I found spider mites on a container-planted dahlia (or rather that's what my nursery said it was - I honestly couldn't see anything that looked like a mite or any evidence such as webby material). I isolated the plant and treated it with Neem Oil, but it was too late. When I sprayed the dahlia, I also sprayed all my other plants (all planted in pots). I've continued to do so every two weeks, even though I see no evidence of any kind of pests. Does Neem Oil (or soapy water) act as a deterrent, or preventive, against pests, or am I just making my life more complicated?

Spider mites are tiny. Usually found on undersides of leaves, they suck the juices from your plants. Yellow spots can show up on the plant- and because they are kin to spiders, ticks and other mites, they spread themselves around to other plants. If you AREN'T seeing them, that's a good thing. Neem oil and soap do work on controlling them- most other pesticides wont do such a good job. 2 weeks is the time it takes for eggs to hatch that were left behind by what you didn't catch the first time.

Neem Oil is a once a year application that will only harm insects that suck on your plants. Use it in the spring before the bugs show up. I use it on my pepper plants as I plant them to ward off the aphids. Use it in the evening so your plants don't burn.

Soapy water is a once a day thing and washes every insect away (until they can climb back up). It won't help until the bugs are there.

Daisy

My neem bottle says to reapply every two weeks. It does a great job though, on aphids, miners, white flies... it didn't do anything on the cabbage moth caterpillars or the carrot seed moth caterpillars. If it works against mites then it is a great treatment to prevent reinfestation. Bonus is that it helps with the fungus too.

Did you get 100% Neem? It makes a difference. I've never had to use it more than once or twice in an entire season.

DaisyI said:Did you get 100% Neem? It makes a difference. I've never had to use it more than once or twice in an entire season.

The container is, but I put in 1 ounce per gallon in the sprayer. It says to use the 1 ounce per gallon mix every 14 days. It needs to be too.. the stuff doesn't stay with residual inside the plant so after a couple weeks if new eggs hatch, you need to reuse it.

I love neem oil but I use it as a systemic, not spray. And, as I said earlier, it doesn't work instantaneously so you have to plan ahead. It only kills the sucky bugs so the good bugs aren't affected. Read this:

http://forums2.gardenweb.com/d...

Well, it has worked as a spray for me, although I've only used it once for white flies and otherwise my use is for fungus and mildew. The instructions are clear, use it every 14 days. Those are pretty common on all the Internet searches too.

Thanks for all the helpful suggestions! My question has been answered: use it every two weeks regardless. What I've been doing is alternating weeks: the first week, Neem Oil, the second week, a half-strength fertilizer. This way the plants get a dose of each every two weeks. Daisyl, that link was very helpful. Thanks!

Actually, I have controlled serious spider mite infestations on my roses by just washing them off with a strong stream of water daily for three days to break the breeding cycle and then once a week on a regular bases when temperatures are high and humidity is low.

However, this is an outdoor treatment and may not be indicated for greenhouse or indoor plants which have a different type of environment.

Something to consider.