A day often does not pass without somebody walking into the store with a leaf, branch, needles or blades of grass and with the question, “What do you have that I can spray on this.”
Many have no clue what the problem may be but they are sure a cure-all is available. In almost all cases, they are looking for a chemical that can be mixed in water and sprayed on the plant.
Sometimes the simplest practices are the first line of defense against many pests.
If you see a tomato hornworm or a bagworm on a plant, simply pluck it off and dispose of it. Problem solved.  Inspect the plant for any more pests and repeat the process. This is often the most efficient and cost effective method of pest control. No need to spray.
In the case of aphids, mites, newly hatched bugs or beetles, it may be possible to grab a garden hose and knock them off the plant with a strong blast of water. It’s highly unlikely the insects will find their way back.
This method is effective as prevention in species that are prone to invasion. I strong shower from all directions on a regular basis may be sufficient to control unwanted visitors.
Sometimes though, it may be necessary to allow chemical technology to offer assistance.
Before using any product, natural or chemical, make sure you have isolated the problem. Make sure that what you are applying is the correct product and dosage.
Improper use of chemicals has many consequences that have the potential to cause more damage than the original problem.
I suggest using the safest products available. Resort to more powerful chemicals in the case of of rapid damage or overwhelming numbers of invaders. More toxic does not necessarily mean more effective or quicker.
If you are using a product for the first time, read the label.  Admittedly, government requirements have made many labels difficult to navigate and decipher.  If you cannot find the information you need, call the store you purchased it from, hopefully us, or contact the manufacturer.
In my own practice, I’m finding frequent inspection and quick action is very effective in keeping garden problems manageable. Visit your plants often, learn to identify warning signs, and seek solutions from people you trust.
If you are a novice, there are many forums and groups online that can be very informative. We do live in the information age.  Some of this has to be filtered and that is why we will be happy to help you succeed in your garden adventure.