An area of growing research and practice is using lighting to help control agricultural pests. This can include horticultural lighting in indoor growing facilities (aka controlled environment agriculture or CEA) or nighttime treatment with specific wavelengths on outdoor crops.
Greenhouse growers have long known that introducing supplemental grow lights to greenhouses can dramatically change the types and severity of pests. It’s possible for indoor growers to consider lighting impacts to increase the effectiveness of fighting pests.
Integrated Pest Management (IPM) is a holistic approach to managing pests that combines multiple methods and strategies, including cultural, physical, biological, and chemical methods. IPM often creates an environment that is less favorable to pests, such as by reducing their access to food, water, and shelter. IPM advocates for the use of the least-toxic option available and only as a last resort. Often IPM utilizes biological controls, such as the use of natural predators or parasites to control pest populations. These biological controls are often referred to as biologicals, biocontrols, or just bios.
Lighting can impact biocontrols through photoperiod, intensity, and disease control:
Insects under stress often go dormant in a process known as diapause, most typically in winter. Hours of light per day (photoperiod) is one of the strongest triggers of diapause. Supplemental CEA lighting can extend the photoperiod for biocontrols and keep biocontrol species active in fighting pests through the winter. This strategy is “breaking diapause” for biocontrols.
Some biocontrol parasites become more effective with increased light intensity as well as increased photoperiods. This makes these parasitic biocontrols better at controlling pests. Research has also shown that increased light intensity can make blue and yellow sticky traps more effective at trapping specific pests. Essentially, insects can see the traps better and are more attracted to the colors under more intense lighting.
Different wavelengths of light have been shown effective at fighting certain plant diseases. Red light suppresses downy mildew in basil and improves plant growth. The red light treatment is done at night to prevent spore spread.
UV light is also being researched to prevent powdery mildew in cucumbers and strawberries. As with more familiar UV disinfection, UV can break down a pathogen’s DNA. Blue light aids in repairing DNA, so combining blue and UV lighting has been shown to be ineffective at preventing the disease. UV applied to strawberries at night was found to be as effective as the best fungicides against powdery mildew.
The LHRC at Mt. Sinai recently published research on UV-C treatments to fight powdery mildew on cucumbers grown outdoors. While the study didn’t find significant prevention of the disease, it delayed onset and also found reflective mulch yielded better outcomes than dark mulch, likely by keeping down soil temperatures, aiding plant health.
Read more of our coverage on agricultural lighting here.