Pecans I can't help you with. Close companion planting among the veggies is a good deterrant; the bugs won't go after what doesn't smell like food to them and a confusion of scents is quite effective. For squashes, encircle the seeds with radishes about 6" from squash seed and again about 10"; use a nice hot/pungent radish variety and let them grow all season (they aren't for us to eat) but their presence does seem to help deter squash bugs and borers. I've never had the bugs on tomatoes, but the one time I forgot to plant marigolds among the peppers and potatoes, they were attacked. Space marigolds about every 2 feet along the row or in-between large plants such as peppers. A regular spray of home-remedy seemed to keep the potato bugs off. My usual home-remedy is 3 large cloves of garlic and one or two jalapeno peppers processed with 1 cup water and soaked overnight. The next day, strain through a coffeee filter and add 1/4 cup sudsy household ammonia and enough more water to fill a quart handsprayer (old windex bottle is good). Test your plant first by saturating a small section and wait a day -- I've never had any get sick from it, but no doubt somewhere there's a plant that won't like it. Then spray over and under all leaves and stems. Spray must be repeated after every rain, which is why it's easier to plant lots of stinky companions to ward off the infestation than it is to fight an established population.