Today we surveyed a patch of the common garden for aphid infestation. I chose my survey area based on observations I made Wednesday morning, during my initial search for aphids. I wanted my square to include at least one heavily-infested plant with ant domatia (dirt structures that ants build to cultivate aphids). Otherwise my choice of positions and rows was random.
Here is a description of today's survey. This weekend I will go over the data and make a map of aphid infestation. Because it's still early in the season for aphids, I hope to repeat this survey one or more times this summer to look for spatial and temporal patterns of infestation. Thank you to the Echinacea team members for your diligent data gathering.
I'm happy to say the survey went smoothly. Everyone seemed to have an easy time recognizing aphid life stages and ant domatia. My only goof-up was accidentally assigning the same row to two people, leaving us one row short, but thankfully we caught it in time to finish up before a thunderstorm hit. Next time I will be more careful about my row assignments.
I would like to repeat this survey several times throughout the summer--maybe once every two weeks. Here are some thoughts I have based on my observations in the common garden:
1. We have observed that plants with heavy infestations early in the season tend to have wrinkly, stunted leaves--possibly due to aphid overwintering. I suspect that these plants may serve as aphid source populations that spread to surrounding host plants. It will be interesting to see whether aphid infestation is more prevalent among plants nearby heavy aphid infestations (i.e. plants with all three aphid life stages, wrinkly leaves, and ant domatia).
2. I noticed that on plants with small infestations, ants seemed to be carrying away gravid females. Perhaps ants play a role in mitigating population-wide aphid infestation by concentrating aphids on a few heavily-infested plants. This survey won't tell me much about the role of ants, but I am curious to see whether some plants lose their aphids throughout the season.
Thanks again everyone for helping me gather my first data set!