Know your enemy (Mites)

Botany and Cultivation
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I’ve done alot of work in Cannabis IPM and have dealt with a wide range of greenhouse pests in a variety of conditions. Since its 90 degrees out and we are firmly in the dog days of summer, atleast in my neck of the woods, I thought I’d talk about Spider Mites right now and maybe some of you guys are dealing with this issue and it might be helpful.

First off, dont panic when you see them. I know alot of people consider them the kiss of death but they are manageable if you keep a cool head and do everything in your power not to spread them during removal. And remove you must; and dont be shy about it either. Better to remove a big chunk of the plant up front then to surrender your hard fought flowers further down the line due to half measures.

Spider mites go through 5 stages in their life cycle, starting with an egg / larvae / 2 nymphal stages / and adult. All take place in the canopy, and all mobile stages are capable of feeding on plant tissue.

You will know them by their signs…mostly the webbing is a dead giveaway. It will start at leaf petioles and spread upwards from there, causing yellowing / bronzing and eventually necrosis and a sense of impending doom in the air.

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The proper management of spider mites, and any pest really, starts with scouting. Make a deliberate effort to inspect your crop for signs of infestation twice a week at a minimum. Once you know what to look for, the signs will pop out at you like a chip in your windshield during crop inspection. Clusters of silver scratches or dots starting at the petiole where the leaflets connect and spreading outward as pictured below are the first signs that you will see.

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Proper and sanitary manual removal of infested foliage is key. Be thorough and bold, or suffer the consequences.

Spider mite infested flower
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Know your allies:

Phytoseilius Persimilis → Probably one of the most effective predators of spider mites. Not hampered by the webbing and endowed with a voracious appetite, apply directly to infested areas.

Amblyseius Fallacis → Useful in its ability to reproduce at higher temperatures in order to keep up with the spider mites reproductive capability, apply directly to problem areas or spread throughout crop.

Amblyseius Andersoni → Hardy and quick to spread, these are available in slow release sachets which are excellent for extended crop protection.

Neosilius Californicus → A useful generalist predator that also makes a habit of eating the spider mite eggs. Reproduction drops off at higher temperatures

Amblyseius Cucumeris → Only really useful in this scenario for eating spider mite eggs, mostly a predator of western flower thrips; also available in slow release sachets

Amblyseius Swirskii → An excellent and hardy generalist predator but considerably more expensive than other options; available in slow release sachets.

I look forward to hearing about your experiences.

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Haven’t had any issues with them at all luckily. Have had some aphids, but my ipm is keeping up, no serious issues. Just a couple here and there…

Venerate, grandevo, em5, silica, DE, Karanja oil, mammoth bio control

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What species of aphid are you seeing? They can be damned hard to get rid of but you seem to have a pretty good arsenal at your disposal. Are you foliar feeding the silica or adding it to your nutrient solution?

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Both ways with the silica. They are white aphids.

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These assholes? They’re probably potato aphids. You can get a species of aphidius wasp thats capable of parasitizing them, Aphidius Ervi. As far as beneficial insects go they are pretty affordable, and i’d consult the manufacturer to confirm but I’m fairly certain they’d be compatible with the chemical controls you have except for Venerate and the Karanja oil.

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Yep, those guys.

I appreciate the input! I am cutting off Karanja oil and DE starting next week (due to flower coming soon). Might order some of these guys and see how they do.

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What were you using the Diatomaceous earth for, soil pests or just as a silica source.

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Mixing in water, spraying mid day. Drys out in about 20 minutes (all other ipm is done in the evening)

Just an easier way than dusting a bunch of plants.

As a “mechanical” form of IPM, because it Kills them after it dries and they move around etc.

I look at my ipm in 4 ways. Oil based, bioinsecticides, mechanical (DE and silica) and beneficial insects.

I have had decent luck with the good ol’ lady bug, for aphids and thrips in the past.

