ladybird nymphs – Not a Horticulturist

Short version:

The invasive southern green shield bugs are not benign like the native green shield bug (England). Let them live to the peril of your berries, fruits and beans. This one species comes in many guises. I can only apologise for the blurry photos, especially the microscope lens ones.

I found these newly hatched bugs whilst harvesting beans. What do they look like? Beetles? Ladybirds? Leave them be I may hear some of you say. Don’t you want a gazillion tiny ladybirds that will become voracious eaters of pests?

No… well yes… I do want that. But no. These are not ladybirds. These are Southern green shield bugs, also known as stink bugs. I know they’re definitely NOT ladybirds. I know because ladybirds start off as alien looking nymphs (click here for last week’s post). In fact when I wrote last week’s post I had put some eggs into the bug jar so I could confirm that they were ladybirds. They hatched and this is what they looked like below. Mini ladybird nymphs.

This is an interesting bug for it’s young alone. After hatching it goes through quite a few stages, known as instars before it becomes the recognisable green shield shaped bug. If you hadn’t seen them before, you wouldn’t be the only one to think that the different instars were different bugs. Now the common green shield bug (palomena prasina) adult looks very similar to the southern green shield bug (nezara viridula) except it has a darker patch at the back of the body. I’ve not seen any of them in the garden so I have no photos, but if I did, I would not mind as the common green shield bug isn’t a berry pirate. The southern one though…

This monster only arrived on our shores fairly recently (reportedly 2003). It is thought they hitched a lift on food produce from Africa. The southern green shield bug does a lot of damage. I first came across them about 6 years ago. My cucamelons had funny little bumps on them and it was only when I saw the shield bugs swarming over them (if a dozen constitutes a swarm) and put 2 and 2 together. I hadn’t really minded them in the last 2 years in this new garden, until they treated my blackberries like juice boxes and damaged hundreds of berries. I wouldn’t mind so much if they ate the whole berry. When half of the drupelets have gone this weird white colour, the berry just isn’t appealing. The individual drupelets then go on to die anyway. So, when the berry isn’t ripe and this damage is done, by the time the berry is ripe, the damaged drupelets are just disgusting. They have needle like stylets which they use for piercing. You can see the entry wound on the individual druplets.

I had harvested many of the blackberries 2 days before and everything looked lovely. In only 2 days they had done this. I knew it was them as, again, I saw them crawling over the berries. After a good old hunt and collect of the berry pirates there was considerably less damage.

They seem to favour berries, beans and tomatoes in our garden. Their eating can cause little bumpy scars on beans and cucamelons, which I don’t mind too much to be honest. Unfortunately when they feed heavily there can be distortion of the beans.

From looking at the young you wouldn’t have thought that they were green shield bugs. This is how they change over time. Just as an FYI they are a giant pain in the butt to kill. I tried to take photos of them alive, but boy do they move fast. I tried to drown them in an old jam jar. I thought they had died and lined them up to take photos. 20 minutes later though they were wandering around… Every…. Single…. One of them! These are hard little devils. I’m afraid my camera is only my iphone, I’m no photographer and my subjects were very reluctant so the photos are not great quality. The young come in stages called instars. I’m not sure how accurate my identification is, but this is a rough estimate of the nymphal stages:

They apparently stay on the egg cases for 48 hours, which is probably why I was lucky enough to spot them and capture a batch before they wreaked havoc. They moult between each stage and as far as I can tell only the adult has wings. The one from the above photo had a damaged wing so they never folded away properly.

As I tried to take a photo of what I thought was a dead shield bug, it started to wiggle and then climbed into my microscope lens. They really are resilient little blighters!

Short version:

Harlequin ladybirds have overtaken the native British ladybirds mostly in the South of England, but they are still great predators to encourage in the garden. They go through a nymph stage, turning into a pupa, before becoming the recognisable beetle shape.

I was actually going to post about berry pirates, better known as the Southern green shield bug but as I was writing I found myself researching an awful lot about ladybirds. You’ll understand when you see next weeks blog. I was also hunting the garden for specimens of both the shield bug and ladybird to take photos of and I found the ladybird in its various stages and thought it might be an interesting read. So pictured here are both ladybirds that are one of the most helpful critters in the garden. Yes, I do realise that pictures are a little blurry, but these are small creatures that are being photographed with an iphone, through a microscope.

Unfortunately, the British native red ladybird (coccinella septempunctata –7 spot or adalia bipunctata – 2 spot) is in decline because the harlequin ladybird (harmonia axyridis) has muscled in. They are all part of the same Coccinellidae family, but the harlequin reportedly came from Asia in 2004 via Europe when it was introduced as a pest predator, according to the natural history museum website. I’m sad to say that I haven’t seen a native ladybird for about 15 years. This is also down to a move from a more rural setting up north to a big southern city, where the harlequin is reportedly more prevalent.

The same website also mentions the STD that the ladybirds are reported to carry. It is a fungus called laboulbenia, and no, it does not affect humans. Phew! I was bitten during my research this week. It hurt but at least there are no lasting effects.

Between the STD and the natural predators like parasitic wasps there will be an equilibrium reached where both native and invasive species should co-exist (so says the website). In the meantime, I’m rather fond of the harlequin ladybirds (even the bugger that bit me) because they are voracious eaters of the aphids that are my most unwelcome garden inhabitants. The photos are all harlequin ladybirds as those are the only ones I seem to have in my garden.

Below are ladybird eggs, I think. I have put them in the bug jar and so will confirm this when they hatch. They were laid on the most aphid infested leaf that was in the garden which is a good indication. Mothers will lay eggs where there is a plentiful supply of food. The leaf would not have made for good eating with that much damage.

Below is a ladybird nymph. They hatch as tiny versions of these. I’m afraid I couldn’t get a photo because bugs that small are hard to find. I did manage to get a photo of a discarded skin though. As the nymph grows it sheds its exoskeleton several times.

They then enter a pupa stage, where its insides change. It then emerges in the beetle shape. This is the adult form with a hard wing case that hides the wings when not in use. They hibernate over winter, ready to lay eggs in the summer.

Despite their very different colouring these are below are all harlequin ladybugs. Their colouring acts as a warning to tell predators that they taste unpleasant and they can extrude a horrible yellow liquid when they feel threatened from their leg joints.

The best way to encourage ladybirds into the garden is to have plenty of food, i.e. aphids, and to not spray pesticides. You can help them to overwinter by providing them with somewhere to hibernate. Apparently the bug hotel of choice is one with narrow tubes of various sizes like a pot stuffed with bamboo and other woody, hollow stems.