A Fall Pest: Grey Aphids


If you grow anything in the brassica family (kale, collard greens brussels sprouts,cabbage, etc…) you have seen them.  Small.  Grey.  In clusters.  Hanging out on the under side of the leaves.  And they tend to make their appearance in late summer, early fall.    What are they?  Grey aphids.

Grey aphids  are also known as cabbage aphids.  If you want to get scientific, they go by Brevicoryne brassicae.  According to the University of California Agriculture & Natural Resources, these pests occur in dense colonies and “prefer to feed on the youngest leaves and flowering parts and are often found deep within the heads of cabbages or brussels sprouts”.  Interestingly, these little critters do not infest noncruciferous crops, so you don’t have to worry about them migrating to your beets or eggplants.  (And for the record, cruciferous crops are kale, collard greens, brussels sprouts, cabbage, etc..).  And if you have ever harvested your brassicas in late summer/early fall, you may have seen the damage done to the leaves: yellowing leaves or curled and mottled leaves.  Aphids do their damage by sucking the plant juices.  And if left unchecked, they can severely stunt the  growth and even delay or prevent flowering of the plant.

grey aphids

grey aphids

Now don’t give up hope.  Grey aphids can be controlled and even eradicated.

Control Methods

  • Natural enemies:  Some of them include parasitic wasps, lady beetles, lacewings, damsel bugs, and syrphid fly larvae.
  • Insecticidal soap, but be careful as the soap can cause leaf damage if applied on a bright, sunny day.
  • Tomato leaf water: Some gardeners have also had success in chopping up tomato leaves and steeping them in water overnight.  The next day, remove the leaves, add a teaspoon or two of dish soap and fill a spray bottle with the tomato leaf infused water, then directly spray the aphids.
  • Onion and garlic water:  Place a small onion and a whole bulb of garlic in a blender with water.  Blend until the mixture is smooth.  Allow to set 4 – 6 hours and strain out the solids.  Fill a spray bottle with remaining liquid and then directly spray the aphids.
  • Remove the infested leaves from the plants.  These leaves can either be destroyed or if you have chickens, feed to your flock.  If you don’t have chickens, you can also compost the leaves.
  • Spray the infested plants with a strong jet of water to knock aphids off the plant.

So if you have grey aphids on your fall brassicas, you can salvage your crops.  Natural predators and organic methods are both effective.  So go ahead select a control.  With some diligence, you can kick the aphids to the curb and enjoy some tasty kale, collard greens brussels sprouts,cabbage, or other brassicas from your fall garden.



2 responses »

  1. Also mineral oil sprayed directly onto infected leaves work well. Just don’t coat leaf too much or it will rot. Worked like a charm.

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