Well, here's a question.
A few days ago, my business partner noticed that the cauliflower leaves were getting nibbled at. This week, the infestation is huge. Over half of our cauliflower seedlings are under attack by an unidentified pest that weaves webbing in the junctions of the new leaves and feeds there. Whatever it is also attacks our pak choi and cabbage seedlings, which look very similar. The little varmint leaves behind stunted and twisted new leaves, tiny round black pellets by the score – eggs? feces? – and eaten leaves. In several cases, it's killed the seedlings outright.
And I haven't seen a single live insect!
As a first line of defense, I brewed up some cinnamon-garlic oil, which I've seen work as a successful pest repellent (though not pest killer). I added neem oil and dropped it into the join on every seedling, just half an hour ago. I'm going through IPM manuals online looking for what this could be – so far, I'm learning a lot about scouting practices and targeted insecticides, and a not a lot about rural West African cabbage pests. Next step in research is, the Trainer's Manual from the Ghana Organic Agriculture Network. Next step in practice…depends on how the treatment works and what else I learn.
So…help! Anyone know what this is? Or what to do about it? Hugs and gratitude to anyone who can shed some light here!
You may have cutworms or other caterpillars that hide during the day. I get cutworms bad but never see them because they hide in the medium when it is light. They come out at night and can mow down many seedlings each night. I use dipel on a weekly basis. Dipel is a bacteria that eats the bacteria in caterpillars and cutworms stomachs. It works very well for me.
Three days ago I noticed similar MO on my Napa cabbage and 'open head' chinese cabbage and a little on the bok choy...Lots and lots of dark tiny spherical droppings (which at fist I thought might have been insect eggs) and ever so tiny webbing. Turned out to be a small greenish larva/caterpillar (found more through dumb luck than anything).
I don't know what the name of the pest is, but I brewed up some pyrethrum spray and haven't seen any droppings or additional damage since.
It might be best though to use Chris' method, as insectisidal spray made from pyrethrum flowers is not fish appropriate (neither is any type of oil or soap though).
Cutworms aka cabbage worms are deterred by Borage.
Dipel dust is a brand name of bacillus thurgensis which is a disease that attacks leaf eating caterpillars. Thuricide is another brand name. It is a spray or dust you apply to the leaves of plants. the caterpillars have to eat some of it before it affects them by giving them a belly ach, they quit eating and die in a few days. It must be used by applying to the parts of the plants that the caterpillars will eat. It is not a systemic and you can't use it by watering it into the soil or pouring it into the AP system.
Thanks so much, everybody! I'll see if I can get some BT or pyrethrum at the big agricultural supply store in Accra tomorrow. They've taken out most of those seedlings by now, but we also want to protect everything else before we put pest screen on the hoop house (should have done that a while ago, hey?).
I found one of the buggers, too - they're little caterpillars, the biggest I saw was about half an inch long. Vlad, it sounds exactly like what you have. We don't actually have any fish in the system yet (we've been fertilizing with semi-fermented plant tea, Bioponics-style), so I don't need to worry about hurting them, but I don't want to upset our bacteria either.
And darn, our borage hasn't survived in this system, it would have been useful.
Don't use the pyrethrum around an aquaponics system!!!!
Dipel or Thuricide are what you are looking for to deal with caterpillars and those are both safe around aquaponics when used according to label directions.
Gotcha! Thanks. We wound up going with neem juice - not the oil, but the tree grows everywhere around here, so we blended up the leaves in water and strained it to make a rich juice. Our agronomist, who's trained in Crop Sciences here in Ghana, thoroughly approves.
(It's not an antiseptic, is it? We're having some issues with our nutrient levels, and I wonder if the neem affected our bacteria...)
Holy crap...your agronomist didn't tell you? Yes, they make antiseptic cremes and dressings from neem leaves. The antiseptic properties of neem leaves are very widely recognized (the leaf and leaf extracts, not just the oil)...
I would imagine your agronomist should know this.
That explains our nitrite spike, then.
This trick worked great for me when my system had cut worms terribly bad. Nothing to buy, no concoction to make, just flood the beds and watch them float up out of their hiding places!