Using Light to Repel and Attract Insects
Editor’s Note: There are several research sources that have discussed the phenomenon of phototaxis. Before buying or installing equipment, make sure to do your research on what insect pests you’re hoping to repel or attract. Growers Network always recommends conducting your own experiments before taking anyone’s word as truth!
I had an interesting experience early in my career at a warehouse in Texas. The facilities manager decided to switch from HPS lighting to metal halides to take advantage of their color rendering index. Within months, the manager noticed that there was a spider problem.
When the manager called me, I realized that the yellow lights had previously been keeping the spiders out. After some painful modifications, the manager switched back to the HPS lights, and, according to what he told me, within minutes spiders were marching down the aisles of the warehouse and out the doors. Within a few days, all the spiders had vacated the building.
This is when Metaphase began developing its own insect-deterrent light.
Editor’s Note: Lights may attract or repel insects depending on the species. For example, it is well-known that moths are attracted to blue light, or that cockroaches are repelled by virtually any light. Every light may have a tradeoff as to what insects it attracts and repels.
A Midwestern university tested our experimental insect deterrent light. They found that it was most effective on aphids, as they would evacuate a growth chamber in which the light had been placed. The chamber was completely bug-free within the week. I followed up the university tests with experiments in cannabis greenhouses located in Colorado and Maine. Aphids consistently moved away from areas illuminated by the lights. This was observed by Tuinier Brothers Flowers when they positioned their hanging baskets, infested with aphids, between the lights.
The same university also was the first to notice that our lights deterred spider mites. Mites would not cross from infested plants to nearby healthy plants that were illuminated by the insect deterrent light. It was as if the light acted as a barrier that the spider mites would not cross. We took this knowledge and field tested the lights in greenhouses of Colorado and Maine that had already had an infestation of spider mites. The lights were positioned on the floor beneath the canopy of the cannabis. The mites hid on the top of the leaves to get away from the light and laid their eggs on non-illuminated plants.
Again, the same university also reported that the light was keeping thrips out of illuminated grain. This grain was even placed inches away from infested plants. The thrips simply stayed away from the light.
Colorado Russet Mites
Brighterside Vertical Farms in Colorado reported that their customers had been experiencing outbreaks of russet mites. They wanted to try the insect lights to see if they would have deter mites that were infesting some cannabis clones. We saw two results:
- The russet mites ran away much faster than expected.
- The clones grew much healthier stems and thicker and longer roots. Whether this was a side effect or direct cause is inconclusive.
Editor’s Note: Lights may attract or repel insects depending on the species. For example, it is well-known that moths are attracted to blue light, or that cockroaches are repelled by virtually any light. Every light may have a tradeoff in what insects it attracts and repels.
A grower I worked with had an infestation of Japanese Beetles. Much to his surprise, the beetles were flying into the light that he was using to repel mites. The beetles would fly into the light and then fall to the floor of his greenhouse. In a clever move, he placed a bucket of water where the beetles were falling. After that, his concern became changing a bucket, not managing an infestation.
Consejo Superior de Investigaciones Científicas, a Spanish agricultural research center, found that the insect light was very effective on whiteflies, but not in the way they were expecting. The research personnel thought that the whiteflies would be repelled by the light, but to their surprise, the whiteflies flew toward the lights. The researchers attached some double-sided film tape over the lenses of the lights, and the whiteflies flew into the tape. After applying some clean tape, the researchers were able to capture and remove each one of a hundred whiteflies.
A US government research facility was looking for a solution to fight psyllids (jumping plant lice). The researchers expected that the psyllids would be repelled from the light, but instead the psyllids were attracted to it. The researchers set up a test area which included a window to the outside (daylight) and a translucent panel located 4’-6’ away illuminated with the insect light. A plant was placed about 6 inches from each panel. The 200 psyllids, which were reared at this facility, were released in the middle of the test area. More than 60% of the psyllids flew toward the insect light while the others ventured towards the daylight. The psyllids that headed for the daylight landed on the plant, while the psyllids that headed toward the insect light flew right past the plant and landed on the illuminated panel.
We’ve scheduled our insect deterrent light for additional tests throughout the world. The light was recently made available for commercial use, and can be found on our website.
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About the Author
I have been in the lighting business for over 20 years. Recently I became the Business Development Manager for the Metaphase Lighting “New Technology” products. I am regularly in contact with growers, researchers, and scientists throughout the US and the world.