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I have a pest situation on my apricot tree caused by the beetle Capnodis tenebrionis (see this question). I am averse to using chemical pesticides, and I read that nematodes can be used to control C. tenebrionis:

I'm considering using this method. My question is can the nematodes themselves become a problem? There are many plant diseases caused by nematodes.

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Jonathan
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    Nematodes are a large group of creatures - as with insects there are ones that might be pests, and others that introduced for control of other pests. However, why is biological warfare acceptable when chemical warfare is not? :-) I guess we all draw the line somewhere and it is never in quite the same place. – winwaed Jul 13 '11 at 19:40
  • I ask because a local agronomist warned against using nematodes in my garden as they can themselves cause problems. My general approach is to prefer to use biological means over chemical means. I assume that pesticides sprayed on a tree will affect a larger number of insects (bees, for example) than introducing a specific predator. – Jonathan Jul 14 '11 at 05:38
  • A large proportion of deliberate introductions of invasive animals have been for 'species control' purposes. Many assume biological solutions are clean solutions - and they rarely are (which is generalisation of what your agronomist is saying). re. pesticides: Chemical pesticides can be more effectively used in spot treatments. – winwaed Jul 14 '11 at 12:26
  • Two major types of nematodes, herbivorous and carnivorous. If you don't have enough of the latter, the prior take over and eat your plant roots (root knot, etc.). The latter also attack burrowing insect larvae, wireworms and a host of other pests. – Fiasco Labs May 18 '14 at 04:51

2 Answers2

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There are "good" & "bad" nematodes, therefore it's vital you get the correct "good" ones for your particular situation.

According to Wikipedia there are 2 kinds of nematodes from a horticulture perspective:

Keep in mind the "good" nematodes will not kill the actual beetles (get rid of the problem this year). The "good" nematodes will feed on the beetle lava, thus reducing the possibility of experiencing the same beetle problem the following year.

As long as I have been listening to (nearly 4 years now), Mike McGrath from You Bet Your Garden, I can honestly say I've never heard him once warn against the use of "good" nematodes ie possible side effects. Yes, I have heard him warn against "bad" nematodes, that is why I believe it's vital you do your research and get the "good" guys.

For total peace of mind, I would do plenty of research... before deciding on the exact type of "good" nematodes you buy and release into your landscape.

Do you have a horticultural service in Israel you can contact directly and seek their specific local advice, expertise?

If you can wait a few days (probably until sometime next week), I can call and speak with a local (Missouri) registered organic farmer and seek his advise. I know for a fact he grows, apples, apricots, peaches & pears on his property.

Here is what I have been able to find out during the past few days:

  • Speaking with a Master Gardener, first they clearly stated they weren't a nematode expert (very! much like myself), but they did say they have never heard of or read anything about beneficial (good) nematodes causing "bad" side effects. Depending on the nematode in question, they do a very! specific job, they do not mutate (change) and start doing something else (be it "good" or "bad").

The above has been my limited experience (I've only used "good" nematodes once), is my understanding from reading up on the subject from an organic gardening approach to controlling unwanted pests, and listening to other people talk on the subject...

  • Spoke with a garden pest control expert (via the Missouri Botanical Gardens), they basically confirmed what the Master Gardener had told me. They also added that beneficial (good) nematodes isn't a "magic bullet" to pest control, will normally take more than one application, which can become expensive depending on the individual situation, and can take 2 or 3 years before seeing real results.

  • Garden pest control expert (via the Missouri Botanical Gardens) also referred me to this, "Beetles - Grubs" "general" article on MOBOT.org

  • Speaking with my local (Missouri) registered organic farmer, he has never used beneficial (good) nematodes as a pest control method. Why? On his size orchard it would be far too expensive to use such a pest control strategy. Instead he uses a product called "Surround™ WP Crop Protectant", which works by protecting the actual fruit on the trees. Since moving to this method of pest control on his fruit tress he has gone from losing up to 70% (really bad years) of his crop to only losing about 20% (per year).

If you're interested in reading a little bit about "Surround™ WP Crop Protectant" the below link contains a small amount of information:

The link goes to the company he buys from (via mail-order).

I think you might also find this, Gardening Naturally with John Dromgoole - Saturday July 23 2011 hr 2, of some interest. Start listening @ 10min:55sec in.

I hope the above proves somewhat helpful and useful to you.

Mike Perry
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  • Most damage is caused by the larva not the adult, so this is a good solution. I'd be happy to hear what your local organic farmer has to say. – Jonathan Jul 14 '11 at 05:49
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One of things that has limited our greater use of nematodes (in turf) in general is their expense and their viability in the environment. I haven't heard of a case of these becoming established to a level that they provide continued control. So multiple applications are typically required. This suggests that there is some self-limiting control on the amount of negative that "could" happen were these to have negative effects.

One negative that this could share with other types of organic control is the potential to kill non-target, beneficial insects. This might not be a concern with this product/species or in your situation.

Finally from what I've read the larvae are the only susceptible stage, so timing the application will be critical. You cannot expect the nematodes to be on site and viable - or at the levels required for effective control - after several weeks. Learn to identify the larvae, learn when (based on growning degree days) the larvae emerge, and apply liberally when you identify them. Follow up with a second application if possible.

That Idiot
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