My basil got little transparent spots on the leafs. I'm not sure how long this is happening but it is like in all the leafs.

I live in the Netherlands and I suppose the light might not be enough but I have the plant for months and it was doing fine so far.

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  • Are any of the leaves curling? – Shule Jul 11 at 22:06

Looks like a spider mite problem - the lighter spots are where they feed on the leaves. If you look closely under the leaves and at the stems, you might find signs of webbing. Spraying them off (aiming especially at the undersides of the leaves) might work, otherwise a horticultural oil spray, see here http://homeguides.sfgate.com/basil-plant-mites-38804.html

  • Under very close inspection, I indeed found some webs between the leafs and the stem. Surprisingly though, there were no insects of any type, is there a chance that they are hiding in the soil or inside the plant's stem? – xpy Jun 12 at 7:32
  • They are very difficult to see; the diagnosis of spider mite infestation is usually made because of the symptoms on the leaves and the presence of webbing - treat for spider mite. As for soil testing, don't waste your money/time - your plant is in a pot, it's fine in terms of soil, ph or otherwise, basil isn't that bothered by soil ph anyway - it has a preference for 5.5 to 6.5 but will grow in up to 8. Spider mite is common on basil indoors. – Bamboo Jun 12 at 9:05

Bamboo could be right about the spider mites, but another possibility is the soil pH might be too high, which could make manganese less available and cause deficiency symptoms, which sometimes look similar to your basil plant's leaves. If the plant continues to grow at the same rate, I doubt soil pH is the issue, though. Adding phosphorus is said to increase the availability of manganese. I'm not sure how true that is. Acidifying the soil increases the availability of manganese (but it can be difficult to do in containers. Adding extra manganese probably won't help unless it's not a pH issue and the soil is manganese deficient.

Also, thrips can cause stipling on leaves, too. Scale insects can sometimes make similar damage.

  • Is there a way that I can measure if the soil PH is right? – xpy Jun 12 at 7:30
  • There are places that do soil testing. You can order strips to test soil. Those are probably the most accurate ways, but you can also get pH testing devices, which may not be so accurate. I haven't used any of these methods. I'm sure there's someone else out there who can say a lot more about it. – Shule Jun 12 at 8:17

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