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My mother is in a furor because the grapevine that she planted last spring and which flourished last year is now infested with little black bugs. From what I can tell, they seem to be flea beetles. (Are those thousands of tiny black spots they have left everywhere feces or eggs?)

I’ve read conflicting information about them being a problem, not being a problem, even being beneficial. She is sure that the level of damage they are doing is certainly harmful since they have already pretty much destroyed most of the few leaves that have managed to bloom so far this year.

The vine is not on the ground; it grows up around the porch (she intends it to be used as a sort of privacy hedge when it thickens), so some pest-management techniques like row-covers or growing repellent companion plants around it likely will not work (also, there are already lots of birds that frequent the area all day and they don’t seem to help).

Can anybody advise on how harmful they are and of a way to deal with them? (Preferably something not involving pesticides since they are poison, cost money, and would require searching town for a supply.)

Figure 1: Vine configuration enter image description here

Figure 2: Leaf damage enter image description here

Figure 3: Army of beetles enter image description here

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3 Answers 3

In "The Organic Gardener's Handbook of Natural Disease and Pest Control", p. 265 talks about Flea Beetles. The adults chew holes in the leaves, the larvae feed on the roots.

They suggest:

  • using garlic spray or kaolin clay to repel the beetles
  • use parasitic nematodes on the roots to control larvae
  • as a last resort, use Beauveria bassiana or spinosad; you may need to repeat treatment

They note that problems are worse during drought; watering may help.

It's worth noting that spinosad, pyrethrin, and diatomaceous earth are broad-spectrum insecticides: they will likely kill your flea beetles, but they also kill beneficials like honeybees.

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I saw garlic, hot peppers, and mint recommended, so I suggested making a pungent spray with them. In the meantime she tried an idea of her own, so we'll try the spray if it doesn't work. –  Synetech May 14 '12 at 19:55

Oh, not good, I am not really an expert on pests, but I would try neem oil, works on all manor of pests... Oh yeah, btw it doesn't smell very good.

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It looks promising; I’ll let her know to keep an eye out for it. –  Synetech May 7 '12 at 4:58

I found these suggestions for commercial grape growers here which confirms @Grady Player suggestion.

They do note that

...treatment with a broad-spectrum insecticide is effective against adults migrating to grapevines from their hibernation sites, but timing is very critical.

At the time larvae and beetles are feeding on the upper surface of grape leaves, they are easily controlled by spraying.

I do not recommend soap to control beetles as they have tough shells. A more effective alternative is spraying with a pyrethrin compound or dusting with a diatomaceous earth.

Cleaning up the area by removing old leaves and branches and working over the soil nearby in the spring to expose overwintering adults is another possible control.

I cannot find any agreement on planting marigolds to deter beetles. Some say yes, many say no.

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the problem with insecticidal soap is that is not too different from herbicidal soap, and on tender young growth it may just kill them both... I agree with the pyrethrin, that may be good, maybe plant some marigolds at the base of the plant to slow them when they pupate. –  Grady Player May 7 '12 at 16:51

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