May 10, 2018

Beneficial Nematodes to Control Flea Beetles

Our garden was infested with flea beetles, the soil was just teaming with them. We had the variety that attacks eggplants as well as the variety that attacks cole crops like cabbage, Asian greens, etc. They were so bad even the tomato plants were badly damaged, normally tomato plants can outgrow the damage caused by their feeding because flea beetles much prefer eggplants.

For the past two years I've been applying beneficial nematodes in the spring because high temperatures during shipping can kill the nematodes. The spring after the first application saw a noticeable reduction in the flea beetle population, especially the one that prefers brassicas/cole crops. The spring after the second application coincided with minimal flea beetle damage to brassicas, although the eggplants were still getting eaten up by flea beetles.

This spring I've noticed no beetle damage on peppers or tomato plants while they've been in the greenhouse or on the front porch, and last fall I had planted the whole garden in greens, turnips, and radishes and there wasn't any damage then either. Another thing I noticed is a lessening in the mosquito population this year, normally they are everywhere in the grass and garden. But it's hard to say whether the diminished number of mosquitoes is due to the cold spring.

Beneficial nematodes prey on larva of insects that live in the soil, so it won't have an affect immediately on the adult beetles, mosquitoes, etc. But they should have an affect on subsequent generations, especially as the beneficial nematode population increases with time.


Michelle said...

Very interesting that the nematodes would have such a significant impact. How gratifying to be rid of such a problem. I wish there was that kind of treatment for rodents. :)

Sue Garrett said...

Interesting that it has been a gradual build up in the way the nematodes have had an effect.

Dave @ HappyAcres said...

I had no idea that nematodes would control flea beetles! I have them eating on my tomatoes and eggplants this year, but they are not bothering the brassicas. I need to think about trying some of the nematodes here.

Phuong said...

Hi Michelle,
They really made the greens and brassicas unsightly and I'm sure it affected the growth of the plants as the larva fed on the roots. I'm hoping you have a better growing season this year, it makes me wonder if you're having a population explosion because the critters seemed excessively bad last year.

Phuong said...

Hi Sue,
I think it would have worked faster if we didn't live in such a hot climate. Supposedly the nematodes are sensitive to heat, so they probably die off a bit during our summers.

Phuong said...

Hi Dave,
The flea beetles must be really bad if they're feeding on your tomato plants as well. They can really stunt the growth on eggplants if there's a large infestation.

I can't believe how well your greens are doing even with the weird spring we've been having. I tried to talk my husband into making cold frames from our old windows but he ended up giving them away instead. :(

Shawn Ann said...

I used some beneficial nematodes near my raspberries for Jap beetle grubs but didn't know they helped with flee beetles. I'll have to use more next time. They seem to like my potatoes every year.

Phuong said...

Hi Shawn Ann,
They sell different kinds of beneficial nematodes for different critters, but I don't know if that makes a difference. Did it help with the Japanese beetles? We're in the midst of a terrible heat wave, it's much too hot to plant bean or corn seeds. Hopefully the rain will bring cooler weather at the end of the week.

Shawn Ann said...

It's hard to know for sure if it helped. Last year was the first year here and I used them around the raspberries then. And we really didn't have a lot of Japanese beetles like we usually do on the raspberries in other locations. So I did it again this year hoping it will still be better this year. I have moved these raspberries twice before bringing them here. And in both other locations the beetles were horrible. All three places are within a mile of each other so it wasn't a big move.
We will see how it goes this year.

Phuong said...

Hi Shawn Ann,
We used to get tons of Japanese beetles as well for years and years at our old place but then there seemed to be a huge die off. We just don't seem to see them anywhere and none of my gardening friends talk about them anymore. I have to wonder whether it's the microorganism controls people are applying to the soil or maybe something else is in play.