Home & Gardens: Take a class with Curt Swift
Free Press Gardening Columnist
Classes at Western Colorado Community College/Colorado Mesa University start on Jan. 21, and I will have 15 weeks to teach a topic that has always been of great interest to me.
It all started with integrated pest management (IPM). Growers of field crops realized they needed a procedure to handle insect, mite, and disease problems affecting their fields of soybeans, corn, onions, and other crops. They consequently came up with a process involving cultural, mechanical, biological, regulatory, and chemical treatments to manage these pests and prevent them from reaching an economic injury level (EIL).
Scientists developed models based on the pests’ biologies, where the grower could predict when the population would reach the EIL. This was based on the economic threshold (i.e. the difference between the cost of the treatment and the anticipated crop loss).
Will the treatment cost more than the crop is worth, should the crop be plowed under and replanted, etc.? The concept of plant health care (PHC) came somewhat later, focusing on landscape ornamentals. One of the problems with using IPM with ornamentals is the economic injury level and especially the economic threshold is not easy to define, thus the same models for treatment cannot be used.
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Plant health care (PHC) focuses on maintenance as a method to control pests (insects, mites, nematodes, rodents, etc.) and disease organisms (fungi, bacteria, fungal-like organisms, etc.).
The semester-long class I’ll be teaching is being called “Integrated Plant Health Management.” This will include plant stress and how it contributes to plant problems. Understanding the soil environment — oxygen and carbon dioxide levels, soil moisture, nutrient levels, temperature — allows the grower to determine what problems their plants are going to have and provide answers as to correction before and after they occur. High soil-nitrogen levels result in an increase of some plant diseases while other diseases are more prevalent when soil nitrogen levels are limiting. Based on the crop being grown, a specific nitrogen level can be chosen which is appropriate for the crop to reduce chances of pest and disease problems. Nutrient levels also have a direct effect on insect and mite populations.
Plant stress results in changing the plant amino acid and protein content which, with certain insects, can increase their size and reproductive activity. In other words, insects like aphids increase in size and produce more young more frequently when feeding on a stressed plant. This results in a more rapid increase in the insect population, resulting in more damage to the plant.
Nitrogen deficiencies can be corrected by adding nitrogen-based organic or synthetic nutrient sources, while excessive levels of nitrogen can be corrected by improving drainage, eliminating soil compacting, and amending the soil with the correct organic matter. When adding a nutrient to the soil, the impact on pH needs to be taken into account as this is directly related to plant health. Applying an organic source high in soluble salts can stress or kill roots. Dead and stressed roots are susceptible to invasion by root pathogens, nematodes, root maggots, etc. Root damage reduces the ability of the plant to produce photosynthates, the sugars and starches that keep the plant healthy. Now that roots are damaged and photosynthesis has been restricted, the roots and other plant tissues are unable to create the phytochemicals needed to ward off attack by other pests and disease organisms.
A number of books have been written on environmental stress and how it impacts yield and plant health. Books have also been written on soil oxygen deficits and pests and diseases. My intention is to put all this together to give the student a greater understanding of the issues that affect plants.
It is not sufficient to simply control the problem, but it’s critical the cause of the problem is understood so you can correct the underlying cause and/or prevent this from happening in the first place.
This is going to be a very informative and fun class.
If you are interested in signing up, contact Western Colorado Community College at 970-255-2670.
GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866, or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.
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