We recently received the following question: I am a home vegetable/herb gardener in San Diego.  I have only been growing for three years, so I am still learning.  I tried to grow cauliflower, broccoli and cabbage last cool season and they looked so wonderful.  I harvested them and got ready to cook, and they were FULL of aphids!  What a disappointment.  I spoke to my local nursery, Walter Anderson, and they advised me to “just give up growing cole crops organically.”  Well, I just refuse to believe that!  Can you help me with some tips on controlling aphids on my cole crops here in San Diego?  I'm in Sunset climate zone 23. Thanks, Jennifer Boles

For the answer, we contacted Nick Sakovich and here are this thoughts.

I wouldn't give up. There are some things to do: The two main organic insecticides you can use are horticultural oils, including neem oil, and soap sprays. These will do a decent job. Spraying when you first see the problem, i.e. when the aphid population is low, is best. Other organic insecticides that can be used -- but are more toxic to humans and beneficial insects -- are the pyrethrins (derived from the chrysanthemum flower) and rotenone. One should always read the labels to make sure the product is registered to be applied to that particular crop. When spraying with insecticides, repeat applications are needed since the sprays usually do not control all stages of the insect’s life cycle. Labels usually recommend at least two applications at 5 - 7 days apart.

Other options (click "read more" for rest of article):

Spraying with a heavy spray of water offers some control. Most of the aphids removed will not return.

Ants play an important roll in keeping natural enemies (of aphids) away. If there are ants around, they need to be controlled. Ant stakes and baits can be used.

Aluminum foil mulches that cover the ground have been found to deter aphids, as the sunlight is reflected.

As the aphid population increases, natural enemies (parasites and predators) should come in and lower the aphid population.  Don't give up.

But, perhaps the most important thing when growing crops organically, is to know that we are going to have to be willing to accept some damage, whether it’s some aphids on cabbage (they will wash off) and some worms in the fruit.

The University of California, San Diego, Cooperative Extension always has good answers on a variety of horticultural problems.

The University of California also runs a statewide program that matches gardeners with a master gardener in their area available to answer questions. The list can be found at the University of California, Davis, Statewide Master Gardener Program website.