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!
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.
Short version: I’m not here to condemn anyone who uses pesticides, as I’ve used them in the past and still use ant bait, but I’ve come to the conclusion that pesticides are terrible for the wildlife in the garden and when it comes down to it they don’t work that well in the long run. Caring for the wildlife in your garden allows creatures to do the job for you and also cares for the pollinators. Encourage small birds, hedgehogs, amphibians and predatory insects. Try other methods like picking infested leaves when harvesting, hunting for pests after dark, traps and cloches.
I have waged a constant war against ‘pests’ in my garden and I’m not slowing down in 2020. I’m afraid I’m not nice. I found a collection of about 30 tiny snails huddled up round the rim of a pot yesterday. They were so tiny and cute. I had to remind myself that they will very quickly become gooseberry sized monsters with voracious appetites. I squished as many as I could find. I then found a load of eggs a little later. I strongly suspected them to be snail eggs, but there is a possibility that they may be worm eggs. The internet failed me. There were matching pictures under both snail and worm egg searches.
Curiosity has gotten the better of me and I have contained them and will check weekly to see what happens. To be honest you can’t worry too much about this kind of thing. There’ll be plenty of snail and worm eggs in the neighbours’ gardens and in soil I haven’t dug. There’s only so much you can control. I took comfort in knowing that I had just removed about 30 definite snails less than 20 mins earlier.
Now I would be a hypocrite if I said that no one anywhere should use pesticides. I have used pesticides in the past. I don’t anymore (except for ant bait because we have evil bitey red ants) and I wouldn’t like to guarantee that I won’t use more pesticides in the future. It’s hard to state absolutes. However, I have concluded that you are better off trying your best not to use pesticides. It’s partly for the environment, but it is ultimately for selfish reasons. They just aren’t worth using. If you are on the fence or fond of using pesticides, then I hope to offer some thoughts.
Food chains and webs
So, those who remember GCSE biology might remember how energy is consumed up a food chain. This is a chain that would be quite realistic in our garden.
Sun –> kale –> caterpillar –> robin –> neighbour’s cat
Poisons tend to accumulate up food chains. Organochlorides (used in pesticides in the 1960s) were found to be the reason for death in birds of prey. Small birds were eating the poisoned pests. The predator birds were eating the small birds and the accumulation of the pesticides were killing the birds of prey or affecting their ability to reproduce (source).
One can assume that many of the smaller birds which weren’t being eaten were also dying. From an ecological point of view this is terrible, but also from a gardener point of view you’ve lost a useful ally that was merrily eating your pests daily.
Taking it back to my garden food chain – yes, the caterpillars drive me mental, but if I poisoned them, they in turn would poison the robins, which would then poison the cats. I don’t like the cats eating the birds and I don’t like the cats poo-ing in my garden, but I certainly wouldn’t want to poison them.
By killing robins, there’ll be less robins to eat the caterpillars.
Predator – prey interactions
Another GCSE Biology topic. When left to its own devices, nature has her own way of controlling populations. E.g. aphids and ladybirds can have intertwined population cycles.
Let’s start with aphids. Let’s say that there is a huge population of aphids. This means that there is a large amount of food available to ladybirds. This means that the ladybird populations thrive and increase. The larger number of ladybirds means that there are more predators to eat the aphids. This means that the population of aphids decrease and there will be more competition for food. At some point the population of aphids will be too low to support the large population of ladybirds. This means that the population of ladybirds will decrease from lack of food and increase of competition. The decrease in population of the ladybirds means less predators for the aphids so their numbers then increase… and we are back to the start of the cycle.
Basically, nature will even out the odds. You may kill off the pests, but you may also be hurting their predators too that were helpfully gobbling them up. Chances are you will find that your pests will be back as it’s impossible to eradicate every last one (certainly not from other people’s gardens too), so the cycle continues in its never-ending loop. You might find that the predator populations affected don’t recover as quickly, giving you a bigger problem later. Why battle the inevitable by introducing harmful chemicals?
Targeting your destruction
In addition, some pesticides will hurt bee populations and other pollinators, like hoverflies, that are essential for pollination. No pollination means no fruit. Don’t forget fruit also includes things like tomatoes, aubergines, courgettes, cucumbers and the plethora of other squashes. There are bee friendly pesticides out there but there have been studies on how a cocktail of ‘non-toxic to bee’ chemicals have been killing off populations (source 1, source 2).
As a last, but rather important note. I also don’t want to kill my child as she grazes unashamedly on all my berries and salads.
Yes, it all sounds like doom and gloom but there are other options. These are some things that I’ve tried with varying degrees of success.
This is the most effective one for aphids and caterpillars and has the added advantage of real time results. Pick the most affected leaves for dinner and then soak them in salted water for 10 mins then rinse until clean. This removes the pests from the garden and washes them down the sink without introducing poisons. Anything too gross to consider eating can be put into the bin (not compost).
I like to grow things that you pick regularly from over a long season e.g. perennial kale that you can pick from all year round, or chard that you can pick for about a year before the plant needs to be replaced. If you’re harvesting from the plants at least once a week (it can be every day in the summer) then you’ll see all the signs of pest damage and can deal with it quickly.
The night hunt
I also like to go ‘hunting’. There is an instinct in many humans to go forage, gather and hunt. There’s no reason why we must go after animals as sport, there’s plenty of satisfaction in going out just after dark (when leaf chomping pests are very active) with a pair of disposable chopsticks and an old jar and capturing slugs, snails and moth caterpillars by torch light. It’s sounds rather disgusting (and it is) but it is also incredibly satisfying. What you do with them after is entirely up to you. I have drowned them and then left them outside to be eaten (or decomposed) or sealed them in a bag and chucked them into the bin. I told you I wasn’t nice.
