Cannabis Forum > Sensi Seeds > Growing Archives > Cultivation Problems
  Sensi Cannabis Seeds Sensi Shop  Sensi Newsletter Newsletter  Cannabis & Marijuana Photos Cannabis Photos  FAQ FAQ  Forum Search   Calendar   Register Register  Login Login

Spider Mites

 Post Reply Post Reply
Author
  Topic Search Topic Search  Topic Options Topic Options
Ganja View Drop Down
Sensi Administrator
Sensi Administrator
Avatar

Joined: 13 June 2003
Posts: 6796
  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Topic: Spider Mites
    Posted: 09 May 2007 at 11:32
Here's a close up of the single most annoying pest most indoor growers encounter - spider mites (spint in Holland).



The thing that make mites so infuriating is the fact that they're hard to kill, and their eggs are even tougher.

A good spray with pyrethrum (concentrating on the undersides of the leaves) will kill all or most adults. But their eggs hatch again within 2-5 days, and you have a fresh infestation.

The important thing to remember is that when spraying for spider mites, once is almost never enough. With a significant infestation, spray three times per week for at least one or two weeks.

There are more effective poisons than pyrethrum, such as tebufenpyrad - a miticide sold as 'Masaii' by Bayer. However, these are also medium-toxic to humans. Growers should avoid using miticides beyond the first couple of weeks of flowering.

A bud that's nearly ready for harvest (like the one pictured) should probably not even be sprayed with a product like pyrethrum, which is virtually non-toxic to humans. At this stage, you could vacuum off the webs if they were a lot thicker than this.

One slightly positive side of the spider mite problem is that they don't usually destroy weed (unless it's a serious infestation) or make buds unsmokeable. When plants are harvested and hung up to dry, the mites head 'upward' which leads them to the tip of the stem, which is now the highest point; they don't remain in the foliage.

Webs can be removed with careful application of a vacuum cleaner, or newly harvested plants can simply be washed under a gentle stream from the shower (they're not going to get much wetter than when they're alive).

Infested plants should be dried far far away from living plants.

Auto-flowering Cannabis Seeds!
No growing questions by PM, please!
Back to Top
Ganja View Drop Down
Sensi Administrator
Sensi Administrator
Avatar

Joined: 13 June 2003
Posts: 6796
  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 11:52
Here's a much more seriously infested plant.









Despite having such a nasty infestation, this plant was given a thorough spray with pyrethrum and is now much healthier.
(JFTR, it's a plant that's not intended to flower. It simply sits in a window, growing with daylight and receiving very little care)
Auto-flowering Cannabis Seeds!
No growing questions by PM, please!
Back to Top
Grasso View Drop Down
Sensi Advanced Grower
Sensi Advanced Grower
Avatar

Joined: 23 July 2005
Posts: 563
  Quote Grasso Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 15:19
Hello,

I made first-hand accquaintance with this species a few days ago when I wondered why the rooted cutting does not grow but becomes less greener. A mite is as small as a resin gland but not as shiny. Now I moved the plant from the inner to the outer window board in the hope that cool nights and UV radiation will drive the buggers off.

The mites could have easily infested other cannabis plants, too, but they seem to leave strong plants alone. A chili plant has some damaged leaves, too, but has got rid of the mites by itself.

Uli
    
Back to Top
Ganja View Drop Down
Sensi Administrator
Sensi Administrator
Avatar

Joined: 13 June 2003
Posts: 6796
  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 16:01
I think strong, healthy cannabis plants have reasonably good defences against mites. A healthy plant may have a small population of mites, but they don't really take over until they've significantly weakened the plant (by feeding on its juices).

Then, at a certain age, like an overwhelmed immune system, the mites swarm across the plant and start building their webs over the buds.

In room with many different plants, mites always seem to be most prevalent on the weakest plant in the room (and contribute to it becoming weaker). If you remove that plant, without spraying, the next weakest plant in the room will often become infested very quickly (even if it's far away from the previous victim)
Auto-flowering Cannabis Seeds!
No growing questions by PM, please!
Back to Top
farmer mick View Drop Down
Sensi Advanced Grower
Sensi Advanced Grower
Avatar

Joined: 28 June 2006
Posts: 1083
  Quote farmer mick Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 16:32
Little bastards! I hate them. A beautiful mother plant whose genetics I retained through cloning for around 18 months got infested on around five branches last year.
 
