Pesticide manufacturers are required by federal law to tell you on the product's label under what circumstances it is legal and effective to use the product. Many insect problems are at their worst in the summer. For example, if your foliage has faded and appears washed-out in color, it is possible that spider mites or lacebugs are sucking the sap out, and dehydrating the plant. Pests like these can easily kill a healthy plant in a matter of weeks. Holes in woody plant trunks or branches, often accompanied by sawdust or oozing sap, are indicators that borers have infected the plant.
Borers are the larval stage of various insects, often beetles or clear-wing moths.
They tunnel under the bark, and when they emerge as adults, an emergence hole is left on the victim plant. A severe infestation of borers will kill the plant, as it destroys its ability to transport water to the leaves. Consider all pesticides as potentially hazardous. Because when used under the proper conditions and wearing the proper Personal Protective Equipment the risk is minimized. The label will instruct you as to whether eye protection is necessary, for instance.