I am currently in a battle royal trying to rid my Euonymus from the dreaded scale. Recently, I began seeing these insects in large numbers on the Euonymus leaves. There seem to be two types- an oval light brown, and a teardrop shaped black version. They are not very mobile. Any ideas?
They appear to be beetle larvae of some kind. The one on the left of the picture is the larva, the one on the right is a pupae. I don't quite think they are lady beetle larvae, though the pupae does look very similar, so I'm thinking it is a related beetle. That might give you a start at somewhere like Bug Guide (bugguide.net).
Unlesss someone knows for sure what the larvae is?
If I come across anything, I'll let you know.
Yes, they do appear to be two different stages of the same insect- as I have been observing specific leaves and watching the appearance of the pupae where once only larva occurred. I was hoping they were asian lady beetles, but they don't appear to resemble the photos I found online. Unfortunately, I cannot find a good reference of beetle larvae to help identify what I have. I need to get aggressive in treating the scale, but surely do not want to do anything that may damage an emerging population of predators.
Mystery solved. Today was an exceptionally nice day here in the Philly area and I was out examining the Euonymus when an unusual ladybug landed on me. Completely black with two red spots. My research revealed this to be a "Twice Stabbed Ladybird Beetle". Further research revealed the larvae: http://bugguide.net/node/view/60789/bgpage
I found several more of these ladybird beetles in the plant- even a mating pair!
Fortunately, they are predators of scale insects. I am interested to see what kind of effect they have on the population of scale(I have a very severe infestation)
It is hard to browse the larvae- the closest things I saw were leaf beatle larvae, but not close enough to mention. I don't think I've ever seen the "twice stabbed" before. Glad it's good news! It's still nice out, I better get busy! What can you do about the scale, do the hort.oils hurt the lady bugs too?
For what it's worth, I haven't had scale problems for awhile. I am probably luckier than the guy down the street, but I also (as I read recommended somewhere) try to clean out leaf debris from underneath, and I leave my hedge on the large size( it is the boring green large euonymus), only trimming about 3 times per year, and try to cut out the thick clumps that form after it's sheared and those little stems grow in. My neighbor's hedge are parents of mine; he tries to keep it a neatly sheared 4 ft high, 3 ft wide, and his is periodically covered in scales or mildew.
I hope this is helpful to someone.
Kudos to you for being patient and finding the beneficials, and not panicking and spraying.
I had scale completely covering a multi-trunked oleander. Along came the twice-stabbed ladybeetle and within a couple of weeks, they had eaten all of the scale. You could actually see the shredded exoskeletons of the scale on the trunks - whitish. I was amazed!! Here is a photo. The whitish stuff is the scale - or rather what's left of the scale. In your photo, the larva is on the left, and the pupa is on the right.
Yes, horticultural oil kills the beneficials too. If I had twice-stabbed present with scale, I would let the ladybugs handle the problem. They are really very thorough....I can testify to that!
This message was edited Oct 8, 2006 5:22 PM
I have scale on my euronomyous, but have not seen any unusual beetles or insects that I can definitely say were produced from the larvae. I have never seen the twice stabbed beetle, and would love to have the benefits of it for my 2 shrubs. Is there anywhere that any body knows that these can be purchased?
No, nature supplies them. If you don't see them, I would start spraying with horticultural oil right away....Euonymous is very scale prone. Lovely, but I don't grow it for that reason.
I looked around, and if anybody were using them, it would be Florida citrus growers, but they have other predators that eat the scale critters. Apparently those occur there naturally
Defoecat, this article may interest you http://findarticles.com/p/articles/mi_m3741/is_n3_v40/ai_12438563
It details the biologic control project in which the Asian Lady Beetle, Chilocorus kuwanae, and another insect Cybocephalus nipponicus, were imported from Asia to help control Euonymus scale. I spent the last few weeks before my discovery trying to find a source of these insects, as I have been battling a severe scale problem for the last 3 years with poor results. For the record, the Twice Stabbed Beetle, Chilocorus stigma, is a close relative of the Asian Lady Beetle, hence the similiar feeding activities. The two Beetles look identicle to my untrained eye.
