It's important to note that most insects that prey on pecan crops are probably in your area. When aphids magically appear in your orchard after a mid-summer rain, they didn't fly up from East Texas. They've been over at your neighbor's orchard all summer, you know, the guy that's slinging water all over his ten acres with his sprinkler system. Pecan weevils are supposedly isolated to specific areas of Texas (see the map below that I uh...borrowed from somewhere.) However, I suspect that the only main difference between a pecan weevil and the infamous boll weevil that plagues the cotton farmers is what they're laying their eggs in...cotton or pecans. (See more pictures below that I uh...borrowed.) The point is...those pecan pests are out there.
Unless the survival of your pecan orchard is in jeopardy, application of pesticides should be based solely on economic variables. If you determine that the loss of pecans due to insect damage will be substantial in a financial sense and that the expense of pesticide application is sufficiently justified to offset these losses, then an insect pest control program is an important factor to successful pecan production. However, to minimize insect infestation which in turn minimizes unnecessary operating expenses, proper orchard management including pest prevention must be exercised on a day to day basis.