Anyone ever had issues with wireworms? I have a client in the state of Washington that has them in the soil and everything that will kill them is not on the approved list for the state. I am trying to find a fix for him. Anyone have a remedy for these nasty bugs?
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There is probably someone that can help you further than myself but I’ll throw a little suggestion out based on my reading and studies beneficial nematodes for soil pest usually work well. I have never had this problem myself (knock on wood). Beneficial Nematodes for your medium.
Thanks team,
-Ralph
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Thank you. I have read a little on it. He is going to try using the nematodes this year and I was hoping to find something else for a better arsenal this season. The life cycle on them are 1-6 years and take a couple years to get out of the larvae stage. That is when they are eating up the roots and traveling up the stocks. By flower stage the plants were getting weak and falling over. Thanks for your help!
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I am going to step out on a limb and guess this is a no-till farm?
Plowing 6-8" helps kill these buggers, it brings them to the surface for birds to eat, dries out soil quickly to dessicate adults, larvae, and eggs.
Destroying any cover crop from tilling early will starve them as well, it may be necessary to go fallow as soon as possible.
Second, I would overhead irrigate prior to planting with a nematode injection. Nematodes will eat eggs.
Crop rotation is desirable, but probably not feasible with the law, as it is with my laws. I cannot just move my production with securing and licensing a new area.
Without tilling (or after tilling), but well before planting and during the growing season: The preferred food of wire worms are potatoes and carrots. Buy a boat load of potatoes and/or carrots, skewer potatoes with a stick and bury to 4 inches or stick a carrot in the ground 4 inches. Wait a few days and remove the potatoes/carrots, check for worm holes, and discard (burn 
). This will also provide a good indicator of population after tilling and nematode application. Repeat until no holes are being found.
Additional info: 1 wire worm sifted out per shovel of dirt over 20 shovels full represents 20,000 adults per acre. 2 wire worms per 10 shovels full is an indication that crops will be damaged. If less than 2 worms per 10 shovels full are found, there should be little damage. Larvae take 2-3 years to reach the adult stage. They don’t like legume cover crops, but can survive of grasses.
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Nate, that’s a easy one… a soil drench with a weak solution of pyretheroids ( Asana,Pounce,generic pyretherin) will kill them immediately…since you are doing a soil drench it won’t be in your tissue and pyretherins are registered on just about everything…Good Luck
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That would be the easiest and most cost effective way to go.
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Thank you guys for the pointers. Sounds like I should have somethings for him to try out. I really appreciate it!
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Nate, you won’t need much, 1 oz in a gallon of water should smoke them right now!!!
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Wow thank you for that @Farmer_Dan. Wouldn’t want him failing any tests. I really appreciate you digging into it. I was having issues finding a good approved solution. I will relay this information.
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Is this a no till farm?
I have read that no-till soil has more problems with wireworm than tilled soil. It is the fall tilling that kills them from exposure. Spring tilling may not help, particularly if they are pushing organic matter under.
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Well he just bores holes in the ground due to poor soil quality and fills it with our Organic coco blend. They cannot do pots due to heat in the summer. But people in his area are complaining saying the problem doubles each year.
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There is a lot of conflicting info. Organic producers says to use pyrethrin followed by beneficial nematodes. Conventional says it isn’t very effective. It is hard to say. The pyrethrin followed by nematodes, might just be the best bet, however conventional information shows azadirachtin as effective. Maybe a pyrethrin/azadirachtin blend follow by nematodes might be more effective.
Are the wireworms just present, or are there crop losses being seen?
Organic matter, such as coco or peat filled holes, plus the added moisture compared to surrounding soil is probably attracting them.
How feasible is a trap crop? Planting some potatoes near the cannabis to attract them to a preferred food source.
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They try to stay as organic as possible. In 2015 they had beautiful plants, 2016 started seeing a small issue that they couldnt pin point, 2017 started seeing a larger loss and found the issue, 2018 could not get a head of the issue and had a loss of whole plants that would fall over from being weak at the base due to them getting in the stocks. This year they are worried and want to figure it out. They should be able to do the potato trick and start ridding the property that way as well.
Is there any kind of liner they could use like a mesh that they couldn’t get through but would still allow airflow and water flow?
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Sounds like they really do enjoy cannabis, maybe they should write a paper? This is good information, despite being bad for their business…
Due to the size of the larva, you would need roughly 30 mesh, ~0.6mm. At least I read a paper indicating that 30 mesh will capture larvae. The eggs are 1mm, so the newly hatch larvae is going to be smaller than that in diameter. If the holes are being reused, I don’t think the mesh will help, unless they are drilling fresh, but even so, soil falling into the hole might have larvae and they will come up from the bottom. Personally, I wouldn’t want to put that much metal in my soil.
On a side note, do you know the soil series on which they are growing? Poor soil doesn’t necessarily mean bad soil for cannabis, though there are some bad soils for cannabis. With the amount of money being spent digging and filling holes, there is a good chance the soil could be ammended and become more conducive to cannabis.
Personally, my soil isn’t ideal, but with some inputs (compost, lime, and minerals) and management practices (plowing to 8 inches, spading to 1ft, and hilling row to 10-12"), it has become very productive. My soil is a pretty heavy silt loam 0-9" and silty clay loam or clay loam to 9-24", somewhat poorly drainded, and half of the field has a 0 inch water table through the winter. I still produce 7ft+ tall plants in a tight stand in that area. We hit 48g per sqft foot average, if loses during drying didn’t occur (working on that this year with a few drying area changes). Even in the poorest area with a good cultivar and extensive russet mite damage on those plants, we hit 45g/sqft. Having culled my low yielding cultivars and replacing with my higher yielding cultivars, better IPM coming this year, and pushing fertigation an extra 2 weeks, I am shooting for 56g per square foot this year (5000lbs usabe on 40ksqft).
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Been doing some reading, while pyrethroids are effective, it seems pyrethrin is not effective.
I am seening Azadirachtin as effective, and the fungus Isaria fumosorosea found in PFR-97 20% WDG as effective. Everything else is banned for cannabis…
Plowing works too, we have nasty nematodes around here that don’t like it when you plow wet, it kills the grubs while I am at it.
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