Biological Pest Control is better

Master Gardeners: Pitting bug against bug in the landscape

March 27, 2013

Biological Pest Control - Dave Phelps

Cagwin & Doraward's Sustainability Manger, Dave Phelps, is also a Marin Master Gardener. He is passionate about organic gardening, biological pest controls, reducing resource use and all things sustainable. He recently wrote the following abriged article published in the Marin Independent Journal . Click here to read the full article.


THE EUGENIA SHRUB, also known as the Australian bush cherry, is a fantastic plant that makes quick, tall hedges that do well with little water. They are, after all, from Australia.

At first, they were a big hit in California, a Mediterranean climate similar to their homeland. Walt Disney used them as topiary plants, turning the glossy plants into large hedged animals at his Orange County theme park. They had few pests and were always beautiful plants — until their native adversary, psyllids, from Australia found their way here.


Disneyland Topiaries on Disney Video

First found in Los Angeles in 1988, the psyllids quickly spread, showing up in Northern California the next year, turning these perfect shrubs into ugly, puckered, black moldy deformities. It was awful. It would have stayed that way if it weren't for Disney.

tamarixia - biological control

He sent a team of entomologists to Australia to find a natural predator for the pest. In New South Wales, they found a tiny parasitoid wasp called tamarixia. The wasps were brought back, tested and released in 1992 at various locations throughout the states. Luckily, the wasps spread and psyllid populations along the coast showed a decrease of 10 percent to 20 percent a year.


Biological Controls Make Sense

Rather than applying toxic pesticides, releasing predators (that have been tested for adverse affects) to hunt the pests is a more sustainable solution. This is called biological control. After physical and cultural controls, it is the preferred control method in any Integrated Pest Management program.

Other similar parasitoid wasps have been found to parasitize the smoke tree sharpshooter, as well as the Asian citrus psyllid nymphs and many others. A more common wasp, encarsia formosa, otherwise known as the greenhouse whitefly parasitic wasp, can be purchased as eggs glued to a card or inside parasitized scale insects. This tiny wasp is an expert at controlling whitefly populations on tomatoes. Trichogramma wasps parasitize pest caterpillars.

Millions upon millions of tiny little wasps are hard at work around the clock parasitizing some of our most damaging pests without the use of toxic pesticides.

Click here to read the full article at the Marin Independent Journal website

The University of California Marin Master Gardeners are sponsored by UC Cooperative Extension. For questions about gardening, plant pests or diseases, call 473-4204 from 9 a.m. to noon, and 1 to 4 p.m. weekdays, or bring in samples or pictures to 1682 Novato Blvd., Suite 150B, Novato.