Mint with white spots on leaves

Mint    Geneva, Switzerland

My mint starts to be full of clear spots on its leaves. Is this a disease or a nutrient deficiency? I have some thyme nearby with the same symptoms.

Posted by: deactivated (6 points) deactivated
Posted: July 23, 2016


Try to look for spider web covering the leaves and the stem, the best way is at night- direct a flashlight and check!! I am not a expert in pests but they do look like spider mites to me.
I suggest to keep this plant away from other plants. Also mix 1TBLS neem oil and dish soup in a gal of water and soak your plants to get rid of mites.

Posted by: reem (9 points) reem
Posted: July 24, 2016

This looks like spider mite damage.

Spider mites are also called webspinning mites. They do damage by sucking the contents out of the cell. They occur often on water stressed plants

"To the naked eye, spider mites look like tiny, moving dots; however, you can see them easily with a 10X hand lens. Adult females, the largest forms, are less than 1/20 inch long. Spider mites live in colonies, mostly on the undersurfaces of leaves; a single colony may contain hundreds of individuals. The names “spider mite” and “webspinning mite” come from the silk webbing most species produce on infested leaves. The presence of webbing is an easy way to distinguish them from all other types of mites and small insects such as aphids and thrips, which can also infest leaf undersides." http://ipm.ucanr.edu/PMG/PESTNOTES/pn...

So, check the underside to see if you establish that it is mites causing the problem

What should you do now?

Water the plants to avoid water stress which can promote them

Spray the underside of the leaves to remove mites. You can use an insecticidal oil or soap (or a combination of the two). Don’t spray when plants are water-stressed or if it is very hot since this will add stress to the plant. Here is some instruction on preparing soaps

Soap solutions can be applied to edible plants. It is just important that they are subsequently washed off. You may want to use a high powered water jet instead

"Spider mites frequently become a problem after applying persistent insecticides such as carbaryl or pyrethroids. These insecticides are not very effective against mites and often kill off natural enemies and stimulate mite reproduction." http://ipm.ucanr.edu/QT/spidermitesca...

Good luck and let us know how it goes

Posted by: David Hughes (55 points) David Hughes
Posted: July 24, 2016

deactivated commented,
Thanks David. Indeed, I've been away for a while and those plants have probably suffered for a lack of water. I'll try to apply a soap solution, but I want to be able to consume this mint at some point… is that not incompatible?
over 4 years ago.

David Hughes commented,
I added something to my answer Yannis. But no, it is not a problem as you will wash the soap off.
over 4 years ago.

In my opinion part of the damage could be also caused by leafhoppers that are quite common on fresh herbs like mint. They are small sucking insects (up to 1 cm long) that jump and fly from leaf to leaf and from plant to plant. It is not so easy to get rid of them even with the use of registered pesticides. At this stage of damage I think it would be useless, therefore it is important to keep the infestation low applying pesticide at the very beginning of infestation.

Posted by: Federico (2 points) Federico
Posted: August 12, 2016

Jackie Robinson commented,
Hi....I have the same problem with my mint, sage and oregano plants which all thrived up to a point where the leaves started to show discolouration. I cut them right back almost to soil level and now they've grown back the same problem has occurred. When I knock the pots a cloud of tiny insects fly off only to resettle on the plant. I've used bug killer spray but it's useless! Close to giving up now...
over 4 years ago.

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