So, after weeks of searching for a source of the beetle, imagine my absolute disbelief and joy when one of the beetles flew out of the euonymus and onto my shirt!!!
In any case, I recently contacted Michael Bryan who ran the USDA study referenced above in regards to aquiring the Asian Lady Beetle and information regarding the effectiveness of control with the Twice Stabbed Beetle. I'll update this thread once I know more.
Edited to add another interesting link http://www.nysaes.cornell.edu/ent/biocontrol/predators/chilocorus.html
This message was edited Oct 12, 2006 10:19 PM
Man, they look alike to me! I eagerly await your update!!!
The USDA has referred me to the New Jersey Department of Agriculture which runs a biological control program. The program offers Cybocephalus nipponicus for sale at a price of $25 for 100 beetles, which is much lower than the price at most retail suppliers.
Chilocarus kuwanae used to be offered for sale by a single large supplier, but they closed recently, and now the insect is unavailable.
In regards to the best control, it would be C. kuwanae as this beetle is the most voracious. C. stigma, the twice stabbed beetle, is a good alternative, but not as voracious as C. kuwanae. Cybocephalus nipponicus is a much smaller beetle with a smaller appetite, but will work well over time to slowly eradicate the scale population. Given my situation, I plan to purchase the C. nipponicus to augment my emerging population of C. stigma and I would anticipate my scale problem would be well under control in 2-3 years. The price of the beetles is well worth it to save the several hundred dollars I have invested in the Euonymus plants.
The idea of battling the scale with biological control really appeals to me also- especially in light of how difficult the scale is to control via spraying. If anyone is interested in the contact information to buy the beetles, just D-mail me!
doc - You may have already killed the scale. It doesn't drop off. It just dies and stays there, clinging to the plant. See if you can flick it off with your fingernail. Live scale will be pinkish underneath - eggs. Dead scale sorta changes color - looks dead. Watch for new growth. Do you see any scale there? That is where it will attack next. You may not need to go to the expense of buying lady beetles that may just fly away... But I also have to tell you that euonymous will continually have a scale problem. Get rid of one batch, another will come along shortly. It would be cheaper to replace the euonymous plants with plants that don't have that problem.
Thanks Ceejay- unfortunately, my scale is alive and spreading- I believe thats why the twice stabbed beetle was attracted in the first place. The entomologist I corresponded with at the NJ Dept of Agriculture also remarked that the C. nipponicus will not fly away- it stays with the plant even with low level infestations- that is why it is sold instead of C. kuwanae- the C. kuwanae is a general predator and will fly away once the scale is gone, whereas the c. nipponicus only feeds on hard scale and stays put.
Besides, All this action on my plants is more entertaining than any replacement plant could be!!
But thay can't stay put if there is no scale there to feed on. They would die of starvation, so that is a misconception. They have to go where the food is. Then the scale comes back, but the beetles have moved on to greener pastures. And you get to go through this whole thing all over again.
I agree that the scale attracted the twice stabbed. It goes where the food is, both for itself and its babies...
Actually, I think the conception of an insect being completely absent is misleading. You never completely rid a plant of scale, nor do you rid it completely of the beetle. As the population of scale decreases due to predation, the population of beetle decreases correspondingly. It eventually reaches a sort of steady state where there is just enough beetles to keep the scale population in check. Then over time, environmental conditions may make it favorable for the scale population to spike, and you would see a compensatory rise in the beetle population over time. The key is to establish the predatory population where it did not exist previously. There would never be a time where there is a complete absence of scale, thus unable to support at least a small population of beetles.
This feedback mechanism is seen throughout nature. Without it, predators would never survive. Through attrition and lower birth rate, the number of predators will always eventually balance the amount of prey. The plant is just a microcosm of the greater environment.
I understand the concept completely. And it is constantly in a state of flux. Balance in nature is never completely balanced. And you can be completely rid of scale. It will just return again someday. Especially if you have plants that attract scale. And I can only ask: Why would you want to buy lady beetles? You already have lady beetles.
