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I live in Portland, OR. Here we have a species of aphid that attacks brassicas (kale, broccoli, gai lan, etc.), and only brassicas. They are a bit larger, and a darker blue-green than regular aphids that attack other plants.

Every method I've tried for eradicating them fails:

  1. We have plenty of ladybugs in the yard, naturally, so much so that regular aphids and whitefly are simply not a problem. However, our ladybugs won't eat the brassica aphids at all.
  2. Spraying them off works breifly, but requires spraying the plants every 24 hours throughout the whole growing season and isn't practical.
  3. Insecticidal soap isn't effective, unless I use it in sufficient quantities to hurt the plants (the soap causes the leaves to lose moisture somehow).
  4. New Zealand Ag recommends Entomophora fungus as a biological control, but that doesn't seem to be something one can buy in the US.

Infestations on my kale and broccoli were so bad it was killing the plants and I had to raze them all. I'd like to be able to plant again. Ideas?

This is related to this question but the only answer there is "ladybugs" and see above.

  • I'm holding off on picking an answer for this until I try both peppermint and Neem oil. – FuzzyChef Jun 28 '18 at 16:49
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Aphids are soft bodied easy to kill insects. You do not want to poison yourself with pesticides meant to do major devastation. NEEM is as far as anyone should go for pesticides on their vegetables. NEEM is very gnarly. One treatment is usually enough. A second a few weeks later.

This is a fun fact; buy lady beetles and they will go anywhere but YOUR property. These insects are programmed to LEAVE the area they awakened. Best is to give your neighbors these insects as a gift? Then you will be more assured they will help you with your aphids and other soft bodied insects.

Don't spray NEEM during the day. I like dunking in a NEEM solution if the plant is in a pot and small enough to fit upside down in a 5 gallon bucket. When spraying, make sure you get all of the plant, the undersides of leaves, the stems the top of the soil. Do it correctly once should suffice. Keep checking, if more signs of aphids appear, 1 or 2 weeks later do another night spraying.

Plants take up pesticides. Neem smells horrid, works just fine, won't be poisonous to humans after washing your harvested vegetables. Other pesticides, forget eating your vegetables!

Pyrethrins are very very toxic, very effective...and guess what? They are from DAISIES! I use predatory flies instead these days. I have to deal with horse manure and flies...predatory flies work well. Just because something is labeled organic and pyrethrins are totally organic does not make them safe to use. LD50 for nicotine in tobacco is far more toxic than any synthetic. Lethal Dose in Half the population. The lower the number the more toxic the chemical or compound.

When we use pesticides we are putting a bandaid on a problem we should not have allowed to happen. I had a pesticide certification for every thing other than water for decades. I was never going to use chemistry in rivers or lakes...I rarely use even soap and water much less NEEM. Had to know what I was doing to tell bosses to go away and let me do my thing and be successful. When I had to deal with bosses. In Washington, it was illegal to use pesticides commercially without a licensed pesticide expert either applying or supervising others applying. I learned once you reach for a pesticide you've already lost and are just trying to recoup.

Aphids are an easy control. Before using NEEM, I use water spray and my fingers to control aphids. Squishy squishy. NEEM is my last resort and on brassica aphids usually the first solution I use for control when I find a problem. I would not use pyrethrins on vegetables...

  • Are you sure you've got aphids? Flea Beetles are just now finishing their reign. – stormy Jun 23 '18 at 10:06
  • I'm sure. They look exactly like the images you get when you search for "brassica aphids". – FuzzyChef Jun 26 '18 at 3:32
  • Anyway, I can try Neem oil (btw, Neem is not an acronym, it's the name of a tree). Mind you, I'll have to decide if I want to grow kale if that means I need to wash it with a soap solution before eating (which treatment with neem requires). – FuzzyChef Jun 26 '18 at 3:33
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    The neem oil appears to have worked after 3 treatments and 2 weeks. As such, selecting this answer. – FuzzyChef Jul 20 '18 at 23:34
  • So very nice to hear positive news! Thanks, Fuzzy! Try washing instead by throwing your veggies into a tub, pot of clean water and hydrogen peroxide. A cup of H2O2 to 5 gallons. You can watch the debris, dust, Neem come off of your plant material. Very satisfying. – stormy Jul 21 '18 at 8:53
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Brassicaea aphids are very difficult to control because they gather on the underside of leaves.

Chemical control is, unfortunately the best and most effective.

The products to use should contain deltamethrin, lambda cyalothrin or cypermethrin .

Products will vary from countries to countries but a green fly, aphid killer should be available from garden centres.

These are synthetic(man made) pesticides and most efficient.

However, they should be used responsibly. There is danger to beneficial insects and to human consumption. Check instructions on products for harvest intervals, numbers of sprays and interval. Do not spray if plants are in flower.

There are many warnings that should be followed.

When your infestation is under control, use natural insecticides: mix clove, rosemary, peppermint, lavender oils(6 drops of each diluted in 1l if water) and spray plant regularly, preferably in the evenings to avoid killing your ladybirds.

Pyrethrum can also be used but it’s expensive and harmful to pollinating insects. If used, spray in the evenings or early mornings. It’s labelled as organic because it is made from Chrysanthemums extract.

  • Thanks even if you have bad news. A friend is testing out peppermint tea as a treatment, we'll see how that goes. I'd rather just not grow kale than use serious pesticides. – FuzzyChef Jun 26 '18 at 3:28
  • One of the best way then is to grow Brassicaea under a net, before an infection. Then if you stay on top of your aromatic oils, it should be ok. You can also squish them or use a hose if possible. If you use a net, of an infection occurs, it’s also easier to use biological control – user33232 Jun 26 '18 at 6:44
  • That would require a net with very small holes ... – FuzzyChef Jun 27 '18 at 5:53
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    Yes. It’s called enviromesh – user33232 Jun 28 '18 at 16:39
  • BTW, not saying peppermint tea didn't work, but since I have to make it by hand for each treatment, and I can buy Neem oil in a sprayer, Neem oil wins. – FuzzyChef Jul 23 '18 at 16:40

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