In retrospect, I could have taken a few clones, but I had a fully flowering crop in the next room and (in a fit of panic) took a knife to the whole plant, stuffed it into a plastic bag and dumped it in the rubbish immediately.
 
Thankfully, I haven't seen a mite since.
 
Ganja, did you let that plant become infested or did you not notice until it was in a bad way? There's always a risk that one of em could get onto your 'good' plants via your clothes or something.
"A rat race is for rats. We're not rats. We're human beings." - Jimmy Reid, RIP
Back to Top
Ganja View Drop Down
Sensi Administrator
Sensi Administrator
Avatar

Joined: 13 June 2003
Posts: 6796
  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 17:04
The plant was (and currently is, after a pyrethrum bath) standing in a window in a different building from the Museum.

The Museum has one of the world's only open grow-rooms that the public may come and view. And to be honest, I'm not sure there's ever been a time when it's been 100% free of spider mites. It's just a case of keeping them in check.

Also, the fact that we never have a room full of plants that are at the same stage of flowering means that we can never get super-serious with pest control and douse the whole room in miticide. There's always a big section of the grow-room that has close-to-harvest plants.

I've actually declared war on the wee bastards this summer, and am hoping to get the room 99% clear (100% would be nice, but I'm not getting my hopes up).
Auto-flowering Cannabis Seeds!
No growing questions by PM, please!
Back to Top
Grasso View Drop Down
Sensi Advanced Grower
Sensi Advanced Grower
Avatar

Joined: 23 July 2005
Posts: 563
  Quote Grasso Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2007 at 20:09
Hello,

all the smoke in the coffeshop does not make the plant healthier, does it, even though nicotine is a faunicide, is it not, Ganja? Cool nights and UV radiation stress most bugs as for example aphids on peppermint. By the way, mint is great to practice the rooting of cuttings on, but it needs more humidity than cannabis does. I think that pest resistence also depends on the strain; that cutting is of Nirvana's Haze another specimen of which showed a microbial or viral leaf illness in seedling stage and which is not the most vigourous strain anyway; also White Russian is said to have few defences against spider mites.

Uli
Back to Top
sergioqweqwe View Drop Down
Sensi Seedling
Sensi Seedling
Avatar

Joined: 23 May 2007
Location: Russian Federation
Posts: 1
  Quote sergioqweqwe Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2007 at 13:58
People i'm sorry to bad english, i russia man :)
Ganga, but i thing what good determination finish growing cycle, she is begin treated for spider with the help water - drying - frost(imho).
Back to Top
Ganja View Drop Down
Sensi Administrator
Sensi Administrator
Avatar

Joined: 13 June 2003
Posts: 6796
  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2007 at 14:17
The webbed bud did indeed make it to harvest. It was cut a couple of days after the picture was taken.

We've found that a good way to save seriously webbed buds that are about to be harvested is to vacuum them (very carefully).
Each bud is cupped in the hand, and a circle is made with thumb and forefinger about a centimetre above the bud. The vacuum cleaner tube is then applied to that circle. Your hand stops the bud from being sucked into the tube, and the vacuumed air passes over the bud and removes most of the infestation.

A carefully applied vacuum cleaner can remove 60-90% of mites (and all of their webs) from a plant, which is a much better option that a poison which may kill 100% of them, and then may be smoked...

The plant from the window is still alive, but will probably never be flowered.

Grasso - nicotine makes an effective (if somewhat toxic) broad-spectrum insecticide when applied as a liquid spray. I'm not sure that nicotine in smoke has a major effect on insects, or I'd expect to see very few bugs on the plants in the cafe window. Smoke probably makes them feel ill, but I don't think it kills them.
Auto-flowering Cannabis Seeds!
No growing questions by PM, please!
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down