The large snails were apparently introduced to Britain by the Romans as food. You could ‘clean’ the snails by feeding them on safe leaves, such as lettuce, (as they accumulate toxins from the plants that they feed on) for a few days and them eat them as escargot, but I’m afraid that is currently a step too far for me. Maybe do some research on this first – please don’t poison yourselves.
Encouraging natural controls
Looking back at the food chain, and the bigger food webs you can see what predators are suitable for your needs and either encourage them into your garden, or even buy some to release.
BIRDS: Encourage small birds into your garden with bird feeders, water trays and some cover, like bushes and trees. You can also plant some bushes with overwintering berries. The trees we added were fruit trees, which are not yet big enough, but some day they’ll provide useful shelter. If you provide nesting conditions you may be rewarded with extra ravenous chicks to eat bugs. Many of the garden birds will happily eat the caterpillars and snails. Even some birds with seed-based diets, like finches, will happily eat aphids for you. Some of the birds may also eat some of my berry harvest but so far, they haven’t been a problem and I wouldn’t begrudge them some as a thank you for eating the pests. If it becomes too much, then I can also use netting to protect the berries. My mum finds that wood pigeons (who don’t really eat insects) are a pest in her garden, eating the young brassica seedlings, but this is also easily solved with a bit of netting.
AMPHIBIANS: Frogs and toads don’t need a pond to make a home in your garden. They only need one for breeding. In our rainy UK weather, our garden seems to have enough damp, as there has been many a frog sighting in the past year. You will need to eliminate chemicals, especially slug pellets. It’s not just what they’re eating, but amphibians have semi permeable skin so even exposure to spraying is harmful. You can also provide places for them to hide, such as an upturned pot with a gap at the bottom or areas of long grass for them to hide in. They love hiding behind the clutter around our waterbutt, in our unkempt grass edges, under the rosemary bushes or behind the Chinese chive patch.
HEDGEHOGS: I’m not entirely sure if we’ve had a hedgehog, but I saw a poo that I really hoped may have been from a hedgehog. I don’t even know if there are any in our area as there are many foxes and cats about. If you have a fenced garden, providing a gap at ground level for them to get in can help. You can provide a hibernating spot with a pile of logs, pile of dead leaves or a compost heap (or even a special hedgehog house). Just be careful if you do clear up piles of leaves or turn your compost. Slug pellets are also terribly bad for them, so another good reason to avoid.
BENEFICIAL INSECTS: The main thing is by avoiding pesticides you protect the beneficial insects. It’s then worth encouraging predatory insects like ladybirds and lacewings by providing somewhere to overwinter. You could investigate a bug hotel of some sorts but do some research into the type of insects you are looking to attract and what they need. Apparently, some of the ones on the market look good but aren’t very functional. They will also need some maintenance and need to be kept in shady, sheltered places. I have picked off ladybird nymphs from roadside trees and put them in the garden in the past. I don’t know if they stayed.
Ladybirds eat spider mites. Spider mites cause most damage when the weather is hot. They do less well in rainy periods. They do respond to pesticides, but then you’ll kill the predatory insects too. In the past I’ve controlled these very effectively by removing all the affected leaves and spraying the plant well with a hose and then spraying with a solution of rosemary oil and water which is said to discourage the mites without harming their predators.
There are also a host of specific parasitic creatures you can buy to target a particular problem. We had a ridiculous amount of whitefly one year and bought sachets of Encarsia Formosa, which is a tiny (smaller than a millimetre) parasitic wasp that lays eggs in the scales of the whitefly. They are really only for use in a greenhouse where you can keep the population captive and protected, but we used them outside, and they were still fairly effective.
The damage to this leaf has been done by a leaf miner which is the larvae of a fly. Pesticides wouldn’t have been much use here anyway as the pest is protected by the leaf. Either a pesticide that is absorbed by the plant (possibly making it inedible) is required, or spraying needs to be timed for when the larvae has turned into a fly and emerges. For leaf miners there is a parasitic wasp you can buy but it’s easy enough to remove and bin affected leaves.
You can buy sticky traps for things like whitefly or you can make a slug trap out of an old plastic bottle and some beer. I’ll do a proper post on this to put in the ‘things to do’ section.
You can buy copper tape that you can stick around pots under the rim. It supposed to work as a barrier that slugs and snails can’t cross as their mucus reacts with an unpleasant feeling. Apparently it need to be fairly thick to be effective or they stretch across. Also be aware that the adhesive sometime is a bit poor. We’ve used these on pots and they seem to be effective. It’s hard to tell though if the plants in those pots would have been fine anyway. There’s plenty of other things they can eat in the garden without having to climb a pot. If the copper is even slightly unpleasant for them they could probably go elsewhere.
Yes, creatures have got to eat, they’re only doing what nature intended them to do. I would just like them to stick to eating a whole leaf at a time and not leave leaf doilies, or could they wait till a plant has grown lovely and big. They could have tender tips then. I wouldn’t mind so much. The frustration of a seedling eaten across a stem or an asparagus tip nibbled to death before it can fulfil it’s slender juicy destiny is the original reason I used to use pellets.
Cloches made out of old bottles have become my go to now for precious seedlings. Alternatively, plant for redundancy. Assume that a few of your seedlings won’t make it and plant a few more.
So… I’m just hoping to encourage the use of methods other than pesticides in the garden. If you have any helpful hints or anything that worked especially well for you, please feel free to share in the comments.