Chapter 6 deals with plant pests, the symptoms of disease and injury that they create, and the principles used to control them. Here, the emphasis is given to the decisions that a landscaper or arborist must make to apply the knowledge of pest control to the maintenance and management of a landscape site. It becomes a three-part judgment call: What is the potential or actual extent of pest damage? What is the quality expectation and/ or tolerance level of the client? What are the environmental ramifications of the proposed method of control?
Whether a professional landscaper or arborist, a property manager, or a home gardener answers the questions, they must be answered. In many cases, the control methods used will be restricted or guided by local laws and regulations. Many states and communities ban or restrict the use of certain pesticides or limit the right to apply them to registered pesticide applicators. Those that are available for general purchase are increasingly limited and have diluted concentrations.
Every state has a college of agriculture that is responsible for approving the use of every pesticide used within the state. Scientists at the
colleges are also responsible for determining the appropriate product and formulation for use against a particular disease, weed, or insect on a particular host at a particular time of year or stage of development. It is increasingly probable that their recommendations will incorporate the latest biological controls and IPM measures. Their recommendations are updated and published each year for use by the states’ professionals. Copies of the recommendations are available directly from the state universities and often from local Cooperative Extension offices. Everyone who uses pesticides must realize that although pest problems may be similar in different states and in different regions within a single state, the environmental conditions can vary in subtle ways not always apparent. Therefore, if a pesticide is not approved for use within a state or region, it is dangerous, unethical, and illegal to purchase the product elsewhere and apply it in the restricted zone. It is also equally dangerous and illegal to increase the dosage or frequency of application beyond that which is recommended.
Managing the landscape in a manner that optimizes plant health is the best way to control pests. Avoiding the use of plants in locations that do not fit their cultural needs will also avoid the costs of labor and materials needed to control the predictable invasion of weeds that will flourish in those locations or the insects and pathogens that will find their way to the weakened hosts planted in unsuitable locations.
Regular scouting of the landscape to monitor the presence, numbers, and stage of development of pests is another mandatory management task in order to determine what controls are needed, where they are needed, and when to apply them for maximum effectiveness.