Tom Dykstra and I discussed the concepts of plant health, nutrition management, and insect resistance in a rapid fire, intense one hour webinar, with a specific emphasis on controlling aphids in sugar beets and flea beetles in canola.
While the conversation was fairly high level, and didn’t get into the nuts and bolts of implementation, Tom’s knowledge of insect metabolism and the type of food sources they require to survive is unparalleled.
If you want to learn how to grow insect resistant crops, this webinar is a must listen. You kind find the recording on KindHarvest.ag here.
Tom uses a refractometer as a research tool, and describes a brix index of plant susceptibility to to different groups of insects at different brix levels. There is a big difference between using using brix as a research tool and using it as a crop management tool. You can read my thoughts on using brix here.
Elementary discussions of plant pathology describe the disease triangle almost without fail.
It has become a standard inclusion in many presentations, and a quick image search will find hundreds of graphical designs that have been developed to describe the idea.
The foundational idea appears quite simple at first glance. For a ‘dise-ease’ to express itself requires a combination of three elements:
a susceptible host,
a potentially pathogenic organism,
the proper environment,
This seems like an obvious and simple explanation. We accept it without much question and move on to the next part of the discussion, which usually revolves around controlling ‘pathogens’ when the combination of these three elements is met.
Rather than moving immediately to the control conversation, and assuming an infection has occurred that we have no influence over, we might dig a bit more deeply into each of the three elements. When we understand these three elements fully, they will give us all the information we need to prevent any ‘dis-ease’ from expressing in the first place. Prevention is often easier and more effective than a cure.
When we consider the definition of a ‘susceptible host’, what are the parameters that define a susceptibility? What are the differences between susceptible and resistant cultivars? Does the organism require a certain amino acid and carbohydrate profile that some cultivars do not provide? What are the resistance mechanisms that are present in some cultivars, and in some growing conditions, but not in others?
What defines a ‘potential pathogen’? We know from the research being conducted on the microbiome, as well as the work described by James White and Don Huber in our podcast discussions, there is no correlation between the presence of a potential pathogen and an actual infection. Soil organisms that might become pathogenic (such as fusarium and verticillium) actually develop symbiotic relationships with plants when the plant has a healthy, disease suppressive microbiome. For an organism to infect a plant and produce disease requires compromised soil biology, and a compromised microbiome.
What defines a ‘proper environment’? Our first thoughts generally go to the external climate, humidity and temperature. What about the plants internal environment, and the soil environment? From Olivier Husson’s breakthough work on the biophysical environment required by different organisms, we know that each organism requires the plant and soil to be in a specific redox state. The plant pH and redox, and soil pH, redox, and paramagnetism each need to be within a defined zone before an organism can infect a plant and produce disease.
The solution to effective disease prevention is actually very straightforward. We need to understand exactly what defines a susceptible host, a disease conducive microbiome, and the internal plant ‘environment’ for each pathogen. When we understand these elements, it becomes very easy to manage the crop in a way that prevents these organisms from producing disease, even when the organism is abundantly present, and the climatic environment is considered ideal for disease expression.
For which ‘disease’ organisms would you like to understand the elements of the disease triangle more deeply?
It is important to propagate aphids in our fields so the beneficial insects such as lady beetles have something to feed on. It is quite easy to produce a tremendous aphid population which can sustain a large number of beneficials and not be negatively impacted. We just need to give them the right environment.
Here are the easy steps to produce an optimal environment for aphids, which require free nitrates in the plant sap.
Step one, apply more nitrogen then the plants can utilize at the current growth stage.
Step two, do not supply magnesium for better photosynthesis.
Step three, do not apply sulfur the plants needs to produce sulfur-bearing amino acids and complete proteins.
Step four, do not supply molybdenum for the nitrate reductase enzyme.
Step five, do not apply any boron that might boost plant immunity.
If you follow these five very simple steps, you can be sure that your crop will provide the perfect food source for aphids. In addition, it will also be the optimal food source for many other larval insects such as corn rootworm, earworm, corn borer, cabbage looper, tomato hornworm, and others. Really for any larvae. Propagating these larvae provides a ready food source for songbirds and beneficial insects, a valuable ecosystem service.
Of course, if you do not desire to propagate these insects on your crops, the solution is obvious. Do the reverse of the five easy steps, and these insects will not be able to use your plants as a food source.