Many years ago when Michael Jordan was dominating the basketball courts, his incredible shooting ability was often described as "nothing but net"--a mark of smooth perfection. To excel as a crop scout, the best tool of the trade is nothing more than a net (sorry, it's my best analogy). I find the sweep net a perfect tool for first detection of insects in soybeans or alfalfa. In a few quick minutes, a field can be swept and the contents examined. If the insect in question is found, then a more thorough process can be implemented to determine the number of insects per plant, square foot, length of row, etc. A sweep net is helpful for scouting bean leaf beetles and caterpillars in soybeans, and is absolutely essential for scouting potato leafhoppers in alfalfa.
I use a hybrid net whose components are made by two different supply houses. I recommend buying the handle from Ward's because of its 3-foot long, strong metal construction and heavy wire gauge hoop, but their net bag is flimsy. I recommend replacing the net bag with one made by BioQuip. The bag from BioQuip is extremely durable--the edge is made of Dacron sail tape--and slides easily through alfalfa and soybeans during sweeping. The Dacron is extremely resistant to abrasion and should last throughout the growing season, plus it will not roll up on the leading edge of the net hoop like the more flimsy net bag from Ward's. Unfortunately, the BioQuip net handle is wood and a short 2-feet long. For these reasons, I suggest buying the parts and making a hybrid sweep net.
The hybrid sweep net is not inexpensive, but it will serve you well in collecting insects in alfalfa and soybeans. I strongly encourage you to get one if you'll be scouting either of these crops this season.
Here are the components for my hybrid net:
Heavy-duty beating net #10V0560
(net has 36" aluminum handle with plastic grip and frame of steel)
Ward's Natural Science Establishment, Inc. 
P.O. Box 92912
Rochester, NY 14692
15" heavy-duty sweep net bag #7215HS
(made of rugged sailcloth banded at top with Dacron sail tape)
$12.55 eachBioQuip Products, Inc. 
2321 Gladwick St.
Rancho Dominguez, CA 90220
This article originally appeared on page 89 of the IC-496 (7) -- April 17, 2006 issue.