1
point
White spots on oregano leaves

Oregano    Lausanne, Switzerland

Like last year, the leaves on my oregano plant have white spots on them as shown in the pictures. Any help in identification of the problem, and its management, would be appreciated.


Posted by: deactivated (25 points) deactivated
Posted: May 27, 2013


Peg Boyles commented,
Growing indoors or outside?
almost 6 years ago.

deactivated commented,
outside
almost 6 years ago.

Peg Boyles commented,
Do the spots go all the way through and show up on the undersides of the leaves?
almost 6 years ago.

deactivated commented,
See added image - I can't see the white spots on the underside
almost 6 years ago.



Answers

3
points
You may actually have more than one pest in there from your pictures. The damage definitely looks like thrips, but the underside with the exoskeletons and the insect makes me think that is an immature Cicadellidae leaf hopper. It looks as though it has a long back leg sticking out on the right, which would be one of the strong back legs they use for hopping around. A lot of plant bugs and leafhoppers can cause damage as nymphs that looks somewhat similar to thrips damage, so your damage may be a mix of both. Can't think of too many options for controlling them given that you want to eat the herbs. You could always just let them hang out and eat the whole package (extra protein). Since they are inducing the plant's defenses, they may also be inducing the production of more tasty compounds in the oregano. You might get a particularly pungent and flavorful crop.


Posted by: Kerry Mauck (58 points) Kerry Mauck
Posted: May 28, 2013


Peg Boyles commented,
Yum! (My mom used to say "You'll eat a peck of dirt and a thousand insects before you die." Pretty sure I met my quota decades ago.)

I'll defer to the experts here and withdraw my "answer." I've learned a lot today, thanks to Charlie, Lindsay, and Kerry.

almost 6 years ago.



2
points
The white spots on the top of the leaves looks like thrip injury to me, with the black specks (frass) being pretty typical.


Posted by: Charlie B. (84 points) Charlie B.
Posted: May 28, 2013


Peg Boyles commented,
Never had thrips before, but Google photos sure do look like them! Thanks! Are those the larvae on the leaf underside? How do you manage them on edible crops?
almost 6 years ago.

Lindsay McMenemy commented,
Agreed, definitely looks like an adult on the leaf, I have added some additional info as an answer
almost 6 years ago.



2
points
From the photo of the leaf underside it looks like thrips - there is an adult clearly visible and you can also see the white casts - that is the skins that the insects cast as they molt. Unlike insects such as butterflies which pupate from a caterpillar that looks nothing like the winged adult, thrips go through two nymphal stages and an inactive stage where they develop into adults. Insects possess a rigid exoskeleton which serves much the same purpose as our own skeletons (i.e. muscle attachment) just that it is on the outside. The nymphs must shed this exoskeleton periodically to allow more room for growth. This is what you can see in your picture - I've highlighted it in the attached image.

As far as the species, I'm not entirely sure but the clear dark stripes on its back resemble that of onion thrips. I've attached an image to see if it aids in identification.

In terms of control, you can prune out really heavy infestations or try to spray them off with a jet of water. Make sure you provide the plants with adequate water to avoid further stress and do not overdo any nitrogen fertilizers as this will promote the insect population on the plants.



Posted by: Lindsay McMenemy (167 points) Lindsay McMenemy
Posted: May 28, 2013




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