Drifting towards the end of summer

I love summer.

And spring.

And autumn.

And even winter too, sometimes.

I love the seasons. I love living somewhere there is always seasonal change on the horizon. Tomorrow is the start of meteorological autumn. I tend to feel slightly sad at the passing of one season, but excited for the next. Spring and summer hold so much promise, but the shorter days and longer nights of autumn and winter help us to value them all the more.

As summer starts to drift to a close, my sadness is tempered by the signs of the changing seasons and the promise that has been growing for half the year. There are signs all around: harvest in the fields, brambles in the hedges and fruit ripening on the trees. The evenings are getting shorter and darker. There will soon be crisp autumn days, glorious colours on the trees and crunchy leaves underfoot.

I’ve been spotting burgeoning blackberries on the bramble bushes for a few weeks already, which seems very early this year (some have even been and gone).

Bramble bushes and Ripe blackberries

The apples are growing on the trees (below left) and sloes appearing on the blackthorn bushes (below middle), although it will still be a while before either are ready for picking. Take extra care with sloes: they should be picked after the first frost (or popped in the freezer before using to flavour gin!) but you should only collect them if you are absolutely sure of what they are. There are impersonators which are not edible! Similar, but larger fruits also with a white matte surface are Damsons, and care should again be taken before picking and eating these to ensure this is what they are. The fragrant elderflowers of late spring have made way for the dark elderberries (below right) which can be used in jellies, cordials and to flavour fruit crumbles.

Of course, other animals also enjoy many fruits and berries and we should ensure that there are plenty left for them.

The guelder rose (below left) berries are an important food source for many birds (but can be mildly toxic to people!). The berries of the white beam tree (right, related to the rowan) are eaten by woodpigeons, crows and thrushes and are edible by humans but must be cooked first.

Whilst the haws (below) of the hawthorn tree look like berries they are actually pomes, like apples and pears. Haws are also an important food for birds and are edible in small quantities by humans when cooked, although the seeds are poisonous (haws are often made into a jelly) – but they don’t actually taste very nice!

When foraging, always ensure you have permission and take a responsible and knowledgeable grown-up with you to make sure you don’t pick anything poisonous. There are many plants with similar looking berries and fruits which could make you very ill. If in doubt, don’t eat it!

The end of summer usually also brings excitement for a new school year, although that is going to look a little different this year. The uncertainties of the world around us are balanced by the comforting familiarity of the turning of the earth and the changing of the seasons as nature continues to get on with life.

What signs of the changing seasons and the end of summer can you spot?

#summer #autumn #winter #spring #seasons #SeasonalChange #SeasonalChanges #year1 €KS1 #keystage1 #PrimaryScience #ScienceCurriculum 

(It’s not autumn but) the leaves are turning brown: plant pests and pathogens

Horse Chestnut (conker)

Although the changing seasons are marked by the changing colour and dropping of leaves (more on this in a future blog post!), it’s still summer and yet many leaves are already turning brown…

There are actually a few reasons why leaves may turn brown, especially in the horse chestnut (conker) tree.

Leaf blotch

A fungus, Phyllosticta paviae (syn. Guignardia aesculi), causes Horse Chestnut leaf blotch – irregular patches of brown on the leaves, sometimes with yellow edges, usually during summer. Severe attacks can cause the leaves to shrivel completely. Leaf blotch isn’t usually seriously damaging, despite looking unsightly.

Leaf Mining moth

Something I’ve spotted a lot more of lately is not leaf blotch, however, but smaller brown lesions, usually sitting between two lateral leaf veins – so often more elongated in shape – which are caused by the horse chestnut leaf mining moth larvae (Cameraria ohridella). It has spread widely in England since 2002 (RHS) and the effect on leaves in late summer can be quite dramatic! Due to the damage to leaves, the plant may have a reduced ability to photosynthesise and this could impact energy stores and resources. Although trees may drop their leaves early, the leaf miner blotches don’t seem to have much effect on the health or growth rate of trees but may affect developing conkers.

The Horse chestnut leaf mining moth larva lives between the top and bottom surfaces of the leaf, so it is hidden and protected from potential predators and can feed undisturbed. The small blotches are pale when they first appear between the leaf veins but turn brown as summer progresses. You can peel the top layer of the leaf away and reveal the larva (caterpillar) hiding beneath:

Leaf mining moth larva on a horse chestnut leaf

There may be several generations of horse chestnut leaf mining moth during a summer. The adult moths lay eggs on the surface of the leaf and the caterpillars then hatch and burrow under the surface to feed. The moth can overwinter in the leaves as pupae and so collecting and burning the leaves may help to stop the spread.

There is a citizen science project (conkertreescience.com) finding out more about the horse chestnut leaf mining moth and scientists are also looking at ways of controlling the pests with biological control – using other insects to control the population.

Caterpillars

Of course, caterpillars (and other animals) often feed on leaves and we are all familiar with leaves with holes in like these (gardeners especially!).

Mullein moth caterpillar

The caterpillar ate through one nice green leaf, and after that he felt much better

The Very Hungry Caterpillar, Eric Carle

You can also see evidence of caterpillar feeding on leaves with these tracks or mines left by moth larvae of the stigmella genus:

Brown leaf edges

You may also spot leaves with brown edges. This could be due to drought stress, but there’s also an unknown condition affecting horse chestnuts resembling this too.

Horse Chestnut leaves with brown edges

These maple leaves have brown edges, which could be maple leaf scorch, caused by drought stress.

Maple Leaf Scorch

One of my science clubbers recently sent me some photographs of some thirsty acer leaves that they managed to rescue this summer:

Galls

Other evidence of insect damage to leaves are galls, including (left to right) the acalitus gall mite, the red gall mite on sycamore leaves and the characteristic circular dots on oak leaves caused by the common spangle gall moth.

Fungus

Fungi may also be evident on leaves, including the black tar spot (Rhytisma acerinum) on sycamore or maple leaves in later summer and autumn. This is a minor, localised infection which doesn’t cause long term issues for the tree.

Black Tar Spot

Turning Brown

These are just a few incidences of the many plant pests, pathogens and disease which afflict trees and leaves. Damaged leaves or stems could also lead to the leaf tissue dying and turning brown. This is different to the slow change of colour and eventual dropping of leaves we will soon see in deciduous trees in the autumn (more on that later). Autumn is on its way, but not quite yet!

#Plants #PlantBiology #PlantScience #PlantDiseases #Pests #Pathogens #SeasonalChanges #Seasons #Trees #Insects #Leaves #Leaf #Moth #Butterfly #Larva #Larvae #Lepidoptera #Caterpillar #Fungi #Galls #Mites