My first time going to the field station independently was on a sunny afternoon in early February. During this visit, I made a species list of all the plants I could observe and identify within an approximately 100 square foot area south-east of pHake Lake. In this species list, I recorded, sketched, and took notes on many plants that would soon become instantly recognizable to me as very common plants of the Field Station. Among those I identified were Cholla cactus (Cylindropuntia californica), yerba santa (Eriodyction trichocalyx), white sage (Salvia apiana), California sagebrush (Atermisia californica), black mustard (Brassica nigra), horehound (Marrubium vulgare), pigweed (Chenopodium californicum), and golden currant (Ribes aureum).
[1] Sketch of white sage (Salvia apiana) from 2/4/20
[2] Image of golden currant (Ribes aureum) from 2/4/20
One plant that stuck out to me during this visit as well as subsequent visits to the field station was yerba santa, a very common plant in the Bernard Field Station. The leaves of yerba santa plants are often covered in spots of black fungus. I was kind of grossed out by the fungus, but at the same time fascinated. I noticed on this first trip to the field station that it seemed like older yerba santa were generally more covered than younger (smaller) plants. On my next visit I noticed that it seemed like plants that were more isolated from other plants (and especially from other yerba santa plants) typically had much less black fungus coverage. I thought it was interesting that almost all yerba santa plants in the Field Station had at least some amount of black fungus coverage, while I hadn’t noticed any other species of plant that housed black fungus. I was really interested in how this mold spread and what caused differences in coverage amounts.
[3] Image of yerba santa (Eriodyction trichocalyx) showing black fungus spots (2/4/20)
Since I found myself consistently drawn to the yerba santa every time I visited the field station, I started reading up and learning a little more about the black fungus. I learned that this black fungus is also known as sooty black mold, and while many funguses can be harmful to plants, this particular fungus is relatively benign to yerba santa. Since this black fungus feeds off of honeydew which accumulates on yerba santa leaves, rather than penetrating and feeding off the plant’s leaves, the fungus doesn’t do much damage to the plant besides causing a decrease in photosynthesis and gas exchange. The honeydew that the black fungus feeds on is secreted by insects such as aphids.
I eventually decided that I wanted to focus my independent project on black fungus coverage of yerba santa leaves. I was interested in the methods of dispersal of the black fungus, and wanted to investigate whether my preliminary observation that more clustered yerba santa had higher black fungus coverage was correct. I decided to investigate whether there was a correlation between black fungus coverage on yerba santa plants and the proximity of the plant to other yerba santa plants. Since I am no longer on campus due to the COVID-19 crisis, I have had to adapt my proposal to accommodate the lack of access to the field station. While I can no longer address my original research question, I’m excited that I’ll be able to use citizen science data available on iNaturalist to continue investigating the factors that impact black fungus coverage of yerba santa. iNaturalist is a citizen science project and online social network that allows naturalists and citizen scientists to log observations of flora and fauna around the world. Using the data that is available for yerba santa, I intend to investigate whether annual rainfall (which theoretically can wash away the honeydew that black mold feeds on) impacts the black fungus of yerba santa.
Media Credits:
[1] Sketch by Lindsey R.
[2] Photo taken by Lindsey R. at the
[3] Photo taken by Lindsey R. at the
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