|A lady bug feasting on green aphids|
When the subject of organic agriculture comes up people often ask, "But what do you do about bugs?" My answer starts with, "well, there are good bugs and there are bad bugs. We do everything we can to encourage the good bugs so they will help us to control the bad ones."
It’s a basic fact of nature that all life is interdependent and is generally in balance until we humans come along and upset things. Where there is a crop damaging pest there is usually a predator present that feeds on that pest. The photos above and below are examples.
|Eggs from the green lacewing (on stalks), a|
major predator of aphids, laid among the aphids
A case study
|Tools of the trade, a microscope and loupe for|
identifying the pest curling these plum leaves
First, following the admonition to "know your enemy," I researched its life cycle and consulted with the county ag commissioner, a supplier of beneficial insects, and UC Davis resources. Eliminating ants is essential to controlling aphids since they "farm" aphids just as humans farm cows, so when ants are present any aphid control effort will have limited success. We had carpenter ants in the plum trees, so step one was to set out ant bait stations to gradually kill the colonies but also to band the trees with sticky Tanglefoot as a barrier to crawling insects.
This particular aphid lays eggs near plum tree buds in the Fall, so step two was to apply two dormant season sprays of an organic mineral oil to smother the over-wintering aphid eggs.
|Strips of legume and mustard cover crop left|
unmowed as habitat for beneficial insects
|Pheromone lures hung in plum trees|
to attract beneficial insects
Step four was to hang pheromone lures in the trees that attract beneficial insects, as well as cards painted with beneficial insect food - a mixture of soy flour, nutritional yeast, and calf milk replacer - to keep the beneficials as healthy as possible. In addition I have found a pheromone attractant to draw the aphids to a sticky card trap.
Even with all these efforts we have had some spot outbreaks, but they are very minor compared to past years. I am currently employing a final step of clipping off the worst aphid infested shoots, dousing them in a bucket of soapy water and discarding in the trash. And here I need to grit my teeth and remember the principle of nature’s balance: there have to be some pests present in order to keep the pest’s predators around. So when I reach to clip off an aphid infested shoot and see lady bugs or lacewings present, I am reminded that in this instance "zero tolerance" is not the best approach. My hope is that the benefits of all these efforts will compound in future years, as the life cycle of the pest is disrupted and the beneficials gain the upper hand.
|Toads live under cover during the day,|
come out and eat slugs at night
Some information and products for natural pest control can be found here:
- Your county Ag Commissioner’s office can help identify plant pests and diseases and suggest remedies
- UC Davis has excellent online pest & disease information at http://www.ipm.ucdavis.edu/
- Cornell University has a great guide to biological controls at http://www.biocontrol.entomology.cornell.edu
- There are a number of online suppliers of natural pest control products, here are two: