I've grown dahlias for like 5 years and never had this problem until this summer. The leaves are getting these tiny yellow spots and there's definitely webbing underneath. I've tried neem oil twice but it's not helping much. Should I just pull them out?
So if you've had a particularly hot or dry summer compared to your usual years that could totally be it. are you watering less frequently this year or is your area just experiencing a drought? also where are you located? sometimes certain pests have population explosions in particular years depending on weather patterns and what ate the mites the previous year.
neem oil works but you gotta be consistent with it and honestly it's not always the fastest solution for established infestations. since you're already seeing webbing that means they're pretty established. i'd suggest spraying every 3-4 days for at least 2-3 weeks, making sure you get the undersides of leaves really well. spray in the evening when it's cooler. some people have better luck with miticide sprays like forbid or avid if neem isn't cutting it, though those are stronger chemicals. you could also just blast them off with water from the hose every few days which sounds tedious but actually works.
don't pull them out unless they're totally beyond saving. dahlias bounce back pretty well once you get the mite population under control. just make sure you're not planting them somewhere too hot and exposed next year, and maybe increase humidity around them a bit if you can. also check if you've got any other plants nearby with mites since they'll just reinfest your dahlias. have you noticed the mites on anything else in your garden?
Spider mites love hot dry conditions so if you've had a hotter drier summer than usual thats probably why. they can show up outta nowhere when the weather changes. neem oil works but you gotta be consistent with it - once or twice usually isnt enough. you need to spray every 3-5 days for like 2-3 weeks to really get them under control, and make sure youre hitting the undersides of the leaves where theyre hanging out.
before you rip them out try increasing humidity around the plants if you can. spray the foliage with water in the morning, that stresses the mites out. if neem isnt cutting it grab some miticide labeled for spider mites - something with sulfur or abamectin works better honestly. honestly the main thing is being more aggressive with treatment than you might think you need to be. also check your other plants nearby cause theyll spread to whatever else is around.
dont give up on them yet. spider mites are annoying but theyre beatable if you actually stay on top of it. just gotta catch them early before they really trash your plants which it sounds like youre already dealing with. definitely make sure its not too dry and hot where theyre planted either, some afternoon shade might help too
Spider mites love hot dry conditions so if you've had an unusually hot/dry summer that could be it - they thrive when plants are stressed. before pulling them out try spraying the undersides more aggressively (early morning or evening when beneficial bugs aren't out) or switch to insecticidal soap since neem needs really consistent applications and mites can get resistant, plus keep the foliage misted if you can since they hate humidity.
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