Fennel Aphids and Nematodes -- What I learned today from the University of Florida

Today UF had an open house packed with exhibits related to agriculture and horticulture. I had a lot of questions answered about root knot nematodes, and the bugs on my fennel.  The big highlight was my talk with Dr. Giblin-Davis in the nematology lab, but regarding nematodes my main carry away was that I'm on the right path. 

Even though nematodes is his specialty, he was the only university staff able to tell me what is on my fennel. He took the infested piece of fennel that I brought in a ziplock, and showed me what these guys look like under a microscope. They're aphids! But smaller than the aphids that were on the cukes. The bug looked happy and healthy on the fennel. In fact I think he was doing a dance and singing "Stayin' Alive"! 


Here's what they look like, but the colors vary from green to beige:



The weird thing is that my garlic/cayenne spray works to repel the cuke aphids, but NOT the fennel aphids. They're not phased by neem oil either! I use either insecticidal soap or 70% isopropyl rubbing alcohol to kill them, but it's time to try some other organic repellent recipes. Next up, I'll try the flour and baking soda mixture on and around the effected plants to repel them.

I saw the image in the preview, but not the post. Some reason I'm having trouble with this one. Here's the link...

https://i.servimg.com/u/f57/18/48/41/90/fennel14.jpg

It shows in your post.

dstack,
Weird about the aphids, probably a mutant that only affects fennel. I've not been bothered with aphids, so cannot help.

I was bothered by nematodes when I first started my SFG. I was told so many things.
2 things I did, which 1 or both worked, I planted French Marigolds. As they got trimmed or died down I turned them under instead of removing them. I also planted mustard. I got some cheap seeds at the farm store and planted it in all beds. If I needed the squares, I just turned it under and planted. I guess I have got rid of the nematodes, but I have plenty of mustard. I have been pulling and putting in the compost bin. Sorry there is no link for the mustard. I did this, then went back and the link was gone! I guess I just will put it forth as my experience only. I got the Marigold info from my county extension service.
Jo

littlejo wrote:dstack,
Weird about the aphids, probably a mutant that only affects fennel. I've not been bothered with aphids, so cannot help.

I was bothered by nematodes when I first started my SFG. I was told so many things.
2 things I did, which 1 or both worked, I planted French Marigolds. As they got trimmed or died down I turned them under instead of removing them. I also planted mustard. I got some cheap seeds at the farm store and planted it in all beds. If I needed the squares, I just turned it under and planted. I guess I have got rid of the nematodes, but I have plenty of mustard. I have been pulling and putting in the compost bin. Sorry there is no link for the mustard. I did this, then went back and the link was gone! I guess I just will put it forth as my experience only. I got the Marigold info from my county extension service.
Jo

Mustard greens are good eating.  Much like turnip greens.

Kay

Solarizing the soil is the best way to kill nematodes. I've not tried that in a SFG box, but should be a lot easier than on the conventional garden.  Yes, you kill a lot of good organisms but they are much more resilient when it comes to heat. The "white hats" reestablish themselves quickly. UC Davis has some great info on solarization. I don't have that link handy either, but I could track it down if needed. Sanderson posted it on one of my threads. 

Does mustard do well in poor soil? In my non-sfg portion of my garden I have marigolds around the papaya plants, and I need to get more aggressive with planting more. Or perhaps I could add mustard plants. Is it any particular variety?

There was no variety mentioned, just the cheapest seed will do. Mustard evidently puts something into the soil which nematodes don't like. They will grow everywhere, poor soil is ok. They can be eaten,um good!
Jo

I just learned why there are such mixed reviews from seasoned gardeners on the use of marigolds for nematodes. Here's a very informative report done in Hawaii...

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-35.pdf

Basically, you have to get your soil tested to see what variety of nematodes you have so you can find out which variety of marigold will be most effective. Certain marigold varieties are only effective at killing one or two varieties of nematodes.  

If you've been successful without doing the soil test, congrats! You lucked out!  

dstack, I had root knot nematodes. They did no testing, I took a green bean plant into my extension office and the folks there just told me what was causing the problem. I let the mustard bloom, which I guess I wasn't supposed to. Here are a couple of links I found, even mentions Mustard.(I grew mine instead of getting mustard meal?)
Jo
http://ucanr.org/sites/Test1/files/92359.pdf

http://www.apsnet.org/edcenter/intropp/PathogenGroups/Pages/IntroNematodes.aspx



http://www.ncbi.nlm.nih.gov/pubmed/17390806


http://westernfarmpress.com/management/nematode-management-strategies

I remember trying to garden in Hawaii; the nematodes were ferocious and for me, anyway, impossible to kill.

Re burying marigolds, I've read that's fine to do in the winter, as their poison will abate quite a bit before spring, but that marigolds can make it hard for other plants to grow if you dig them in, otherwise.

Marc Iverson wrote:I remember trying to garden in Hawaii; the nematodes were ferocious and for me, anyway, impossible to kill.

Re burying marigolds, I've read that's fine to do in the winter, as their poison will abate quite a bit before spring, but that marigolds can make it hard for other plants to grow if you dig them in, otherwise.

According to nematodologists at UF, the nematode killing power is only in effect while the marigolds are alive.  This report (below) puts a few myth about marigolds and nematodes to rest, but it also explains why there's so much confusion on the subject. Some marigolds will actually HOST some races of root knot nematodes! So if you don't know what variety of R.K.N you have, you may be making the infestation worse. The French marigold is the most effective at killing the widest range of these parasites....


University of Florida IFAS Extension Report:
http://edis.ifas.ufl.edu/ng045