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Right on, I don’t think ive ever come across DE used that way thats fascinating I’m gonna tuck that away in the filing cabinet for a future crop. I’m on board with your approach to IPM ; nothing beats preventative maintenance of the crop for managing your risk and especially proactive applications of bio-insecticides to both the canopy and the root zones is a really effective tool in our boxes. I typically rely on preventative applications of Horticultural oils, and bio-fungicides and insecticides during the vegetative period of growth and switch over to a broad regiment of predator insects once my flower buds set. Generally though, I think alot of people focus most intently on their canopies and somewhat neglect their root zones; its simple and effective to do scheduled chemical applications to the root zone or even better, maintain a presence of beneficial nematodes or soil predators. That is integral to managing things like Thrip, fungus gnat, springtails, all things that have a life stage in the soil.

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I don’t really have issues in my rootball. I add mosquito bits to my soil blend and use mosquito dunks in my reservoirs all year.

I get some beneficial mites and springtails. Nothing else from what I can see. (I have pretty decent layer of mulch, so I don’t mind these guys being there)

I also focus on actual dry out cycles, unlike some living soil guys.

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Agreed on the necessity of the dry down. I keep an eye on my moisture sensors to try and push my rooms as far as I feel comfortable before irrigating, keeps the water and fertilizer usage down and helps to manage the population of soil annoyances. You seem to keep a real vigilant eye on your crop, i respect that.

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i use to would agree w predator mites

untill i releaased 100x more than their suggestions and still couldnt knock em out

spidwr mites are kinda like a cancer i hate to say it. once u got bad infestation theh hard af to get rid of
and i always caughf them before they got that bad

tbh spider mitez caused me to quit growing i hate the fucking things

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Mums are supposed to be fall flowers, but they start showing up in big box stores in late july and august. I saw a big table of them at menards that was one giant web of mites. The employees had no clue. So I’d say to be mindful of any flowers that anyone in your household might bring home, especially late summer mums.

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There’s a special place in hell for spider mites thats for sure, but you can send em there with enough deliberate effort. Mechanical removal is the first and one of the most important steps, but not just cutting out the bad shit but the stuff thats nearby the infestation site too, and make sure that you’re making slow careful motions as you cut and remove it from your trellis or what have you, and bag it immediately before it can make contact with any nearby plants or surfaces. Then spot treat with neem oil or something like that if you can, then release the beasts so they start off on a strong foot.

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Absolutely. Unless you’re growing outside or in a greenhouse the most likely vector for mites to be introduced to your garden is hitching a ride on you or someone else in the house unfortunately; or the plants they bring in in this case.

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Thanks for the write up @Gregory I love hearing about other peoples IPM regimen and am always trying to stay informed to what people are doing in their gardens to keep plants healthy, if you get super bored one day you should do a big IPM write up for the people like me with very little knowledge, on how to get started and the biggest factors to having a good system.

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Thanks for the shoutout, IPM has always been fascinating to me and until I was pulled into middle management my career trajectory was focused firmly on greenhouse pest management strategies. So its something thats near and dear to my heart, and I was planning on doing multiple of these “know your enemy” posts for different pests if this one kicked up some good discussion so keep an eye out for those if youre interested and if you have any specific questions about spider mite control methods just shout em out here and I’ll do my best to help.

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Thanks, I worked in a 100k Sq Ft Green house for 2 years and was introduced to it then and it’s awesome how effective it can be when done right! Yeah I am going to search and see if theres a thread that already discusses the basics to start reading in on, because I really want to know what are the main parts of prevention are to keep on.

In my 2 years at the GH we didn’t have one single out break that wasn’t controllable, they were always identified and dealt with before it could take out any significant amount of plants. I wish I had pestered him for info more during my growing days.

As for Spider mites, what are your prevention tasks to keep them from getting started in the first place? Are there set groups of predators you use when you switch to flower to keep everything in check, as well as sprays and then if problems arise you then go into containment mode? How often are people usually spraying and putting out new predatory insects for prevention?

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Old head grower chiming in here…

Grow spearmint and chrysanthemums in your grow

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Hey what is your ratio for your DE/h2o? I’ve always used neem oil in the past. I’m tryin to use alternatives. Thanks…