applestar wrote:It sounds like you had what I call a "hatching event". Many spiders lay an egg sac in the fall and die -- remember Charlotte's Web? When it warms up in spring, they hatch and many tiny babies spin a glider silk and fly off ...and land wherever the silk catches to settle. But after that it's a competition, and if there is not enough food, they can turn cannibal.
While it's possible that you do have spidermites as well, the baby spiders are tiny enough to be mistaken for mites at first, but they will rapidly get bigger and will become identifiable as spiders, in fact. Their numbers should diminish if you just let nature take its course. While they are tiny, they catch the tiny bugs that are problems -- like aphids, fungus gnats, (even mites when just hatched babies but they get too big to catch/eat/be satisfied with the tiny mites).
I know many folks are not comfortable with spiders, but they are mostly harmless to people... and teeny ones could hardly have enough venom... though I can understand if anyone is allergic.
...If they are spidermites, you should see the plants suffering by the time the webbing are evident. I mean Rosemary is a prime candidate to have spidermites on them, but are the leaves turning crispy and falling off? Are there sticky residue on the stems? Tiny white spots on the otherwise healthy-looking leaves? If you have spidermites, almost any measure used to eradicate the spidermites will likely kill the spiders, too.
...If you really don't care about the spiders performing their Garden Patrol duties and just want to get rid of the webs, then you can easily disrupt them by taking a soft hand/dust-broom to the webbing and brushing them out of the plants.
At this point, I think both are happening in my garden. I see web crossing one pole to another pole which is around 2ft away and some other similar situation like that. I also see webs on my rosemary plant and the fabrics of the grow bag handles.
By looking at the rosemary plant, yes, a lot of leaves turned brown and crispy in just a week. I remember seeing few small white spot on leaves few weeks ago. I think it has spread to my tomato grow bags since I saw few leaves turning pale white already. I started spray more neem oil solution to the plant then my usual, but else would you suggest?