Question: What are these? Are they harmful to the tree or anything else? This picture was taken in the parking area of Davis Community Garden on Fifth Street. At first glance, these look like pretty apples, but they are not.

Answer: These interesting growths are the native oak tree’s response to a foreign invader, in this case a tiny wasp that has laid its eggs in the oak’s tissue. The growths are considered benign, and there is no recommended control. A young naturalist in your house might like to harvest one of these “apples” and, with your help, dissect it to see if anything is inside.

Eventually, the gall will turn brown, but it may stay on the tree for some time. You can read more about these insects at www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/INVERT/gallmakers.html.

Question: My compost pile has a lot of sow bugs in it. Is this a problem? How can I reduce the number of sow bugs to improve the quality of my pile?

Answer: Just as a quick review of a compost pile, there are four basic ingredients: nitrogen, carbon, water and air. Nitrogen usually comes from green or wet material while carbon comes from brown or dry material. (There are some notable exceptions to this rule of thumb, such as coffee grounds, which are brown and a good source of nitrogen.) A healthy pile needs to have both types of material, layered or mixed in equal parts.

One may need to lightly water the compost pile, but only to the point of being moist. The bacteria that does the work of digesting the material is aerobic (needs and likes air), so too much moisture can drown the little organisms. You can also get more air in the pile by fluffing it with a pitchfork.

Sow bugs are soil-dwelling crustaceans. Usually the presence of sow bugs in the compost pile is a good sign. They like to feed primarily on dead, decaying plant material, so they help with composting by decomposing organic material. It is possible if you see abundant sow bugs that your compost pile has become soggy, or you have piled on too much fresh vegetation.

If you don’t want to spread the sow bugs in your garden, spread the good, rich compost near the compost pile in the sun. The sow bugs will crawl back to the darkness of the compost pile.

Sow bugs occasionally will munch on new roots, seedlings and leaves, and have been known to eat vegetables and fruits that are lying directly on the ground. If you have a vegetable garden, check around all your plants, especially watermelons and pumpkins that have a smooth skin and lie on the ground.

You can prevent damage by watering early in the day, to allow time for the soil to dry out, and by hand watering directly at the base of the plant.

If you are really interested, the city of Davis has a brochure called “Food Scrap Composting.” You can download a copy at http://recycling.cityofdavis.org/Media/Recycling/Documents/PDF/PW/Recycle/food-scrap-composting.pdf. Or call the Public Works Department at 530-757-5686.

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Watch this space next month for a list of fall gardening workshops at Woodland Community College, Central Park Gardens and Grace Garden.

— Send questions, addressed to the “Garden Doctor,” by email to [email protected], voice mail to 530-666-8737, or regular mail to UCCE Master Gardeners, 70 Cottonwood St., Woodland, CA 95695. Be sure to include your contact information because any questions not answered in the Garden Doctor column will be answered with a phone call or email to you.

You can request the Yolo Gardener newsletter delivered by email and learn more about the Master Gardener program in Yolo County at http://ceyolo.ucdavis.edu/Gardening_and_Master_Gardening.

garden doctor AugustW

These “apples” are the oak tree’s response to a foreign invader, in this case a tiny wasp that has laid its eggs in the tree’s tissue. The growths are considered benign, and there is no recommended control. Courtesy photo

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