Odds of Getting In
If you have the appropriate background, this is the sort of field you can just sort of fall into. Don't get us wrong, if you're fascinated by keeping pests off of crops, this is certainly the career for you, but you may find yourself drawn to it simply because you enjoy research and experimentation.
If you're out there with a degree that qualifies you to do the heavy-lifting science involved in pesticide research, and applying to every job you can, you just might get a call back from Dow Chemical or book that random gig you applied to at the Office of the Indiana State Chemist, which is apparently a real thing. Otherwise, there are plenty of smaller companies and agencies vying for their spot in the pesticide game.
The world population keeps growing, and so must our food supply. If you want to work in the field, er, so to speak, you probably won't have that hard of a time getting in.