Pesticides come in various forms, as solid, liquid or gas—in general, insecticides kill insects, herbicides kill plants (i.e. weeds) and fungicides make short work of, well, fungi, but even these classifications can be further broken down. With insecticides, a stomach poison must actually be ingested, while a contact poison needs merely to be touched by the insect. A systemic insecticide can be applied to one part of the plant from where it spreads by itself to the rest, although it may need to be applied in a particular way to be properly effective, such as at the root or on the leaves.
Herbicides can also be selective, in that they go after a certain species of plant. Residual herbicides provide long-term control, sometimes for up to three seasons. However, timing is important—they must be applied when the plants to be protected are strongest and the weeds at their weakest. You might find pre-plant, pre-emergence or post emergence types, which really speak for themselves.
A protectant is a fungicide designed to protect the plant rather than do damage to a fungus. Eradicants are used when it's too late. In with the mix may be an inert substance, which might be talc in a dust formulation, or a petroleum product to assist emulsification.
Aerial Application, in UK, at least, takes place under a “Certificate”, which is broadly comparable to an AOC. Other countries will have a similar system. Under the terms of this, a Ground Operations Manager must always be present, who must have certain minimum qualifications. There should also be a field support engineer, who monitors aircraft performance and attends to routine servicing (the same person could do both jobs). There may also be a flagman, who marks out the areas to be sprayed and the routes to be followed. Other ground staff include loaders, who mix and load the solution, which usually requires fast action to keep things going as much as possible, but, when things are happening quickly, there is more danger of spillage and contamination.