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I noticed some brown leaves on my box plants and thought it may be blight. A week later I was watering close to the biggest, 7feet topiary trimmed, specimen when I noticed a rotten farmyard odour. On inspection I noticed an infestation of caterpillars. I understand there is no treatment for this problem. I am in the process of digging up all of my box plants, some almost forty years old. Is t worth keeping the cutting which I took some weeks ago or is the problem with me forever. I have destroyed many of the caterpillars but have noticed the moths flying about so it looks like other local box plants are in for an infestation.

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    There is a maxim for pesticide; only to be used IF a positive ID has been done. Please send pictures. To start attacking some insect or disease you've not ID'd positively, it is irresponsible and very dangerous to just pull out the artillery to use against an unknown enemy. Box or Buxus are tough plants. Do not pull them up until we are able to ID for you for sure, okay? Caterpillars have a very cool BT that is specific for caterpillars. Very specific. It is the toxin produced by a bacterium that when eaten by the caterpillar causes that caterpillar to stop eating immediately. They die – stormy Aug 23 '17 at 20:42
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    ...from starvation. Amazing huh. You didn't really dig these plants up did you? 7 foot topiary? How is your septic doing? Or your sewer lines? There must be a reason for that odor. Leaf miners are the worst I've seen with boxwood. Need to know if you've got Buxus sempervirens. What environmental conditions have been occuring... – stormy Aug 23 '17 at 20:49
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You don't say where you are in the world, and that's a consideration when trying to give a sensible answer. That said, if its Box Tree Caterpillar, you should have noticed plenty of webbing over the plants, but you haven't mentioned this feature at all. There is treatment for Box Tree Caterpillar, but its true to say it's an ongoing battle, and it sounds like, as yours is advanced (if that's what it is) you may need to use a neonicotinoid spray such as Bug Clear Ultra. If you do use this, ensure you don't spray when bees are working, and that the spray does not drift onto any flowering plants in the vicinity. More information here https://www.rhs.org.uk/Advice/Profile?pID=760&cID=1247

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    That would be at night...to spray anything should be done at nighttime when bees are safety tucked away. – stormy Aug 23 '17 at 20:37

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