22 Jun Webinar: How Does Light Spectra Affect Insect Activity?
Did you know the color of light impacts the behaviors of insects, which in turn can have an impact on plant growth and development? Understanding this important interaction is crucial to successful crop management. To further explore this interplay, Fluence recently hosted a panel discussion featuring in-house horticulturists as well as insect experts from Biobest, an industry-leading sustainable crop management firm based in Belgium.
Fluence horticulture services specialist Tim Knauer led off the panel discussion with a short presentation explaining the response of pollinators (bees) to light, as well as that of harmful and beneficial insects.
What do insects see?
Pollinators “see” UV, blue and green wavelengths. They function most effectively when all three spectra are available in appropriate quantities. This means that in low-light conditions when narrow-spectrum LED lights are used, bees are not at their best because the higher red content and lack of middle wavelengths suppress pollination activity. Similarly, HPS, which is notoriously high on the red-yellow spectrum, does not provide optimal light quality for bee activity, particularly in low light conditions.
When it comes to navigation, bees in greenhouses use the naturally-occurring UV light from the sun along with blue light to aid their orientation. Incidentally, photoperiod has no direct effect on the foraging habits of bees, as long as intensity and spectrum are optimal. In addition to ensuring pollinators are exposed to adequate levels of broad-spectrum lighting, cultivators should also take into account other environmental factors, such as carbon dioxide levels and air temperature, which can impact pollinators.
Pests and beneficials have a relationship with light similar to that of pollinators, according to Tim. Overall, pests and beneficials both increase activity in higher light levels — assuming temperature and food sources aren’t limiting factors.
Selected Questions and Answers
Following Tim’s presentation, three additional panelists joined the conversation: Brian Poel, Fluence research projects manager; Amanda Brown, Biobest biological crop protection specialist; and Sam Gui, Biobest IPM and pollination specialist. Some of the questions asked of these panelists follow. See the entire discussion here.
Q: Do you recommend foliar spraying when deploying beneficial insects?
A: It definitely depends on the active ingredient you’re applying. In IPM programs, it’s very important to focus on establishing your beneficials, but it’s not to say foliar sprays are forbidden.
Q: If you are using 600-watt LEDs as your primary light source (not LEDs as intercropping lighting) in a greenhouse, are beneficials and pollinators attracted to this heat source or is the spectrum the concern with HPS?
A: The concern with HPS is the high surface temperature that will kill pollinators. While insects can be attracted to either HPS or LED spectra, LEDs don’t have the lethally high surface temperature.
Q: How do various spectra affect beneficial insects’ ability to find prey?
A: It affects the beneficials that require light to find their host. A lot of beneficials have cues they use to find their hosts. In fact, the absence of light mostly affects flying insects. Wasps, for example, benefit from visible light to find their prey. For many insect species, however, light isn’t necessary for them to do their job as they have different ways of finding their host.
Q: Many indoor cannabis growers use UVC to control powdery mildew. How does this light affect beneficial insect populations?
A: We are not sure if this has been studied yet, although we do know that UVC has been shown to affect the survival of predatory mites. We also know that both pests and beneficials have learned to go below the leaf surface. That gives them the lower light levels that they need for survival.