Talkback: Bug hunt and rosemary leaf beetle - Talkback

28/05/2008 at 08:48

Although the others you describe are probably the harlequin ladybird, Harmonia axyridis, your metallic stripy 'ladybird' is almost certainly a rosemary leaf beetle, Chrysolina americana. Look out for the pale grey grubs, up to 10 mm long, sitting hard up to the stems, nibbling the edges of the leaves. The beetle rarely does much damage and it is such a wonderful looking insect.

Gardeners' World Web User

01/06/2008 at 18:36

I have just discovered a multitude of rosemary beetle on my rosemary. Is it the cause of frothy collections at the base of some of the sprouting shoots?

Gardeners' World Web User

02/06/2008 at 22:24

You say these plants are resilient,but our small rosemary bush was almost destroyed last year, and this year,with only a tiny amount of greenery visible, once again is covered in them. It has no chance!

Gardeners' World Web User

03/06/2008 at 21:05

I think that sophie's frothiness at the base of the plant's stems is probably cuckoo spit which is made by the froghopper, nymph of the broad-headed bugs (red and black backed).

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05/06/2008 at 08:39

Claire is right you have cuckoo spit. Which of course is a terrible slight on cuckoos, which I am sure never expectorate in public. The froth is made by the nymph of a plant hopper, Philaenus spumarius (from the latin for spume/ froth). It sucks plant sap and whips up its watery excrement into a protective coating of bubbles. They keep it warm when it is cold, cool when it is hot, hide it from predators and parasites and are a useful byproduct from its liquid diet. Many sap-suckers have the problem of sucking so much food to get enough protein to grow that they have to find some way of getting rid of the copious liquid that must pass through their bodies. Aphids give off honeydew to ants to solve the problem. The adult 'froghopper', 3.5 to 5.0 mm long has a wide variety of patterns from pale beige, mottled grey/ brown to black and is very common. I'd like to say that it never causes any problems, but I said that about rosemary beetles and as you can see felix says different. All I can say is that they are not pests unless they reach pest proportions.

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08/06/2008 at 16:55

I have just been trying to establish what was on my rosemary then I saw this blog entry. Can I easily get rid of them and can I still eat the rosemary?

Gardeners' World Web User

10/06/2008 at 08:52

As with lily beetles, the best way to get rid of rosemary leaf beetles is to hand pick them. Also look out for the C-shaped grey grubs which are the main leaf-eating culprits. The rosemary is still edible.

Gardeners' World Web User

17/06/2008 at 23:08

My sage, thyme and rosemary are covered in these pretty beetles. I can't spot the grubs, but the sage in particular is being demolished. Very annoying!

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21/06/2008 at 02:08

Last year my three year old rosemary bush got some kind of disease and it killed the entire plant. I dug up the plant, put down new soil. This spring I plant two new rosemary plant, not in same spot and it now is getting the same disease. There is a frothy looking substance on every branch, sticky. The plant was getting so full and beautiful. I cut back the plant to about eight or ten inches but they now have all the frothy stuff on them. I cannot find out what it is, nor how to get rid of it.

Gardeners' World Web User

25/06/2008 at 10:49

Reply to Lynn. It sounds like you have the spittle bug, Philaenus spumarius, also called cuckoo spit bug. The nymphs make froth blobs to hide in whilst they suck sap. Pippa recently put up a note about them. They are usually more or less harmless to plants, but can cause problems if too numerous.

Gardeners' World Web User

26/06/2008 at 16:38

Thanks, i was trying to find out what this bug was - now i know. It first appeared all over our lavender bush 2 years ago, and now the bush is not dead but is only ever bare, which is a shame as we never see the bees anymore. It is all over the rosemary too but there's a lot more of that to get through.

Gardeners' World Web User

29/08/2008 at 15:50

I have just found my first Rosemary Beetle - on my young avocado. I must say the beetle is very striking - so I don't think I will be able to destroy it. I will probably be think differently when the single beetle becomes an infestation!! Earlier in the year I found a 2cm long bright metallic beetle on the ceanothus flowers. Was this a Rose Chafer?

Gardeners' World Web User

18/04/2009 at 19:16

Just had to dig up a loved Rosemary bush that had been attacked and killed by the dreaded Beetle. I have another even bigger Rosemary bush in my allotement, that has been trying to recover, but it is touch and go at the moment wether it survives! I had not idea what the problem was, until a fellow allotementeer told me about the Rosemary Beetle, and looking down at my poor dead bush, I quickly spotted one! It lived another 6 seconds whilst I admired its beauty. Then I squashed it with relish. The next half an hour I spent at my other bush, doing a search and squash mission. Poor bush, I just so love cooking with Rosemary, and dry enough of it to last a whole year..... am keeping my fingers crossed it lives!

Gardeners' World Web User

02/06/2009 at 21:46

I have also found these beetles on my roseamry. I have examined the collection of bubbles found on the plant and there are "small green beetles within". They look like baby beetles growing inside. The beetles have also spead to the honeysuckle and they are now munching on that. Does insecticide kill these damn things??

Gardeners' World Web User

09/06/2009 at 13:25

Reply to Beetle Hunter The blobs of froth are spittle bug nymphs, Philaenus spumarius. They turn into froghopper bugs when they are adult. They don't do too much damage, but if you think they are unsightly give them a spray with the hosepipe.

Gardeners' World Web User

21/06/2009 at 18:24

I have grown lavendar and rosemay for years. Yesterday we found our first Rosemary Leaf Beetles (lots of them)! They are beautiful. Having read about them on the RHS website, which is a great gardening resource, we killed them all (such a shame) BUT reading this I now need to go back to the plants and look for the grubs...

Gardeners' World Web User

21/04/2010 at 16:15

Help. My rosemary and lavender is being stripped bare by the Rosemary-leaf beetle! What do i do to get rid of the pest and save the sick-looking plants

Gardeners' World Web User

21/04/2011 at 13:14

My rosemary and another neighbour's rosemary in the same street are not thriving. No evidence of beetles or spittle bugs. Leaves dull green and some dying off. Some leaves look like they have been part-eaten. There is some new growth at the top of some branches just in the last 10 days or so. Very few flowers this year, on a couple of branches only. There is some sort of webbing visible on some of the branches but no critters found. Any suggestions what this could be and/or what I can do to save the plant? I'd be grateful for any tips!

Gardeners' World Web User

28/11/2011 at 18:31

I have just found a very strange ladybird on my mum's French lavender. It is a metallic colour of green and red stripes (my dad has taken a photo of it. Ever since Monty told us about the harlequin ladybirds we have found a couple but this is our first stripy one the others have been black with yellow or red spots and seem to love our camillia and levatoria bush especially.

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