Insect Helpers

Early May 2008 047 copy Recently I promised to show a photo of a soldier beetle. Here it is, cleaning up the pahids that were eating my Rosa chinensis. This is the first one I have seen in my San Francisco garden, though I have seen them several times in the East Bay. A colleague at City College tells me that they are often in his Noe Valley garden.

There are over 100 species of soldier beetles in California. The larvae feed under bark or in soil litter on eggs and larvae of butterflies, beetles, moths and other insects. The adults of some species eat pollen and nectar, but the adults of other species eat aphids and insect eggs and larvae. In this case you can see the shed skins of aphids on the stem of the rose bud, but I think the soldier beetle ate up all the aphids and was just wandering around hoping for more. As soon as I saw the soldier beetle, I ran back in the house for my camera, and when I got back it was gone. I was sure it had flown away , but I waited, and soon it wandered back into view.

You can recognize soldier beetles by their narrow shape, and by their soft black, gray, or brown wing covers and often a red, orange, or yellow head and abdomen. All these details are from the Natural Enemies Handbook, by Mary Louise Flint and Steve Dreistadt, Statewide Integrated Pest Management Project, 1998.

Soldier beetles are just one of many naturally-occuring helpful insects that show up when you avoid the pesiticides that kill them along with pests. You don't buy soldier beetles, just give them a chance to help you.


Soil Temperature and Organic Methods of Gardening

Last week the soil temperature in our garden at City College of San Francisco finally reached 60 degrees F, warm enough for reasonably quick germination of summer crops such as beans and squash.

The beans we put in are Purple Podded Bush beans, which are reputed to be able to grow in slightly colder soil than other garden beans. We put them in about 3 weeks ago, when the soil was in the mid fifities. The first leaves started out tinged with yellow around their edges, which looked like they had some kind of disease, but I knew that it was caused by inability to get enough nutrition in the cold soil. This week they are looking almost completely green.

Cold soils are the Achilles heel of organic gardens. My cousin, who raises organic seedlings in the Midwest each spring, in an unheated greenhouse, and then sells them to gardeners, says that they suffer more from chilly weather than they would if they were being grown with synthetic fertilizer. Why? Because organic fertilizer needs some action from soil bacteria to release its nutrients, the simple, water soluble elemental compounds that plants can use for growth.

Synthetics are manufactured to provide the compounds without any bacterial action, but at a cost to the earth. First, they require considerable petroleum energy to create. Second, they are so water soluble that the plants have to catch what nutrients they can while the fertilizers are on their way through the soil into the groundwater. So you have to apply more. Synthetic fertilizers that enter groundwater will pollute it. If they run off they pollute nearby bodies of water. If you can get your organic fertilizer from nearby sources, or make compost from wastes found on site, you can save the petroleum needed to transport your fertilizer. (Think twice before you decide you have to have bat guano from South America.)

So maybe my seedlings get a bit slower start, but I'm sure they catch up, and I feel good knowing that my garden is less of a burden on the earth.