Located in the hills behind Cal’s Memorial Stadium, the UC Botanical Garden (UCBG) hosts a prized collection of over 13,000 types of plants from around the world. To protect these plants from a host of natural pests, including fungi and insects, UCBG has traditionally employed synthetic chemicals, but throughout the years has recognized the potential to reduce the usage of these chemicals.
The campus and UCBG had been developing an Integrated Pest Management (IPM) system for campus use for a few years before gaining the sudden impetus to actually start implementing one aspect of the system: composting. By pursuing composting, UCBG would be able to reduce the use of synthetic fertilizers and herbicides which have known negative environmental impacts such as unintentionally killing non-targeted biota or finding their ways into our watersheds and foods. This goal of weening off from synthetic chemicals in campus gardens realized its beginning in the form of a composting “tea” system. Contrary to its name (and hence the quotes), the compost tea system actually utilizes a brew of high quality compost or vermi-compost (uses earthworms in addition to compost mix), plus optional additions of “humic acid, fish hydrolysate, and cold-processes sea kelp.” All of these materials are mixed in a suspended, aerated bag within a 100-gallon polyethylene container, in which they are left to aerate for 24 hours. After the aerated “tea” is emptied into spray dispensers, the liquid can be sprayed directly on plants in place of chemical pesticides, fungicides, and fertilizers. The tea system also provides staff with the option of creating specialty brews that target certain pathogenic fungi or fertilize special plant types.
With the help of a $15,000 TGIF grant and some horticulture experts from Santa Barbara, the UC Botanical Garden established its “Reduction in Chemical Use at UC Botanical Garden” project in 2010.
After learning about the best methods for implementing the compost strategy from the experts, the UCBG purchased its 100-gallon compost tea brewing unit, spray application equipment, a vermi-compost bin, and some additional organic nutrients. Next, with the help of staff from the Watsonville, CA company Liquid Biotech, the project trained UCBG staff and demonstrated to students in the IB 112 class “Horticulture Methods” in the skills of composting, vermi-composting, and tea production. (Read more about this in a previous interview.)
As a result of the program, the UCBG did not make any purchases of chemical fertilizers and fungicides during the Spring 2011 growing season, and inspired the team to move forward towards an “entirely organic fertility regimen.” UCBG staff attest its success by noting that plants that had been stagnant in growth for years were suddenly blooming, which proved compost tea an excellent substitute for synthetic chemicals.
Now, UCBG and its IPM student intern apply compost tea at a large-scale in various UCBG collections on a bi-weekly basis and continues to minimize synthetic fungicide and fertilizer purchasing. The system continues to prove its valor: the Garden of Roses, which was once the site of intensive fungicide and fertilizer treatment, is as healthy or healthier than before. The Asian collection at the Garden has notably less pest and disease and more beneficial insects.
The Green Garden Intern, the IPM intern that is also funded through a 2012 TGIF grant, works for the UCBG to develop a knowledge base for monitoring pests, diseases, and other biotic and abiotic problems in the plant collection. While expanding the UCBG’s regimen in using non-chemical methods to manage their plants, the intern also assists in training and demonstrating horticultural methods to around 10 IB 112 students per semester. One exciting new strategy UCBG is currently implementing with its intern is the release of beneficial insects, including specific predatory beetles and wasps, to control the growth of insects like aphids and mealy bugs on certain plants.
If you’re a student at Berkeley, admission to the UCBG is free, so be sure to check it out in your spare time if you like plants or flowers!
-article by TGIF Program Associate Kareem Hammoud, special thanks to UC Botanical Garden staff Anthony Garza and Chris Carmichael.