Wasp in jail

Long time ago, I used to accompany my father in the woods. He worked for the French State Forests Department. He taught me all he knew about trees, birds, stars… He stressed the importance of biodiversity and sustainable development. 

I enjoyed asking him the name of every plants and animals on our path. One day I found a small ball on an oak leaf. He explained that this was due to a parasite but was not putting the life of the tree in danger. However I was impressed by the name he put on this: oak gall. 

Galls or cecidia are a kind of swelling growth on the external tissues of plants or animals. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors. They can be caused by various parasites, from fungi and bacteria, to insects and mites. 

Plant galls are often highly organized structures and because of this the cause of the gall can often be determined without the actual agent being identified. On the picture above, the parasite is the gall wasp, also called gallflie (Cynipidae): Cynips quercusfolii. 

Many parts of the tree can develop a gall of very diverse shapes depending on the parasite species and the season. Here on a small branch the parasite is Andricus kollari:

Inside the gall, the larva will be protected and find food during its development. But the gall is also a form of protection for the tree as it insulates the parasite.

If opened, the larva is to be found in the middle of the gall:

Some Cynipidae have two generations every year and two different galls like Neuroterus quercusbaccarum on white oak or Plagiotrochus quercusilicis on Kermes oak. 

Other trees can have galls, namely beech, lime tree, elm, dog-rose and maple, like this one, largely infected:

More trees of the Sant valley

Pearls of November

Pristine morning dew

Dressed for the winter

Even if the sun is still there, the autumn is coming to an end and the deciduous trees have lost their leaves, all of them except marcescent trees.

Marcescence, the term used to describe leaf retention, i.e. when dead leaves stay on the tree after autumn until the following spring at the latest, is most common with many of the oak species (pictured here), American beech, witch hazel, hornbeam (musclewood) and hophornbeam (ironwood). It is often young trees or branches close to the soil when those on the top have lost their leaves already.

Several reasons could explain this modification in the abscission process, where the cell layer allowing the decay of the leaves is not formed: genetic variation related to the hydric regime of the plant, biomass cycle or even protection against predators because those leaves are less appetent.  

http://extension.psu.edu/natural-resources/forests/news/2012/winter-leaves-that-hang-on

More trees of the Sant valley

Fireworks in the forest

Yellow, the maples (in my back),
Red, the chestnut trees (left),
Green, the beeches (right),

But no blue today, it’s raining.

And the forest is shining

Like this ivy (male) on the bark of an ash,

Or this branch of oak.

More trees of the Sant valley

Appetizers for squirrels

October 2015: even if the forest is still green, fruits from autumn are there already. They fall earlier than usually, probably due to last nice sunny summer.

Here and there you can see on trails soil the gift mother Nature grants to woods animals, helping them making storage before winter.

Everywhere below oaks are raining acorns, sweet appetizers for squirrels. 

Funny squirrels (English translation)

More trees of the Sant valley