If you thought whiteflies were small, dear reader, thrips are usually one millimeter or less in length. They have cigar shaped bodies that taper towards their tail end, and this tail has a tendency to move in a whip-like motion. There are around six thousand described species of thrips, and not all of them are actually pests. Some are beneficial predators of other pests and mites, or as pollinators for certain species of plants.
The thrip species that are considered agricultural pests are particularly damaging as they prefer to feed on the developing shoots and flowers of the plant. As they are minuscule in size, it is often hard to detect thrips by sight alone. Instead, a more obvious visual sign of thrip infestation is usually the shriveling and bunching of the shoot tips and flowers of your plant.
Thrips are especially difficult to control because they tend to live and reproduce in enclosed spaces. As plant shoots and flower buds are these enclosed spaces that thrips favor, these pests are also usually harder to reach with pesticidal control methods. They tend to be shielded away from the pesticides after all. Thus, systemic pesticides are considered better for the purpose of killing thrips. Dinotefuran has been shown to be a fairly effective pesticide against thrips, for example. However, as mentioned with whiteflies, this is a neonicotinoid pesticide, which again has been implicated in honeybee colony collapse disorder, and is fairly toxic to many other insects as well. If you must use this, use it with caution, and only as a last resort.
Less toxic pesticidal methods such as neem oil, neem’s more refined form of azadirachtin oil, or pyrethrins combined with piperonyl butoxide have been shown to be much more effective in controlling thrips. Less toxic means they tend to have less of an effect on other insect populations, and are also less toxic to humans and pets. Use these pesticidal oils to thoroughly cover the shoots and buds and other parts of the plant where thrips have been observed. Again, thrips reproduce quicker than you think, so apply these pesticidal oils regularly to eradicate your infestation. For small gardens and farms, Perla laundry soap, which counts coconut oil as its main ingredient, is your friend here. Froth up a soapy, bubbly solution and spray thoroughly on shoots, buds, and other places where you see the hallmark shriveling and bunching damage caused by thrips.
As most thrips are even smaller than whiteflies, there really isn’t much point trying to protect your plants from them with netting as a cultural/mechanical control method. They very easily penetrate fine mesh nets, and as with whiteflies, can escape their natural predators this way. Greenhouse farmers beware, as thrip populations explode and overwhelm greenhouse crops if not managed properly. Instead, two cultural/mechanical methods have been observed to help in controlling thrips. Thrips are highly attracted to bright floral colors like white, blue, and yellow. Sticky glue traps with these colors can once again help you control thrip populations, as they will attempt to feed on what they think are tasty flowers. The other method is more costly, but also more interesting. Scientists in Japan have shown some promising research on red light illumination reducing thrip reproductive activity.
You may be surprised to learn that, rather unfortunately, biological controls are not as effective against thrips, for the same reasons that pesticidal control is not as effective. Because thrips hide in enclosed spaces, they don’t have many predators who can also squeeze into those spaces to eat them and their eggs. Since thrips tend to congregate in these spaces, pesticidal oils can be applied in target locations instead of a general application, and thus are safer to use against them without as much risk of affecting other insect populations. As such, pesticidal oils are generally accepted as the most effective method of controlling thrips.