Saturday, July 6, 2013

Common-sense pest control: Aphids

Here in the Willamette valley, one of the most reliable plants to grow for food are the brassicas: broccoli, cauliflower, cabbage, Brussels sprouts, and so on. Unfortunately, humans aren't the only creatures who like to eat these delicous, healthy greens. Aphids famously form colonies on the undersides of the leaves and in the secluded crevices of the plants -- including among the parts we like to eat. Fortunately for gardeners, one of the most effective methods to get rid of aphids is simply to wash them off with water and your fingers. They simply don't travel far and aren't likely to wind up back on your plants. If you only discover a few, this is the perfect cure. However, it's easy to forget to look under your leaves for a week or two (or ten) and find you've got an extensive infestation. You could end up washing every leafy by hand, and even one bed of plants could be a lot of work. It's good to know that Aphids are an "added protein" pest -- just wash them off and if a few end up in your salad, no harm will come.

Still, it's not fun and can stress the plants resulting in lower yield, inferior flavor, and early bolting. However, if you have a balanced web of life in your garden, you will have a few powerful allies in the fight against this pest!

The most famous aphid cure is ladybugs. Nearly everyone loves ladybugs, and most have been introduced to the fact that these guys are aphid killers! What isn't so well known is that they eat more aphids in their larval stage than they do as adults. So it's important to provide a habitat for the full life-cycle of the ladybugs if you want to maximize the benefit these creatures provide. 

Plenty of other insects eat aphids -- lacewings are another great consumer of aphids. 

Picture credit: Wikimedia Commons.

Another awesome ally is fungus. Fungus like Entomophthorales waits on plant leaves and infects the slow-moving aphid colonies, turning them into white "aphid mummies".

Picture credit: Wikimedia Commons.

However, rather than fungi and ladybugs, I am here to brag about my wasps. Parasitic wasps are pretty awesome. It seems like for nearly every species of insect, there is a species of parasitic wasp that infects it. The ones that infect aphids are hard workers, as you can see below.


This leaf from my garden is covered in aphids. But few of them are still kicking! Most of them have fallen victim to parasitic wasps, probably from the group Pemphredoninae. The light-colored ones are the unlucky ones. The more orange ones have been left alive. But this infection has been drastically slowed. If I used a chemical control, I would kill the wasp larvae and make future infestations worse. Instead, I am moving toward balance in my garden ecosystem.

1 comment:

  1. So cooool with the plant science. Keep up your good work.

    ReplyDelete