one of these trees on the 7th of June was accompanied by three fully to overdeveloped fruitbodies of Russula amoenolens, an ectomycorrhizal symbiont, which normally fruits in October, a phenomenon which must be diagnosed as panic reproduction of the mycelium, taking more energy from the roots of the oak then the tree can afford at that time of the year when it still needs to fruit itself, producing seeds, which contain an energy reserve for five years.

All of these phenomenons have proven to be directly associated with the ammonia depostion coming from overmanured mais fields, no longer produced for cattle food, the criterium for EU-susidies, but used as fuel for the biogas installations of farmers also using neo-nicotine, which causes honeybee populations to die, as insecticides on their mais fields.

In The Netherlands, recently was discovered, that OPM not only produces nests in the crowns and on the trunks of the affected trees, but also builds nests up to 30 centimetres underneath the soil surface, which makes fighting and killing OPM even more problematic.

And a question : is known how OPM came to England ? Of OPM is noted, that the moth can not fly over long distances and also can not cross rivers or large open waters. I was the first to hypothesize, that its enormous and fast spreading over The Netherlands from the southeast to the north was brought about by caterpillars long distance travelling on top of lorries with canvas covers, which had parked for some time underneath affected oaks standing aside the parking spaces along the German and southern Dutch highways, which later was proven to be the case.

[janey]

... And a question : is known how OPM came to England ? Of OPM is noted, that the moth can not fly over long distances and also can not cross rivers or large open waters. I was the first to hypothesize, that its enormous and fast spreading over The Netherlands from the southeast to the north was brought about by caterpillars long distance travelling on top of lorries with canvas covers, which had parked for some time underneath affected oaks standing aside the parking spaces along the German and southern Dutch highways, which later was proven to be the case.

 

That's very interesting reading and thank you for posting it

 

OPM was first identified in it's larval form in this country only in 2006, so the population hasn't had the opportunity to reach such levels where it has caused significant defoliation, either in a single season or year upon year. However, common sense says that in an already highly stressed urban tree population, any additional drain on photosynthate production is going to have consequences.

 

Adult males have infrequently arrived in this country from mainland Europe for many years, with recorded sightings going back to the early 1900s. The Channel has always proved to be an effective barrier to the lazy females, who prefer to stay put and let the males come to them - as it should be . The original outbreak can be traced to a batch of imported Q robur "fastigiata" that were used in a water authority site in Kew, SW London. I don't know where these trees were sourced from. Anacdotally, there was another introduction on some more infested saplings in W London along the A40, which is one of the main routes into the city, but I don't know how accurate that is.

[Fungus]

The Channel has always proved to be an effective barrier to the lazy females, who prefer to stay put and let the males come to them - as it should be .

 

If that was the main reason , then how did the female moth of Operophtera brumata arrive in England, as they can hardly fly to not fly at all and have to walk on "lover's lane", i.e. up the tree, to await and meet male partners ?

Edited May 9, 2011 by Fungus

[janey]

If that was the main reason , then how did the female moth of Operophtera brumata arrive in England, as they can hardly fly to not fly at all and have to walk on "lover's lane", i.e. up the tree, to await and meet male partners ?

 

Club 18-30 package holiday?