I've looked at other forums and I believe it to be either sclerotia or psuedonomas or a blight infection. (Based off another forum and another website.)This is the first time I've experienced this and we've owned this plant for years. Could a pesticide work on it? It's not on all of the plant but it's turned some lower branches brown. It's in a raised bed near other plants so could it spread to other plants? (Near it I've planted Spring onions, chives, carrots and beetroot.) Also, there is a new Rosemary plant next to it but it doesn't seem to have any of that on it. Any help is appreciated.
The brown splodges, you mean? I think those are pupae of some kind of beetle. (That is the third stage of a beetle’s lifecycle, after the caterpillar and before the adult beetle.)
I say they may be the pupae of rosemary beetles, but I’m not certain. They may be the pupae of some completely innocent beetle that just happened to find a nice quiet spot to change from its caterpillar form to its beetle form.
So before you go blasting your plant with stuff, maybe take a little time to wait and see what they turn into. Could be something lovely.
The brown blobs look like very pregnant scale insects to me. If white 'fluff' appears at one end in the next few weeks, that would be a definite. Some here:
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I say they may be the pupae of rosemary beetles, but I’m not certain. They may be the pupae of some completely innocent beetle that just happened to find a nice quiet spot to change from its caterpillar form to its beetle form.
So before you go blasting your plant with stuff, maybe take a little time to wait and see what they turn into. Could be something lovely.