Pesticide use directions describe both site (greenhouse, interiorscape, etc.) and application method (foliar sprays, soil/medium treatments, aerosols and fumigants, etc.) for treating ornamental plants. The size of the planting and the sizes and structure of plants to be treated are also important considerations. The best application equipment for a particular situation is that which provides thorough coverage within a reasonable amount of time and effort.
High-volume foliar sprays. High-volume hydraulic applicators provide good coverage, particularly if care is taken to direct the nozzle(s) properly. Most pesticides are applied to the point of runoff to both the under- and upper-surfaces of foliage. However, some products (e.g., Bacillus thuringiensis, insect growth regulators and others) are applied to wet foliage only and instructions say to avoid runoff.
Coverage. When making applications, every effort should be made to determine if target surfaces are being reached. For less toxic, contact materials such as horticultural oils, insecticidal soaps, microbial insecticides and insect growth regulators, applying sprays directly to the pests or pest-infested surfaces is essential for good control. Coverage is relatively less important when using systemic pesticides – those containing an active ingredient that moves through plant tissue (e.g., acephate, imidacloprid, abamectin). There are several dye products available that can be mixed with the sprayer contents to reveal areas where pesticides have been applied.
Soil-applied systemic insecticides. The use of soil-applied systemic insecticides before pest infestations occur is often referred to as a preventive treatment. Although these applications are convenient, they may or may not be justifiable either economically or environmentally unless there is a history of repeated, predictable infestations.
It has been claimed that systemic insecticides are less harmful to natural enemies, since these organisms do not contact or directly ingest the pesticide. However, the period of protection offered by systemics varies. After application, landscape managers should continue to monitor for outbreaks of secondary pests and determine the length of the product’s activity.