Interplanting sweet allysum for aphid control
We might ask the question, “What is the root cause that allows aphids to feed on this plant?”
When we pursue the wormhole of information needed to answer this question, we can develop a description of the carbohydrate profile within plant sap that aphids are dependent on. The carbohydrate profile changes dependent on the critical minerals plants require as enzyme co-factors to develop functional enzyme systems. The mineral profile is determined by the soil biology’s capacity to supply specific nutrients. These are layers of empowering answers which indicate the management tools needed to prevent aphids from becoming a problem. You can find my previous blog posts related to aphids here.
We might ask a similar question at a different level of thinking, “Why are aphids showing up in this ecosystem?”
When we ask questions at a different level, we arrive at very different answers. How are we managing the field ecosystem that allows the aphids to proliferate unchecked? When we have a continuous mono-crop of plants with an incomplete carbohydrate profile, it is a near-perfect environment for aphids to proliferate. We are supplying them with an abundant food source, and no habitat for their natural predators. When we spray an insecticide, we improve the environment for the aphids even more, because now we have removed all the predators, and weakened the plants even further.
A natural followup to the previous question is, “How can we manage the ecosystem differently so that aphids are no longer present?
Thanks to Klaas Martens for pointing me to Eric Brennan’s research on inter-planting sweet alyssum in lettuce and broccoli as a biological control for aphids. As I followed the wormhole of published research on biological control for aphids at an ecosystem level, I was pleased to discover that adding relatively few insectary plants per acre like sweet alyssum can attract enough hoverflies to provide complete control of aphids.
I estimate that additive intercropping with about 500 to 1000 alyssum transplants per acre, distributed throughout the field should provide sufficient pollen and nectar for hoverflies to control aphids in transplanted romaine lettuce. ~ Eric Brennan
This limited population of sweet alyssum has no negative impact on lettuce yields, and seems unlikely to have a negative impact on yields of other crops. Sweet alyssum can be direct seeded, and seed is inexpensive. This seems like an imminently practical and scalable solution for other crops with aphid pressure.
What other practices or plants provide control of different diseases and insects? This is a topic I am would like to learn more about.
1. Brennan, E. B. Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids. Biol. Control 65, 302–311 (2013).
2. Brennan, E. B. Agronomy of strip intercropping broccoli with alyssum for biological control of aphids. Biol. Control 97, 109–119 (2016).
3. Ribeiro, A. L. & Gontijo, L. M. Alyssum flowers promote biological control of collard pests. Biocontrol 62, 185–196 (2017).
4. Harris, A. S. Integrated Organic Management of Cabbage Aphid on Brussels sprouts. (University of New Hampshire, 2019).
5. Quinn, N. F., Brainard, D. C. & Szendrei, Z. Floral Strips Attract Beneficial Insects but Do Not Enhance Yield in Cucumber Fields. J. Econ. Entomol. 110, 517–524 (2017).
6. Mollaei, M., Fathi, S. A. A. & Nouri-Ganbalani, G. Effects of strip intercropping of canola with faba bean, field pea, garlic, or wheat on control of cabbage aphid and crop yield. Zhi Wu Bao Hu (2020).