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Insect specialization, pests and predators/beneficials

Posted by purpleinopp 8b AL (My Page) on
Fri, Oct 5, 12 at 12:14

Monarch butterfly caterpillars only eat Asclepias (milkweed.) So the following concepts are not so different, but definitely interesting.

Chartreuse sweet potato vine always gets white flies, and the wildling morning glories (so talking about two different species of Ipomoea) always have something wrong with them, often the same thing, sometimes aphids. Can't decide if they're attracting these pests to the yard or luring them away from other plants. I've seen no evidence of the pest problems on these plants spreading to other plants. These pests rarely kill these plants so I suspect whatever eats them is out there, doing some of that. No way I know what every bug in the yard is...

If you build it, they will come...

In order for beneficial, predatory bugs to come to your garden, you'll need some pests. If you're out there all the time, micro-managing with 'cide, soap, oil, whatever, there could be some serious difficulty with achieving a balance of the natural order of things. Obviously, it's killing the food source of the desired "hero" bug. And if your hero is on the scene, he's probably going to be killed too. Not saying anyone shouldn't put up a fight if pests threaten to actually kill plants you've bought or plants you need to put food on the table, and I don't have the same attitude regarding house plants, but just saying that it's probably not be the best idea, long-term, to try to be proactive about every chewed leaf or critter on ornamental plants.

Found an interesting article at CO State Univ about how lady bugs have specialized diets, and this similar article about predatory bugs in general. So if one can ID their lady bug, might it be a clue about what pests are present? Also seems like good info to have if you're inclined to spend money buying beneficial bugs/insects. You'd want to buy a kind that will eat the pests you have.

What do you think?

Follow-Up Postings:

RE: Insect specialization, pests and predators/beneficials

Home gardeners seldom, if ever, need to buy beneficial insects.

If you ensure that your place is hospitable, they will come of their own accord. But in order them to do so, you must always have a few pests hanging around to serve as lunch. Fortunately, a few pests aren't any sort of problem for healthy, vigorous plants.

RE: Insect specialization, pests and predators/beneficials

We don't see too many people here in the GardenWeb overly interested in micromanagement, thank goodness. The many requests for identification are a good sign that people are interested in learning.

Ladybugs are MUCH more likely to be generalists, purple. That would probably not even be on my list of tools I would use to ID pests, unless I happened upon a batch of Vedalia Beetles devouring cottony cushion scale and that isn't likely to happen any time soon. I remember an outdoor session I had with some entomology students where we happened upon five different species of ladybugs! One was the Ashy Gray, which I had never seen in person before.

It can be helpful to know what kind of plant is being attacked. Some insects are somewhat host specific. Also, some plants are so attractive to certain insects that it's almost not worth it to bring those plants into the yard. Plant selection is one of the steps of IPM, and one that I think is very important.

RE: Insect specialization, pests and predators/beneficials

It is true that home gardeners seldom need to buy beneficial insects, but they do need to provide a habitat that these beneficials will live in and that means much more then simply not spraying poisons around. Much is made of about creating backyard bird sanctuaries, wildlife habitat, but there is little about planting insectaries.
Many of the predators of the insect pests would stay close by even if populations of their target insects dropped if they had another food source, pollen from some flowers.
One plant that is a large attractor of these predators is the Queen Annes Lace that many pull or poison because they think it a "weed".

RE: Insect specialization, pests and predators/beneficials

Every spring I find loads of aphids on my spirea's new growth. I used to spray them off with a garden hose...But I found that lady bugs and their larvae would soon take care of the problem. Now I look forward to finding them. The spirea always blooms beautifully and is very healthy.

Planting for beneficial insects is very smart and makes the yard much more interesting. They are a free and enthusiastic labor force! But we must be careful not to take all of their food away.

RE: Insect specialization, pests and predators/beneficials

Never bought beneficial insects, but I have translocated a few.

A ninebark shrub was a black aphid magnet the first two years I had it. Then one spring, as the weather warmed, some lady beetles started showing up on my windows (as they are wont to do). Over the next week or two I dutifully collected about a dozen or so and put them on my ninebark.

No more aphids.


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