Thrips control can be nearly impossible given the wide variety and their incredibly small size. There are over 6000 species of thrip and only a small percentage of them are harmful, but the ones that are can reek havoc on vegetable crops and greenhouse plants. The tiny thrip literally sucks the life from plant cells damaging stems and leaves and scarring and deforming plants. There are ways to combat these insects and these tips below can help provide a basis for an effective thrips control program.
Know thy enemy
The first key in effective thrips control is scouting the enemy. Shaking plants gently over a clean piece of paper or laying sticky traps around affected areas can provide samples to let you know exactly which variety of thrip is plaguing your crop or greenhouse. Once proper identification is made then the steps can be undertaken to combat them.
The best way to battle many common thrips is to never have to battle them in the first place. When possible, especially for greenhouse owners, defense is the best offense. A vegetation free perimeter should be established around the greenhouse to a distance of at least ten feet. A weed barrier fabric should be laid and covered with mulch or gravel. This isolation barrier can prevent thrips from taking up residence on nearby plants before infecting your valuable crops.
Another way to prevent infestation is with a tightly woven insect screen covering all ventilation and exhaust areas to the greenhouse. Thrips are incredibly small (only around 1/20th of an inch); so make sure the mesh is very tight.
Inspect any new plants very closely before bringing them into contact with thrip free plants. A magnifying glass should be sufficient to identify potentially infected plants.
The enemy of my enemy is my friend
Sometimes the best way to stop a predator is with another predator. Introducing predatory mites or even ladybugs can be an effective treatment. There are also certain wasps and beetles that also eat thrips. A local county extension agent should be able to recommend safe biological thrips control insects and suppliers to you. Many environmentally friendly pest control products can be found on sites like gardensalive.com and others.
Sometimes, the only choice for thrips control is to resort to a pesticide or natural oil. For thrips that are damaging vegetable crops this is often the only solution left. Many thrips only damage the plant and leave the fruit untouched and usually a natural oil repellent can be used. Again, each case is unique based on plant and thrip affecting the plant.
As you can see, there are many steps to effective thrips control and it takes constant defense to keep these tiny insects from causing extensive damage to your plants. Fortunately, most thrips are harmless but there are treatments widely available for the harmful ones.