Trapping can be an efficient and informative monitoring tool. Traps can alert growers to pests early before crop damage occurs and before pests become abundant and more difficult to control.
Yellow Traps covered with sticky material attract and capture the adults of various flying insects. Pests captured by yellow sticky traps include adults of fungus gnats, thrips, and whiteflies, aphids, psyllids, and sharpshooters.
Blue sticky traps are sometimes used for thrips because this color is more attractive to thrips.
Sticky traps can indicate localized spots of high pest abundance or periods of migration of adult pests into crops. Traps can also provide a relative measure of insect abundance and whether pest density is decreasing, increasing, or remaining about the same over time.
Orienting traps horizontally (facing the soil or upwards) is sometimes recommended when monitoring pests such as fungus gnats and shore flies that emerge from or rest upon growing media. However, to catch a wider range of targeted insects, orient the longest part of the trap vertically (up and down). Place each trap so that its bottom is even with the top of the plant canopy. For rapidly growing crops, locate trap bottoms a few inches above the canopy so that the plants do not soon overgrow the traps. As plants grow, move each trap up so that its bottom remains about even with the top of the canopy or somewhat higher. For example use one or two clothespins to attach each trap to a bamboo post or wooden dowel embedded in the growing media or a stand. Alternatively hang traps from rafters or wires strung between posts.