Plant Health Care, called PHC by professional arborists, was coined by the International Society of Arboriculture to more clearly define Integrated Pest Management (IPM) techniques as they apply to tree and shrub maintenance around the yard.
If you’re unfamiliar with IPM, it’s the term used when discussing core management strategies of pests in urban trees. They include cultural methods, mechanical methods, use of bionaturals, and use of organic and manufactured pesticides. IPM helps to maintain your trees value, minimize pest damage, limiting health-related hazards, and reducing environmental hazards. Application methods of IPM principals are crop specific because insect and disease problems vary significant;y between crops. For instance, IPM techniques used in an alfalfa field will be vastly different than those used in an apple orchard.
PHC is a holistic approach to landscape management. We use these techniques to grow healthy plants, and while doing so, minimize the effects of pests. Concepts of PHC include the following:
- Plant needs change in different stages of their life cycle. During the growth of the plant in their life cycle, they will need irrigation, fertilizer, pruning, and tolerance to pests. In PHC, cultural practices change relating to the life cycle.
- Healthy plans have fewer pests. Plants and trees are usually only attacked when they are under stress. Minimizing this stress will prevent the attack of common pests. For example, some funguses and insects only attack the trees under the stress of soil compaction and drought.
- Healthy plants are more tolerant of pests. Aphids on shade trees generally do not warrant management efforts. An important exception is that trees under water stress (dry soils, non-established root systems, etc.) are intolerant of aphid feeding.
- Problems arise from a combination of stress factors. For example, over-mature forest coupled with drought leads to bark beetles in Western pine forests while soil compaction and drought leads to Cytospora. This concept is known as the PIC cycle.
It’s important when using PHC that you understand that plant problems generally arise from a combination of stress factors, not just one. The PIC cycle has three parts:
- Predisposing factors that reduce a plant’s tolerance to stress. These factors should be considered when choosing your trees and shrubs.
- Inciting factors happen when a healthy tree is attacked by primary insects, diseases, and abiotic disorders, ultimately resulting in acute stress.
- Contributing factors are those of secondary insect, disease, and abiotic disorders that attack trees already under stress. Unfortunately, these factors can lead to tree death and are hard to control.